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Key Engineering Materials
ISSN: 1662-9795, Vol. 753, pp 321-325
© 2017 Trans Tech Publications, Switzerland
Submitted: 2017-03-23
Revised: 2017-04-10
Accepted: 2017-05-12
Online: 2017-08-28
Influence of Void in Mix on Rutting Performance Hot Mix Asphalt
Pavement with Crumb Rubber Additive
Rerhard Halomoan Limbong1,b, Sigit Pranowo Hadiwardoyo1,a *,
Raden Jachrizal Sumabrata1,c and Raden Hendra Ariyapijati1,d
Universitas Indonesia, UI Campus Depok, Indonesia
[email protected], [email protected], [email protected], [email protected]
Keywords: Pavement, Rutting, Crumb rubber, Temperature
Abstract. Pavement construction is expected to support vehicle loads and be weather- and waterresistant. In tropical regions with high temperatures and high rainfall intensity, pavement design and
construction must consider the effects of temperature. The addition of crumb rubber (CR) can
improve the performance of asphalt concrete in response to vehicle loads and ambient temperature.
Fiber-shaped CR can be mixed with the aggregate and bitumen in asphalt concrete. In this study,
CR was added to the aggregate in a type of asphalt concrete for wearing courses known as hot mix
asphalt (HMA). A series of tests were conducted using the Marshall standard or immersion and
wheel tracking machine (WTM). CR was added to the HMA at 5%, 10%, 15%, and 20% in
aggregate and further mixed with bitumen with 60/70 penetration grade. The additive materials
increased the value of the Marshall stability compared to the virgin asphalt mixture. However, this
result was not obtained in the WTM test; the addition of CR increased rutting compared to the
asphalt mixture without additive. The addition of CR to HMA reduced the voids in the mix, and
weakened the capacity of the asphalt concrete to support repeated vehicle wheel loading.
The nature of the bitumen can be influenced by the nature of the crude oil used during the
refining process. Bitumen performance is unpredictable given its sensitivity to the weather—it is
hard in cold weather and soft in hot environments. These properties can be overcome with the
addition of polymers, which are known to improve the performance of bitumen and its viscoelastic
behavior [1, 2]. Asphalt concrete is directly influenced by factors such as sunlight, moisture,
oxygen, etc. These factors interact with each other and change physical, chemical, and rheological
properties, which can reduce the durability of asphalt concrete [3].
This paper discusses the influence of temperature on the characteristics of a type of pavement
made with crumb rubber (CR) from recycled automobile tires. Waste rubber powder is highly
effective in reducing the rutting depth of asphalt at a temperature. The reduced thermal sensitivity
of asphalt mixed with a rubber powder additive can increase its resistance to permanent deformation
[4]. The use of hot mix asphalt (HMA) with CR has been the subject of research in some
laboratories, including studies to determine the effect of CR, can which modify the bitumen or
replace fine aggregate. CR-modified asphalt shows improved mechanical properties; it could be
used as an alternative to virgin asphalt. However, in some cases, modifiers not only decrease the
workability of HMA but are also not cost-effective [5]. Additives have been widely used to improve
the performance of asphalt mixtures. Local materials and used tires are often used to increase the
economic value of the asphalt mixture. However, research using material additives must be
supported by sufficient test equipment to demonstrate the performance of asphalt in dealing with the
effects of wheel loads, temperature, and water [6]. In general, CR causes a change in volume that
appears after compaction, which is insignificant when the percentage of added rubber is below 3%.
The increase in volume after compaction is directly proportional to the amount of rubber added [7].
Therefore, studies have shown the potential of this asphalt concrete mixture as a structural layer and
the need for further evaluation of the importance of rubber gradation.
All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans
Tech Publications, (#102734754, University of Missouri-Columbia, Columbia, USA-27/10/17,21:35:37)
International Symposium on Advanced Material Research
Two methods are used to incorporate CR particles into bituminous mixtures, commonly known
as the "wet process'' and "dry process'' [8]. The wet process involves mixing the CR into the
bitumen, while the dry process involves mixing CR into aggregate. Adding CR to virgin asphalt
significantly increases binder viscosity. The viscosity of asphalt rubber is critical to mixing and
compaction temperatures and binder workability [9]. While the addition of CR increases the
demand for asphalt binders and mixing and compaction temperatures, the modified binder can
improve the resistance to high-temperature deformation and the long-term performance of HMA
[10, 11].
The addition of CR to high modulus asphalt mixtures increases their stiffness and improves
bearing and stress distribution capacities. Nevertheless, when these materials are subjected to high
strain, additives can decrease fatigue resistance, resulting in premature failure of this type of
mixture when deflections in the pavement layers are high [12]. There are some anti-aging elements
for CR powder, such as carbon black, which can prevent aging of the asphalt binder or asphalt
mixture. CR can also increase the viscosity and elasticity of the asphalt binder [13].
This paper evaluates the permanent deformation performance of mixtures containing an asphalt
rubber binder prepared through a wet process. It considers the impact of changes in temperature and
vehicle wheel grooves.
Materials and Method
Different types of HMA wearing courses of asphalt concrete were used, with the addition of CR
additives to the asphalt with 60/70 penetration grade. Virgin asphalt mixed with the additive
materials had altered characteristics due to bitumen modification. The modified HMA mixtures
were used to determine the rutting characteristics using a wheel tracking machine (WTM) at
temperatures of 30 ºC, 40 ºC, and 60 ºC.
Aggregates. The materials consisted of coarse and fine aggregates with the largest size at 19 mm
and dense gradation.
Asphalt Binder. The asphalt mixture samples were prepared using two different types of binders.
The base binder with 60/70 penetration grade from shell- and CR-modified bitumen was selected
for this study. The CR-modified bitumen was prepared, the asphalt binder was heated up to 170 ºC,
and the powder CR (10%, 15%, and 20% by weight of 60/70 bitumen) was added gradually to the
bitumen in a high shear mixer at a speed of 800 rpm until a homogeneous blend was achieved.
Crumb Rubber. The CR used in this study was obtained from scrap tire rubber in the form of a
fine powder through sieve no. 30 (0.6 mm). CR particles resulting from ambient processing had an
irregular shape and a rough texture due to the tearing and shredding action of the rubber particles in
the cracker mills. The CR particles produced by the cryogenic method, on the other hand, had
smooth surfaces, which resembled shattered glass [14].
Experimental Design and Test Procedures
All testing in this study was conducted using bitumen-type HMA with 60/70 penetration grade
and dense aggregate gradation. The different forms of HMA were analyzed using the Marshall
standard and WTM tests. Two types of samples were tested: virgin asphalt, and modified asphalt
concrete with optimum bitumen content of 5.7%.
The Marshall test was performed on a 101.6 mm diameter and 67.2 mm tall specimen compacted by
2 × 75 punches, whereas the WTM test was performed on a 300 × 300 × 50 mm3 specimen
compacted to a density equal to the Marshall test sample using a standard WTM test compactor.
The WTM test used a wheel load of 4.4 kg/cm2, which is equivalent to a standard single-axle
double wheel load of 8.16 tons. The sample was traversed for 3780 cycles for 3 h at a speed of
21 cycles (42 tracks) per minute at 30 ºC, 40 ºC, and 60 ºC. The WTM test was used to assess the
permanent deformation resistance of asphalt mixtures under conditions that simulated the effects of
Key Engineering Materials Vol. 753
Results and Discussion
Marshall Standard and Immersion. Fig. 1(a) shows changes in the stability values resulting from
the Marshall standard and immersion tests. The addition of 5% CR to HMA increased the Marshall
stability value, and achieved the highest residual strength value with the addition of 10% CR.
Otherwise, Fig. 1(b) shows a decline in the voids in mix (VIM) with the addition of CR. VIM
continues to decrease with increasing amounts of CR.
(a) Marshall Stability
(b) Voids in Mix
Fig. 1 Marshall stability and void in mix performance with CR additive.
Rutting Performance. Fig. 2(a) shows that the rut depth at the beginning of the cycle increased
rapidly, especially for the HMA with CR at 30 ºC. The HMA without additive had a rut depth
smaller than the HMA with the additive at the beginning of the cycle. Increasing CR in HMA
increased the depth of the wheel groove or rut depth. The curve for HMA with 20% CR additive
shows that the grooves increased rapidly at initial loading, which was the largest rut depth
compared to the other curves.
(a) Loading Cycles at 30 ºC
(b) Loading Cycles at 60 ºC
Fig. 2 Rutting performance at 30 C and 60 ºC with CR additive.
Fig. 2(b) shows the loading cycles at 60 ºC for HMA with and without additive. WTM tests at
60 ºC showed that the rut depth was almost equal between the asphalt concrete mixture with 10%
CR and without CR. The addition of CR to dense-graded HMA did not increase the durability of
Dynamic Stability and Deformation Rate. The dynamic stability (DS) of HMA without additive
continuously declined with increasing temperature. At 30 ºC, Fig. 3(a) shows that DS reached
3000 cycles/mm. However, the addition of increasing amounts of CR caused DS to continuously
decline. The addition of CR to the asphalt concrete wearing course reduced the VIM of the asphalt
concrete and decreased HMA resistance to loading and temperature.
International Symposium on Advanced Material Research
Fig. 3(b) indicates the change starts from the deformation speed and HMA without the addition
of CR by 10% to 20%. The addition of CR increased the deformation rate. Rising temperature
further increased the deformation rate.
(a) Dynamic Stability
(b) Deformation Rate
Fig. 3 Dynamic stability and deformation rate according to CR content.
The addition of CR to asphalt concrete changed the VIM and rutting performance under the
following conditions:
1. The addition of CR improved Marshall stability and the resistance of HMA to the immersion
2. The addition of CR reduced the VIM of HMA, which in turn increased the durability of
HMA under repeated loading and rutting compared to the HMA without CR.
3. The addition of CR decreased the DS, especially at 30 °C. At higher temperatures, the
addition of CR did not yield significant benefits.
4. The addition of CR to HMA, in this case, should consider the existence of CR as the fiber so
that there should be a reduction of fine aggregate to provide sufficient space of the VIM.
5. The dynamic loading of the WTM has completed performance information HMA with
additive materials CR. However, in this case, the Marshall test did not reflect the actual
The authors express their gratitude to the Directorate for Research and Community Service at the
University Indonesia, which provided funding in a 2016 Research Grant for this research activity
(Hibah PITTA). The experimental work was completed in the Material and Structure Laboratory of
University Indonesia and the Research Centre and Development for Road and Bridge LaboratoryMinistry of Public Works Republic of Indonesia.
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Key Engineering Materials Vol. 753
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