Study on the Characteristics of Hot Mix Asphalt Compacted at Rain Water Simulation Sri Sunarjono # , Rudi Septian Rahmat Pamungkas * , Meilina Hardikasari * # Centre for Transportation Studies, Department of Civil Engineering, Faculty of Engineering Universitas Muhammadiyah Surakarta, Indonesia Sri.Sunarjono@ums.ac.id * Engineer, Graduate of Civil Engineering Department, Faculty of Engineering Universitas Muhammadiyah Surakarta, Indonesia Abstract — This paper reports the investigation results of hot mix asphalt compacted at rain water simulation (HMA-CARS). Objectives of the research are to analysis the characteristics of HMA-CARS and reclaimed HMA-CARS after certain treatments. Research method was developed through the two main programs. First, is to investigate the characteristics of hot mix asphalt compacted using roller slab with water spraying. Second, is to investigate the characteristics of reclaimed HMA- CARS with developing three alternatives treatments. The results can be described in two main points. First, due to water spraying during compaction process, the performance of HMA-CARS decrease and does not meet the general specification of Bina Marga 2010. Second, the performance of reclaimed HMA-CARS can be improved by the treatments; however it cannot help the reclaimed mixture to meet the specification requirements. Key words - Hot mix asphalt. Rain water simulation. Compaction. Density. Reclaimed materials. I. INTRODUCTION Construction process of asphalt road pavement can be started from mixing, spraying, leveling, and compacting prior open traffic. Based upon field observation, some of the contractors are still spreading and compacting asphalt mixture on the road pavement surface in spite of rain. Although it is prohibited in the general specification of Bina Marga 2010 [1], it is still often happen due to the weak of supervision or the materials have been already produced in large scale. Therefore, research into hot mix asphalt compacted with rain water simulation (HMA-CARS) is very demanding There are two fundamental questions. First, does the quality of hot mix asphalt compacted at rain water simulation (HMA-CARS) material still meet the specification? Second, if the HMA- CARS material is processed again in plant (called as reclaimed HMA-CARS), does this reclaimed material still able to be improved to meet the specification? This paper reports the results of research that addressed to answer those two questions. The objectives of research are to analysis the characteristics of HMA-CARS material, and to analysis the characteristics of the reclaimed HMA-CARS material after certain treatments. Research into this material type is very demanding, because engineers need to understand the quality of HMA-CARS in order to make a good adjustment in field. II. COMPACTION AND WATER/TEMPERATURE EFFECT Compaction is a process in which the solid particles are denser by mechanistic force so that void in the mixture decrease and then the density of the mixture increase [2]. Crispino et al [3] added that one of the important aspect in compaction process is to distribute aggregate particles in the mixture, so that it results the optimum aggregates configuration in order to achieve the target of density. Gudimettla et al [4] agreed that the workability of asphalt materials in compaction process is affected by mixture properties, i.e. mixture temperature, bitumen and aggregate properties, and compactor type. When a pavement is compacted at rainfall, the pavement temperature will decrease and it affect the workability of compaction. It can be understood that water is not only affect the temperature of mixture, but it can infiltrate to the bitumen- aggregate bonding. Water infiltration affect the adhesion between aggregate particles and bitumen, and cause the bitumen strip from the aggregate surfaces. Arifin et al. [5] found that temperature affect significantly the Marshall characteristics of asphalt mixture. Specimens compacted at low temperature (less then 110 o C) will have high air void (VIM) and low stability (Marshall Stability). In the investigation of water effect, Arifin et al. [6] found that the effect is not significant and the performances of asphalt mixture still meet the specification. It is found that water infiltration caused the VIM, VMA, and MS values decreased. Sentosa et al [7] investigate the effect of compaction temperature on the asphalt mixture using Retona Blend 55. Based on SNI 6-2489-1991, bitumen viscosity for compaction should be on 280±20 Cst. For Retone Blend 55, it was found that at temperature of 156 o C, the viscosity will be 280 Cst. The temperature range of 146 o C to 186 o C was studied in order to investigate it effect to the mixture properties. It was found that with increasing temperature, the VIM values decrease, and the density and stability increase significantly. In this study, the temperature of 156 o C was selected as the compaction optimum temperature which produced the best mixture performance. Widodo et al [8] stated that the effect of both short ageing (oven 135 o C for 4 hours) and long ageing (oven 85 o C for 2 days) on the asphalt concrete wearing course (ACWC) stability is very significant. Marshall Stability of ACWC -- Page 147 of 436 -- ICETIA 2014 ISSN 2407-4330