STUDY ON MIXTURE DESIGN AND MECHANICAL PERFORMANCE OF
WARM MIX ASPHALT CONTAINING RECLAIMED ASPHALT PAVEMENTNagaoka University of Technology

Mezatio Zebaze Mickel-Sadrack
19504081
Highway Engineering

1. INTRODUCTION
Nowadays due to the need of a low cost, good quality and eco-friendly asphalt pavement, many
researches have been done on recycling of asphalt at high and medium temperatures. In other words the useof reclaimed asphalt pavement (RAP) has been increasing during the past years. RAP is a recycled
aggregate which is produced by crushing old asphalt concrete and screening the particle size. Generally
RAP in high proportions is often incorporated in new mixtures with the help of rejuvenator (T-RIBAIBU)
which restore the original properties of aged (oxidized) asphalt binder in RAP.
Based on this perspective of environmental protection, warm mix asphalt (WMA) has been used in somedeveloped countries, especially in European countries. WMA is hot mix asphalt (HMA) mixture that is
produced at reduced temperatures of about 20 ℃ to 40 ℃ lower than that of conventional HMA mixtures.
WMA has some advantages, such as less CO2 emissions, less energy consumption, less fumes, less bitumen
ageing, and less wear on machines and resources.
When WMA is produced at HMA facilities, an additive is required to reduce viscosity of the asphalt
binder. “Sasobit” is a typical additive of WMA and is a fine crystalline long chain aliphatic hydrocarbon.
It is completely soluble in asphalt at 115 ℃. When it is added to asphalt, it helps to reduce the production
and compaction temperatures. Sasobit is manufactured from natural gas using the Fisher Tropsch process ofpolymerization.
Depending on countries and states in Europe and America, RAP content in WMA mixtures are limited toabout 30% and 20% respectively. In Japan many continue to use the conventional method of HMA,
because little information is made available to recycle asphalt using the WMA approach which may offer
better advantages than the conventional one. The objective of this research therefore was to produce WMA
with Sasobit by adding RAP of different proportions to the Japanese dense-graded asphalt concrete of 20mm maximum particle size, evaluate its performance and compare this to that of its equivalent HMA.HMA.
2. METHODOLOGY
Investigation of the research was done as shown on Table 1 below.

Table 1: Research investigations
Selectedgradation
andRAP%
content

Hot Mix

Warm Mix (Sasobit)

Prd: 154-162 ℃

Prd: 129-137 ℃

Com: 142-147 ℃

Com: 117-122 ℃

Binder type

Binder type0%

Grade 60/80

Grade 60/80+ Sasobit

10%

Grade 60/80

Grade 60/80+ Sasobit

Grade 60/80+ 20% TRIBAIBU
Grade 60/80+ 20% TRIBAIBU
Grade 60/80+ 20% TRIBAIBU
Grade 60/80+ 20% TRIBAIBU
Grade 60/80+ 20% TRIBAIBU

Grade 60/80+ Sasobit+ 20% TRIBAIBUGrade 60/80+ Sasobit+ 20% TRIBAIBU
Grade 60/80+ Sasobit+ 20% TRIBAIBU
Grade 60/80+ Sasobit+ 20% TRIBAIBU
Grade 60/80+ Sasobit+ 20% TRIBAIBU

20%30%
40%
50%
60%

Performance test
Wheel
trackingtest

Directtensiletest

Observations andAnalysis

12.1 Selected gradation size
Excel sheet was used to calculate the percentage of RAP content of each mixture.

Table 2: Selected gradation size
Sieve size（mm）Percentage PassedLower
limit
particlesize

26.5 10019.09513.2754.75
452.36350.6
180.3
100.1560.075 4

Upper
limit
particlesize

10010090
65
50
30
21168

Planned particle
size

RAP %
0%

10%

20%

30%

40%

50%

60%

100.0
99.8
83.1
55.2
38.8
25.4
12.6
8.1
6.1

100.0
99.8
84.1
54.4
41.9
28.7
14.9
8.2
6.0

100.0
99.8
83.1
54.4
41.5
28.6
15.1
8.0
5.7

100.0
99.8
82.6
55.0
41.8
29.0
15.3
7.9
5.5

100.0
99.8
82.5
55.0
41.4
29.1
15.7
8.1
5.6

100.0
99.8
82.6
56.7
41.2
28.4
15.0
7.6
5.1

100.0
99.8
84.0
55.3
42.2
29.5
15.9
7.8
5.1

100.0
99.8
82.6
55.2
42.2
28.6
14.4
7.9
5.9

2.2 Determine the Designed asphalt content
The designed asphalt content was obtained to be 5.5% of the total mixture, using the standard procedure
recommended by NAPA. At each RAP content the old asphalt presence in RAP, the percentage of Sasobit
added (3% by weight of OAC obtained), and T-RIBAIBU added (20% by weight of old asphalt present inRAP) were taken considerations.
3. EXPERIMENTS AND RESULTS ANALYSIS
After producing the HMA and WMA mixtures at temperatures as shown in table 1 above theperformance test were conducted and results obtained as follows;
3.1 Wheel tracking (WT) test
Wheel tracking test evaluate the permanent deformation of asphalt concrete (rutting resistance). It was
carried out in the following conditions

Table 3: Condition for WT test
Items
Condition
Dimensions
300x300x50
Number of compactor rolling (time)
15
Temperature (°c)
60Curing time (min)360
Test time (min)60
Number of round trips (time)
1260
Wheel load (N)686
Wheel material
Solid rubber
Fig 1: Wheel tracking test results
From these results, the DS values of both HMA and WMA mixtures increased as RAP content increased. In
general the HMA mixtures had higher rutting resistance than WMA mixtures. However there wereexception at 30%and 40% RAP content for WMA mixtures which performed better than HMA mixtures.
3.2 Direct tensile test
The direct tensile test shows the cracking resistance of asphalt concrete. This test evaluates thedisplacement of the specimen when it is subjected to force in the axial direction. The stress and strain of thesample are also obtained from this test.

Table 4: Condition for DT test
Item

Condition

Specimen Dimensions (mm)Test temperature (°c)
Displacement ratio (mm/min)
Curing time

40x40x240
20
15hours or more2

From the direct tensile test results, the strain atfailure shows higher cracking resistance for
HMA than WMA mixtures at all RAP content.
Also it was noticed that as the RAP content
increased the cracking resistance（strain atfailure）of both mixtures decreases.

Fig 2: Direct tensile test results

Table 5: General Performance observation
Hot Mix

Warm Mix (Sasobit)

Prd: 154-162 ℃

Prd: 129-137 ℃

Com: 142-147 ℃

Com: 117-122 ℃

Binder type0%

Selected
gradation
andRAP%
content

Performance test

Binder typeWheel
trackingtest

Directtensiletest

Grade 60/80

Grade 60/80+ Sasobit

HMA

HMA

10%

Grade 60/80

Grade 60/80+ Sasobit

HMA

HMA

20%

Grade 60/80+ 20% T-RIBAIBU

Grade 60/80+ Sasobit+ 20% T-RIBAIBU

HMA

HMA

30%

Grade 60/80+ 20% T-RIBAIBU

Grade 60/80+ Sasobit+ 20% T-RIBAIBU

WMA

HMA

40%

Grade 60/80+ 20% T-RIBAIBU

Grade 60/80+ Sasobit+ 20% T-RIBAIBU

WMA

HMA

50%

Grade 60/80+ 20% T-RIBAIBU

Grade 60/80+ Sasobit+ 20% T-RIBAIBU

HMA

HMA

60%

Grade 60/80+ 20% T-RIBAIBU

Grade 60/80+ Sasobit+ 20% T-RIBAIBU

HMA

WMA

Fig 3: Mixtures binder contents3

3.3 Analysis of mixtures binder physical properties

Table 6: Test performed to determine the mixtures binder physical properties
Properties
determined
Temperaturesusceptibility

TestStandards used

Penetration of bituminous materials

ASTM D5

Softening point of bitumen

ASTM D36

Hardness

Viscosity determinations of unfilledasphalts using the brookfieldthermosel apparatus

ASTM D4402-87

Fluidity

ASTM D113Tenacity

Force ductility of bituminous
materials

Fig 4: Results of mixtures binder physical properties
4. CONCLUSION
In a nutshell the main findings to this research were as follows
1) Up to 30% to 40% RAP content in the Japanese dense grade of 20 mm maximum size could bemixed with WMA mixture including Sasobit.
2) The rutting resistance and the cracking resistance of HMA mixture were generally higher than WMA
mixtures due to the decrease in binder consistency.
3) Sasobit modified binder by increased the softening point and tenacity, while the penetration andviscosity grade decreased leading to increase in temperature susceptibility and stiffness of WMA binder.

4