Key Engineering Materials ISSN: 1662-9795, Vol. 753, pp 321-325 doi:10.4028/www.scientific.net/KEM.753.321 © 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 1 Universitas Indonesia, UI Campus Depok, Indonesia a [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. Introduction 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 . 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 . 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 . 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 . 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 . 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, www.scientific.net. (#102734754, University of Missouri-Columbia, Columbia, USA-27/10/17,21:35:37) 322 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'' . 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 . 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 . 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 . 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 . 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 traffic. Key Engineering Materials Vol. 753 323 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 o 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 HMA. 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. 324 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. Conclusion 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 process. 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 performance. Acknowledgments 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. References  H. H. Kim, S. 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