DEAS 1207 : 2024  
ICS 93.080.20  
 
© EA C 2024                                                                                                                              First Edition  2024   
                     DRAFT EAST AFRICAN STANDARD  
Asphalt paving mix design  — Code of practice  
EAST AFRICAN COMMUNITY  DEAS 1207  2024  
ii © EAC  2024  – All rights reserved  
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Violators may be prosecuted . DEAS 1207: 2024  
© EAC  2024  – All rights reserved  iii 
 Contents  Page 
1 Scope  ................................ ................................ ................................ ................................ ......................  1 
2 Normative references  ................................ ................................ ................................ ............................  1 
3 Terms and definitions  ................................ ................................ ................................ ...........................  2 
3.8 Terms related to asphalt mix classification  ................................ ................................ ........................  3 
3.9 Terms related to mix specific gravity  ................................ ................................ ................................ .. 3 
3.10  Terms related to mixture volumetric parameters  ................................ ................................ ...............  4 
3.11 Terms related to desired properties considered for mix design  ................................ ...........................  5 
4 Symbols and/or abbreviated terms  ................................ ................................ ................................ ..... 5 
5 Volumetric Properties of Compacted Paving Mixtures  ................................ ................................ ..... 6 
5.1 General  ................................ ................................ ................................ ................................ ...................  6 
5.2 Bulk (dry) specific gravity of aggregate  ................................ ................................ ..............................  6 
5.3 Calculating Gmm at trial binder contents  ................................ ................................ ...........................  10 
5.4 Percent air voids in compacted mixture, Pa ................................ ................................ .....................  11 
5.5 Percent VMA in compacted mixture  ................................ ................................ ................................ .. 11 
5.6 Percent VFA in compacted mixture  ................................ ................................ ................................ ... 12 
5.7 Binder absorption  ................................ ................................ ................................ ................................  13 
5.8 Effective binder content of a paving mixture  ................................ ................................ ...................  13 
5.9 Dust to binder ratio  ................................ ................................ ................................ .............................  14 
5.10  Selecting a design aggregate structure (DAS)  ................................ ................................ .................  14 
6 Asphalt mix design methodologies  ................................ ................................ ................................ ... 18 
6.1 Superpave HMA Mix Design System  ................................ ................................ ................................ . 18 
6.2 Marshall Method of Mix Design  ................................ ................................ ................................ ..........  28 
6.3 Hveem Method of Mix Design  ................................ ................................ ................................ ............  40 
7 Recycled Asphalt Pavement (RAP) Materials in the Mix Design Process  ................................ ..... 59 
7.1 Reclaimed Asphalt Pavement (RAP)  ................................ ................................ ................................ . 59 
7.2 RAP properties  ................................ ................................ ................................ ................................ .... 59 
7.4 Developing the mix design  ................................ ................................ ................................ .................  62 
A.1 General  ................................ ................................ ................................ ................................ .................  66 
A.2 Selection of trial binder contents, compaction temperatures and mixing times  .........................  66 
A.3 Laboratory compaction ................................ ................................ ................................ .......................  69 
A.4 Determining bulk specific gravity, G mb ................................ ................................ .............................  70 
A.5 Effect of binder content G mb and G mm ................................ ................................ ...............................  71 
B.1 General  ................................ ................................ ................................ ................................ .................  72 
B.2  Methods of recycling ................................ ................................ ................................ ..........................  72 
B.3 Suggested method of sampling existing asphalt  ................................ ................................ ............  73 
B.4 Methods of obtaining RAP  ................................ ................................ ................................ .................  73 
B.5 Stockpiling RAP  ................................ ................................ ................................ ................................ ... 74 
B.6 Use of RAP as unbound granular material  ................................ ................................ .......................  74 
B.7 Cold mix recycling  ................................ ................................ ................................ ...............................  74 
B.8 Plant hot mix recycling  ................................ ................................ ................................ .......................  75 
B.9 Blending with a soft bitumen  ................................ ................................ ................................ .............  76 
C.1 Axial Loading Slab Test  ................................ ................................ ................................ ............................  77 
C.2  Wheel Tracking Tests ................................ ................................ ................................ .........................  77 
C.4  Recommended Test Procedure for Rutting Evaluation  ................................ ................................ .. 81 
C.5 Performance testing for fatigue evaluation of asphalt wearing courses  ................................ ...... 81 
C.5 Four Point Bending Beam Test  ................................ ................................ ................................ ..........  82 
C.6  Fatigue Evaluation of HMA Bases  ................................ ................................ ................................ .... 86 
C.8 Constant Head Permeability Test  ................................ ................................ ................................ ...... 88 
C.9  Moisture Sensitivity (Modified Lottman Test)  ................................ ................................ .................  89 DEAS 1207  2024  
iv © EAC  2024  – All rights reserved  
 C.10   Compressive strength of hot mi asphalt  ................................ ................................ .........................  90 
 DEAS 1207: 2024  
© EAC  2024  – All rights reserved  v 
 Foreword  
Development of the East African Standards has been necessitated by the need for harmonizing requirements 
governing quality of products and services in the East African Community. It is envisaged that through 
harmonized standardization, trade barriers that are encountered when goods and services are exchanged 
within the Community will be removed.  
The Community has established an East African Standards Committee  (EASC)  mandated to develop and 
issue East African Standards  (EAS) . The Committee is composed of representatives of the National 
Standards Bodies in Partner States, together with the representatives from the public and private sector 
organizations  in the community . 
East African Standards are developed through  Technical Committees that are representative of key 
stakeholders including government, academia, consumer groups, private sector and other interested parties. 
Draft East African Standards are circulated to stakeholders through the National Standards Bodies in the 
Partner States. The comments received are discussed and incorporated before finalization of standards, in 
accordance with the Principles and procedures for development of East African Standards.  
East African Standards are subject to review, to keep pace with technological advances. Users of the East 
African Standards are therefore expected to ensure that they always have the latest versions of the standards 
they are implementing .  
The committee responsible  for this document is Technical Committee EASC /TC 028, Construction of Roads , 
Rail, Air and Water Transport Infrastructure . 
Attention is drawn to the possibility that some of the elements of this document may be subject of patent 
rights. EAC shall not be held responsible for identifying any or all such patent rights.  DEAS 1207  2024  
vi © EAC  2024  – All rights reserved  
 Introduction  
Roads are vital to economic development, but can be very expensive, especially if the performance of the 
road’s surface is poor. It is therefore important that suitable methods of design are developed for the wide 
range of conditions that road surfaces are expected to endure. The principal roads in most countries are 
surfaced with Hot Mix Asphalt (HMA) , that is,  a mixture of aggregate materials bound together with bitumen. 
Asphalt pavements are the predominant pavement type in the world. Asphalt is used for all types of 
applications, from residential streets to expressways, from par king lots to harbour  facilities , and from bike 
paths to airport runways. Depending on traffic, climate, available materials and the location within the 
pavement structure, the type of mix selected and mix design criteria will be different. Road conditions are, 
however, not static; for example, continuing developments in vehicle and tyre designs often increase the 
stresses that are applied to the road. In most countries , traffic levels are also increasing, sometimes beyond 
the limits of the empirical data on which designs are based. In some countries there is a shortage of materials 
of sufficient quality for road surfaces and therefore innovative solutions need to be sought.  Environmental 
concerns are becoming increasingly important and influence the techniques available; for example, 
encouraging the recycling of existing materials. For these reasons, amongst others, research into improving 
the design and performance of HMA road surfaces continues to be undertaken.  
This standard was prepared with these goals in mind. It contains the latest information for the design of 
asphalt paving mixtures to meet the demands of modern traffic conditions and to ensure optimal performance 
of asphalt pavements. The overall objective for the design of asphalt paving mixes is selecting the gradation of 
aggregates and proportioning of asphalt that yields a mix having the desirable properties.  
Successful mix design requires understanding the basic theory behind the steps and following the intent of the 
written instructions. It also includes having proper training in laboratory techniques and effectively interpreting 
the results of laboratory tests. A properly designed asphalt mixture provides a balance of engineering 
properties and economics that ensures a durable pavement that satisfies both its users and owners. The 
overall objective of this standard guideline is to help engineers responsible for roads and gives guidance on 
the design, manufacture and construction of HMA pavement materials in the E ast Africa n Community  region.  
 WORKING DRAFT EAST AFRICAN STANDARD  WDEAS 1207 : 2024  
 
© EAC 2024  – All rights reserved  1 
 Asphalt paving mix design  — Code of practice  
1 Scope  
This Draft East Africa n Standard provides  guidelines on the design of asphalt paving mixtures to be used for 
general asphalt  pavements . 
These guidelines are applicable to the design of Hot Mix Asphalts (HMA) produced from new (virgin) asphalt 
materials and Reclaimed (Recycled) Asphalt Materials in the design process.  
NOTE  The guidelines for mix design given in Clause 7 a re based on commonly used asphalt design methods mainly 
Superpave HMA Mix Design System, Marshall Method of asphalt mix design and Hveem method of  asphalt mix design.  
2 Normative references  
The following documents are referred to in the text in such a way that some or all of their content constitutes 
requirements of this document.  For dated references, only the edition cited applies. For undated references, 
the latest edition of the referenced document (including any amendments) applies.  
D2041/D2041M -19, Standard Test Method for Theoretical Maximum Specific Gravity and Density of Asphalt 
Mixtures  
ASTM C127 , Standard Test Method for Density, Relative Density (Specific Gravity), and Absorption of Coarse 
Aggregate  
ASTM C128 Standard Test Method for Density, Relative Density (Specific Gravity), and Absorption of Fine 
Aggregate  
ASTM D6926, Preparation of Bituminous Mi xtures Using Marshall Apparatus  
ASTM D6927, Standard Test Method for Marshall Stability and Flow of  Bituminous Mixtures  
D1188/D1188M -22, Standard Test Method for Bulk Specific Gravity and Density of Compacted Asphalt 
Mixtures Using Coated Samples  
D2726/D2726M -21, Standard Test Method for Bulk Specific Gravity and Density of Non -Absorptive 
Compacted Asphalt Mixtures  
D6927 -22, Standard Test Method for Marshall Stability and Flow of Asphalt Mixtures  
D5581 -07A ( 2021) , Standard Test Method for Resistance to Plastic Flow of Bituminous Mixtures Using 
Marshall Apparatus (152.4mm/6 in. Diameter Specimen)  
D1560 -15, Standard Test Methods for Resistance to Deformation and Cohesion of Asphalt Mixtures by Means 
of Hveem Apparatus  
D2041/D2041M -19, Standard Test Method for Theoretical Maximum Specific Gravity and Density of Asphalt 
Mixtures   
2 © EAC  2024  – All rights reserved  
 D5404/D5404M -21, Standard Practice for Recovery of Asphalt Binder from Solution Using the Rotary 
Evaporator  
D6752/D6752M -23, Standard Test Method for Bulk Specific Gravity and Density of Compacted Asphalt 
Mixtures Using Automatic Vacuum Sealing Method  
M 323, Standard Specification for Superpave Volumetric Mix Design,  
R 30, Standard Practice for Laboratory Conditioning of Asphalt Mixtures,   
T 30, Standard Method of Test for Mechanical Analysis of Extracted Aggregate  
T 164, Standard Method of Test for Quantitative Extraction of Asphalt Binder from Hot Mix Asphalt (HMA),  
T 308, Standard Method of Test for Determining the Asphalt Binder Content of Asphalt Mixtures by the Ignition 
Method  
T 209, Standard Method of Test for Theoretical Maximum Specific Gravity (Gmm) and Density of Asphalt 
Mixtures  
M 323, Standard Specification for Superpave Volumetric Mix Design,   
M 320, Standard Specification for Performance -Graded Asphalt Binder  
3 Terms and definitions  
For the purposes of this document, the following terms and definitions apply.  
ISO and IEC maintain terminological databases for use in standardization at the following addresses:  
— IEC Electropedia: available at http://www.electropedia.org/  
— ISO Online browsing platform: available at http://www.iso.org/obp  
 
3.1  
asphalt  
a mixture of asphalt binder  (bitumen ) and aggregates. The mixture may also include other materials.  
3.2 
asphalt pavement  
a structure consisting of one or more prepared layers of asphalt mix atop one or more supporting layers of 
unbound, modified, or treated subgrade, subbase or base materials  
 
3.3 
asphalt mix  
homogeneous paving product consisting of sized mineral aggregates, possibly including additives and filler, 
collectively and uniformly coated with binder  
3.4 
hot mix  
asphalt mix in which the aggregates and asphalt binder(bitumen) are heated before mixing   
© EAC  2024  – All rights reserved  3 
 3.5 
Bitumen /asphalt binder  
dark brown to black cement -like residuum obtained from the distillation of suitable crude oils, naturally 
occurring sources, or combinations thereof.  
3.6 
asphalt mix stability  
maximum load resistance in Newton , that the standard test specimen will develop at 60°C when tested as 
outlined in  methodologies described in  Clause 6. 
3.7 
asphalt mix flow value  
total d eformation, in units of 0.25 mm , occurring in the specimen between no load and the point of maximum 
load during the stability test. 
3.8 Terms related to asphalt mix classification  
3.8.1  
Dense -graded asphalt mixes  
asphalt mix with a  well-distributed aggregate gradation throughout the entire range of sieves used.  
Note 1 to entry: It is the most commonly specified type of mix and can be used in the base, intermediate layers and 
surface of a pavement structure.  
3.8.2  
open-graded asphalt mixes  
asphalt mixture designed  with a large volume of air voids (typically 18 to 22 percent) so that water will readily 
drain through the pavement layer.  
Note 1 to entry: It is used as an Open -Graded Friction Course (OGFC)  to provide a skid -resistant pavement surface and 
as a porous base layer (also called Asphalt Treated Permeable Base, or ATPB) to provide for positive drainage under 
either an asphalt or Portland cement concrete pavement surface.  
3.8.3  
gap-graded or Stone Matrix Asphalt (SMA)  
an asphalt mixture with high -coarse aggregate content (typically 70 to80 percent), a high asphalt content 
(typically more than 6 percent) and a high -filler content (approximately 10 percent by weight).  
Note 1 to entry: Gap-graded or Stone Matrix Asphalt (SMA)  is durable mixture that has excellent stone -on-stone contact 
and that is very resistant to rutting.  
3.8.4  
Warm Mix Asphalt (WMA)  
any mix produced at lower temperatures using a variety of technologies while maintaining the workability 
required to be successfully placed.  
3.9 Terms related to mix specific gravity  
3.9.1  
binder Specific Gravity G b  
ratio of the mass of a unit volume of binder to the mass of the same volume of water. Binder specific gravity 
typically ranges from 1.00 to 1.05.  
3.9.2  
bulk (dry) Specific Gravity G sb  
ratio of the oven -dry mass of  a unit volume of aggregate (including both the  impermeable and water -
permeable void volumes)  to the mass of the same volume of water.   
4 © EAC  2024  – All rights reserved  
 3.9.3  
apparent Specific Gravity G sa  
the ratio of the oven -dry mass of a unit volume of aggregate (including only the impermeable void volumes) to 
the mass of the same volume of water.  
3.9.4  
effective Specific Gravity G se  
ratio of the oven -dry mass of a unit volume of aggregate (including both the impermeable void volumes and 
the water  permeable voids not filled with absorbed asphalt) to the mass of the same volume of water.  
3.9.5   
theoretical Maximum Specific Gravity G mm  
the ratio of the oven -dry mass of a unit volume of asphalt mixture (including the volumes of the aggregate and 
binder only) to the mass of the same volume of water.  
3.9.6  
bulk Specific Gravity G mb  
the ratio of the oven -dry mass of a unit volume of asphalt mixture (including the volumes of aggregate, binder 
and air) to the mass of the same volume of water. G mb is applicable to any laboratory - or field -compacted 
specimen including cores, beams, slabs, etc.  
3.10 Terms related to m ixture volumetric parameters  
3.10.1  
percent  Air Voids P a  
The volume of air voids in a compacted mixture, expressed as a percentage of the total mix volume.  
3.10.2 
voids in the Mineral Aggregate (VMA)  
voids created by the aggregate structure of a compacted asphalt mixture, expressed as a percentage of the 
total mix volume. VMA represents the volume of air voids and effective (nonabsorbed) asphalt binder.  
3.10.3 
voids Filled with Asphalt (VFA)  
percentage of the VMA filled with effective (nonabsorbed) asphalt binder.  
3.10.4 
percent  Aggregate P s  
total percentage of aggregate in the asphalt mixture, expressed as a percentage of the total mix mass.  
3.10.5 
percent  Binder P b  
total percentage of asphalt binder in the asphalt mixture, expressed as a percentage of the total mix mass. 
Note that P s + P b = 100%.  
3.10.6 
percent  Binder Effective P be  
functional portion of the asphalt binder that coats the aggregate in the asphalt mixture but is not absorbed into 
the aggregate, expressed as a percentage of the total mix mass.  
3.10.7 
percent Binder Absorbed P ba  
portion of the asphalt binder that is absorbed into the aggregate, expressed as a percentage of the total 
aggregate mass.  
3.10.8 
specific gravity  
dimensionless number defined as the ratio of the density of a material to the density of water (assumed to be 
1.000 g/cm3 at temperatures used in asphalt testing).   
© EAC  2024  – All rights reserved  5 
 3.11 Terms related to desired properties considered for mix design   
3.11.1  
stability  
resistance to p ermanent deformation results from the accumulation of small amounts of unrecoverable strain 
(small deformations) from repeated loads applied to the pavement.  
Note 1 to entry: Stability depends primarily on the internal friction provided by the aggregate particles and to a lesser 
extent the cohesion provided by the asphalt binder.  Unstable pavement develops ruts and other signs of mixture shifting.  
3.11.2  
fatigue resistance  
resistance to repeated bending under wheel loads (traffic). The result of a fatigue failure is fatigue cracking, 
often called alligator cracking.  
3.11.3  
moisture resistance —impermeability  
ability of asphalt mix to prevent water or water vapor from penetrating between the asphalt film and the 
aggregates, thereby preventing the breaking of adhesive bond between the aggregate and the asphalt binder 
film.  
3.11.4  
durability  
ability to resist factors such as aging of the asphalt, disintegration of the aggregate and stripping of the asphalt 
film from the aggregate.  
3.11.5  
skid resistance  
ability of an asphalt surface to minimize skidding or slipping of vehicle tires, particularly when the roadway 
surface is wet.  
3.11.6  
workability  
the ease with which a paving mixture can be placed and compacted.  
4 Symbols and /or abbreviated terms  
HMA  Hot Mix Asphalt  
RAP Reclaimed Asphalt Pavement  
OGFC  Open -Graded Friction Course  
ATPB  Asphalt Treated Permeable Base  
SMA  Stone Matrix Asphalt  
WMA  Warm Mix Asphalt  
DAS Design Aggregate Structure  
CKE Centrifuge Kerosene Equivalent  
VFA  Voids Filled with Asphalt  
  
6 © EAC  2024  – All rights reserved  
 5 Volumetric Properties of Compacted Paving Mixtures  
5.1 General  
The volumetric properties of a compacted paving mixture are important criteria by which the quality of an 
asphalt mixture is evaluated. The volumetric properties are determined using the mass and/ or volume 
measurements of a mixture and its constituent components (binder, aggregate, air). The term “volumetric,” as 
applied in the asphalt industry, actually uses measurements of an asphalt mixture by both mass (M) and 
volume (V) to de termine various percentages (P). Volumetric  properties are often specified design elements of 
the total mix, the aggregate only or the binder only. The relationship between mass and volume is determined 
by the material’s specific gravity (G).  
NOTE  The principal of using specific gravity is essential in that actual laboratory measurements are by mass, yet 
mixture criteria are a function of volume. Usage of specific gravity principles enables us to readily calculate mass or 
volumetric data based on the available data. Some specific gravity values use an aggregate volume that also includes the 
water -permeable voids, while others include only the portion of the water -permeable voids not filled with absorbed asphalt. 
(Because liquid water is always at a lower viscosity than asphalt binder, the asphalt can never penetrate the aggregate 
voids as much as water.)  
It is helpful to represent a compacted mixture in terms of the different masses and volumes used in volumetric 
calculations. This representation , shown in Figure 1, is called a phase diagram. It breaks down the 
components into air, effective asphalt (nonabsorbed), absorbed asphalt and aggregate.  
 
Figure  1 — Phase Diagram  
The various specific gravity types discussed i n this clause  are either directly determined or calculated from 
laboratory tests on the binder, aggregates or asphalt mixture. Several equations have been derived to allow 
calculation of each volumetric property without the use of a phase diagram. Th e equations shown in this 
clause are simplified, as the value of  density of water ( ρ) is assumed to be 1.000.  
5.2 Bulk (dry) specific gravity of aggregate   
It is recommended that the bulk (dry) specific  gravity ( Gsb) of each aggregate be determined on  samp les 
submitted for mix design. Some stockpiles will  be essentially coarse (retained on the No. 4[4.75 mm] sieve), 
some will be fine (passing the No.4 [4.75 mm] sieve) and some will have both coarse  and fine portions.   
© EAC  2024  – All rights reserved  7 
 5.2.1 Determining bulk (dry) specific gravity of coarse aggregate   
The Gsb of coarse  aggregate  is determined using ASTM C127.  The size of the test sample is  specified and 
determined by the nominal maximum  aggregate size. This procedure requires that the dry  aggregate be 
saturated to determine the volume of  the aggregate plus the water -permeable voids.  
 
Notice that this equation mirrors the equation in the test procedure:  
 
where  
Gsb is bulk (dry) specific gravity of the  aggregate  
A is mass of the oven -dry test sample  
B is mass of the saturated surface -dry (SSD)  test sample in air  
C is mass of the saturated sample in water  (ρ is not shown because its numerical  value is 1)  
Therefore, B–C = volume of the aggregate plus the  water -permeable voids.  
5.2.2 Determining fine aggregate G sb  
The fine  aggregate  Gsb is determined using ASTM C128.  The dry aggregate is again saturated  to account for 
the volume of the aggregate plus the  water -permeable voids.  
 
where 
Gsb is bulk (dry) specific gravity of the aggregate  
A is mass of the oven -dry test sample  
B is mass of the pycnometer filled with water  
S is mass of the saturated surface -dry (SSD) specimen  
C is mass of pycnometer with specimen and water to calibration mark  
This time, B + S – C = volume of the aggregate  plus the water -permeable voids.   
8 © EAC  2024  – All rights reserved  
 5.2.2.1 Determining mineral filler Gsb 
The bulk specific gravity of mineral filler is difficult to determine accurately. However, the apparent specific 
gravity ( Gsa) of mineral filler is more easily determined. This can be done for filler only, as the amount of 
mineral filler added is typically small and the difference between Gsb and Gsa is relatively small.  
5.2.3 Determining the composite  Gsb for one stockpile  
For stockpiles that include both a coarse and fine fraction, one value must be determined for the stockpile. 
The average Gsb can be calculated as follows:  
 
where  
Gsb   bulk (dry) specific gravity of the aggregate  
Pcoarse   percentage by weight retained on the No. 4 (4.75 mm) sieve  
Pfine   percentage by weight passing the No. 4 (4.75 mm) sieve  
Gcoarse   bulk (dry) specific gravity of the coarse fraction  
Gfine   bulk (dry) specific gravity of the fine fraction  
5.2.4 Calculate the Gsb for the aggregate blend  
Once the bulk (dry) specific gravity for each  stockpile has been determined, the combined bulk  (dry) specific 
gravity for the total aggregate blend is  calculated as follows:  
 
where  
Gsb  is bulk (dry) specific gravity of the aggregate  
P1, P2, Pn  is percentages by weight of aggregates  1, 2, through n  
G1, G2, Gn is bulk (dry) specific gravity of aggregates  1, 2, through n  
 
NOTE  This equation is useful for estimating G sb during trials in the design process. The calculated coarse and fine 
Gsb can be verified by batching the combined aggregates, splitting them on the 4.75 -mm sieve and determining the coarse 
and fine G sb for the design. This process of splitting the aggregate blend on the 4.75 - mm sieve and only running G sb 
values on the coarse and fine fractions of the blend is often utilized for mix design verification and quality control  testing on 
plant -produced mix in the field.  
5.2.5 Calculate the G sa and absorption for the aggregate blend  
Laboratory testing to determine the bulk specific gravity (G sb) also provides data to easily determine two 
additional aggregate properties, the apparent specific gravity (G sa) and the water absorption of the aggregate. 
These calculations are not required to determine mixture volumetric properties; however, they are valuable  
© EAC  2024  – All rights reserved  9 
 tools for the mix designer to monitor. The absorption of the aggregate indicates several characteristics of the 
final mixture. Highly  absorptive aggregates will require additional binder to fill the permeable voids in the 
aggregate, which increases cost. It is not uncommon for aggregates to absorb a binder amount equal to 40 –
80 percent of the water -permeable voids.  
In order to determine these values for the total blend of aggregate, the methodology used will depend on the 
manner in which the G sb was determined. If G sb testing was conducted on individual stockpiles, then the G sa 
and absorption will need to be determined for each stockpile and then combined to determine the final values 
for the blend. If individual G sb samples were determined for the coarse and fine fractions of any individual 
stockpile, then  the equation shown in clause  5.2.1 can be used to determine the G sa and absorption values for 
the stockpile.  
Once G sa values of individual stockpiles are known, they will need to be combined into one value for the 
blend.  This can be accomplished using  the same equation shown in section 5.2.4, but for G sa instead of G sb. 
The equation for calculating the absorption of t he blend is shown in section 5.2.5.2. If G sb data are determined 
directly from the blend (during a mixture verification or a field sample obtained from the belt carrying 
aggregate into the plant), the designer can simply use the equation fro m section 6 .2.3 to directly determine the 
Gsb, Gsa and absorption data for the blend.   
5.2.5.1 Apparent specific gravity (G sa)  
Gsa is the ratio of the mass of the oven -dry aggregate to the volume of the aggregate excluding the volume of 
the voids occupied by absorbed water. The G sa volume is less than the volume used to calculate the G sb; 
therefore, the G sa value will always be larger than the G sb value.  
 
Notice that this equation mirrors the equation in the test procedure:  
  
where  
Gsa   is apparent specific gravity of the aggregate  
A is mass of the oven -dry test sample  
C is mass of the saturated sample in water (ρ is not shown because its numerical value is 1)  
Therefore, A − C = apparent volume of the aggregate minus the water -permeable voids.  
5.2.5.2 Water absorption (A)  
The amou nt of water absorption is determined from the G sb test data. The absorptiveness of aggregate is of 
significant interest to the mixture designer and specifier. Absorption can be an indicator regarding aggregate 
quality along with increased binder demand. The binder absorption is typically 40 –80 percent of the water 
absorption rate. The water absorption rate is calcu lated by the following equation.  
 
where  
10 © EAC  2024  – All rights reserved  
 B is mass of the saturated surface -dry sample  
A is mass of the oven -dry test sample  
The average water absorption for the total aggregate blend is calculated as follows:  
 
where  
P1, P2, Pn is percentages by weight of aggregates 1, 2, through n  
A1, A2, An is absorption of aggregates 1, 2, through n  
5.3 Calculating Gmm at trial binder contents  
The theoretical maximum specific gravi ty of an asphalt mixture ( Gmm), is the specific gravity of the binder 
coated aggregate only, with no air voids. In order to calculate the volumetric properties of a mixture, a Gmb and 
Gmm must be determined at each trial binder percentage utilized in the mix design. Compaction procedures 
provide the G mb values for each sample, which are then averaged for each trial binder content. The 
appropriate G mm value must also be determined at each trial binder percentage.  
5.3.1 Determining the G se — effective specific gravity of the aggregate  
When only one G mm is conducted in the laboratory, the designer should select a binder content that is equal to 
or greater than the anticipated design binder content in order to assure thorough coating and minimize water 
intrusion into the aggregate during vacuum testing. After finding the average of two G mm samples at a single 
binder content (or if desired, at every trial binder percentage), G se can be calculated using the following 
equation:  
 
where  
Gse   is effective specific gravity of aggregate  
Ps is percentage of aggregate by total mix weight  
Pb is percentage of binder by total mix weight, at which the G mm test was performed  
Gmm is maximum specific gravity of paving mixture  
Gb is specific gravity of binder  
5.3.2 Determining G mm at other binder contents  
The G se used to calculate G mm at each of the other binder contents. This step is not necessary if the designer 
has performed G mm testing at each trial binder percentage. G mm can be visually determined from the phase 
diagram in Figure 1 and is defined by the following relationship:  
  
© EAC  2024  – All rights reserved  11 
 where   
Gmm is maximum specific gravity of asphalt mixture  
Ps is percentage of aggregate by total mix weight  
Pb is percentage of binder by total mix weight  
Ps + P b = 100  
Gse  is effective specific gravity of aggregate  
Gb is specific gravity of binder  
Mmb is bulk mass of paving mixture (which would be the same as Mmm, since the air has no mass), 
typically in g  
Vmm is volume of aggregate and binder, typically in cm3 ρ = dens ity of water, 1.000 g/cm3  
 
NOTE  The binder content increases, G mm always decreases. This is because the percentage of aggregate, which 
has a higher specific gravity, necessarily decreases for a unit volume with an increase in the percentage of binder, which 
has a lower specific gravity.  
5.4 Percent air voids in compacted mixture , Pa 
Pa is the percentage of air voids by volume and Va as the measured volume of air voids. They consist of the 
small air spaces between coated aggregate particles. The property Pa can be visually determined fr om the 
phase diagram in Figure 1, and is defined by the following relationship:  
 
Although the Pa can be calculated several different ways, the following equation is most commonly used:  
 
where 
Pa is air voids in compacted mixture, percentage of total volume  
Gmm  is maximum specific gravity of paving mixture  
Gmb  is bulk specific gravity of paving mixture  
5.5 Percent VMA in compacted mixture  
The VMA is calculated on the basis of the bulk specific gravity of the aggregate and is expressed as a 
percentage of the bulk volume of the compacted paving mixture. Therefore, the VMA can be calculated by 
subtracting the volume of the aggregate determined by its bulk specific gravity from the bulk volume of the 
compacted paving mixture. VMA can be visually determined f rom the phase diagram in Figure 1 and is 
defined by the following relationship s:  
12 © EAC  2024  – All rights reserved  
 
 
VMA is most readily calculated utilizing the following equation:  
 
where  
VMA is voids in the mineral aggregate  
Gmb is bulk specific gravity of paving mixture  
Ps is percentage of aggregate by total  mix weight  
Gsb  is bulk (dry) specific gravity of the  aggregate  
Va  is volume of voids in compacted mixture, typically  in cm3 
Vbe  is volume of the effective ( nonabsorbed) binder , typically in cm3 
Vmb   total volume of compacted mixture, typically  in cm3  
The equations shown above are for analyzing mixture compositions that are determined as percent by weight 
of the total mixture.  If the mixture composition is determined as percent by weight of aggregate, the following 
equation must be utilized to calculate VMA:  
 
NOTE  Because the VMA does not include the water permeable voids in the aggregate, the bulk dry  Gsb must be 
utilized in calculating VMA. Since the target air voids (Pa) typically remains the same, the VMA must increase to allow 
sufficient room for the additional asphalt binder.  
5.6 Percent VFA in compacted mixture  
VFA, like VMA, also tends to increase as the mix becomes finer and gains more total aggregate surface area. 
The VFA can be calculated with either of the following equations.  VFA can be illustrated by the phase diagram 
in Figure 1 and can be calculated by the following equation : 
 
 
 
VFA is most readily calculated with the following equation:  
 
where   
© EAC  2024  – All rights reserved  13 
 VFA   is voids filled with asphalt  
VMA  is voids in the mineral aggregate  
Pa is air voids in compacted mixture, percentage of total volume  
Vbe  is volume of the effective (non - absorbed) binder, typically in cm3 
Va is volume of voids in compacted mixture, typically in cm3 
5.7 Binder absorption  
The percent binder absorption (P ba) is the percentage by mass of binder that is absorbed into the aggregate. It 
is assumed that the amount of binder absorbed into the aggregate is a constant value; therefore, it is 
calculated based on the mass of the aggregate. Note that if the absorption was calculated based on the total 
mass of the mix, the percent absorption would change based on the amount of binder added to the mix.  
Pba can be visually determined from the phase diagram in Figure 1 and is defined by the following relationship:  
 
Pba is most readily calculated with the following equation:  
 
where  
Pba  is absorbed binder, percentage by mass of aggregate  
Gse  is effective specific gravity of aggregate  
Gsb  is bulk (dry) specific gravity of the aggregate  
Gb is specific gravity of binder  
Mba   is mass of the absorbed asphalt, typically in grams  
Ms  is mass of the aggregate, typically in grams  
5.8 Effective binder content of a paving mixture  
The effective binder content (P be) of a paving mixture is the percentage by mass of binder that stays on the 
outside of aggregate particles and is not absorbed. It is effective or usable, as the  
“glue” that binds the mix together and governs the performance of an asphalt paving mixture. Note that P be is 
expressed as a percentage of the total mix mass. That means that mathematically, P ba + P be ≠ P b, the total 
binder content, because P ba is a percentage of the total aggregate and P be is a percentage of the total mix. 
However, the mass of the total aggregate and the mass of the total mix are so close in magnitude that in a 
practical sense, when c alculated to the nearest 0.1 percent, the absorbed and effective binder contents added 
together usually equals the total binder content. It can be calculated as follows:  
From the phase diagram, P be can be defined as:   
14 © EAC  2024  – All rights reserved  
 
 
Pbe is most readily calculated with the following equation:  
 
where 
Pbe  is effective binder, percentage by mass of mix  
Pb  is total binder, percentage by mass of mix  
Pba  is absorbed binder, percentage by mass of aggregate  
Ps  is total aggregate, percentage by mass of mix  
Mbe  is mass of the effective binder, typically in grams  
Mmb   is mass of the total mix, typically in grams  
5.9 Dust to binder ratio  
The dust to binder ratio (P 0.075/Pbe) of a paving mixture, sometimes referred to as the “dust proportion,” is the 
ratio of the percentage of aggregate passing the 0.075 -mm (No. 200) sieve (P0.075) to the effective binder 
(Pbe). The typical allowable range for this property is 0.6 –1.2, with the following exceptions:  
a) for 4.75 -mm mixes, the allowable range is 0.9 –2.0; and  
b) for coarse -graded mixes whose gradation plots below the Primary Control Sieve (PCS) on a 0.45 power 
chart, the allowable range may be increased to 0.8 –1.6. 
In general, this property addresses the workability of asphalt mixtures. A low P 0.075/Pbe often results in a tender 
mix, which lacks cohesion and is difficult to compact in the field because it tends to move laterally under the 
roller. Mixes tend to stiffen as the P0.075 increases, but too much will also result in  a tender mix. A mix with a 
high P0.075/P be will often exhibit a multitude of small stress cracks during the compaction process, called 
check -cracking. This property is usually calculated for dense -graded mixes only.  
 
5.10 Selecting a design aggregate structure (DAS)  
Meeting the minimum VMA requirement at the design binder content is often difficult to achieve. It is not 
uncommon for a mixture designer to complete a laboratory mixture design only to learn that the VMA does not 
meet the volumetric criteria specified. Careful analysis of the DAS results provide the designer with valuable 
information upon which to make design changes or decisions on whether or not to proceed with a full mixture 
design and performance testing.  
The Superpave mix design process  discussed in  6.1 originally  included a procedure called Selecting a Design 
Aggregate Structure (DAS) to assess the ability of multiple gradations to meet specified VMA criteria at the 
design binder content. This process can be used to evaluate different aggregate combinations before or after 
the initial mixture design is completed. The process can  be summarized as an analysis of multiple aggregate 
combinations at one estimated design binder content dur ing a single laboratory session.   
© EAC  2024  – All rights reserved  15 
 The following step -by-step process is conducted for each trial blend prepared. The basic DAS process is 
suitable for Marshall and Superpave designed mixtures. Additional steps are required that are specific to 
gyratory compacted mixtures.  
Step 1—Calculate P a initial  
 
where  
Pa initial is % air voids in the mix at P b initial 
Gmb initial  is bulk specific gravity of the mix at P b initial 
Gmm initial  theoretical maximum specific gravity of the mix at P b initial 
Step 2—Calculate VMA initial 
 
where  
VMA initial is voids in the mineral aggregate at P b initial  
Gmb initial  is bulk specific gravity of the mix at P b initial  
Ps   percent  is aggregate in the specimen  
Gsb  is bulk specific gravity of the aggregate blend  
Step 3—Calculate the %G mm @ N des– for gyratory compacted mixes only  
 
where  
%G mm @ N des is percent of theoretical maximum specific gravity at N des using P b initial  
Pa initial  is % air voids in the mix at N des using P b initial  
Step 5—Calculate the Correction Factor for G mb @ N ini–for gyratory compacted mixes only  
 
where 
C  is the correction factor  
Ht.@Ndes   is a height of the specimen at N des   
16 © EAC  2024  – All rights reserved  
 Ht.@Nini    is height of the specimen at N ini 
Step 6—Calculate the G mb @ N ini– for gyratory compacted mixes only  
 
Step 7—Calculate P b estimated  
 
where  
Pb estimated   is the asphalt content needed to   obtain a mixture at the design Pa  
Pb initial  is the initial binder content of the  trial blend  
Pa initial  is percent air voids in the mix at P b initial   
0.4  is a value derived from the slope of the  Pa curve which equates to a 0.4%  change in binder = 1% 
change in  air voids  
4.0 = the design air void level  
Pb estimated  is an estimated value of how much  binder should have been added to the trial blend  to achieve the 
design air voids in the compacted  mixture. The following steps calculate the typica  volumetric properties in the 
mixture assuming that  
Pb estimated had been added to the trial blend.  
Step 8—Calculate VMAestimated  
 
where  
VMA estimate d  is the estimated VMA had the trial  blend used Pb estimated  
VMA initial   Voids in the mineral aggregate  at P b initial 
C (Constant)    is equal to   0.1 if Va is less than 4.0%  and  0.2 if Va is greater than 4.0%  
Pa initial  is % air voids in the mix at P b initial 
4.0  is the design air void level  
The VMA in a compacted mixture is a result of the  aggregate properties, binder properties, temperature  and 
perhaps the most significant, the type and  amount of compactive effort exerted on the specimen.  Minute 
changes in binder content in close proximity  to the design binder content have little effect on VMA,  but are 
accounted for in the above -referenced C value.  
  
© EAC  2024  – All rights reserved  17 
 where  
 VFAestimated   the estimated VFA had the trial blend used P b estimated  
VMA estimated   the estimated VMA had the trial blend used  
Pb estimated 4.0   is the design air void content  
Step 10—Calculate P be estimated  
The effective asphalt binder content is calculated using  
 
where 
Pbe estimated  is the estimated effective binder content had the trial blend used P b estimated  
Ps  is aggregate content, percent by total mass of the mixture  
Gb  is specific gravity of the asphalt  
Gse  is effective specific gravity of the aggregate  
Gsb  is bulk specific gravity of the aggregate  
Pb estimated   is the asphalt content needed to obtain a mixture at 4.0% air voids  
Step 11—Calculate Dust Proportion  
The requirement for the dust proportion is  calculated as the percent by mass of the material  passing the 
0.075 -mm sieve (by wet sieve analysis)  divided by the effective asphalt binder content  (expressed as percent 
by mass of mix).  
 
where  
Pbe estimated  is the estimated effective binder content had the trial blend used Pb estimated  
P0.075   is aggregate content passing the 0.075 -mm sieve  
Finally, for Superpave gyratory compacted mixtures:  
Step 12—Calculate %G mm,estimated@Nini  
 
where  
4.0 = the design air void content   
18 © EAC  2024  – All rights reserved  
 6 Asphalt mix design methodologies   
6.1 Superpave HMA Mix Design System  
The Superpave system as implemented consisted of two interrelated elements: an asphalt binder specification 
and a mix design system that specifies aggregate criteria and volumetric properties.  The Superpave mix 
design method uses a gyratory compactor to make test specimens and volumetrics to determine the optimum 
binder content. Moisture resistance, and in some cases, performance testing are included to verify the 
suitability of the designed mixture.  Superpave is a system which rely on the principle that a pavement mixture 
will not perform successfully on the roadway unless the appropriate binder and aggregate materials are 
incorporated into the work.  
6.1.1 Superpave materials selection and mix design criteria  
6.1.1.1   Asphalt binder  
The asphalt binder to be used in the mix is chosen based on environmental conditions and traffic loadings. 
The grade of asphalt binder to be incorporated into the HMA is usually specified during the project design and 
is not a variable considered during the mix design phase.  
6.1.1.2  Mineral aggregate specifications  
Superpave mix design system contain detailed aggregate requirements. The detailed mineral aggregates 
characteristics are described in Annex B.  Certain aggregate  characteristics were essential  to design a well  
performing  HMA.  These characteristics were  broken into  consensus and sources characteristics as outlined 
below :  
a) The consensus aggregate properties  
These are specified in the Superpave system are the following: coarse aggregate angularity; fine aggregate 
angularity; flat and elongated particles; and clay content (Sand Equivalent). The criteria for these properties 
are based on the traffic level and position within the pavement structure. Table 1 gives the requirement for the 
aggregate  consensus properties   
© EAC  2024  – All rights reserved  19 
 Table  1 — Aggregate consensus properties requirement  
 
b) Source aggregate properties  
These are requirements specific to local areas because of the variety of aggregate types available in different 
geographic areas, and are not broad, all -inclusive requirements like Superpave consensus properties. Source 
property tests are typically specified to set limits on aggregate properties mainly toughness, soundness and 
deleterious materials. Table 2 lists some recommended source property tests and typical requirements.  
Table  2 — Recommended superpave source property teste and typical requirements  
 
6.1.1.2.1  Gradation  
Superpave graduation  requirements are shown in Table 3. Control points have been established to define the 
type of mix. It is important to note that the recommended gradation control points are limited in number when 
compared to traditional HMA gradation specifications. The following gradation control points should be 
regarded  as a requirement for mixture design only. The Superpave gradation requirements shown are only 
useful if the aggregates meet the consensus and source properties and the completed asphalt mixture meets 
the volumetric and/or performance requirements.   
20 © EAC  2024  – All rights reserved  
 Table  3 — Superpave grad uation requirements  
 
 
 
6.1.1.3 Superpave mixture requirements  
6.1.1.3.1 Nini, Ndes, Nmax 
6.1.1.3.1.1  Table 4 designates specified levels of laboratory compaction (density) at three different 
levels of gyration based on expected traffic loading and referenced as N initial, Ndesign and Nmaximum . These  terms, 
more commonly designated as N ini, N des and Nmax, refer to the number of gyrations estimated to  result in 
different levels of field densification.  Ndes is the number of gyrations specified to reach the target density of the 
mix and is based on the estimated field density in the middle of its service life. Nini is a measure of the 
compactability of the  mix and is based on the estimated field density  obtained behind the  screed before 
compaction.  Nmax is an estimate of the final density expected  in the field at the end of its service life after years  
of further densification by traffic. It is capped at 98  percent for all traffic levels.   
© EAC  2024  – All rights reserved  21 
 Table  4 — Superpave gyration compaction effort  
 
6.1.1.3.1.2 The number of design gyrations was established by comparing lab -molded densities at different 
gyration levels to resulting field densities. Once the design gyration levels were established, the initial and 
maximum gyration levels were established by the following equations:  
 
 
Table 5 lists the specified levels of densificationalong with all of the required Superpave volumetric  
parameters.  
 
 
 
 
  
22 © EAC  2024  – All rights reserved  
 Table  5 — Superpave mixture requirements   
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  
© EAC  2024  – All rights reserved  23 
 6.1.2 Test equipment  
6.1.2.1   Superpave gyratory compactor  
The typical superpave gyration compactor  consist  of: 
a) reaction frame, rotating base and motor;  
b) loading system, loading ram and pressure gauge;  
c) height measuring and recordation system;  
d) mould and base plate; and  
e) specimen extruding device.  
The main parameters governing the compaction effort are:  
a) the vertical pressure, 600 ± 18 kPa;  
b) the gyration angle of the mold, 1.16 ± 0.02° (internal);  
c) gyration rate, 30.0 ± 0.5 gyrations per minute; and  
d) the number of gyrations, variable —based on expected traffic level.  
6.1.2.2  Additional test equipment  
1) ovens —thermostatically controlled, for heating aggregates, asphalt and equipment;  
2) mechanical mixer , commercial bread dough mixer 10 -liter (10 -qt.) capacity or larger, equipped with 
metal mixing bowls and wire whips, or a 5 -gallon laboratory bucket mixer;  
3) flat-bottom metal pans for heating aggregates and conditioning mixtures;  
4) round metal pans —approximately 10 -liter capacity for mixing asphalt and aggregate;  
5) scoops for batching aggregates ; 
6) containers , gill-type tins, beakers or pouring pots, for heating asphalt;  
7) thermometers or other thermometric devices , armored, glass or dial -type with metal stem, 10°C to 
235°C, for determining temperature of aggregates, asphalt and asphalt mixtures;  
8) balances ,10-kg capacity, sensitive to 1 g, for weighing aggregates and asphalt; 10 -kg capacity, 
sensitive to 0.1 g, for weighing compacted specimens;  
9) large mixing spoon or small trowel ; 
10) large spatula;  
11) welders gloves (or similar) for handling hot equipment; 12. paint, markers or crayons, for identifying 
test specimens;  
12) paper disks, 150 mm, for compaction;  
13) fans, for cooling compacted specimens; and   
24 © EAC  2024  – All rights reserved  
 14) computer/printer for data collection and recording.  
6.1.3 Specimen preparation and compaction  
6.1.3.1  Preparation of aggregate  
The following samples must be prepared to conduct a Superpave mix design:  
a) a minimum of 8 specimens to be compacted to N des; 
b) a minimum of 2 specimens for maximum theoretical specific gravity (G mm) testing;  
c) a minimum of 6 specimens with a height of 95 mm. These samples require approximately 3,700 
grams of aggregate for moisture sensitivity testing . 
d) a minimum of 2 specimens for N max verification; and  
e) any other samples required for specified performance testing.  
Three aggregate sample sizes are used in conducting a Superpave mix design, depending on their final use.  
For compacted G mb samples, the specimen size is 150 mm (diameter) by 115 mm (height) and requires two 
samples of approximately 4,700 grams of aggregate to be prepared for each trial asphalt content tested plus 2 
additional specimens for N max verification testing.  
A minimum of two samples need to be prepared for determination of maximum theoretical specific gravity 
(Gmm). These samples remain uncompacted, and  their size varies by the nominal maximum aggregate size 
(NMAS) of the mixture and ranges  from 1,000 to 2,500 grams. These samples will be mixed at an asphalt  
binder content at or above the final e stimated design binder content. The  Gmm values for the remaining trial 
binder contents may be back -calculated according to the equations shown in clause 5. 
6.1.3.2   Preparation of binder  
Samples of asphalt binder to be used in the mix design shall be representative of the materials to be used in 
the project and should be of a size that is manageable in the laboratory. Care should be taken not to overheat 
the binder nor maintain elevated temperatures for an extended period of time. The mixture design will require 
the molding of mixture specimens at a minimum of four different binder contents. It is recommended that 
specimens be molded at the anticipated design binder content and at –0.5, +0.5 and +1.0 percent binder 
bracketing the anticipated design binder content.  
6.1.3.3  Laboratory mixing and compaction temperatures  
The mixing and compaction temperatures shall be determined according to  Annex A . Preheat  the aggregate 
samples in an oven set approximately 15°C higher than the mixing temperature. Two to four hours are 
required for the aggregate to reach the mixing temperature. Preheat the asphalt binder to the predetermined 
mixing temperature.  
The time required for this step varies depending on the container size and method of heating. Care should be 
taken to adjust the preheating time in a manner that does not expose the binder to elevated temperatures for 
an extended period of time.  
6.1.3.4 Preparation of mixtures  
a) Place the hot mixing bowl on a balance and zero the balance.  
b) Charge the mixing bowl with the heated aggregates and mix thoroughly.  
c) Form a crater in the blended aggregate and weigh the required asphalt in the mixture to achieve the 
desired batch weight.   
© EAC  2024  – All rights reserved  25 
 d) Remove the mixing bowl from the scale and mix the asphalt and aggregate using a mechanical mixer.  
e) Mix the specimen until the aggregate is thoroughly coated (30 –90 seconds).  
f) Place the mix in a flat shallow pan at an even thickness ranging between 25 and 50 mm.  
g) Place the mix and pan in the conditioning oven at a temperature equal to mixture’s specified compaction 
temperature ± 3°C.  
h) Condition the prepared mixtur e in accordance with (Annex  A) 
i) Repeat this procedure until the desired number of specimens is produced.  
j) Proper timing of the gyratory compaction steps can be achieved by spacing approximately 20 minutes 
between mixing each specimen.  
k) At the end of the short -term aging period, proceed to ASTM D2041  if the mixture is to be used to 
determine maximum theoretical specific gravity. Otherwise, proceed with compaction.  
6.1.3.5 Compaction of volumetric specimens  
6.1.3.5.1  Molding procedure for specimens at a specified number of gyrations  
6.1.3.5.1.1  Prepare at least two replicate specimens for each trial binder content at the N des gyration level. 
Gmb specimen heights after compaction should be 115 ± 5 mm. Generally, placing approximately 4,700 grams 
of mixture into the mold for blends with aggregate specific gravities between 2.55 and 2.70 will result in a 
compacted specimen meeting height requirements.  
6.1.3.5.1. 2 Prepare the SGC while the mixture specimens are conditioning in the oven. Turn on the main 
power to the SGC for the manufacturer’s recommended warm -up period. Further preparations include 
verifying the compaction pressure of 600 kPa, verifying the gyration internal angle of 1.16°, and verifying the 
gyration speed of 30 revolutions per minute. Set the SGC to the proper number of gyrations according to 
Table  4. Lubricate any bearing surfaces according to manufacturer instructions.  
6.1.3.5.1. 3 Approximately 45 to 60 minutes before compaction of the first specimen, place the molds and 
base/top plates in an oven set at the compaction temperature. Remove the mold and base plate from the 
oven, place the base plate inside the mold and place a paper disk (to prevent the mix from sticking to the base 
plate) on top of the base plate.  
6.1.3.5.1. 4 Place the conditioned mixture at the compaction temperature in the mold in one lift using a 
material handling chute, taking care to avoid segregation of the mix. Level the mix, place another paper disk 
on top of the mix and place the top plate (if required) in the mold. Load the charged mold into the SGC, 
centering it under the loading ram.  
6.1.3.5.1. 5 Depending on the SGC make and model, the following steps will either be performed 
automatically after pressing a “start” button or be initiated by the user:  
a) Lower the loading ram until it reaches a pressure of 600 kPa;  
b) Apply the 1.16° angle; and  
c) Proceed with gyrations to the preset number.  
During compaction, the ram loading system will maintain a constant pressure of 600 kPa. The specimen 
height will be continually monitored during compaction, and a height measurement is recorded after each 
gyration.  
The compactor will cease compacting after reaching the user -specified number of gyrations, the angle of 
gyration will be released and the loading ram will be raised. Remove the mold containing the compacted  
26 © EAC  2024  – All rights reserved  
 specimen from the compactor and slowly extrude the specimen from the mold. Most mixes can be removed 
immediately, but some mixes may require a 5 - to 10 -minute cooling period before they can be removed 
without distortion.  
6.1.3.5.1. 6 Remove the paper disks from the top and bottom of the specimen and then allow the specimen 
to cool on a flat surface, undisturbed. Place the mold and base/top plates back in the oven to reach 
compaction temperature for the next specimen. Additional molds will avoid the delay caused by this step.  
6.1.3.5.1. 7 Repeat the compaction procedure for each specimen. Identify each specimen with a suitable 
marker.  
6.1.3.5.2   Molding procedure for specimens at a specified height  
6.1.3.5.2 .1  The actual molding procedure is the same, except that the SGC is set to “height” mode 
instead of “ Number  of gyrations” mode. This will cause the molding process to stop after reaching the 
specified height, rather than stopping after a specified number of gyrations.  
6.1.3.5.2.2  Some procedures, call for specimens to be molded to a specific height with a specific 
percentage of air voids. To accomplish this, the designer must determine the appropriate mass of asphalt 
mixture to place in the mold that will result in the proper air void content at the proper height.  
6.1.3.5.2 .3 There are multiple ways to make this determination. One method requires the designer to mix 
and mold two extra specimens. A slightly higher -than-the-finalanticipated mass is placed in one mold and a 
slightly lower -than-the-final anticipated mass is placed in the other. After each specimen is molded to the 
specified height, the first specimen will have slightly lowerthan - target air voids and the second specimen will 
have slightly higher -than-target air voids. The designer can then interpolate the masses to achieve the proper 
air voids.  
6.1.4 Superpave data analysis  
6.1.4.1  Determine %G mm at N ini for each binder percentage  
An additional step unique to Superpave is the  calculation of %G mm at N ini, N des and N max. Using the  data 
provided by the SGC, an estimated mixture  bulk specific gravity, G mb,estimated , can be calculated  based on the 
diameter of the mold and the height  of the specimen. This G mb,estimated value can be  calculated for every 
gyration. The final product of  the compaction process is an actual specimen with  known height at N des. 
Step 1—Obtain the height of the Specimen at N des (hNdes). 
Step 2—Obtain the height of the Specimen at N ini (hNini). 
Estimating the G mb,estimated at N ini using the smooth mold dimensions would not account for surface 
imperfections in the sample. These surface  imperfections are accounted for when the sample  compacted to 
Ndes is actually weighed in the lab. By  using the following correction factor, the estimated  Gmb at N ini can be 
more accurately calculated.  
Step 3—Calculate the correction  factor C, as follows:  
 
Step 4—Calculate G mb, estimated @ N ini  
 
Step 5—Determine the average G mb @ N ini  value for each trial binder content.   
© EAC  2024  – All rights reserved  27 
 Step 6—Calculate %G mm values as follows:  
 
 
6.1.4.2  Superpave volumetric analysis  
The remaining volumetric properties for P a, VMA, VFA, P be and DP are calculated as show n in Clause 5. The 
results are plotted to provide curves of asphalt content versus %G mm @ Nini, % G mm @ N des, air voids (P a), 
voids in the mineral aggregate (VMA), voids filled with asphalt (VFA) and dust proportion (DP).  
6.1.5 Design asphalt binder content  
After the data have been plotted, the designer will pick an asphalt binder content that will provide  4.0 percent 
air voids at N des, which is equal to 96.0 percent G mm@Ndes . The designer must then  verify the mixture conforms 
to the specifications by determining the values for percent G mm@Nini , voids in the mineral aggregate (VMA), 
voids filled with asphalt (VFA) and dust proportion (DP) from  the other curves. The recommended Superpave 
volumetric mixture design requirements are shown  in Table 5 
6.1.6 Nmax determination  
The N max parameter must be determined and  verified that the G mm@Nmax does not exceed  98 percent. Early 
versions of the Superpave mix  design system required designers to compact all of  the mixture specimens 
discussed above to N max.The values for N ini and N des are then both back -calculated  as was discussed for N ini.  
The average of these two sets of  data will be used to directly calculate the  %G mm@Nmax . Verify that the result is 
less than 98  percent of the G mm at the design binder content.  
6.1.7 Moisture sensitivity testing  
The next step in the mixture design process is to  conduct moisture sensitivity testing. The mixture  must meet 
all of the aggregate and volumetric  criteria prior to proceeding. All samples prepared  for performance testing 
will be mixed at the  design b inder content determined . The Superpave system requires that the designed  
mixture meet the specified moisture sensitivity requirements.  
6.1.8 Performance testing  
Although not a formal requirement of the  Superpave design system, it is recommended that strong 
consideration be given  to conducting some type of additional mixture  performance testing, especially on 
critical, high  volume  projects.  
 
 
 
 
 
  
28 © EAC  2024  – All rights reserved  
 6.2 Marshall Method of Mix Design  
6.2.1 General  
The Marshall method of mix design is for dense graded HMA mixes. For a single selected aggregate 
gradation, five different asphalt contents are tested for various volumetric and strength criteria to select the 
optimum binder content. The test results should always be reported as the average for three compacted, 
“identical” specimens. The selection of the optimum binder content requires engineering judgment, depending 
on traffic, climate and experience with the local materials used. In most cases, the optimum binder content 
should be selected for which the compacted specimens have 4 percent air voids.  
The original Marshall method is applicable only to hot mix asphalt paving mixtures containing aggrega tes with 
maximum sizes of 25 mm  or less. A modified Marshall method has been developed for aggregates with 
maximum sizes up to 38 mm . 
6.2.3 Outline of method  
The procedure for the Marshall method starts with the preparation of test specimens. Steps preliminary to 
specimen preparation are:  
a) all materials proposed for use shall meet the physical requirements of the project specifications;  
b) aggregate blend combinations shall meet the graduation requirements of the project specifications; and  
c) for the purpose of performing density and voids analyses, the bulk specific gravity of all aggregates used 
in the blend and the specific gravity of the asphalt cement are determined.  
These requirements are matters of routine testing, specifications and laboratory technique that must be 
considered for any mix design method.  
The Marshall method uses standard test specimens of 63.5 -mm height by a 101.6 -mm diameter. These are 
prepared using a specified procedure for heating, mixing, and compacting the asphalt -aggregate mixture. The 
two principle features of the Marshall method of mix design are  
a) a density -voids analysis and  
b) a stability -flow test of the compacted test specimens.  
6.2.4 Preparation of test specimens  
6.2.4.1 General  
6.2.4.1.1  In determining the design asphalt content for a particular blend or gradation of aggregates by the 
Marshall method, a series of test specimens is prepared for a range of different asphalt contents so that the 
test data curves show well -defined relationships. Tests should be planned on the basis of 0.5 percent 
increments of asphalt content, with at least two asphalt contents above the expected design value and at least 
two below this value.  
6.2.4.1.2  The expected design  asphalt content can be based on any or all of these sources: experience, 
computational formula, or performing the centrifuge kerosene equivalency and oil soak tests in the Hveem 
proced ure (see 6.3). The  expected design asphalt content, in percent by total weight of mix, could then be 
estimated to be approximately equivalent to the percentage of aggregate in the final gradation passing the 75 -
μm (No. 200) sieve.  
One example of a computational formula is this equation:  
P = 0.035a + 0.045b + Kc + F   
© EAC  2024  – All rights reserved  29 
 where 
P is approximate asphalt content of mix, percent by weight of mix  
a  is percent of mineral aggre gate retained on 2.36 -mm (No. 8) sieve  
b is percent of mineral aggregate passing the 2.36 -mm (No. 8) sieve and retained on the 75 -μm (No. 200) 
sieve  
c is percent of mineral aggregate passing 75 -μm (No. 200) sieve  
K 0.15 for 11 –15 percent passing 75 -μm (No.  200) sieve , 0.18 for 6 –10 percent passing 75 -μm (No. 200) 
sieve , 0.20 for 5 percent or less passing 75 -μm (No. 200) sieve  
F is 0 – 2.0 percent. Based on the absorption of light or heavy aggregate, in the absence of other data, a 
value of 0.7 is suggested.  
6.2.4 .1.3  To provide adequate data, at least three test specimens are prepared for each asphalt content 
selected. Therefore, a Marshall mix design using five different asphalt contents will normally require at least 
15 test specimens. Each test specimen will usually require approximately 1.2 kg of aggregate. Assuming 
some minor waste, the minimum aggregate requirements for one series  of test specimens of a given blend 
and gradation  will be approximately 23 kg. About 4 liters of asphalt cement will be adequate.  
6.2.4.2 Equipment  
The equipment (calibrated as needed) required for the preparation of test specimens is:  
1) flat-bottom metal pans for heating aggregates;  
2) round metal pans or a mixing bowl, approximately 4 -liter capacity, for mixing asphalt and aggregate; oven 
and hot plate, preferably thermostatically controlled, for heating aggregates, asphalt and equipment;  
3) scoop for batching aggregates;  
4) containers:  gill-type tins, beakers, pouring pots and sauce pans for heating asphalt;  
5) thermometers or other thermometric devices: armored, glass or dial -type with metal stem, 10°C to 235°C, 
for determining temperature of aggregates, asphalt and asphalt mixtures;  
6) balances: 5 -kg capacity, sensitive to 1 g, for weighing aggregates and asphalt, and 2 -kg capacity, 
sensitive to 0.1 g, for weighing compacted specimens;  
7) large mixing spoon or small trowel;  
8) large spatula;  
9) mechanical mixer (optional): commercial bread dough mixer 4 -liter capacity or larger, equipped with two 
metal mixing bowls and two wire stirre rs, or an equivalent type mixer.  
10) compaction pedestal (shown in Figure 2), consists  of a 200 × 200 × 460 mm wooden post capped with a 
305 × 305 × 25 mm (12 × 12 × 1 in.) steel plate. The wooden post should be oak, pine or other wood 
having a dry weight of 670 to 770 kg/m3. The wooden post should be secured by four angle brackets to a 
solid concrete slab. The steel cap should be firmly fastened to the post. The pedestal should be installed 
so that the post is plumb, the cap level, and the entire assembly free from movement during compaction. 
Compaction hammers can be either manually or mechanically operated, as shown in Figure 2.  
Mechanically operated hammers drop the hammer at a rate of 64 ± 4 blows per minute. Mechanical 
hammers can also have single or multiple hammer and mold sets for compacting single or multiple 
specimens at a time. Some mechanically operated hammers are designed with a rotating base 
mechanism which rotates at 18 to 30 revolutions per minute;   
30 © EAC  2024  – All rights reserved  
  
 
 
 
Figure  2 — Manual and Mechanical Hammer Configurations  
11) compaction mold, consisting of a base plate, forming mold and collar extension. The forming mold has an 
inside diameter of 101.6 mm and a height of approximately 75 mm; the base plate and collar extension 
are designed to be interchangeable with either end of the forming mold. with a 114.3 -mm height  
12) compaction hammer, consisting of a flat, circular tamping face, 98.4 mm in diameter and equipped with a 
4.5-kg weight constructed to obtain a specified 457 - mm height of drop, should conform to requirements 
of ASTM D6926;  
13) mold holder, consisting of spring -tension device designed to hold compaction mold centered in place on 
the compaction pedestal, should conform to requirements of ASTM D6926;  
14) paper disks, 100 mm;  
15) steel specimen extractor, in the form of a jack and a disk with a diameter not less than 100 mm and 13 
mm thick for extruding compacted specimen form mold.  
16) The steel specimen extractor for the 6 -inch mold is 151.5 to 152.5 mm in diameter and 13 mm thick;  
17) welders’ gloves, for handling hot equipment. Rubber gloves for removing specimens from water bath; and   
© EAC  2024  – All rights reserved  31 
 18) marking crayons, for identifying test specimens.  
6.2.4.3  Preparation of test specimen   
These steps are recommended  steps for preparing Marshall test specimens  
a) Number of specimens —prepare at least three specimens for each combination of aggregates and 
binder content.  
b) Preparation of aggregates —dry aggregates to co nstant weight at 105°C to 110°C  and separate the 
aggregates by dry  sieving into the desired size fractions. These  size fractions are recommended:  
1) 25.0 to 19.0 mm  
2) 19.0 to 9.5 mm  
3) 9.5 to 4.75 mm  
4) 4.75 to 2.36 mm  
5) Passing 2.36 mm  
c) Determination of mixing and compaction  temperature —the temperature to which  the asphalt must be 
heated to produce  viscosities of 170 ± 20 centistokes kinematic  and 280 ± 30 centistokes kinematic shall 
be established as the mixing temperature and  compaction temperatures, respectively. These  
temperatures can be estimated from a plot of  the viscosity (log -log centistokes scale) versus  temperature 
(log degrees Rankine scale,  °R = °F + 459.7) relationship for the asphalt  cement to be used.  
For mixing and compaction  temperatures for modified binders, refer to Annex  A. 
d) Preparation of mold and hammer —thoroughly  clean the specimen mold assembly and the  face of the 
compaction hammer and heat  them in a water bath or on the hot plate to a  temperature between 95 and 
50°C. 
e) Preparation of mixtures —weigh into separate pans for each test specimen the amount of each 
aggregate size fraction required to produce the required gradation and a batch that will result in a 
compacted specimen 63.5 ± 1.27 mm in height. This will no rmally be about 1.2 kg .  
It is generally desirable to prepare a trial specimen prior to preparing the aggregate batches. If the trial 
specimen height falls outside the height limits, the amount of aggregate used for the specimen should be 
adjusted using:  
for International System of Units (SI),  
 
Place the pans in the oven or on the hot plate and heat to a temperature not exceeding 28°C  above the 
mixing temperature specified in (c). (If a hot plate is used, provision should be made for dead space, 
baffle plate or a sand bath beneath the pans and the hot plate to prevent local overheating.)   
32 © EAC  2024  – All rights reserved  
 Charge the mixing bowl with the heated  aggregates and dry mix thoroughly. Form a crater in  the dry 
blended aggregate and weigh the required  amount of asphalt cement into the mixture in  accordance with 
the calculated batch weights.  At this point the temperature of the aggregate  and the asphalt must be 
within the limits of the  mixing temperatures established in paragraph  (c). Asphalt cement should not be 
held at mixing  temperatures for more than one hour before using.  Mix the aggregate and asphalt cement, 
preferably  with a mechanical mixer or by hand with a trowel,  as quickly and thoroughly as possible to yield 
a mixture having a uniform distribution of asphalt.  
The standards requirements recommend  that Marshall mixes be co nditioned according to AASHTO R 30. 
f) Packing the mold —place a filter or non -absorbent paper disk cut to size in the bottom of the mold. Place 
the entire batch in the mold with collar, and then spade the mixture vigorously with a heated spatula or 
trowel 15 times around the perimeter and 10 times over the interior. Smooth the surface to a slightly 
rounded shape. The temperature of the mixture immediately prior to compaction shall be within the limits 
of the compaction temperature established in paragraph (c); otherwise, it shall be discarded. In no case 
shall the mixture be reheated.  
g) Compaction of specimens —place a paper disk on top of the mix and place the mold assembly on the 
comp action pedestal in the mold holder. As specified according to the design traffic category (see Table 
7), apply  35, 50 or 75 blows with the compaction hammer using a free fall of 457 mm. Hold the axis of the 
compaction hammer as nearly perpendicular to the base of the mold assembly as possible during 
compaction. Remove the base plate and collar, and reverse and reassemble the mold. Apply the same 
number of compaction blows to the face of the reversed specimen. After compaction, remove the base 
plate and the paper disks and allow the specimen to cool at room temperature until no deformation will 
result when removing it from the mold. When more rapid cooling is desired, electric fans may be used, but 
not water unless the specimen is in a plastic bag. Remove the specimen from the mold by means of an 
extrusion jack or other compression device, and then place on a smooth, level surface until ready for 
testing. Normally, specimens are allowed to cool overnight.  
6.2.5 Conducting Marshall Test  
6.2.5.1 General  
In the Marshall method, each compacted test specimen is subjected to these tests and analysis in  the order 
listed:  
a) specimen height determination;  
b) bulk specific gravity determination;  
c) density and voids analysis; and  
d) stability and flow test.  
6.2.5.2 Bulk specific gravity determination  
The bulk specific gravity test may be performed  as soon as the freshly compacted specimens have  cooled to 
room temperature. This test is performed  according to ASTM D1188  when using Paraffin -Coated Specimens 
and ASTM D2726,  when using Saturated Surface -Dry Specimens.  
6.2.5 .3 Equipment for stability and flow tests   
The equipment required for the testing of the 101.6 -mm diameter  by 63.5 -mm height  specimens is as follows:  
• The Marshall testing machine  is a compression  testing device conforming to ASTM D 6927. It is designed 
to apply loads to test specimens  through cylindrical segment testing heads  [inside radius of curvature of 51 
mm] at a constant loading rate of 51 mm ) per minute. Two perpendicular guide posts  are included to allow the 
two segments to  maintain horizontal positioning and free  vertical movement during the test. It is  equipped with  
© EAC  2024  – All rights reserved  33 
 a calibrated proving ring  for determining the applied testing load,  a Marshall stability testing head for use in  
testing the specimen, and a Marshall flow  meter (or automatic recording device) for  determining the amount of 
deformation at  the maximum load in the test. A universal  testing machine equipped with suitable load  and 
deformation indicating devices may be  used instead of the Marshall testing frame.  
• The water bath  must be at least 150 mm deep and thermostatically controlled to 60°C ± 1°C. The tank 
should have a perforated false bottom or be equipped with a shelf for susp ending specimens at least 50 mm  
above the bottom of the bath.  
6.2.5 .4 Stability and flow test procedures  
After the bulk specific gravity of the test specimens has been determined, the following stability and flow tests 
are performed:  
(a) determination of specimen height;  
(b) immerse specimen in water bath at 60°C ± 1°C for 30 to 40 minutes before testing, or in an oven at the 
same temperature for 120 to 130 minutes; and  
(c) use an automatic recording device, or use a proving ring and flow meter . Place the flow meter over the 
marked guide rod and “zero” the flow meter while holding it firmly against the upper segment of the testing 
head while the load is being applied.  
NOTE  The same assembly of the testing head and flow meter must be used in testing all specimens. Specimens 
should be 101.6 ± 0.25 mm. Otherwise, an initial and final reading of the flow meter is required for the determination of the  
flow value.  
(d) Thoroughly clean the inside surfaces of the testing heads. Temperature of heads shall be maintained 
between 21.1 and 37.8°C using a water bath, when required. Lubricate guide rods with a thin film of oil so that 
the upper test head will slide freely without binding. If a proving ring is used to measure applied load, check to 
see that the dial indicator is firmly fixed and “zeroed” for the “no -load” position.  
(e) With the testing apparatus ready, remove the test specimen from water bath and carefully dry surface with 
a towel. Place specimen in lower testing head and center; then fit upper testing head into position and center 
complete assembly in loading device. Place flow meter over marked guide rod as noted in (c) above.  
(f) Apply testing load to specimen at a cons tant rate of deformation, 51 mm  per minute, until failure occurs. 
The point of failure is defined when the maximum load reading is obtained. The total force in Newtons (N) 
required to produce failure of the specimen shall be recorded as its Marshall stability value.  
(g) While the stability test is in progress (if not using an automatic recording device), hold the flow meter firmly 
in position over the guide rod and remove immediately when the load begins to decrease, take reading and 
record.  
This reading is the flow value for the specimen, expressed in units of 0.25 mm. For example, if the spe cimen 
deformed 3.8 mm , the flow value is 15.  
(h) The entire procedure for both the stability and flow measurements, starting with the removal of the 
specimen from the water bath, shall be completed within a period of 30 seconds.  
(i) The Marshall stability is corrected for specimens with a height diff erent than 63.5 mm (see Table 7 ).  
34 © EAC  2024  – All rights reserved  
 Table  7 — Stability Correlation Ratios  
 
6.2.5.5 Density and voids analysis  
After the completion of the stability and flow test, a density and voids analysis is made for each se ries of test 
specimens. The calculations for the voids analysis are fully  described in Clause 5. 
(a) Average the bulk specific gravity values for all test specimens of a given asphalt content; values obviously 
in error shall not be included in the average. The average value of bulk specific gravity for each binder content 
shall be used in further computations of voids data.   
© EAC  2024  – All rights reserved  35 
 (b) Determine the average unit weight for each asphalt content by multiplying the average bulk specific gravity 
value by the density of water (1,000 kg/m3).   
(c) Determine the theoretical maximum specific gravity ( Gmm by ASTM D2041) for at least two asphalt 
contents, preferably on mixes at or near the design asphalt content. An average value for the effective  specific 
gravity of the total aggregate is then calculated from these values.  This value may then be used for calculation 
of the maximum specific gravity of mixtures with different asphalt contents . 
(d) Using the effective (G se) and bulk specific gravity (G sb) of the total aggregate, the average bulk specific 
gravities of the compacted mix (G mb), the specific gravity of the asphalt (G b), and the maximum specific gravity 
of the mix (G mm) determined above in (c), calculate the percent absorbed asphalt (P ba) by weight of dry 
aggregate, percent air voids (Pa), percent voids filthe mineral aggregate (VMA). These values and 
calculations are more fully described in clause 5. 
6.2.6 Interpretation of test data  
6.2.6.1 Preparation of test data  
Prepare the stability and flow values and void data.  
a) Measured stability values for specimens  that depart from the standard 63.5 mm thickness shall be 
converted to an  equivalent 63.5 mm value by means  of a conversion factor. Applicable correlation  ratios 
to convert the measured stability  values are set forth in Table 7 Note that the  conversion may be made on 
the basis of either  measured thickness or measured volume.  
b) Average the flow values and the final converted  stability values for all specimens of given  asphalt content. 
Values that are obviously in  error shall not be included in the average.  
c) Prepare separate graphical plots for the  following values and connect plotted points  with a smooth curve 
that obtains the “best fit”  for all values, as illustrated in Figure 3.  
1) percent air voids (Pa) versus asphalt content;  
2) percent voids in mineral aggregate (VMA)  versus asphalt content;  
3) percent voids filled with asphalt (VFA) versus  asphalt content;  
4) unit weight of total mix versus asphalt  content;  
5) stability versus asphalt content; and  
6) flow versus asphalt content.  
  
36 © EAC  2024  – All rights reserved  
 
 
Figure  3 — Test property curves for hot mix design data by the M arshall method  
d) Determine the optimum binder content and  properties of the mix by using these graphs,  as further 
discussed in 7.2.5.4.  
 
 
 
  
© EAC  2024  – All rights reserved  37 
 6.2.6 .2 Criteria for a satisfactory paving mix  
Deciding whether the asphalt paving mix will be  satisfactory at the selected design asphalt content  is guided 
by applying certain limiting criteria to  the mixture test data. The Marshall method mix  design criteria in Table 7  
are recommended by the  Asphalt Institute.  
6.2.6.3 Determination of preliminary  design asphalt content  
The optimum binder content of the asphalt  paving mix is selected by considering all of the  data discussed 
previously. In general, it is recommended to choose the asphalt content  at the median of the percent air voids 
limits, which  is 4 percent. If all of the calculated and measured  mix properties at this asphalt content meet the  
mix design criteria in Table 7, then this is the  optimum binder content for the mix design.  
However, if not all of the design criteria are  met, then some adjustment or compromise is  necessary or the mix 
may need to be redesigned  (see Footnote 7 of Table 7).  A number of  considerations are discussed in 6.2.5.4  
that should be weighed even if all the design criteria are met.  
6.2.6.4 Selection of design binder content  
The final selected mix design should be one whose aggregate structure and binder content, compacted to the 
design number of blows, results in 4 percent air voids and satisfactorily meets all of the other established 
criteria in Table 7. Deviations from the recommended design criteria should be clearly specified in the project 
documents and must be appropriate for the inten ded use of the asphalt mixture. The mixture should contain 
as much asphalt binder as possible to maximize durability, while also maintaining the stability required to 
support the intended loads for the life of the pavement.  
If the recommended design criteria are modified, experienced designers are encouraged to carefully evaluate 
project variables such as traffic type and loading, location, materials and climatic region. Two common 
methods of modifying the mixture design parameters are changing the target air void content and/or changing 
the laboratory compaction level.  
EXAMPLE  The FAA P -401 specifies a 3.5 percent design air void content to maximize durability, and it also 
specifies a compaction level of 75 blows for heavy aircraft along with stringent volumetric parameters to ensure the 
necessary stability.  
A usage with much lighter loads, such as a bike path, may specify 3 percent air voids and reduce the 
compaction to only 35 blows for increased durability.  For a discussion on how to evaluate such parameters as 
VMA, compaction level, air voids and VFA, reference is made to clause 5. 
 
 
 
 
 
 
  
38 © EAC  2024  – All rights reserved  
 Table  7 — Marshall mix design criteria  
 
6.2.7  Modified Marshall method  for large aggregate  
A modified Marshall method for  152.4 mm  diameter  specimens has been standardized by ASTM D5581  for 
mixes composed of aggregates with maximum  size up to 38 mm. The procedure is basically the same as  the 
original Marshall mix design method except  for these differences that are due to the larger  specimen size:  
a) The hammer weighs 10.2 kg and has  a 149.4 -mm flat tamping face. Only  a mechanically operated device 
is used for the  same 457 -mm drop height.  
b) The specimen has a 152.4 mm diameter  by 95.2  mm height.  
c) The batc h weights are typically 4,050 g . 
d) The equipment for compacting and  testing (molds and breaking heads) are  proportionately larger to 
accommodate the  larger specimens.  
e) The mix is placed in the mold in two  approximately equal increments, with spading  performed after each 
increment.  
f) The number of blows needed for the larger  specimen is 1.5 times (75 or 112 blows) of  that required for the 
smaller specimen (50 or  75 blows) to obtain equivalent compaction.   
© EAC  2024  – All rights reserved  39 
 g) The design criteria should be modified as well.  The minimum stability should be 2.25 times,  and the range 
of flow values should be 1.5  times the criteria listed in Table 7.  
h) Similar to the normal procedure as shown  in Table 6 , if the actual specimen thickness  varies from 92.5 
mm, the correction  values as listed in Table 9 should be used to  convert the measured stability values to 
an equivalent value for a specimen with a  92.5-mm thickness.  
Table  8 — Stability Corrections for Large Stone Marshall Mixes in 6" Molds  
 
 
 
  
 
 
 
 
 
 
 
  
40 © EAC  2024  – All rights reserved  
 6.3 Hveem Method of Mix Design  
6.3.1 General  
The Hveem method of mix design  is specifically useful for the design of rut -resistant  mixes  and it has been 
extensively used in regions where hot climates and desert areas are prevalent. The Hveem method is 
applicable to paving mixtures using either asphalt cement or cutback asphalt and containing aggregates up to 
25 mm maximum size. The method presented here is applicable to the design of dense -graded HMA paving 
mixtures.  
This method tests the stability of the aggregate  structure in a compacted mix specimen. Typically,  the 
optimum binder content determined with the  Hveem method is approximately 0.3 percent lower  than that 
determined with the Marshall method.  For a given aggregate gradation, one specimen  is made for each of four 
binder contents and tested  for various criteria. Using a decision pyramid, the  optimum binder content is 
determined in three  steps, selecting each time the highest binder  content that meets the criteria.  
Test procedures  for determining resistance to deformation and cohesion of bituminous mixtures by means of 
Hveem Apparatus are found  in ASTM D1560  
6.3.2 Outline of method  
The Hveem method begins with the preparation  of test specimens. Steps preliminary to specimen  preparation 
are: 
a) determining that the proposed materials  meet the physical requirements of the project  specifications;  
b) assuring that the aggregate blend combinations  meet the gradation requirements of the project  
specifications; and  
c) having an ample supply of aggregates, which  have been dried and sized into fractions.   
NOTE  These requirements are matters of routine  testing, specifications and laboratory technique,  which must be 
considered but are not unique to any  particular mix design method.  
6.3.3 Approximate asphalt content  by the centrifuge kerosene  equivalent method  
The first step in the Hveem method of mix design  is to determine the “approximate” asphalt content.  This can 
be based on past experience or determined  by the Centri fuge Kerosene Equivalent (CKE) method. With a 
calculated surface area and the factors  obtained by the CKE method for a particular  aggregate or blend of 
aggregates, the approximate  asphalt content is determined by using a series of  charts  that are presented in 
this Clause .  
6.3.3.1 Equipment  
The equipment and materials required for  determining the approximate asphalt content  (Figure 4) are:  
a) small sample splitter for obtaining  representative samples of fine aggregate;  
b) pans, 114 mm  diameter by  25 mm  deep;  
c) kerosene, 4 liters ; 
d) oil, SAE No. 10, lubricating, 4 liters;  
e) beakers, 1500 ml;  
f) metal funnels, 89 mm  top diameter,  114 mm height, 13 mm  orifice  with piece of 2.00 mm (No. 10) sieve 
soldered  to bottom of opening;   
© EAC  2024  – All rights reserved  41 
 g) timer;  
h) centrifuge, manual or power -driven, complete  with cups, capable of producing 400 times  gravity as seen 
in Figure  4; and  
i) filter papers, 55 mm diameter.  
 
Figure  4 — Apparatus for Hveem CKE Tests  
            
6.3.3.2  Surface area  
The gradation of the aggregate or blend of  aggregates employed in the mix is used to  calculate the surface 
area of the total aggregate.  This calculation consists of multiplying the total  percent passing each sieve size 
(in decimal form)  by a “surface -area factor” as set forth in Table 9. Sum these products and the total will 
represent  the equivalent surface area of the sample in terms  of square meters  per kilogram. It is important to 
note that all the surface  area factors must be used in the calculation. Also, if  a different series of sieves is 
used, different surface  area factors are necessary.  
NOTE  These surface -area factors have been used to  calculate an average film thickness using the volume of  asphalt 
binder in the mix. Although this determination  of asphalt film thickness can provide a broad, relative  indication of mix 
durability, the Asphalt Institute  strongly recommends against comparing this calculated  value with specific mix design 
criteria because of  inherent inaccuracies. These surface -area factors do  not take into account the specific aggregate 
shape,  but are intended only as an index factor. In addition,  in a compacted mixture, some of the asphalt and fine  particle 
mastic is actually shared by adjacent particles  rather than each being in an isolated state as assumed.   
42 © EAC  2024  – All rights reserved  
 Table  9 — Surface Area (SA) Factors  
 
6.3.3.3  CKE procedure for fine aggregate  
The centrifuge kerosene equivalent method  involves these steps:  
a) Place exactly 100 grams of dry aggregate (representative of the passing 4.75 -mm [No. 4] material being 
used) in a tared centrifuge cup assembly fitted with a screen and a disk of filter paper.  
b) Place bottom of centrifuge cup in kerosene  until the aggregate becomes saturated.  
c) Centrifuge the saturated sample for two  minutes at a force of 400 times gravity. (For the  manual 
centrifuge, this force can be developed  by turning the handle approximately 45  revolutions per minute.)  
d) Weigh sample after centrifuging and determine  the amount of kerosene retained as a percent of  the dry 
aggregate weight; this value is called the  Centrifuge Kerosene Equivalent (CKE).  
Note:  Duplicate samples are always prepared in order  to balance the centrifuge and to check results.  The average of the 
two CKE values is used  unless there is a large discrepancy, in which  case the test is rerun.  
e) If the specific gravity of the aggregate samples  is greater than 2.70 or less than 2.60, make a  correction 
to the CKE value using the formula  at the bottom of the chart in Figure 5.  
© EAC  2024  – All rights reserved  43 
 
 
Figure  5 — Chart for Determining Surface Constant for Fine Material, Kf from C.K.E., Hveem Method of 
Design  
  
44 © EAC  2024  – All rights reserved  
 6.3.3.4  Surface capacity test for coarse  aggregate  
The surface capacity (or “oil soak”) test for the  larger aggregate involves these steps:  
a) Place exactly 100 grams of dry aggregate that  passed the 9.5 -mm sieve and is retained  on the 4.75 -mm 
(No. 4) sieve into a metal  funnel (this fraction is considered to  be representative of the coarse aggregate 
in the mix).  
b) Immerse sample and funnel into a beaker  containing SAE No. 10 lubricating oil at room  temperature for 5 
minutes.  
c) Allow to drain for 2 minutes.  
d) Remove funnel and sample from oil and drain  for 15 minutes at a temperature of 60°C.  
e) Weigh the sample after draining and determine  the amount of oil retained as a percent of the  dry 
aggregate weight.  
NOTE Duplicate samples  are prepared to check results. Average value  is used unless there is a large discrepancy, in  
which case the test is rerun.  
f) If the specific gravity of the aggregate is greater  than 2.70 or less than 2.60, make a correction  to the 
percent oil retained using the formula at  the bottom of the chart in Figure 6 . 
6.3.3.5  Estimated design asphalt content  
These steps are used to make a preliminary  estimate of the design asphalt content:  
a) Using the CKE value obtained and the chart  in Figure  5, determine the value Kf (surface  constant for fine 
material).  
b) Using the percent oil retained and the chart  in Figure 6, determine the value Kc (surface  constant for 
coarse material).  
c) Using the values obtained for K f and K c and the chart in Figure 7, determine the value Km  (surface 
constant for fine and coarse aggregate  combined). K m = K f + correction to K f. The  correction to K f 
obtained from Figure  7 is positive if (K c− K f) is positive and is negative if  (Kc− K f) is negative.  
d) The next step is to determine the approximate  bitumen ratio for the mix based on cutback  asphalts of RC -
250, MC -250 and SC -250 grades.  With values obtained for Km, surface area and  average specific  
gravity, use Case 2 procedures of  the chart in Figure 8 to determine the oil ratio.  
e) Determine the asphalt content (bitumen ratio)  for the mix (see Figure 9) corrected for the  grade to be 
employed, using the surface area  of the sample, the grade of asphalt and the oil  ratio from Figure 8 .  
© EAC  2024  – All rights reserved  45 
 
 
 Figure  6 — Chart for Determining Surface Constant for Coarse Material Kc, from Coarse Aggregate 
Absorption, Hveem Method of Design   
46 © EAC  2024  – All rights reserved  
 
 
 
Figure  7 — Chart for Combining K f and K c to Determine Surface Constant for Combined Aggregate, 
Km, Hveem Method of Design  
 
 
 
 
 
 
  
© EAC  2024  – All rights reserved  47 
 
 
Figure  8 — Chart for Computing Oil Ratio for Dense -Graded Bituminous Mixtures, Hveem Method of 
Design  
 
 
  
48 © EAC  2024  – All rights reserved  
 
 
 
Figure  9 — Chart for Correcting Bitumen Requirement Due to Increasing Viscosity of Asphalt, Hveem 
Method of Design  
 
  
© EAC  2024  – All rights reserved  49 
 6.3.4 Preparation of test specimens  
6.3.4.1 Equipment for preparation  of Hveem test specimen  
The equipment required for the preparation of test  specimens is:  
a) pans, with a minimum dimension of 250 mm  diameter by 50 mm deep, for  quartering and mixing fine 
aggregate, or an  equivalent 8 × 12-inch rectangular pan;  
b) pans, 200 mm diameter by 45 mm  deep, for batching and heating  aggregates;  
c) pans, 305 mm diameter by 64 mm  deep, for mixing aggregate and  asphalt;  
d) pans, 280 mm by 180 mm by  25 mm for curing mix;  
e) large sample splitter for mixing and  quartering fine aggregate;  
f) electric hot plate, with a surface measuring at  least 460 mm by 305 mm, for heating aggregates, asphalt 
and equipment as  required;  
g) large oven, thermostatically controlled,  capable of 110°C (230°F) temperature, with a  tolerance of +/ - 5°F; 
h) large oven, thermostatically controlled,  capable of 60°C (140°F) temperature with a  tolerance of +/ - 5°F; 
i) large oven for drying and preheating  aggregates, capable of temperatures up to  165°C (325°F);  
j) large scoop for handling hot aggregates;  
k) beakers or metal cans, 800 ml, for adding  asphalt;  
l) thermometer, armored, 35°C (100°F) to 205°C  (400°F);  
m) balance, minimum 5 kg capacity, sensitive to  0.1 g for weighing aggregates and asphalt;  
n) small pointed mixing trowel;  
o) large mixing spoon;  
p) mechanical mixer (optional);  
q) mechanical compactor designed  to consolidate the material by a series of  individual “kneading action” 
impressions  made by a roving ram having a face shaped  as a sector of a 101.6 -mm diameter  circle . The 
compactor must be  capable of exerting a force of 3.45 MPa beneath the tamper foot. Accessories  with the 
compactor should include two mold  holders, an insulated mix feeder trough  460 mm long by 102 mm wide  
by 64 mm deep, a paddle shaped to  fit the trough, and a round -nosed steel rod 9.5  mm diameter by 406 
mm long;  
r) steel compaction molds, 101.6 mm inside diameter × 127 mm high ×  6.4 mm wall thickness;  
s) paper disks, heavy paper, 100 mm in  diameter, to place in bottom of mold during  compaction;  
t) hydraulic compression machine, 222 kN capacity ; 
u) steel shim, 6.4 mm thick by 19.0 mm wide by 63.5 mm  long; and  
v) gloves, heavy and sturdy, for handling hot  equipment.  
  
50 © EAC  2024  – All rights reserved  
 6.3.4.2  Batch weights  
These guidelines are suggested for estimating the  aggregate requirements:  
a) Compute batch weights for the blend and  gradation of aggregates desired.  
b) The necessary dry weight of the aggregate for  the stabilometer specimens is that which will  produce a 
compacted specimen 63.5 +/ - 1.3mm in height. This volume  of aggregate will normally weigh about 1,200  
grams. To determine the exact batch weight, it  is generally desirable to prepare a trial specimen  prior to 
preparing the actual aggregate batches.  If the trial specimen height falls outside the  limits, the amount of 
aggregate used for the  specimen may be adjusted using:  
For International System of Units (SI),  
 
For U.S. Customary Units,  
 
 
6.3.4.3  Preparation of batch mixes  
These steps are provided as a guide in preparing the  mixtures for testing:  
a) Weigh the various -sized fractions of dry  aggregates into suitable pans in accordance  with the calculated 
batch weights.  
b) Thoroughly mix each individual batch of  aggregate and preheat in oven to desired mixing  temperature. 
Asphalt should be preheated  at the same time. The temperature of the  aggregate and the asphalt at the 
time mixing  begins is indicated below for the paving grade  of asphalt cement being used.  
PG grades and modified asphalt binders should  be heated as directed in  Annex A . 
Table  10 — Temperature ranges for preheating aggregates  
Grade  Temperature range  
 Minimum  Maximum  
AC-2.5, AR -1000 or 200/300 Pen . 99°C (210° F) 121°C (250 °F) 
AC-5, AR -2000 or 120/150 Pen.  110°C (230°F)  135°C (275°F)  
AC-10, AR -4000 or 85/100 Pen  121°C (250°F)  149°C (300°F)  
AC-20, AR -8000 or 60/70 Pen  132°C (270°F)  163°C (325°F)  
AC-40, AR -1600 or 40/50 Pen  132°C (270°F)  163°C (325°F)  
 
c) When the aggregates and asphalt have reached  the desired mixing temperature, form a crater  in the 
aggregates and weigh in asphalt in  accordance with the calculated batch weights.   
© EAC  2024  – All rights reserved  51 
 d) Place pan containing aggregates and asphalt  for batch mix on hot plate to maintain mixing  temperature. 
Vigorously mix aggregates and  asphalt by hand with a pointed trowel or by  mechanical mixing until all 
particles are coated.  Take special precaution not to overheat the  materials.  
e) After mixing is complete, transfer the batch mix  to a suitable flat pan and cure for two or three  hours at a 
temperature of 146 ± 3°C (295°F ±  5°F) in an oven equipped with forced draft air  circulation. Caltrans 
uses the CT 304 procedure  to cure the mixture for 15 to 18 hours at 60 ±  2.8°C (140°F ± 5°F).  
f) After curing is complete, place batch mix in  heating oven and reheat mixture to 110°C  (230°F). The batch 
mix is then ready for  compaction.  
6.3.4.4  Compaction  
The compaction of the test specimen is  accomplished by means of the Hveem Kneading  Compactor, a 
mechanical compactor that imparts  a kneading action type of consolidation by a series  of individual 
impressions made with a ram having  a face shaped as a sector of a 101.6 -mm diameter  circle. With each 
push of  the ram, a pressure of 3.45 M Pa is applied,  subjecting the specimen to a kneading compression  over 
an area of approximately 2000 square  millimeters. Each pressure  application is maintained for approximately  
0.4 seconds. The detailed compaction procedure  follows.  
6.3.4.5  Stabilometer specimens  
a) Preheat the compaction molds, feeder trough  and round -nosed steel rod to approximately the  mix 
compaction temperature.  
b) Heat the compactor foot to a temperature  that will prevent the mix from adhering to it.  The temperature of 
the compactor foot may  be controlled by a variable transformer.  
c) Place the compaction mold in the mold holder  and insert a 100 -mm diameter paper  disk to cover the base 
plate. The steel shim  is temporarily placed under the edge of the  mold, so the base plate will act as a 
freefitting  plunger during the initial compaction  operation.  
d) Spread the prepared mixture uniformly on  the preheated feeder trough. Using a paddle  that fits the shape 
of the trough, transfer  approximately one -half of the mixture to the  compaction mold . 
e) Rod the portion of the mix in the mold  20 times in the center of the mass and 20 times  around the edge 
with the round -nosed, steel  rod. Transfer the remainder of  the sample to the mold and repeat the rodding  
procedure.  
f) Place mold assembly into position on the  mechanical compactor and apply approximately  20 tamping 
blows at 1.7 Mpa pressure  to achieve a semi -compacted condition of the  mix so that it will not be unduly 
disturbed  when the full load is applied. The exact number  of tamping blows to accomplish the 
semicompaction  shall be determined by observation.  
g) The actual number of tamping blows may vary between 10 and 50, depending upon the  type of material, 
and it may not be possible to  accomplish the compaction in the mechanical  compactor because of undue 
movement of the  mixture under the compactor foot. In these  instances, use a 178 kN  static load  applied 
over the total specimen surface by the  double -plunger method, in which a free -fitting  plunger is placed 
below and on top of the  sample. Apply the load at the rate of 1.3 mm  per minute and hold for 30 ± 5  
seconds.  
h) After the semi -compaction, remove the shim  and release mold tightening screw sufficiently to  allow free 
up-and-down movement of mold and  about 3 mm side movement of mold.  
i) To complete compaction in the mechanical  compactor, increase compactor foot pressure  to 3.45 Mpa  
and apply 150 tamping  blows.   
52 © EAC  2024  – All rights reserved  
 j) Place the mold and specimen in an oven at  60°C (140°F) for 1 hour, after which a “leveling  off” load of 56 
kN (12,600 lb.) is applied by the  “double -plunger” method head speed = 6 mm/min  and released 
immediately.  
NOTE  The specimen shall not be pushed to the  opposite end of the mold.  
6.3.4.6  Swell test specimens  
a) Prepare the compaction mold by placing a  paraffin -impregnated strip of ordinary wrapping  paper 19 mm 
wide around the inside of  the mold 13 mm  to 19 mm from  the bottom to prevent water from escaping from  
between the specimen and the mold during the  water immersion period of the test. The paper  strip is 
dipped in melted paraffin and applied  while hot. Compaction molds are not preheated  for swell test 
specimens.  
b) The remainder of the compaction procedure  for swell test specimens is the same for the  stabilometer test 
specimens except when  compaction is completed in the mechanical  compactor, remove mold and 
specimen from  compactor, invert mold and push specimen  to the opposite end of mold. Apply a 56 kN  
static load head speed 6 mm/min. with the “original” top surface  supported on the lower platen of the 
testing  press. It is advisable to place a piece of heavy  paper under the specimen to prevent damage  to the 
lower platen.  
6.3.5 Test procedures  
6.3.5.1  General  
In the Hveem method, the compacted test  specimens are used in these tests and analyses and  are normally 
performed in the order listed:  
a) stabilometer test;  
b) bulk density determination; and  
c)   swell test.  
The swell test is performed only on specimens  prepared for this purpose; the stabilometer and  bulk density 
tests are performed on each of all  other test specimens.  
6.3.5.2  Equipment for Hveem  swell and stability testing  
The equipment required for the testing of the  101.6 -mm diameter specimens is:  
a) bronze disks, perforated, 98.4 mm  diameter by 3.2 mm thick, with  adjustable stem, for swell 
measurement (see  Figure 11); 
b) dial gauge, mounted on tripod, with reading  accuracy to 0.025 mm ; 
c) scale (ml), graduated to read the water volume  on top of the specimen, in the 101.6 -mm diameter mold 
at 25 ml intervals, for the  purpose of measuring the percolation of water  during swell test;  
d) round aluminum pans, 190 mm diameter by 64 mm deep;  
e) The Hveem stabilometer (see Figure  11) is a triaxial testing device consisting  essentially of a 
cylindrical metal body shell (containing a liquid which registers the horizontal pressure developed by a 
compacted test specimen as a vertical load is applied), a flexible rubber diaphragm, a pressure gauge, 
a screw -type hand pump assembly and an air chamber fitted with a needle valve for adjusting the 
quantity of air in the system. The pump provides a means of obtaining a standard quantity of air in the 
liquid system of the stabilometer; and   
© EAC  2024  – All rights reserved  53 
 f) scale or other measuring device to accurately determine the height of the compacted test specimen.  
 
 
Figure 10  — Swell Test Apparatus  
 
Figure 11  —Diagrammatic Sketch Showing Principal  Features of Hveem Stabilometer 6.3.5.3 
Stabilometer test procedures  
The stabilometer measures the lateral pressure  transmitted through the specimen from the applied  vertical 
load. The ratio of a given applied unit  compressive stress to the transmitted lateral or  horizontal pressure is 
used to determine an index,  on a scale ranging from 0 to 100, of the ability of  the material under test (at the 
test temperature) to  resist deformation.  
NOTE  Frequent calibration of the stabilometer should  be made during the day as temperature change  has 
considerable effect upon the pressure exerted  within the hydraulic system.   
54 © EAC  2024  – All rights reserved  
 These are the steps for measuring the Hveem  stability (refer to Figures 11): 
a) Place specimens for stabilometer tests  (compacted and contained in mold) in oven at  60 ± 3°C for 3 to 4 
hours.  
b) Adjust compression machine for head speed  of 1.3 mm/min. with no load  applied.  
c) Check displacement of stabilometer with a  calibration cylinder and, if necessary, adjust to  read 2.00 ± 
0.05 turns  
d) Adjust the stabilometer base so that the  distance from the bottom of the upper  tapered ring to the top of 
the base is 89 mm . 
e) Every effort should be made to fabricate test  specimens with an overall height between  61 mm and 66 
mm; however, if the height is outside of this range,  the stabilometer value should be corrected as  
indicated in Figure 12. 
 
Figure 12  —Chart for Correcting Stabilometer Values to Effective Specimen Height of 64 mm (2.50 in.)  
 
f) Remove the mold with its specimen from the  oven and place on top of stabilometer. Using  the plunger, 
hand lever and fulcrum, force the  specimen from the mold into the stabilometer.  
g) Take care that the specimen goes in straight  and is firmly seated. Instead of using the hand  lever and 
fulcrum, this can be done with the  compression machine.  
h) Place follower on top of specimen and position  the entire assembly in compression machine  for testing.   
© EAC  2024  – All rights reserved  55 
 i) Using the displacement pump, raise the  pressure in the stabilometer system until the  test gauge 
(horizontal pressure) reads exactly  34.5 kPa. (Tap test gauge lightly to  assure an accurate reading.)  
j) Close displacement pump valve, taking  care not to disturb the 34.5 kPa initial pressure. (This step is 
omitted on stabilometers that are not provided with a  displacement pump valve.)  
k) Apply test loads with the compression machine  using a head speed of 1.3 mm/min. (0.05 in./min.). 
Record readings of the stabilometer test  gauge at vertical test loads of 13.4, 22.3 and  26.7 kN.  
Warning:  Do not continue loading if the horizontal  pressure gauge exceeds 125 psi.  
l) Immediately after recording the horizontal  pressure reading, under maximum vertical  load (26.69 kN, 
reduce total load  on specimen to 4.45 Kn. 
m) Open the displacement pump angle valve and  by means of the displacement pump adjust test  gauge to 
34.5 kPa . (This will result in a  reduction in the applied vertical load that is  normal and no compensation is 
necessary.)  
n) Adjust dial gauge on pump to zero by means of  small thumbscrew.  
o) Turn the displacement pump handle smoothly  and rapidly (two turns per second) and to the  right 
(clockwise) until a pressure of 690 kPa  is recorded on the test gauge.  
NOTE  During  this operation, the load registered on the  testing press will increase and in some cases  exceed the 
initial 4.45 kN load. This  change in load is normal and no adjustment  or compensation is required.  
Record the exact  number of turns required to increase the test  gauge reading from 34.5 kPa to 690 
kPa as the displacement on specimen  (2.5 mm dial reading is equivalent to  one-turn displacement).  
p) After recording the displacement, first remove  the test load and reduce pressure on the test  gauge to zero 
by means of the displacement  pump; then reverse the displacement pump an  additional three turns and 
remove specimen  from stabilometer chamber.  
6.3.5.4  Bulk density determination  
The bulk density test is performed on these  specimens after the completion of the stabilometer  tests as soon 
as the specimens have cooled to  room temperature. The procedure for this test is  presented in ASTM D1188, 
using p araffin - coated Specimens  and ASTM D2726, u sing saturated surface dry specimens.  
6.3.5.5  Swell test  
These steps outline the swell test procedure.  
a) Allow compacted swell test specimen to stand  at room temperature for at least one hour. (This  is done to 
permit rebound after compaction.)  
b) Place the mold and specimen in 190 mm diameter by 64 mm deep  aluminum pan (see Figure 10). 
c) Place the perforated bronze disk on the  specimen, position the tripod with the dial  gauge on the mold and 
set the adjustable stem  to give a reading of 2.54 mm on the  dial gauge (see Figure 10). 
d) Introduce 500 ml of water into the mold on top  of the specimen and measure the distance from  the top of 
the mold to the water surface with  the graduated scale.  
e) After 24 hours, read the dial gauge to the  nearest 0.025 mm and record the  change as swell. Also, 
measure the distance  from the top of the mold to the water surface  with the graduated scale and record 
the change  as permeability or the amount of water in ml  that percolated into and/or through the test  
specimen.   
56 © EAC  2024  – All rights reserved  
 6.3.6 Interpretation of test data  
6.3.6.1  Calculations  
There are no calculations required for the swell  test since the results are reported directly as  differences.  
The stabilometer measures the lateral pressure  resulting from the dilation of the specimen  caused by the 
applied vertical load. The ratio of a  given applied unit compressive stress (Pv) to the  transmitted lateral or 
horizontal pressure (Ph) is  used to determine the S -value), on a scale ranging  from 0 to 100, of the ability of 
the material to resist  deformation. The higher the S -value, the higher the  resistance to deformation. The S -
values for Hveem  compacted asphalt mixture specimens are typically  a minimum of 35.  
The remainder of the calculations are:  
a) Stabilometer value (S); calculate as:  
 
Where,  
S = stabilometer value  
D = the number of turns of the air  displacement pump handle needed to  increase the lateral pressure 
from 5 psi to  100 psi  
Pv   vertical pressure (typically 2.76 Mpa  [400 psi] = 22.24 kN  total load)  
Ph  the horizontal pressure (stabilometer  pressure gauge) reading taken at the  instant the vertical 
pressure Pv is  2.76 MPa or 400 psi (= at 5,000 lbs.  vertical load)  
b) Density and voids analysis. Using the bulk  specific gravity of the test specimens and the  maximum 
specific gravity of the paving mixture  determined using ASTM D2041, compute the percent air voids. 
These values may be plotted as a function of asphalt content as shown in Figure 13, similar  to the 
Marshall  procedure, to assist in design.  
 
  
Figure 13  —Test Property Curves for Hot Mix Design Data by the Hveem Method   
© EAC  2024  – All rights reserved  57 
 6.3.7 Design criteria  
The suitability of the hot mix design by the  traditional Hveem method is determined on the  basis of whether 
the asphalt content and aggregate  grading will satisfy the requirements in Table 11: Calculate the air voids 
content of each specimen.  
In applying these requirements, the design  asphalt content should be the highest percentage  of asphalt the 
mix will accommodate without  reducing stability or void content below  minimum values. The design asphalt 
content is  determined from observations of surface flushing  or bleeding of specimens after compaction, the  
stabilometer values and percent air voids.  
Table  11 — Hveem mix design criteria  
Quality Characteristic  Traffic Category  
 heavy  medium  light 
Air voids content (%)  4.0  4.0  4.0 
Voids in mineral aggregate (% min.)  
4.75-mm grading  17.0 17.0 17.0 
9.5-mm grading  15.0 15.0 15.0 
12.5-mm grading  14.0 14.0 14.0 
19-mm grading  13.0 13.0 13.0 
Stabilometer value (min.)  
12.5mm and 19 mm gradings  37 35 32 
Swell  less than 0.762 mm (0.030 in.)  
Notes:  
1. Although not a routine part of this design method,  an effort is made to provide a minimum percent of  air voids of 
approximately 4 percent.  
2. All criteria, and not stability value alone, must be  considered in designing an asphalt paving mix.  
3. Hot mix asphalt bases that do not meet these criteria  when tested at 60°C (140°F) are satisfactory if they  meet 
the criteria when tested at 38°C (100°F) and  are placed at 100 mm (4 in.) or more below the surface. This 
recommendation applies only to regions  having a range of climatic conditions similar to those  prevailing throughout 
most of the United States. A  different lower test temperature may be considered  in regions having more extreme 
climatic conditions.  
4. Traffic classifications:    
Light: Traffic conditions resulting in a Design  EAL <104 
 Medium: Traffic conditions resulting in a Design  EAL between 104 and 106 
 Heavy: Traffic conditions resulting in a Design  EAL >106 
 
6.3.8 Determination of Optimum  Binder Content (OBC)  
a) Using Figure 14, insert in Step 1 of the  pyramid the asphalt contents used for  preparing the series of mix 
design specimens.  Insert the asphalt contents in order of  increasing amounts from left to right, with the  
maximum asphalt content used in the square  on the right.  
b) Plot percent air voids versus percent asphalt  content, and determine by interpolation the  percent asphalt 
content that has 4.0 percent  air voids.   
58 © EAC  2024  – All rights reserved  
 c) Select from Step 1 the three highest asphalt  contents that do not exhibit moderate or heavy  surface 
flushing and record on Step 2 of the  pyramid. Surface flushing and/or bleeding is  considered “Slight” 
(acceptable) if the surface  has only a slight sheen. It is considered  “Moderate” (unacceptable) if sufficient 
free asphalt is apparent to cause paper to stick to  the surface but no distortion is noted.  
d) Surface  flushing is considered “Heavy” (unacceptable)  if there is sufficient free asphalt to cause  surface 
puddling or specimen distortion after  compaction.  
e) Select from Step 2 the two highest asphalt  contents that provide the specified minimum  stabilometer 
value and enter them in Step 3 of  the pyramid.  
f) From the plot in (b), determine the theoretical  asphalt content that has 4 percent air voids and  is within 
the asphalt range listed in Step 3 of  the pyramid. Always stay as close to 4 percent  air voids as possible. 
The selected percent  asphalt content is entered in Step 4, and is the  optimum binder content (OBC) for 
the job mix  formula (JMF).  
g) The asphalt content in Step 4 is the design  asphalt content. However, if the maximum  asphalt content 
used in the design set (Step 1)  is the asphalt content entered on Step 4 of  the pyramid, additional 
specimens must be  prepared with increased asphalt contents  in 0.5 percent increments and a new design  
asphalt content determination should be made.  
h) At the final OBC, compact three additional  Hveem specimens and determine the final  values for Hveem 
stability and volumetric  properties as the average of each of the three  test values.  
i) Additional mix design voids criteria are  contained in clause 5 as well as some factors to  consider when 
selecting the final design asphalt  content.  
 
 
 
 
Figure 14  —Procedures for selecting design asphalt content, Heveem Method of Design   
© EAC  2024  – All rights reserved  59 
  
 
 
 
 
 
 
7 Recycled Asphalt Pavement (RAP) Materials in the Mix Design Process  
7.1 Reclaimed Asphalt Pavement (RAP)  
7.1.1  Recycled asphalt pavement (RAP) uses recycled materials that meets all of the specified 
requirements for mixes produced with the specified requirements for mixes produced with 100 percent virgin 
materials.  Most RAP is produced from milling . It also produced from any existing asphalt pavement by 
processing it to an appropriate size to be used as a component of a new asphalt mixture. RAP consists of the 
same components as virgin HMA  (aggregate and asphalt binder ), it can readily be i ncorporated into a new 
mixture.  
7.1.2  Guidelines for recycling  of bituminous materials  are given in Annex B.  
7.2 RAP properties  
The amount of RAP that is used in the asphalt  mixture dictate what properties are needed  to be known before 
the RAP can be used. For all  levels of RAP, asphalt binder content and gradation  will need to be known. At 
higher levels of RAP, the  physical properties of the asphalt binder will also  be needed so that blending charts 
can be used to  select the appropriate grade of virgin, or newly added, asphalt binder.  
7.2.1 Determining asphalt binder content and aggregate gradation  
Regardless of the amount of RAP that is used in the mixture, the mix design technologist will need to know the 
asphalt binder content of the RAP so that the total asphalt binder content (RAP binder plus virgin binder) can 
be properly determined.  
The asphalt binder content of RAP is determined using either of the following :  
a) ignition oven procedure  which is detailed  in AASHTO T 308, and  
b) solvent extraction  as detailed in AASHTO T 164.  
At the conclusion of the procedure, the recovered aggregate should be saved for determining the gradation 
using AASHTO T 30, “Mechanical Analysis of Extracted Aggregates.”  
NOTE  Although either procedure can be used, there are disadvantages associated with each. With the ignition oven, 
degradation is possible with some aggregates , which could lead to a gradation that is finer than the actual gradation of the 
RAP. The ignition oven also requires a correction factor  that may have to be estimated for the RAP and  not measured. 
Experience with local aggregates  can indicate if the ignition oven is an appropriate  procedure to use. The biggest 
inconvenience with  the second option using the extraction procedure is  that it uses solvents.  
Both procedures should be capable of producing  a sufficient sample size after extraction so that the  extracted 
aggregate can be tested for gradation.  Additional extraction or ignition oven runs may be  needed to complete  
60 © EAC  2024  – All rights reserved  
 other aggregate property tests  as specified.  Although either procedure may be used for  determining asphalt 
binder content and aggregate  gradation, the solvent extraction procedure should  be selected if asphalt binder 
properties are needed.  
7.2.2 RAP aggregate specific gravity  
There are two main ways of determining the combined specific gravity of the RAP aggregate.  
a) RAP Specific Gravity Method 1  uses the RAP aggregate that is obtained following a solvent extraction 
or ignition oven procedure. The aggregate is split into coarse and fine fractions, and individual specific 
gravity tests are performed. The combined RAP aggregate specific gravity is then determined.  
b) RAP Specific Gravity Method 2 , which uses the RAP as is to determine the maximum theoretical 
specific gravity, G mm, of the RAP. If the asphalt binder content of the RAP is known (or determined), 
then the effective specific gravity, G se, of the RAP aggregate can be calculated. This value can then be 
used as a substitute for the bulk specific gravity, G sb, of the RAP.  
 • RAP Specific Gravity Method 2a  uses the same methodology as Method 2 with the exception that an 
asphalt absorption rate is determined or assumed and the G sb of the RAP aggregate is calculated.  
7.2.2.1  Determining RAP G mm 
Before performing the G mm test on RAP, it is important that the RAP is properly prepared, as described below:  
1. Dry the test sample to constant mass in a forced draft oven at 110 + 5°C (230 + 9°F).  
2. Break up the sample similar to a standard G mm sample.  
3. Mix the RAP sample thoroughly with a spatula to allow the old RAP binder to coat th e uncoated aggregate 
particles.  
Determining the maximum theoretical specific gravity on recycled asphalt or core samples can be confounded 
by the uncoated faces that result from  
To prevent intrusion of water into the sample, add a measured quantity of new binder in the range of 1 –3 
percent of the total sample weight, as needed to fully coat all particles. Preheat the mix to 60 –120°C as you 
would during a normal  mix design, place it in the mixing bowl and add the  additional binder to thoroughly coat 
the mixture  and let it cool. When G mm testing is completed,  simply back out the added asphalt mass and 
volume  from the original procedure using the following  equation when the “Mass Determination in Air”  from 
AASHTO T 209 is utilized:  
 
where  
A is mass of the oven -dry sample in air, g;  
D is mass of the container filled with water at  25°C (77°F), g;  
E is mass of the container filled with the sample  and water at 25°C (77°F), g;  
J is mass of the added asphalt binder in air, g;  
K is= volume of the added asphalt binder, cc or  
  
© EAC  2024  – All rights reserved  61 
 where  
Gb is the specific gravity of the binder added.  
 
 
 
 
7.2.2.2  Calculating RAP Gse and Gsb  
After determining the G mm, the designer can calculate the G se (assuming the asphalt binder content is known) 
using the equation below:  
 
Where  
 Gse(RAP)  is effective specific gravity of the RAP  
Gmm(RAP)  is measured maximum theoretical specific gravity of the RAP  
Pb(RAP)   is asphalt binder content of the RAP  
Gb(RAP)  is specific gravity of the RAP asphalt binder  
The G mm(RAP) and P b(RAP) are determined from  testing. While the G b(RAP) can be determined  by testing, it would 
require that the asphalt  binder be extracted and recovered. As such, it is  recommended that an assumed 
Gb(RAP)  be used.  In the absence of other guidance, a G b(RAP) value of 1.04 is recommended . 
Theequation for determining Gsb of the RAP aggregate is shown below:  
 
Where  
 Gsb(RAP)  is bulk specific gravity of the RAP  
Gse(RAP)  is effective specific gravity of the RAP  
Pba(RAP)  is asphalt binder absorption of the RAP  
Gb(RAP)  is specific gravity of the RAP asphalt binder  
In the preceding equation, the G mm and asphalt binder content of the RAP are used to calculate G se(RAP), as 
shown earlier. As before, a G b(RAP) value of 1.04 is recommended as an estimated value. Mix design 
technologists can always measure the G b(RAP)  if desired.   
62 © EAC  2024  – All rights reserved  
 7.2.2.3  Consensus aggregate properties  
RAP aggregate, like virgin aggregate, must meet the consensus property requirements established in 
AASHTO M 323. It  is important to remember that the consensus property requirements apply to the blend of 
aggregates, virgin and RAP, and not specifically to the individual aggregates.  
To test RAP aggregate individually, it must first be separated into coarse and fine fractions by splitting the 
sample. Material retained on the 4.75 -mm (#4) sieve is used for determining coarse aggregate angularity and 
flat/elongated particles. Material finer than the 2.36 -mm (#8) sieve is used for the fine aggregate angularity 
test. The sand equivalent test is not conducted on RAP aggregate since it has already been coated with 
asphalt binder and the clay content, if any, will have been removed during the extraction or ignition oven 
procedure.  
7.2.2.4  RAP asphalt binder properties  
At higher levels of RAP, it may be necessary to know the properties of the RAP asphalt binder so that an 
appropriate virgin asphalt binder grade can be selected. If RAP binder properties are needed, then a solvent 
extraction/recovery procedure should be performed on a sample of the RAP. Solvent extraction and recovery 
of asphalt binder can be performed following the procedures in AASHTO T 164, followed immediately by 
binder recovery followin g the procedures in ASTM D5404.  
Once the asphalt binder has been recovered, it should be tested using the procedures in AASHTO M 320 to  
determine the critical temperatures (sometimes called the “true grade” or “continuous grade” temperatures) 
where the specification criteria is exactly met. Determination of critical temperature requires testing at two or 
more temperatures, preferably bracketing the specification value.  
7.2.2.4.1  Using RAP asphalt binder properties to select an appropriate virgin binder grade  
The following guidelines  given in Table  12 are recommended for  selection of RAP mixture  
Table  12 —  Binder Selection Guideline for RAP Mixtures  
 
NOTE  Selection of an asphalt binder grade to use in a mixture is usually left up to the project designers. The selected 
binder grade is based on a number of factors such as climate and anticipated traffic loading at the project site. This is 
referred to as the project binder grade. Because of the time and testing expense of determining RAP binder properties for 
blending, many asphalt mixture designers elect to use a percentage of RAP that will not require binder properties and 
blending charts and/or equations.  
7.4 Developing the mix design  
7.4.1 Determining combined aggregate gradation  
RAP should be treated like any other aggregate when determining the combined aggregate gradation —except 
that the mix designer must remember that the RAP contains aggregate and asphalt binder. Unlike virgin  
© EAC  2024  – All rights reserved  63 
 aggregates, the percentage of aggregate in the RAP will always be less than the total percentage of RAP 
added to the mixture.  
To determine the combined gradation, the RAP Blend percentage (i.e., how much RAP total will be used) is 
multiplied by the RAP aggregate percentage to get a stockpile percentage for determining combined mixture 
gradation. The equation is shown below:  
 
where  
RAP stockpile    the stockpile percentage of the RAP used in aggregate blending calculations  
RAP Blend   the total amount of RAP used in the mixture, in percent  
Pb,RAP   asphalt binder content of the RAP, expressed as a percent  
The next step is to adjust the stockpile  percentages of the virgin aggregates. This is done by  first dividing the 
amount of each virgin aggregate  used by the total amount of virgin aggregate in the  mix and then 
proportioning that percentage as a  function of the difference between the RAP  stockpile  and RAP Blend. The 
equation is as follows:  
 
where 
VirginAgg stockpile  is the stockpile percentage of a virgin aggregate used in blending calculations  
VirginAgg Blend,n   is the amount of a virgin aggregate (n) used in the mixture, in percent (where n  = 1 is 
Stockpile #1, n = 2 is Stockpile #2, etc.)  
RAP Blend   is the total amount of RAP used in the mixture, in percent  
RAP stockpile   is the stockpile percentage of the RAP used in aggregate blending calculations  
7.4.2 RAP batching and handling in the lab  
When preparing to conduct a mix design, the virgin aggregates are batched according to their stockpile 
percentages and blended into a combined batch that is then preheated at the mixing temperature (actually 
slightly above mixing temperature, as discussed earlier, to account for heat loss during weighing) prior to 
beginning the mix design process. When using RAP, the RAP aggregate and asphalt binder are batched 
together and must be kept separate and not heated like the virgin aggregates.  
7.4.3 Heating of RAP and virgin aggregates in the mix design process  
Normally, virgin aggregates are batched, combined and placed in an oven overnight at the appropriate mixing 
temperature. Unfortunately, since RAP contains asphalt binder, it cannot be heated in the same manner 
without affecting its properties.  
For RAP mixtures, it is recommended that the RAP be batched separately in no more than 1 - to 2-kilogram 
(1,000 to 2,000 gram) batches and heated for no more than two hours at 110°C (230°F). This is a sufficient  
64 © EAC  2024  – All rights reserved  
 time to heat the RAP and remove any extraneous surface moisture. Higher temperatures and longer heating 
times have been shown to change the properties of some RAP materials.  
To compensate for the introduction of a lower temperature material, the virgin aggregate should be heated 
above the mixing temperature by a certain amount. Although actual mix temperatures vary, a good rule of 
thumb is to increase the temperature of the virgin aggregates by 0.5°C  (0.9°F) for every percent of RAP used 
in the mix (RAPBlend). Thus for a mixture with RAPBlend = 25 percent, the mixing temperature of the virgin 
aggregates should be raised by 12.5°C (22.5°F).  
The mixing temperature of the virgin asphalt binder should not be adjusted. To mix each sample, the pre -
batched virgin aggregate is added to a mixing bowl (or bucket mixer) and the heated RAP is added and 
quickly mixed with the virgin aggregates. A crater is formed just as in the normal mixing process, and the 
virgin asphalt binder is added in the appropriate amount and the mixing process is started.  
7.4.4 Determining new virgin binder quantity   
Because the pre -batched RAP sample contains asphalt binder in addition to aggregate, the weight of the RAP 
binder must be accounted for so that the total asphalt binder content is correct. This is done by calculating the 
total weight of asphalt binder to be used for a specified asphalt binder content and then subtracting the RAP 
binder to get the weight of the virgin asphalt binder to be added. This is shown in the equation below:  
 
where 
Virgin Binder Weight  the weight of the virgin binder to be added  
Total Agg Weight   is the total weight of virgin and RAP aggregates  
Pb  desired asphalt binder content, percent  
Ps  aggregate content, percent (100 – Pb)  
RAP  Batch Weight  total weight of RAP that was batched  
RAP  Aggregate Weight  weight of RAP aggregate in the blend  
 
 
 
 
 
 
 
 
  
© EAC  2024  – All rights reserved  65 
  
  
66 © EAC  2024  – All rights reserved  
 Annex  A 
(normative)  
 
Laboratory Mixture Testing  
A.1 General  
Laboratory asphalt mixture testing is primarily conducted to determine two fundamental asphalt mix properties 
the bulk specific gravity of the mixture (G mb) and the theoretical maximum specific gravity of the mix (G mm). 
These values are utilized in calculating volumetric properties discussed in ( clause 5 ) which are specified 
requirements for most asphalt mix design procedures. Laboratory asphalt mix specimens are also prepared 
for further mixture testing such as moisture sensitivity or other recommended or specified performance tests. 
The specific gravity of aggregates, binders and asphalt mixtures are determined using standardized 
procedures.  
A.2 Selection of trial binder contents, compaction temperatures and mixing times  
A.2.1  Selecting the trial binder content  
Most asphalt mixture design procedures are conducted by preparing multiple trial mixtures at different binder 
content percentages. Decisions to be made regarding what binder contents to use in  the mix design process 
include the number of trial binder contents, the increments between binder contents and the range of binder 
contents to be covered by the trial blends. The most commonly selected increment between binder 
percentage points is 0.5 percent. However, if the designer is unfamiliar with aggregates being used, or if other 
materials or additives are used such as RAP, RAS, lime, WMA, etc., more points at smaller increments over a 
wider range may be  needed.  
The ultimate goal is to prepare batches that bracket the anticipated design binder content. The designer 
should evaluate the aggregate type, the aggregate structure and any additional materials or additives before 
selecting the beginning and ending binder points. There are several guidelines to keep in mind:  
a) binder demand increases as the nominal maximum aggregate size of the mix decreases;  
b) absorptive aggregates have a greater binder demand;  
c) for a given nominal maximum aggregate size, a fine aggregate gradation will require more binder than a 
coarse aggregate gradation;  
d) if higher VMA is anticipated due to hard, angular aggregates, more binder will be required;  
e) mixes with a higher P200 tend to require more binder than those with a lower P200; and  
f) ask the manufacturer for guidance when proprietary additives are used.  
In the end, the designer should never extrapolate a higher or lower design binder content from outside the 
range of trial points.  
A.2.2 Mixing and compaction temperatures  
For years, asphalt mix design procedures have used equiviscous temperature ranges for selecting laboratory 
mixing and compaction temperatures. The purpose of using equiviscous mixing and compaction temperatures 
in laboratory mix design procedures is to normalize the effect of asphalt binder stiffness on mixture volumetric  
© EAC  2024  – All rights reserved  67 
 properties. By using this procedure, a particular asphalt mixture of the same aggregate structure will exhibit 
very similar volumetric properties regardless of whether a hard or soft asphalt binder is used.  
In the equiviscous method, the viscosity of the asphalt binder is determined at two test temperatures, 
establishing a relationship between temperature and viscosity as shown in Figure  A.1. Compaction 
temperatures are determined where the viscosity -temperature line crosses the compaction viscosity range of 
0.28 ± 0.03 Pa -s. Mixing temperatures are determined where the viscosity -temperature line crosses the 
mixing  viscosity range of 0.17 ± 0.02 Pa -s. 
 
Figure  A.1 — Mixing and compaction temperature chart  
A.2.3  Laboratory mixing operations  
The goal of laboratory mixing operations is to produce uniform batches of properly coated HMA mixtures. 
Mixing is typically done w ith either a planetary mixer  with wire whips or a five -gallon bucket mixer (see Figure 
A.2). The following points are important to remember in the mixing operation:  
a) Place the aggregate and binder in the oven at the mixing temperature for at least two hours before 
mixing. To avoid excessive aging of the binder, do not allow it to stay at the mixing temperature for much 
over the time needed to bring it to temperature and complete the mixing operation.  
b) Place all mixing bowls, whips and molds in the oven 30 minutes to an hour before mixing. Keep enough 
molds in the oven to rotate their use, always keeping a hot mold available.  
c) Keep the binder in smaller containers (no more than a gallon) to avoid aging it from constant reheating. 
Transfer the hot binder to quart cans or other small containers as needed to make it safer and easier to 
pour. Small stainless steel pitchers from commercial restaurant supply stores work very well.  
d) Place the spatula blade on a hot plate, making sure that the wooden handle does not touch the hot plate 
(usually a heavier nonflammable object is placed on the blade to keep the spatula from slipping off).  
e) Keep a stack of paper squares next to the scale to intercept the poured binder stream when it is about to 
reach the proper weight and to dip out excess binder.  
f) It is good practice to place something on the scale to protect the electronics from overheating when the 
hot bowl/bucket is placed on it.   
68 © EAC  2024  – All rights reserved  
 g) “Butter” the mixing bowl and whip by mixing a dummy batch before subsequent design batches to coat 
the equipment with binder as an aid in maintaining consistent binder contents.  
h) Make sure to have an oven set at the compaction temperature ready to receive the freshly mixed 
batches.  
 
 
 
Figure A.2 — Mixing machines (Five -gallon bucket mixer on left  side and Weighing binder into mixing 
bowl  on right side)  
When you are ready to mix, place the mixing bowl/bucket on the scale and tare it. Pour the heated aggregate 
batch into the bowl and verify the required weight. Form a crater in the center of the aggregate to receive the 
binder and keep it from flowing to the edges of the bowl. Add the correct number of grams of binder, dipping 
out any excess binder with a folded paper dipper. Mix until all of the aggregate is thoroughly coated.  
It is suggested that  the mixing should be for approximately 60 seconds for single specimen batches and 
approximately 120 seconds for multiple specimen batches.  
When transferring the mixture from the mixing bowl to the conditioning pans, make sure to thoroughly scrape 
the mixed fines and asphalt from the bowl and whips into the conditioning pans with a hot spatula.  
A.2.4  Mixture conditioning  
It is recommended that all G mb and G mm mixture samples be conditioned a minimum of 2 hours prior to the 
compaction of G mb samples and the cooling and testing of G mm samples, regardless of the mix design 
procedure utilized. Aggregate sources that have high water absorption values (above 2.0 percent) should be 
conditioned for an extended period of time (up to 4 hours).  
A.2.4.1  Equipment  
The equipment required for conditioning the mixture includes:  
a) oven —a forced -draft oven capable of maintaining the desired temperature setting within ± 5.4°F (3°C);   
© EAC  2024  – All rights reserved  69 
 b) thermometers —having a range of 122°F (50°C) to 500°F (260°C), readable to 1.8°F (1°C); and  
c) miscellaneous —a shallow metal pan for heating uncompacted asphalt mix, a metal spoon or spatula, tim  
A.2.4.2  Procedure  
a) Place the mixture in a shallow metal pan and spread it to an even thickness between 25 and 50 
millimeters in depth. Place th e mixture and pan , in the oven for 2  hours ± 5 minutes at a temperature 
equal to the mixture’s compaction temperature ± 5.4°F (3°C).  
b) Note that the conditioning time may need to be increased to be more representative of field conditions 
when higherabsorptive aggregates (more than 2 percent) are used, subject to agency approval.  
c) Stir the loose mixture every 60 ± 5 minutes to maintain uniform conditioning.  
d) Remove the mixture and pan from the oven after 2 hours ± 5 minutes. The mixture is now conditioned for 
further testing. The procedure for short -term conditioning for mixture mechanical property testing is 
similar to that for volumetric mix design, but the conditioning time is 4 hours ± 5 minutes, and the oven 
temperature, 275°F (135°C) ± 5.4°F (3°C).  
A.3 Laboratory compaction  
A.3.1  Generaal  
The laboratory compaction effort is intended to replicate the ultimate or final compacted condition of the 
pavement after being exposed to several years of traffic loading. The designer should understand that 
different compaction methods affect the aggregate orientation and density profiles within the specimen. 
Therefore, different types (not meaning different models within the same type) of compaction methods should 
not be used for mix comparison. The goal of laboratory compaction is to both simulate the compaction 
expected in the field and ensure sufficient repeatability for acceptable consistency between different labs and 
technicians. The steps preliminary to specimen preparation are:  
a) ensure all materials used in the design process have been sampled according to an accepted procedure 
and are representative of the materials to be used on the project;  
b) ensure all materials proposed for use meet the physical requirements of the project specifications;  
c) determine the appropriate mixing and compaction temperatures, either through the use of a viscosity 
versus temperature chart or by local agency specification; and  
d) determine the bulk specific gravity of all aggregates used in the blend and the specific gravity of the 
asphalt binder for performing density and voids analyses.  
These requirements are matters of routine testing, specifications and laboratory technique that must be 
considered for any mix design method.  
This following are the three most common compaction methods for volumetric mix design and quality control 
testing:  
• Gyratory —Superpave;  
• Impact —Marshall; and  
• Kneading —Hveem.  
Detailed discussion of these compactors and their use can be found in  their respective design methodology in 
Clause 6 .  
70 © EAC  2024  – All rights reserved  
 A.4 Determining bulk specific gravity, G mb  
Determining the bulk specific gravity (G mb) of lab -molded specimens and roadway cores is a fundamental 
component of asphalt mix design and testing. All specific gravity computations involve a mass divided by a 
volume multiplied by the unit mass of water. In this case, the mass includes both the mass of the aggregate 
and the mass of the binder. The volume includes the effective volume of the aggregate, the volume of the 
binder and the volume of the air voids within a compacted specimen . 
There are three main standardized methods for determining the bulk specific gravity in the laboratory. The 
most common is outlined in  ASTM D2726 , is intended for relatively nonabsorbent (impermeable), 
densegraded specimens and uses the saturated surface  dry (SSD) mass in the calculation.  
There  other two methods are intended for relatively absorbent (permeable) specimens. The first is the 
CoreLok method, which is outlined in ASTM D6752  and the paraffin -coated method described in ASTM D1188 
intended to be used for compacted mixture specimens with water absorption (infiltration) greater than 2.0 
percent by volume.   
A.4.1   Determining theoretical  maximum specific gravity, G mm  
Determining the theoretical maximum specific gravity (G mm) of loose asphalt mixtures is another fundamental 
component of asphalt mix design and testing that involves a mass divided by a volume multiplied by the unit 
mass of water. In this case, the mass includes both the mass of the aggregate and the mass of the binder. 
The volume includes only the effective volume of the aggregate and the volume of the binder. If G mb and G mm 
samples had the same dry weight in air, the numerators of the specific gravity equation would be the same for 
Gmb and G mm, but the denominator of the G mm calculation is smaller because it does not include the volume of 
air. Therefore, G mm must always be a larger number than G mb. Theoretically, if a G mb sample could be 
compacted until 0 percent air voids remain, the G mb and G mm would be equal.  
The most commonly used practice for determining the theoretical maximum specific gravity is oulined in 
ASTM D2041.  
There are basic steps in determining the theoretical maximum specific gravity are as follow:  
e) The loose mix is warmed and separated into loose, individually coated aggregates.  
f) A minimum mass, of the dry loose mix is split out and placed in a metal bowl or calibrated pycnometer 
and covered with water.  
g) A vacuum lid is fitted and secured to the bowl or pycnometer and placed on a vibratory shaker table. A 
vacuum pump is started and the manometer or absolute pressure gauge reading is used to determine 
the proper vacuum adjustment. Once the proper (almost absolute, 27.5 mm Hg) vacuum is obtained, the 
shaker table is started. This provides gentle agitation to help in the removal of any air between particles. 
The agitation ensures that the air in the mixture is as close as possible to zero.  
h) The theoretical maximum specific gravity is calculated using the equation for the specific procedure 
utilized. Gmm is the mass of the coated aggregate divided by the volume of coated aggregate. Air voids 
are calculated from the bulk and maximum specific gravities (Gmb and Gmm). The ratio of these two 
specific gravities is actually the percent by volume of solids (in decimal form).  
NOTE  A common source of error with this test is that technicians do not calibrate (verify) the mass of the vacuum 
container filled with water often enough. This is not usually a problem in labs where only distilled water is used for the te st, 
but field labs often have water tanks that serve the entire lab and are refilled periodically, sometimes from different 
sources. Because it only takes a few minutes to calibrate, more consistent results will be generated if the vacuum 
containers are calibrated daily or even before each test.  
  
© EAC  2024  – All rights reserved  71 
 A.5 Effect of binder content Gmb and G mm  
The effects of asphalt binder content (P b) on G mb and G mm are illustrated in Figure A.3. It is important to 
remember that G mb is measured on a compacted mixture sample. As P b increases, more lubricity is added to 
the mixture which allows the specimen to compact and slightly reduce the volume, while at the same time the 
mass of the specimen is also increasing as the binder fills the voids within the compacted aggregate structure. 
The slight reduction in volume in combination with the increasing mass causes the specific gravity (density) of 
the compacted sample to increase. As the voids become filled with binder, the volume of the sample begins to 
increase. This increasing volume is due entirely to the additional binder being added which begins to reduce 
the overall specific gravity of the compacted specimen.  
The effects of increasing P b on G mm are quite different. As the P b increases the percent stone (P s ) decreases. 
Since there is no compaction or air voids involved with the measurement of G mm, the volume of a G mm sample 
always increases because the volume of binder being added is roughly 2.5 times the volume of stone that is 
being removed from the mixture. This makes the G mm property very sensitive to binder content. This also 
shows the importance of obtaining representative samples of mix when conducting G mm testing. If a sample is 
segregated and is too coarse, the P b will be artificially low, resulting in a G mm value that is too high. If the 
segregated sample is too fine compared to the mixture being produced, the binder content of the material  
tested will be high and the resulting G mm test result too low.   
 
Figure A .3 — Gmm and G mb relationship to binder content  
 
 
 
 
 
 
 
 
  
72 © EAC  2024  – All rights reserved  
 Annex  B 
(normative)  
 
Recycling of bituminous materials  
B.1 General  
The use of thick bituminous surfacings in developing countries is increasing as traffic loads increase. When 
they become worn out the recycling of such materials reduce costs and damage to the environment by 
reducing the exploitation of local natural resources. The types of asphalt that are most likely to be available for 
recycling are those that have become severely age -hardened and cracked or surfacings that have failed 
through plastic deformation.  Aged asphalt can be expected to be brittle and to contain very hard bitumen. In 
contrast, asphalt that has deformed plastically is likely to contain bitumen that has suffered very little age 
hardening. These two types of material present different problems for recovery, stockpiling and re -use. 
It is therefore important to determine the variations in properties of the bitumen in RAP and how this will be 
taken into account in the mix design process.  
B.2  Methods of recycling  
B.2.1 Reclaimed Asphalt Pavement (RAP), or millings, are crushed and used as granular materials for fill 
or lower pavement layers or re -used in a bituminous material, either by cold mix or hot mix recycling. These 
recycling processes can be carried out either in -place or at a central plant. The greatest cost savings will be 
obtained when RAP is used to produce good quality bitumen - bound material and it’s use as unbound material 
should be regarded as the minimum target for recycling.  
B.2.2 The decision to recycle asphalt, its appropriate use and the quality that can be achieved, will be 
determined by a number of factors which include the following:  
a) availability of suitable recycling plant;  
b) the thickness of the existing bituminous layer;  
c) the effect on traffic management  
d) the level of quality control that can be achieved in the recycling process; and  
e) the variability in the properties of the existing material.  
B.2.3 Standard ‘cutting -out’ and crushing equipment can be very effective for producing well graded RAP 
from brittle age -hardened asphalt. This material, modified if necessary by the addition of fresh aggregate, may 
be suitable for use in any pavement layer. However, it is recommended that RAP is not used to manufacture 
bituminous wearing courses unless it can be demonstrated that the high degree of uniformity and the close 
tolerances required for this critical layer can be achieved.  
B.2.4 The wider tolerances allowed for bituminous road base and, to a lesser extent, for binder courses, 
make these mixes more suitable for incorporating RAP. The uniformity and quality of the RAP and the type of 
recycling plant will determine the percentage of RAP that can be used in the mixes. Typically, this will range 
from 20 to 50 %.  
B.2.5 When RAP is to be used in a pavement layer, good quality control of the RAP stockpiles will be vital 
to the manufacture of consistent HMA. This may require a considerable amount of testing. The presence of 
old multiple surface dressings may be acceptable if they have age -hardened. However, where there has been  
© EAC  2024  – All rights reserved  73 
 heavy patching or the quality of the seal is variable, recycling may be limited to in situ pulverisation and 
stabilisation.  
B.2.6 Powerful pulverisers are available which makes it possible to carry out cold in situ recycling with 
fresh materials being incorporated as necessary to produce a layer of the required quality.  
B.3 Suggested method of sampling existing asphalt  
B.3.1 A feasibility study will be necessary to assess the variability of the existing material, to establish that 
a suitable mix design can be achieved, and that it can be manufactured with the available plant. During the 
feasibility study, samples must be cut from the existing asphalt for analysis. A balance must be found between 
costly and time consuming testing and the need for sufficient samples to determine material variability. The 
sampling pattern should take account of visually obvious variability such as:  
a) contaminated ‘oil lanes’;  
b) wheelpaths that look ‘rich’ in bitumen, indicating a dense material in which bitumen hardening may not 
be as severe as elsewhere in the pavement;  
c) material which looks rich in bitumen and may have deformed plastically; and  
d) cracking or fretting indicating that appreciable bitumen hardening has occurred.  
B.3.2 Identification of road lengths with apparently uniform appearance will help to establish short 
representative sections which can be tested. Based on these sections a suitable pattern of testing can be 
established. The intention should be to stockpile separately severely age -hardened materials, typically with 
penetration values of less than 20, from less hardened materials and to discard badly contaminated material 
from ‘oil lanes’. Detailed assessment of stockpile management should be finalised after a desk study has been 
carried out to show how the various RAP materials can be combined with fresh aggregate to produce 
acceptable mixes. The following tests should be carried out to determine material properties:  
a) particle size distribution;  
b) bitumen content;  
c) viscosity of recovered bitumen; and  
d) an assessment of crushability.  
B.4 Methods of obtaining RAP  
B.4.1 General  
RAP can be obtained by milling or it can be cut from the road in lumps which must be crushed. An 
assessment of the likelihood of obtaining a well crushed material with the available plant must be made, 
preferably at the feasibility stage. Milling is particularly useful where traffic access must be retained during the 
removal of damaged asphalt. Either method is suitable when the road is closed to traffic during the 
rehabilitation work.  
B.4.2 Asphalt millings  
Asphalt millings are obtained by planing, in a layer by layer fashion, using a mobile plant and are typically 
consistent in their lump -size distribution. They can normally be used as granular material, as won, or with 
minimum screening to remove any over -size material.   
74 © EAC  2024  – All rights reserved  
 B.4.3 Crushed asphalt  
Crushed asphalt is commonly obtained by using horizontal impact crushers or hammermill impact crushers. 
Jaw/roll combination crushers are not suitable for processing RAP which contains ‘soft’ bitumen because 
‘pancaking’ can occur on warm days and the material will remain agglomerated.  
B.4.4 Granulated asphalt  
Granulated asphalt is produced in a specialised plant, known as a granulator, or in milling/grinding units. 
These units are not crushers and are designed only to break the bitumen -asphalt bond.  
B.5 Stockpiling RAP  
B.5.1 The stockpiling of RAP is a very important part of the recycling process. The full benefits of 
comprehensive testing of the in situ asphalt layers can easily be lost if equally meticulous control of the 
stockpiling process is not put in place. Depending upon the variability found during testing, it may be 
necessary to build separate stockpiles of materials taken from different sections of the road.  
B.5.2 The tendency for RAP to agglomerate will be affected by both the hardness of the bitumen in the 
RAP and the ambient temperature. The most effective method of stockpiling must be  established by trial and 
error . A 250 -300mm crust may form at the surface of the stockpile and this should be scalped off and 
reprocessed prior to recycling. Higher stockpiles should, therefore, provide more usable RAP.  
B.5.3 RAP can hold up to 7 -8% moisture which seriously reduces the amount of material that can be hot 
mixed, raises fuel costs and limits productivity. Although covering a stockpile with a waterproof sheet does 
keep off rain water, condensation may occur within the stockpile. Ideally RAP for hot mixing should be stored 
under a roof in an opensided building.  
B.5.4 Stockpiled RAP destined to be used as unbound granular material may be watered to prevent 
agglomeration of particles in warm weather and this also aids compaction on site.  
B.6 Use of RAP as unbound granular material  
B.6.1 Age-hardened asphalt can be recycled as an unbound granular material. It may be produced as 
millings, crushed asphalt from lumps or as granulated asphalt. The RAP can be mixed with fresh aggregate to 
produce a particle size distribution appropriate to the layer in which it will be used. The harder the bitumen in 
the RAP the easier it will be to crush, handle and recompact in the new layer.  
B.6.2 In contrast, an asphalt which has failed by plastic deformation will have suffered little or no bitumen 
hardening in the wheel paths. In the oil lane the bitumen may have softened over time whilst material outside 
of the wheelpaths or oil lane may have significantly age -hardened. This type of material is difficult to process 
and the best results can be expected by selective milling and stockpiling before reblending and adding fresh  
B.7 Cold mix recycling  
B.7.1 Cold mix recycling can be done at partial or full depth in an asphalt pavement with mixing carried out 
in-place or off -site at a central plant. The process preserves aggregate and bitumen, air quality problems are 
minimised and energy requirements are low. The existing pavement layers are reprocessed with the addition 
of fresh aggregate if this is required. During the reprocessing operation, hydraulic stabiliser, such as Portland 
cement or emulsified or foamed bitumen, is mixed in to produce a new material with the required properties.   
© EAC  2024  – All rights reserved  75 
 B.8 Plant hot mix recycling  
B.8.1 General  
Hot-mix recycling is most likely to be done off -site at a central plant. Asphalt containing tar should not be 
recycled because of the high risk of generating carcinogenic material.  
B.8.2 RAP feed to plant  
To avoid blockages that will substantially reduce output, RAP should be metered into the plant through cold 
feed bins having the following characteristics:  
a) The sides should be steeper than those of an aggregate feed bin.  
b) The bottom of the bin may be longer and wider than that of an aggregate feed bin.  
c) The bottom of the bin may slope downwards, to match an angled feed belt, and the end wall is sometimes 
left open.  
d) Vibrators should not be used.  
e) RAP should be delivered slowly into the cold feed bin from the front -end loader.  
The level in the bin should be kept fairly low. This means that the bin must be fed more frequently than is 
necessary for a normal aggregate cold feed bin.  
Material should not be left in the cold feed bin for more than one hour. It is more economical to run out the 
contents of the bin than to clear it sometime later.  
B.8.3 Batch plant recycling  
Because cold aggregate travels towards the heating flame in this type of plant the introduction of RAP would 
result in excessive smoke and other problems. The technique of conductive heat transfer, which involves the 
super heating of fresh aggregate and adding cold RAP via the elevator or directly into the weigh hopper 
minimises the likelihood of air pollution. The percentage of RAP that can be used depends upon the following 
factors:  
a) The temperature to which the virgin aggregate is heated.  
b) The temperature and moisture content of the RAP.  
c) The required temperature of the final mix. Under ideal conditions, batch plant recycling can blend up to 40 
per cent RAP with superheated fresh aggregate but 15 to 25 % is more typical.  
B.8.4 Batch mixers with a separate heating drum (parallel drum)  
B.8.4.1  In this system RAP is heated in a separate drum to about 130ºC. Fresh aggregate is separately 
heated to a high temperature and both materials are weighed to produce the required blend in the mixing unit. 
The final temperature of the blend is about 160º C. Preheating allows 50 % of RAP to be used in the blend, or 
even more if a consistent quality of output can be guaranteed.  
B.8.4.1  Preheating the RAP allows the production of a more uniform mix and better control of mix 
temperature and this is the preferred method of recycling. However, development continues and other types of 
plant specifically designed for recycling bituminous materials are becoming available.   
76 © EAC  2024  – All rights reserved  
 B.9 Blending with a soft bitumen  
B.9.1 General  
If a softer bitumen is added with the intention of bringing the blended bitumen within specification, the 
penetration (P) of the fresh bitumen can be calculated using equation given below:  
 
where,  
P is specified penetration of final blend.  
Pa is penetration of RAP bitumen.  
Pb is penetration of virgin bitumen.  
A is percentage of RAP bitumen in the final blend.  
B is percentage of virgin bitumen in the final blend. In this relationship the ‘blend’ is the total quantity of 
bitumen only, i.e. A+B = 100.  
B.9.2 Limitations of bitumen blending  
B.9.2.1  Bitumen in RAP recovered from a cracked asphalt will typically have a penetration of less than 15 
and satisfactory blending of the new and old bitumen cannot be expected. For example, to obtain a final 
penetration of 80 in a blend of 60 per cent of fresh bitumen and 40 per cent RAP bitumen in which the bitumen 
had hardened to a penetration of 15, would require the use of a fresh bitumen with a penetration of 
approximately 200. It is highly likely that some fresh aggregate would only be coated with the soft fresh 
bitumen and this could play a dominant role in mix performance with a risk of failure through plastic 
deformation.  
B.9.2.2 The most reliable method of obtaining a robust design with brittle asphalt is, therefore, to regard the 
bitumen in hardened RAP as being part of the aggregate structure and to use a 60/70 or 80/100 penetration 
grade bitumen, rather than a soft binder. This will prevent the possibility of plastic deformation in the new mix.  
B.9.2.3 In the case of RAP from areas of plastic deformation the effect of the softer existing bitumen can be 
taken into account during the mix design process. Testing of laboratory and plant mix asphalt to ensure that 
requirements for volumetric design and Marshall properties are met, will be required just as for new material 
and therefore the Marshall procedures should be followed. Additional information from a performance test 
such as the wheel tracking test will also be very helpful in this evaluation.  
B.9.2.4 The percentage of RAP that can be used will be controlled by the mixing temperature that can be 
achieved in the blended material. The temperature must be high enough to ensure that the fresh bitumen is at 
a suitable viscosity for mixing.  
 
 
 
 
  
© EAC  2024  – All rights reserved  77 
 Annex  C 
(normative)  
 
Mechanical performance evaluation of asphalt mix   
C.1 Axial Loading Slab Test  
The axial loading slab (ALS) test with the associated probabilistic analysis is recommended for high volume 
roads or applications where a level 3 rating is obtained for the rutting as a design objective.  
The test involves a small slab of asphalt compacted to the specified field density by means of a slab 
compactor or extracted from the field. The slab is placed in a steelmould, and on a synthetic support with a 
known stiffness. Three types of synthetic  materials (representing low,medium and high stiffness supports) can 
be selected to approximate the support conditions for the planned asphalt layer. The asphalt slab is 
repetitively loaded in the axial direction using a loading platen with a 100 mm diameter. The test is performed 
at three temperature levels.  
The ALS test data can be used to develop a regression equation which estimates permanent deformation as a 
function of number of load applications, temperature and stress level. This equation can be used to evaluate 
the mix rut potential at different loads and temperatures. Such an analysis can be performed using a computer 
spreadsheet. Ideally, the ALS data and regression equation should be used in a Monte Carlo simulation to 
estimate the development of permanent deformation under cumulative traffic. Computer programs such as the 
PRORAS (Probabilistic Rut Analysis System) computer program can be used to perform the Monte Carlo 
analysis. The ALS test and associated PRORAS analysis system were developed to simulate field conditions 
as closely as possible as far as rate of loading, stress state, temperature and traffic load distribution is 
concerned. The probabilistic analysis takes into account the variation in loading due to random variations in 
temperature and load as well as traffic wander. In addition, both the daily and monthly temperature variation is 
taken into account in the analysis. The PRORAS system therefore provides a quantified estimate of actual 
rutting performance. However, because the laboratory test is accelerated and scaled down, the results still 
need to be interpreted in a somewhat relative manner, and comparison with similar mixes tested in the past is 
recommended.  
C.2  Wheel Tracking Tests  
Although wheel tracking tests appear to be well correlated with rutting in the field, there are at present no 
quantified relationships to link wheel tracking test results to rutting in the field under variable traffic loading and 
environmental conditions. For this reason,wheel tracking tests cannot be used to provide a quantitative 
estimate of rutting in the field. The test does, however, provide a reliable estimate of the rutting potential of a 
mix relative to similar mixes that have been tested in the past. Wheel tracking tests are particularly 
recommended for the evaluation of rutting performance on stone skeleton mixes, or mixes which involve 
modified binders, as experience has shown that these mix types cannot be properly evaluated by means of 
conventional test methods such as the dynamic creep and ITS. Currently, two types of wheel tracking devices 
are used for rutting evaluation .  
C.2.1  Model Mobile Load Simulator (Mk.3 MMLS)  
The MMLS is operated and distributed by the University of Stellenbosh. The MMLS differs from most wheel 
tracking devices in that trafficking is achieved with 4 bogies instead of a single wheel Figure C.1 MMLS  Mk.3  
(see Figure 6.1). Each bogie consists of a single 300 mm diameter wheel, with a maximum inflation pressure 
of 800 kPa and a maximum load of 2,7 kN.   
78 © EAC  2024  – All rights reserved  
 A major advantage of the MMLS, as compared to other wheel tracking devices, is its high rate of trafficking: 
more than 10,000 simulated axle loads per hour can be applied. Another significant dvantage of the MMLS is 
that it can be transported to field sites for the testing of full scale asphalt pavements. The weight of the 
Mk.3MMLSis approximately 800 kg (including deadweight ne eded for 2.4 kN load per  
wheel
  
Figure C.1 — MMLS Mk.3  
C.2.2  Transportek Wheel Tracking Device  
The Transportek wheel tracking device was developed to assess the rutting susceptibility of  asphalt mixes and 
also to enable the measurement of strains under moving wheel loads. The  device is used both to compact and 
test asphalt slabs. A segment of a steel wheel roller is used  for compaction, while a solid rubber wheel (400 
mm diameter, 100 mm wide) is used for rutting  evaluation. Slab dimensions can be 280 by 320 mm or 350 by 
660 mm, with the latter slab size  being used most often for rutting evaluation. Figure C.2 shows the 
compaction of a slab before  testing. Figure C.3 shows the wheel tracking device in operation, and Figure 6.4 
shows a  transverse section of a slab after wheel track testing.   
© EAC  2024  – All rights reserved  79 
 
 
Figure C.2 — Compaction of Slab for Wheel Tracking Test  
 
Figure   C.3 —  Wheel Track Testing   
80 © EAC  2024  – All rights reserved  
 
 
Figure   C.4 —  Deformation of Slab after a Wheel Tracking Test  
Typically, the level of compaction aimed for in the wheel tracking test will be the same as that  which is 
specified for field compaction. The level of compaction achieved during the compaction  process can be 
accurately controlled with the Transportek wheel tracking device. However, the  actual density achieved is 
dependent on the accuracy and applicability of the MTRD and mass  calculations used to determine the 
amount of material that should be used to compact a slab. Itis therefore recommended that more than one 
slab be compacted for the monitoring of the voids and  density that is achieved after slab compaction. If the 
wheel tracking tests are carried out at the  design stage, it is imperative that the MTRD of the design mix and 
that of the eventual plant mix  be compared to ensure that the rut performance of the constructed mix  is 
comparable to that obtained  during wheel tracking tests. Ideally, the plant mix should also be tested in the 
wheel tracking  device to ensure that the properties of the design mix are the same as those of the plant mix . 
Because wheel tracking test results are evaluated in a relative manner, data post -processing is  minimal and 
therefore the cost of testing is significantly lower than that of the axial loading slab  test. The test is therefore 
recommended for applications where rutting has a medium to high  importance as a design objective, but 
which do not j ustify the higher cost associated with a  quantitative estimate of rutting performance.  
The standard test protocol for the Transportek wheel tracking device is to performthe test at 60°C  and at a 
load of 600 kg (which equates to a contact pressure of approximately 900 kPa). For this  test protocol, the 
limits shown in Table C.1 can be  used as a tentative guideline to the evaluation  of rutting performance.   
© EAC  2024  – All rights reserved  81 
 Table  C.1 —  Interim guidelines for the interpretation of wheel tracking results  
 
C.4  Recommended Test Procedure for Rutting Evaluation  
The three approaches to rutting evaluation provides designers with a flexible and cost effective approach to 
rutting evaluation which can be adapted to suit most design situations. Designers should become familiar with 
the advantages and disadvantages of the different rut evaluation procedures so that the most cost effective 
and appropriate evaluation method can be selected for a particular design situation. Table C.2 provides a 
recommended test selection matrix for different design situations.  
Table  C.2 —  Recommended rut evaluation tests  
 
C.5 Performance testing for fatigue evaluation of asphalt wearing courses  
Apart fromthe four point bending beam fatigue test, very fewlaboratory tests provide a consistent evaluation of 
the fatigue performance of wearing courses. As four point bending beam fatigue tests are relatively expensive 
to perform, they are therefore mostly used for applications on high trafficked roads. For the design of wearing 
courses on pavements with low traffic volumes, where expensive performance tests are not always warranted, 
the indirect tensile strength (ITS) test parameters, coupled with the evaluation of binder durability, can be used 
to determine whether there is a risk of premature fatigue failure and whether four point bending beam fatigue 
tests are warranted. Table C.3 provides guidelines for the interpretation of ITS data (measured at 25°C) for  
the fatigue evaluation of asphalt wearing courses.   
82 © EAC  2024  – All rights reserved  
 Table  C.3 —  Guidelines for the Interpretation of ITSresults for fatigue performance evaluation  
 
Note: The above recommendation is only valid for relatively thin wearing courses. For asphalt base courses, 
the ranking would be the opposite of that shown above, where the designer should strive to achieve high ITS 
values.  
Wearing coursemixes for which Table C.3 suggests  a poor fatigue performance should be further  evaluated 
bymeans of a detailed binder evaluation and an evaluation of the spatial composition.  In such instances, 
designersmayalso consider performing bending beam fatigue tests to validate  the indication given by the less 
exact ITS test.  
C.5 Four Point Bending Beam Test  
Figure C.5 shows a schematic representation of the four point bending beam fatigue test. During the test, 
rectangular beam specimens are subjected to a repeated load. Tests are normally performed at 5°C, using a 
sinusoidal load with a frequency of 10 Hz. Two modes of loading can be applied. In the constant strain mode 
of loading, the strain at the bottom of the beam is preselected and kept constant for the duration of the test. 
Failure is defined as the point at which the stiffness of the beam is reduced to 50 per cent of its initial stiffness. 
In the constant stress mode of loading, the load is kept constant and the strain is allowed to vary. The test is 
terminated when the beam fails (i.e. cracks). The constant strain test is normally used for thin (< 70 mm) 
surfacing applications, the constant stress mode being used for the evaluation of thick (>70mm) asphalt 
bases.  
  
© EAC  2024  – All rights reserved  83 
 Figure C.5 — Compacted Sample using Rolling Wheel Compaction  
 
Figure C. 6 — Compacted Sample using Rolling Wheel Compaction  
Owing to the small strains induced during testing, as well as the dynamic nature of the loading,  bending  beam 
tests require sophisticated loading and data acquisition equipment. For this reason,  bending beam fatigue 
tests are normally performed in specialist laboratories.  
Bending beam samples are cut from a larger slab of material which is normally prepared using  a rolling wheel 
compactor (see Figure 7.2) with the compaction effort and quantity of material  being controlled so as to allow 
the design voids content to be attained. Approximate dimensions  of beam samples are: 400 mm long x 60 mm 
wide x 50 mm high. Samples are preconditioned  at the testing temperature by placing them in an oven set to 
the test temperature, several hours  before they are tested.  
C.5.1  Interpretation of Results  
Table C.4 provides guidelines for the interpretation of four-point  bending beam fatigue results. It  should be 
noted that the limits shown in Table C.4 pertain to constant strain tests performed at  5°C and at a loading rate 
of 10 Hz. In these tests, the point of failure was defined as the number  of load repetitions at which the original 
beam stiffness had decreased by 50 per cent. The  repetitions to failure referred to in Table C.4 cannot 
therefore be interpreted as the number of  axles before the onset of fatigue cracking.   
84 © EAC  2024  – All rights reserved  
 Table  C.4 —  Guidelines for the interpretation  of Bending Beam fatigue data (Constant stain)  
 
In an HMA design, Table C.4 can be used as follows:  
Step 1:  The designer should calculate the expected strain level for the given design situation.  Conventional 
multilayer elastic models can be used for this calculation. The calculated  strain level is used to determine the 
approximate working strain regime for the design  situation, as defined in Table C.4. 
Step 2:  Perform four-point  bending beam tests at a strain level which falls inside the strain range  shown in 
Table C.4 for the appropriate strain regime. For, example, for the low strain  regime, tests can be performed at 
220 microstrain. It is recommended that a minimum  of 3 beams be tested at the appropriate strain regime.  
Step 3:  Use the bending beam test results together with the ranges shown in Table C.4 to evaluate the 
relative fatigue performance of the design mix. Use Table C.5 to estimate  the design fatigue life of the design 
mix. 
As can be seen from Table C.5, the fatigue life increases dramatically if the working strain limit is below 
approximately 230 microstrain. For designs for high traffic volumes, it is therefore strongly advised that the 
recommended support conditions be observed to ensure that the mix will operate in the low strain regime.  
Mixes that operate in the low strain regime are likely to fail because of climatic influences (embrittlement due 
to oxidation etc.) rather than traffic loading. The fatigue life is thus likely to be  coupled to time rather than to 
the number of load applications. Experience indicates that a typical  effective fatigue life of thin asphalt mixes 
is between 8 and 12 years. Mixes with a good bending  beam fatigue performance can be expected to last to 
the upper limit of this range,  while those  with a poor fatigue performance may last only to the lower limit.  
Designers should be aware that  mixes that operate in the  medium to high strain regimes are very  sensitive to 
variations in load and support conditions. It is recommended that mixes which are  designed for these 
conditions, and which require a low risk of failure, be improved either by  modification with bitumen rubber, or 
by increasing the binder content to ensure greater flexibility  and durability.  
Table  C.5 —  Guidelines for fatigue life estimation (Constant stain)   
 
Quality Characteristic  Traffic Category  
 heavy  medium  light 
Air voids content (%)  4.0  4.0  4.0 
Voids in mineral aggregate (% min.)  
4.75-mm grading  17.0 17.0 17.0 
9.5-mm grading  15.0 15.0 15.0  
© EAC  2024  – All rights reserved  85 
 12.5-mm grading  14.0 14.0 14.0 
19-mm grading  13.0 13.0 13.0 
Stabilometer value (min.)  
12.5mm and 19 mm gradings  37 35 32 
Swell  less than 0.762 mm (0.030 in.)  
Notes:  
1. Although not a routine part of this design method,  an effort is made to provide a minimum percent of  air voids of 
approximately 4 percent.  
2. All criteria, and not stability value alone, must be  considered in designing an asphalt paving mix.  
3. Hot mix asphalt bases that do not meet these criteria  when tested at 60°C (140°F) are satisfactory if they  meet 
the criteria when tested at 38°C (100°F) and  are placed at 100 mm (4 in.) or more below the surface. This 
recommendation applies only to regions  having a range of climatic conditions similar to those  prevailing throughout 
most of the United States. A  different lower test temperature may be considered  in regions having more extreme 
climatic conditions.  
4. Traffic classifications:    
Light: Traffic conditions resulting in a Design  EAL <104 
 Medium: Traffic conditions resulting in a Design  EAL between 104 and 106 
 Heavy: Traffic conditions resulting in a Design  EAL >106 
 
 
As determined by bending beam fatigue tests and through Table 7.2.  
** MESA = Millions of Equivalent Standard Axles.  
  
86 © EAC  2024  – All rights reserved  
 C.6  Fatigue Evaluation of HMA Bases  
Fatigue testing for HMA bases is normally performed in the constant stress mode of testing. To  date, no 
constant stress tests using modern testing equipment have been performed in South  Africa. Consequently 
guidelines for the interpretation of constant stress test results cannot be  provided at this stage. Until more 
experience is gained in the interpretation of constant stress  data, it is recommended that HMA base mixes be 
tested in the constant strain mode, at a strain  level of 220 microstrain. The fatigue performance of the mix can 
then be evaluated in a relative  manner using Table C.4. Although this approach does not provide a reliable 
estimate of mix  fatigue life, it may alert designers if the mix is likely to have unusually low fatigue 
properties. C.7 Indirect Tensile Strength (ITS) Test  
C.7.1  Test Description  
The indirect tensile strength (ITS) test is commonly used to evaluate the cohesive strength of  asphalt mixes. 
This property can be used to evaluate tensile strength (related to toughness and  durability) and is also an 
important component of rutting resistance in the medium temperature  range. The test does not require 
sophisticated testing equipment and can be performed on  briquettes manufactured in the laboratory, as well 
as on cores obtained from the field.  
In the ITS test the sample is loaded on its diametral axis, as illustrated in Figure C.7 shows a sample 
positioned in the testing frame. The widths of the loading strips are prescribed  by ASTM D41236 and are 13 
mm for a 102 mm diameter specimen and 19 mm for a 152 mm  diameter specimen.  During testing, the 
sample is loaded at a fixed rate of loading (a rate of 50 mm per minute is  typically used) until a significant loss 
in applied load is noted. The peak load is used to calculated  the indirect tensile strength. The formula for 
calculation of the ITS (in kPa) is as follows:  
 
Where:  
Pult = Ultimate applied load, in kN;  
t = Thickness of the specimen, in mm, and  
D = Diameter of the specimen, in mm.  
 
  
© EAC  2024  – All rights reserved  87 
 
 
Figure   C.7 — Sample positioned for ITS testing  
Figure 8.2  
ASTM  D 41236 prescribes sample dimensions and preparation for the indirect tensile strength and resilient 
modulus test. Specimens for the ITS test can be prepared using laboratory compaction techniques such as 
the Marshall or Gyratory compaction devices. Specimens can also be obtained from the field bymeans of 
coring. Specimens should have a thickness of at least 51mm and a diameter of 102 mm or larger for 
aggregates of up to 25 mm maximum size. For aggregates with a maximum size of between 25 and 38 mm, 
the minimum thickness and diameter should be increased to 76 mm and 152 mm, respectively. Care should 
be taken to ensure that cores have smooth parallel surfaces.  
C.7.2  Interpretation of Results  
The indirect tensile strength of asphalt mixes provides an indication of the cohesive strength of asphalt mixes 
and is therefore strongly influenced by the characteristics of the binder. As an indicator ofmix cohesion, ITS 
values provide an overall indication of mix stability in the low to midtemperature range (10 to 40°C) and can 
be expected to be related to rutting resistance as well as durability and stripping potential.  
The minimum value for ITS in South Africa is 800 kPa. However, designers should be aware that limited field 
studies have suggested that rutting potential tends to increase for ITS values below approximately 1000 kPa. 
At the same time, ITS values in excess of 1700 kPa may indicate a tendency to brittleness and low flexibility. 
An ideal range for ITS values would seem to be between 1100 and 1500 kPa. Table C.6 shows some 
statistical parameters that are typically associated with ITS values. The comments in Table C.6 refer to 
relatively thin asphalt wearing courses.  
Table  C.6 —  Typical ITS Results   
Statistical Parameter  Typical ITS results (in  
kPa) at 25°C  Comments/Interpretation**   
95th percentile value  1650  Value s above this may be  
indicative of brittleness or poor  
flexibility of wearing courses  
75th Percentile Value  1200  Values close to this are indicative  
of good rutting performance   
88 © EAC  2024  – All rights reserved  
 Average  1100  None  
25th Percentile Value  900  Values below this may be  
indicative of poor rutting or  
stripping performance  
* Based on 33 observations.  
** SMA mixes and mixes manufactured with some polymer -modified or bitumen -rubber  
binders may have low ITS values and still exhibit good performance. The comments and  
interpretations may therefore not be applicable for such mixes.  
 
C.8 Constant Head Permeability Test  
C.8.1  Compaction of Briquettes  
Combine the aggregates in the correct proportions to meet the final design grading. Add the  required amount 
of binder to the aggregate after heating the ingredients to the correct  temperature as defined in Method C2 of 
TMH1 -1986. Mix thoroughly. The mixture is compacted  by applying 70 blows with the Marshall hammer, 35 
blows to each side of the specimen. Remove  the specimen from the mould by means of an extraction jack 
after cooling sufficiently. Measure  the density of the briquette as described in Method C3 and C4 of TMH1 -
1986.  
C.8.2  Preparation for permeability test  
Apply a thin layer of silicone sealant around the perimeter of the compacted briquette. Leave to  dry, then 
place in a steel casting mould with 122 -125 mm internal diameter and 93 mm high which  results in a 12.5 mm 
wide void around the sample (Figure C.8). Seal the void between the sample  and the inside of the mould 
using Plaster of Paris taking care not to contaminate the upper and  lower surfaces of the briquette with the 
Plaster of Paris. Allow the Plaster of Paris to dry and apply  silicone sealant to the upper and lower exposed 
edges of Plaster of Paris between the mould and  the sample. After the silicone sealant has cured, steel cover 
plates fitted with an “O” ring to form  a watertight seal on the top and bottom edges of the mould, and also fitted 
with two ball valves,  one for water entry and one to act as a bleed valve, are bolted on to the mould. The 
bottom ball  valve of the mould is connected to a constant head permeameter with a water head of 1.0 m and  
readings of the volume of water coming out of the mould are taken at 5 -minute intervals. The test  is stopped 
when the volumes measured for each 5 -minute interval are reasonably constant.  
  
© EAC  2024  – All rights reserved  89 
 
 
Figure   C.8 — Typical Set -Up for the Laboratory Water Permeability Test  
 
The permeability (expressed in per square metre per hour) of the asphalt sample is determined  by using the 
following formula:  
Permeability = Q/A where Q = flow in /h and A = area in m2  
C.9  Moisture Sensitivity (Modified Lottman Test)  
C.9.1  Test Description  
The Modified Lottman test for measurement of moisture sensitivity relies on indirect tensile  strengths 
measurements taken before and after conditioning by freeze -thaw cycles. The test is  performed according to 
the ASTM D48676 protocol (note: an alternative method is provided in  AASHTO 2838 , but ASTM D4867 is 
preferred). In the test, six samples are compacted to within  a void content range of 6 to 8 per cent (or to the 
field voids) and partially saturated with water  (saturation limit of between 55 and 80 per cent). Three of the six 
samples are frozen for at least  15 hours and subsequently immersed for 24 hours in a hot bath set at 60°C 
(i.e. “conditioned”  samples). All six samples are then brought to a constant temperature and their indirect 
tensile  strengths determined. The ratio of the indirect tensile strengths of the conditioned  and unconditioned 
samples is referred to as the tensile strength ratio (TSR).  
C.9.2  Interpretation of Results  
For routine mix design purposes, a minimum TSR of 0.7 is usually specified. For mixes in high  rainfall areas 
and high traffic applications, a minimum TSR of 0.8 is recommended. Table C.7 provides TSR criteria based 
on the permeability of the mix and the climate in which the mix will  operate.   
90 © EAC  2024  – All rights reserved  
 Table C.7  —  TSR criteria based on mix permeability and climate  
 
C.10   Compressive strength of hot mi asphalt  
The compressive strength of hot mix asphalt can be determined by the method given in AASHTO, T 167 -10  
© EAC  2024  – All rights reserved  91 
 Bibliography  
[1] MS-2, Asphalt Mix Design Methods  
[2] Overseas Road Note 19 , A guide to the design of hot mix asphalt in tropical and sub -tropical countries  
[2] Interim guidelines for the design of hot -mix asphalt in south Africa  
 DEAS 1207 : 2024    
 
© EAC 2024 – All rights reserved