IRF GLOBAL R2T Conference
November 7-9, 2018 – Las Vegas, NV USA
PAPER TITLE
TRACK
AUTHOR(Capitalize Family Name)
Katsura ENDO
CO-AUTHOR(S)(Capitalize Family Name

Development of the Multipurpose Chemical Additive for Warm Mix Asphalt
2- Innovative Materials and Technology
2.2 Asphalt Concrete
POSITION
Chief Researcher

Technical Research Institute
The Nippon Road Co., Ltd.

POSITION

Tadashi TSUNEMATSU

Senior Researcher

Akane IKEDA

Researcher

E-MAIL(for correspondence)

ORGANIZATIONCOUNTRYJapan

ORGANIZATION
Technical Research Institute
The Nippon Road Co., Ltd.
Technical Research Institute
The Nippon Road Co., Ltd.

COUNTRY
Japan
Japan

katsura.endou@nipponroad.co.jp

KEYWORDS:
Warm mix asphalt, Multipurpose chemical additive, RAP

ABSTRACT:
A multipurpose chemical additive is newly developed for Warm Mix Asphalt. This new additive enables producing andapplying at a temperature around 30 to 50 degrees in Celsius lower than an equivalent Hot Mix Asphalt. General dosage
is around 0.5 to 1.0% by weight of asphalt, i.e. only 250 to 500g by weight of 1,000kg mix in case of 5% of asphalt
content. Low dosage means cost effective even supposing that the unit price of the additive is a little high. This additiveis effective for not only straight-run asphalt, but also any polymer modified asphalt and specific decoloring asphalt
which are commercially available in Japan. And this additive is effective for any graded mixtures and for both virginand RAP used mixtures. Furthermore, the thermal oxidative aging using this additive is evaluated in two ways. First,
dense-graded mixtures with straight-run asphalt and this additive are compacted after 72-hour heated at 160oC. Second,dense-graded mixtures with 50% of RAP and this additive are compacted after 24-hour silo storage without anti-oxidant.
Few changes in mixture properties are found in both cases. These effects are verified through many paving projects inJapan. For example, porous asphalt pavement with polymer modified asphalt is well paved under -1 degrees in Celsius
in daily average temperature with light snow. These pavements are still in good condition compared to adjacent general
pavements.

Development of the Multipurpose Chemical Additive
for Warm Mix Asphalt
Dr. Katsura Endo 1
Tadashi Tsunematsu 1
Akane Ikeda 1
1 The Nippon Road Co., Ltd., Tokyo, JAPANkatsura.endou@nipponroad.co.jp

1 INTRODUCTION
Conserving the global environment has been one of the major problems for a long time. Act on
promotion of procurement of Eco-friendly goods and services by the State and other entities (Green Purchasing
Law) has been in effect since May 31, 2000 in Japan and business operators and citizens in Japan are toendeavor to select Eco-friendly goods to the extent possible when purchasing or leasing goods and/or receiving
the provision of services. The designated procurement items list which includes Eco-friendly goods is
documented and items on the list are promoted to be used.

Paving works are same. For example, hot mix asphalt (HMA) with reclaimed asphalt pavement(RAP) has been on the list since March 2004 and warm mix asphalt (WMA) without RAP has been on the list
since February 2010. WMA technologies has been studied since early 1990s in Japan and some commercialized
technologies were developed. Most were oil-based technologies and few were chemical foaming technologies.

The Nippon Road had also two technologies for WMA but these had some disadvantages comparing
to other products. The first is that these depend on asphalt, i.e. the oil-based technology is only for straight-run(non-modified) asphalt and the chemical foaming technology is only for modified asphalt. The second is that
dosage depends on volume of newly adding asphalt in case of WMA with RAP. And the third is that total binder
tends to increase in case of HMA and/or WMA with RAP because rejuvenator is required.

The authors have been developed a new multipurpose chemical additive for the use of WMA andovercame above disadvantages. This paper describes the outline of the additive, some examples of mix
properties with this additive, some case studies and so forth.

2 BACKGROUND OF NEEDS FOR A MULTIPURPOSE ADDITIVE

2.1 Trends of HMA Production in Japan

Publish investment has been decreased and decreased since Japan's overheated stock and real estate1

markets had also been collapsed in early 1990s. Concerns about improvement of infrastructure including roadbuildings and pavement repairs declined at the same time. Figure 1 shows the amount of HMA production from1984 to 2016 (Japan Asphalt Mixture Association 2018). Maximum total amount was about 80 million tons in
1992 and it falls to about one-half in 2016 according to the latest statistics.

On the other hand, HMA with RAP has been gradually increased ever since then. As a heavy blackline in this figure shows, percentage of HMA with RAP was about 15% in 1992, it reached to 50% in 1998 andis about 77% in 2016.

90
80

100

90
80

70

70

60

60

50

50

40

40

30

30

20

20

10

10

0

0

Percentage of HMA with RAP(% )With RAP
Without RAP
Percentage with RAP

1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016

Amount of HMA Production(million ton)100

Figure 1. Amount of HMA Production in Japan (Japan Asphalt Mixture Association 2018)
As noted above, WMA without RAP was on the designated procurement items list in 2000. Virgin
HMA was no longer main product at that time. WMA without RAP is one of the products of virgin HMA. It
was said that percentage of WMA was under 1% of all HMA products.

2.2 Trends of Polymer Modified Asphalt in Japan

Japan has currently more than 1.2 million km road network. As shown in Figure 2, maximum numberof large vehicles was about 21 million in 1991. Since then, severe rutting has been one of the major sources ofconcern for not only road authorities but also road users. Using polymer modified asphalt (PMA) is one of thesolutions for that. PMA type I includes rubber as the modifier and PMA type II includes a kind of resin as themodifier. Both have become a general product in 1988. Since then totally seven PMA have been developed andused in Japan according to theirs purpose and application, as shown in Table 1. The amount of production of
HMA using PMA was about 380,000 tons. It is about 11% of all HMA. And the amount was 480,000 tons andabout 16% of all HMA, according to the latest statistics (Japan Modified Asphalt Association 2015). PMA
usually used for virgin HMA or WMA. As already shown in Figure 1, about 23% of total production is virgin

2

HMA and this means that PMA is used for about 70% (=16/23) of virgin HMA.

From these, any additives for the use of HMA or WMA using virgin asphalt only was not needed.
And development goal should be one additive for the use of HMA or WMA using PMA and HMA or WMA
with RAP.

Number of Vehicles (million)

90

80

All Vehicles

70

Large Vehicles

60

50
40

30
20
10
1966
1968
1970
1972
1974
1976
1978
1980
1982
1984
1986
1988
1990
1992
1994
1996
1998
2000
2002
2004
2006
2008
2010
2012
2014
2016

0

Figure 2. Number of Vehicles in Japan (Automobile Inspection & Registration Information
Association 2017)
Table 1. Types of PMA and Its Application in Japan (Japan Modified Asphalt Association 2006)
PurposeApplication

Type I

Type II

Type III Type III-W Type III-WF Type H Type H-F

General road Very good
Very good
Heavy duty
road
Very good
Good
Good
Heavy dutyroad andcrossing
Very good Very good
Good
Good
Good
Wearing
Cold andsnowy area
Good
Good
Very good
Water
Concretesensitivity
deck bridge
Good
Good
Very good
Flexibility
Steel
deck
bridgePermeability Surface
Available mixture
Dense-graded, fine-graded, coarse-graded mixtures
Permanent
deformation

Very good Very good
Good

Good

Very good Very good

Porous asphalt
mixture2.3 Study about Another Option

The authors understand that foaming technologies for WMA are mainly used in the United States(NAPA 2007). The Nippon Road imported one of the foaming technologies from USA about eight years ago

3and made some tries to produce WMA with the foaming process. Finally, the Nippon Road decided that thefoaming technology is not applicable as WMA in Japan because it was hard to decrease producing and paving
temperature about 30 degree in Celsius comparing to generally produced HMA and asphalt pavement laid using
this technology ‘moved’ slightly after opened to traffic. This phenomenon sometimes led to rutting in earlystage.

3 BRIEF DESCRIPTION OF DEVELOPED CHEMICAL ADDITIVE

Figure 3 shows developed chemical additive. It is white and solid and flake form at ambient
temperature and melting point is 53 degree in Celsius. This additive is easy to dissolve in any asphalt, so it is
not necessary to extend mixing time when producing WMA. This additive has high-temperature stability, thenit is applicable for silo storage and long-distance hauling of produced mixtures. pH is 7.1, i.e. this is neutral.
No need to care about environmental affairs due to acidity and alkalinity, if this additive leaks from pavement
after service.

Figure 3. Developed Chemical Additive
Actual dosage depends upon mixtures and asphalt contents, and general dosage is 0.5% to 1.0% by
weight of asphalt. So only 250g to 500g addition is required to produce 1,000 kg of WMA with this additive
when asphalt volume is 5.0%.

Figure 5 shows effects to asphalt penetration according to dosage of this additive and Figure 6 shows
effects to asphalt softening point. In these figures, 0.0% of dosage mean the original values of asphalt used.
Penetrations are slightly increase with dosage of additive. But it seems that the impacts are limited when dosage
is under 1.0%. Softening points show almost same values of the original asphalts. Thus this additive is not a
modifier of asphalt.

4Penetration (1/10mm)

100
90
80

70

Pen. 80-10060Pen. 60-80

PMA Type II

50

PMA Type H

40

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

Dosage (% by weight of Asphalt)

Softening Point (Degree C)

Figure 4. Effect to Penetration of Asphalt

120Pen. 60-80

110

Pen.80-100

100

PMA Type II

90

PMA Type H

80
70
60
50
40

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

Dosage (% by weight of Asphalt)

Figure 5. Effect to Softening Point of Asphalt
4 CASE STUDIES

4.1 Mix Design of Dense-graded Asphalt Mixture
The Marshall mixture design method is still adopted in Japan. Figure 6 shows the comparison of air
voids of cylindrical specimen. Selected aggregates measured to meet dense-graded mixture requirement. PMA
type II is used in this case with a purpose of higher deformation resistance. Recommended mixing temperatureof this PMA is 170 to 185 degree in Celsius and recommended compaction temperature is 160 to 170 degree
in Celsius. Some trial mix are mixed at 178 degrees in Celsius and compacted at 168 degrees in Celsius.
According to the Marshall method, OAC is 4.9% and shows 3.6% air voids. No additive is used in this stage.
Specification of air voids for dense-graded mixture is 3 to 6%. This mixture meets all specifications including
air voids. This is referred as ‘general HMA’ in Figure 6.

Other specimens are made with the new chemical additive. This additive is used after introducing
asphalt during mixing. Dosage is 0.8% by weight of asphalt, i.e. only 0.5g for about 1,200g mixture. To confirm
the effect of this additive both mixing and compaction temperatures have been changed as showed in Table 2.

5

Specification of air voids of dense-graded mixture is 3 to 6% in Japan. Air void of general HMA is3.6%. On the other hand, air voids of WMA with this additive are 2.7%, 2.7%, 2.9% and 3.3% when compaction
temperatures are 170, 150, 130 and 110 degree in Celsius respectively. This result indicate that this additive
can improve the compactability of asphalt mixture and enables compaction temperature drop more than 50
degree in Celsius relative to general HMA.

WMA
General HMA

8
Air Voids (% )76Specification : 3 - 6%

5
4
3
2
90

110
130
150
170
190
Compaction Temperature (Degree)

Figure 6. Comparison of Air Voids of Cylindrical Specimen
Table 2. Mixing and Compaction Temperatures when new additive is used

Case 1Case 2
Case 3
Case 4General HMA

Mixing Temperature(degree in Celsius)
175
( -3)
155
(-23)
135
(-43)
115
(-63)
178

Compaction Temperature(degree in Celsius)
170
( +7)
150
(-13)
130
(-33)
110
(-53)
163

Note: Number in a parenthesis means temperature difference relative to general HMA

4.2 Field Test Pavement

The authors conducted small test pavements to confirm the temperature drop efficiency of thisadditive at a private field in Tsukuba, Japan. Dense-graded mixture, coarse-graded mixture and porous asphalt
mixture were constructed. Maximum aggregate sizes are 13mm, 20mm and 13mm, respectively. Test section
had 2.8m in width and 90m in length. Thickness was 5cm. Table 3 shows mix design results for each mixture.
The new additive is not used in mix design stage. After some trial mix, dosages of the additive are decided as
0.7%, 0.5% and 0.7% by weight of asphalt, respectively. And target temperature drop of mixing are 30 degree
in Celsius in every case.

6

Table 3. Mix Design Result
Asphalt used
Asphalt Content (%)
Air Void (%)
Density (g/cm3)
Stability (kN)
Mixing Temperature (degree in Celsius)

Dense-Graded
Pen. 60-80
5.5
3.9
2.387
10.9
152

Coarse-Graded
Pen. 60-80
4.7
3.9
2.416
10.6
152

Porous Asphalt
PMA Type H
4.8
20.5
1.980
6.4
170

All mixtures were produced at a batch plant. This test filed was at adjacent to the asphalt plant, so
paving works were carried out after one hour hauling to simulate general paving works at public roads.
MF43WD asphalt finisher made by Mitsubishi was used to spread the produced asphalt mixtures. The SW650
tandem roller with 7 tons made by Sakai was used for the first compaction and the TX701 pneumatic-tired
roller with 15 tons made by Sakai was used for the finishing compaction. A steel-tired roller is generally used
for the first compaction in Japan, however it was not able to use due to the narrow filed width. Table 4 showsa series of measured temperatures of asphalt mixtures at each construction stage. Mixture production
temperatures and spreading temperatures are almost on target and/or below target.

Table 4. Measured Temperatures of Asphalt Mixtures at Each Construction Stage

Target Production Temperature
Production Temperature
Mixture Temperature After Hauling
Spreading TemperatureFirst Compaction Temperature
Finishing Compaction Temperature

Dense-Graded
Coarse-graded
MixtureMixture122 (-30)
122 (-30)
122 (-30)
119 (-33)
123
123
101 (-39)
100 (-40)
80
78
52
54

PorousAsphalt
Mixture140 (-30)
140 (-30)
140
98 (-57)
88
75

Note: Unit is degree in Celsius. Number in a parenthesis means temperature difference relative to general HMA

Six cores with 100 mm in diameter are sampled at each mixture site and measured their densities
and air voids. And percent of lab-compacted densities are calculated. These results are shown in Table 5.
Percent of lab-compacted density means density of WMA core divided by lab-compacted HMA specimen’s
density. These results show three WMA are well compacted even though production temperature is dropped
30 degree relative to general HMA.

Table 5. Density and air voids of Sampled 100mm Cores

Density (g/cm3)
Air Voids (%)
Percent of lab-compacted density (%)

Dense-Graded
Mixture
2.421
4.2
98.1

Coarse-graded
Mixture
2.450
4.0
98.2

PorousAsphalt
Mixture
2.051
19.4
99.0

4.3 Construction Work at a National Road
The Nippon Road made a contract on a national road in Tokyo. This was a construction for wire

7

common conduct. The wire common conduct was buried under a road in service and pavement should berestored daily to open traffic. This work was carried out at night. So actual construction hours were very limited.
Taking consideration of shortening the construction hours, it sometimes faces higher temperature of HMA. The
Nippon Road decided to adopt WMA. And as previously noted, this WMA should be included RAP due toGreen Purchasing Law.

As a result of mix design, WMA with 50% RAP was adopted for asphalt stabilized base material forthe base course, coarse-graded mixture for binder course and dense-graded mixture for surface course. Table 6
shows the mixture properties and conditions. Every mixture is WMA with RAP, but no rejuvenator is usedbecause this new additive also acts like a rejuvenator (Endo et.al. 2016).

Table 6. Asphalt Mixtures Properties and Conditions

Asphalt Content (%)
Air Void (%)
Lab-compacted Density (g/cm3)
Production Temperature (oC)Compaction Temperature (oC)
Penetration of Adding Asphalt (1/10mm)
Additive Content (%)
RAP Content (%)
Rejuvenator

WMA for Surface
Course
5.2
3.8
2.402

WMA for Binder WMA for Base
CourseCourse
4.7
4.0
3.9
6.7
2.414
2.365
132 - 140
124 - 130
Pen.80-100
0.8 (by weight of asphalt)
50
N/A

This was two-year long project. General HMA with RAP was also in this work. Figure 7and Figure
8 show temperature drop comparison between HMA with RAP and WMA with RAP after placing binder courseand surface course. HMA data were collected during winter season and average air temperature was 3.1oC.
And WMA data were collected during fall season and average air temperature was 11.2 oC. Red dotted line
shows a target temperature to enable opening for traffic. 20 minutes reduction for binder course construction
and 15 minutes reduction for surface course construction in case of WMA with RAP comparing to HMA with
RAP. Taking account for the air temperature, it is expected that WMA with RAP has more reduction of
construction hours effect.

Table 7 shows the percentage of lab-compacted density of filed sampled cores of HMA with RAP
and WMA with RAP. Specification of percentage is 96% or above. All cases meet this specification and WMA
with RAP are well compacted like HMA with RAP even though WMA with RAP were produced andconstructed about 30oC temperature decrease comparing to HMA. HMA with RAP property was not noted inthis paper, rejuvenator was used. These facts show that developed new additive act well as not only warm-mix
additive but also rejuvenator. Other mixture properties like stability, rutting resistance and so forth were on
same levels.

8

Surfase Temeratur (o C)

170

HMA with RAP

150

WMA with RAP

130

Reduction of
construction hours

110
90

70
50
30
0

20

40

60

80

100

Elapsed Time after Placing AC Mixture (min)Surfase Temeratur (o C)

Figure 7. An example of Surface Temperature Drop after Placing Binder Course

170

HMA with RAP

150

WMA with RAP
Reduction of
construction hours

130
110
90
70
50
30
0

20

40

60

80

100

Elapsed Time after Placing AC Mixture (min)Figure 8. An Example of Surface Temperature Drop after Placing Surface Course
Table 7. Percentage of Lab-compacted Density of Filed Cores
WMA with RAP

HMA with RAP# Asphalt Stabilized Material
1
100.4
2
101.4
3
101.4
4
101.2
Ave.
101.1
1
98.9
2
102.5
3
100.5
4
100.6
Ave.
100.6

Coarse-graded Mixture
98.7
101.5
99.5
101.3
100.3
100.3
102.1
101.0
101.1
101.1

Dense-graded Mixture
96.6
96.9
97.6
98.5
97.4
97.5
99.5
98.5
98.5
98.5

4.4 Other Projects
Some examples of other projects are shown in Table 8. This list summarized in 2012 and old data
because this additive was developed in 2010 and the authors eagerly collected such data at that time. After that,the authors had few interested in these records because this additive is communized within the Nippon Road.
As well-known, WMA has other aspect, i.e. it enables longer distance hauling than HMA and also enablesenough compaction of pavement during cold weather. Fiscal year in Japan starts in April and ends in next

9March. It is said that this leads to more construction works in winter season. This list includes such cases.

Table 8. Examples of Other Projects (As of 2012)
Area
Osaka
Ibaragi
Fukushima
Kanagawa
Hiroshima
Hiroshima
Kouchi
Hokkaido
Fukushima
Tokushima
Kouchi
Iwate
Other

MixturesCoarse-graded, Asphalt Stabilized
Coarse-graded, Asphalt Stabilized
Dense-graded
Dense-graded
SMA
SMA
Porous asphalt pavement
Porous asphalt pavement
Coarse-graded, Asphalt Stabilized
Coarse-graded, Asphalt Stabilized
SMA
Dense-graded with RAP
Dense-graded with RAP

Asphalt
Pen.60-80
Pen.60-80
PMA Type II
PMA Type II
PMA Type II
PMA Type II
PMA Type IH
PMA Type IH
Pen.60-80, PMA Type II
Pen.60-80
De-colored Asphalt
Pen. 60-80
Pen. 60-80

Amount of Production (tons)
2,300
9,000
500
2,000
200
300
100
780
11,000
300
200
430
4,000

5 CONCLUSIONSThis paper concludes like followings.
- A new chemical additive for WMA was developed.
- This additive does not affect to asphalt properties.
- This additive can use for any asphalts including polymer modified asphalt.
- This additive can use for any asphalt mixtures.
- General dosage of this additive is only 0.4 – 0.8% by weight of asphalt.
- This additive enables 30 – 50 oC temperature decrease comparing to general HMA.
- This additive acts like rejuvenator when this is used for WMA and/or HMA with RAP.
- Some case studied are shown to understand above features.

REFERENCES

Automobile Inspection & Registration Information Association (2017). Number of automobiles in Japan (inJapanese)Endo, K., Tachibana, N., and Ando, M. (2016). Study on quality improvement of recycled asphalt pavement,
MAIREPAV 8
Japan Modified Asphalt Association (2006): Changes of name of polymer modified asphalt and general
performance (in Japanese)
Japan Modified Asphalt Association (2015): Modified asphalt pocket guide (in Japanese)
Japan Asphalt Mixture Association (2018). Trends of amount of asphalt mixture production (nation wide) (inJapanese)
NAPA (2007). Warm-mix asphalt: best practices

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