Hot mix recycling is the process in which reclaimed asphalt pavement (RAP) materials are combined with new materials to produce hot mix asphalt mixtures. This paper details a laboratory study in which the effects of different RAP contents were evaluated on the performance of hot recycled mixes. The objective of this study is to evaluate the rutting resistance of asphalt mixes containing different percentages of RAP. The Marshall mix design method was adopted in this study to determine the OBC for the asphalt mixes containing four aggregate combinations with RAP contents of 0% (control), 15%, 25% and 35%. Volumetric analysis was performed to ensure that the result is compliance with specification requirements. The resilient modulus test was performed to measure the stiffness of the mixes while the Hamburg wheel tracking test was used to evaluate the rutting performance of these mixes. The results obtained showed that there were no substantial differences in volumetric properties, stability values and stiffness properties between the control mix and recycle mixes. It can be concluded that recycled mixes performed as good as the performance of conventional Hot Mix Asphalt (HMA) in terms of resilient modulus and rutting.

A good asphalt mixture is very important to maintain the triangle of sustainability. Many accidents occur due to pavement damage such as permanent deformation caused by the external loads induced by heavy traffic. Stone Mastic Asphalt (SMA) has a low resistance to moisture and other performances. Many researchers have conducted on SMA using various types of fiber. However, not much research has been done using steel fiber in the SMA mixture and has analyzed the result obtained using a statistical approach. The objective of this research was to identify the optimum amount of steel fiber in a modified asphalt mixture and characterize the performance of steel fiber in the SMA mixture using the statistical approach of Response Surface Methodology (RSM) in Design Expert Software. In this study, various steel fiber proportions of 0 percent, 0.3 percent, 0.5 percent, and 0.7 percent by the total weight of the SMA mixture were used. The Marshall stability and flow test, dynamic creep and moisture susceptibility test, and ultimately, RSM analysis were used to evaluate the properties and performance of the steel fiber-modified SMA, which contained 6.2 percent of PEN 60/70 asphalt binder content. The testing findings unmistakably demonstrated that the addition of steel fiber greatly improves the SMA mixture’s resistance to moisture and permanent deformation. An amount of 0.3 percent was found to be the most optimum steel fiber content from the optimization by using Response Surface Methodology, thus proven with additional steel fiber in the SMA mixture enhancing the performance of the mixture. As a result, it can be determined that the addition of steel fiber to SMA asphalt mixtures has improved the properties and performance in the construction of asphalt pavements, and the RSM method is an efficient statistical method for producing an appropriate empirical model for relating parameters and predicting the best performance of an asphaltic mixture.

Stone Mastic Asphalt (SMA) is a gap-graded asphalt mixture that depends on the stone-to-stone contact to provide its load carrying capacity against rutting. However, binder draindown is a problem for SMA mixtures, due to its intentional high binder content. This paper details the performance evaluation of two different cellulose fibres used in SMA14 mix; synthetic fibre (Viatop66) and natural fibre (Kenaf) to prevent binder drainage. The cellulose fibres, 0.3 percent by weight of the mixture, were uniformly combined with the dried aggregate before the asphalt cement was added during mixing process. Laboratory specimens were prepared using 50 blows of the Marshall hammer per side. The Optimum Binder Content (OBC) for the SMA14 mix with Viatop66 was found to be 6.1 percent, while the OBC for the SMA14 mix with Kenaf was found to be 5.9 percent. Rut depth obtained for SMA14 mix Kenaf was lower (1.6 mm) compared with SMA14 mix with Viatop66 (1.8 mm). The tensile strength ratio recorded for both mixes are greater than 80 percent, indicating adequate stripping resistance. The fibres were found to interact well with other substances in the SMA14 mix using the Environment Scanning Electron Microscopy (ESEM). This indicates that the natural fibre could efficiently retain the binder in the mix. Therefore, natural fibre (Kenaf) could be an alternative material to replace the synthetic fibre for the SMA14 mixture.

Pavement evaluations provide crucial information regarding the performance and service life of asphalt concrete (HMA). They examine the structure of an existing pavement before deciding on different maintenance alternatives. The Klang Valley, as part of one of the developing areas in the state of Selangor, generates a high volume of traffic every day due to the increasing number of vehicles crossing the area. Every day, the impact of axle loads caused by vehicles has a negative impact on flexible pavement, resulting in road deterioration due to extreme distress. Pothole failures are one of the most common causes of distress. Five research areas in the Klang Valley area that have deteriorated owing to pothole failures were chosen as case studies. The objective of the study is to investigate the existing flexible pavement conditions by means of laboratory testing consisting of physical, volumetric, and performance tests using collected core samples. As a result, the data collected was compared to the Malaysian Public Work Department’s (PWD) standard. Data from laboratory tests was analyzed using Response Surface Methodology (RSM) to determine correlations with parameters influencing distress. Historical data design was carried out between test components and responses, which consisted of laboratory parameters. Axial strain, tensile strength ratio, and stability were the responses measured in the RSM. The created models between the independent variables and responses revealed a high level of correlation. The binder content, degree of compaction, and stiffness were the most significant operating parameters from the 3D plots. Optimized performance due to asphaltic pavement failure was observed at binder content (5.1%), degree of compaction (97%), and stiffness (3.1 kN/mm) to achieve ultimate axial strain (5000 microstrains), tensile strength ratio (80%), and stability (9.2 kN). The study showed that the response surface methodology (RSM) is an effective statistical method for providing an appropriate empirical model for relating parameters and predicting the best performance of an asphaltic mixture to reduce flexible pavement failure.

The pavement industry is currently forced to find alternative ways to produce asphaltic concrete with the dwindling supply of new resources and the spiraling cost of materials. Warm Mix Asphalt (WMA) using reclaimed asphalt pavement (RAP) offers a sustainable solution to the problem by reducing energy requirements for production and the reuse of old pavement materials. The effects of warm mix asphalt additive (Sasobit) on mixes containing different percentages of RAP were investigated in the laboratory. Three different concentrations of RAP (30%, 40% and 50%) with 1.5% Sasobit by weight of binder were added, and Marshall method was used to produce all samples investigated. Two different mixing and compaction temperatures were used, 155°C and 135°C for mixing and 135°C and 120°C for compaction. The performance of the mixes in terms of stiffness and moisture damage were investigated by carrying out the Indirect Tensile Resilient Modulus Test (ASTM D4123) and moisture susceptibility test (ASTM D 4867). The results obtained showed that there were no substantial differences in volumetric properties, stability and stiffness values of reclaimed mixes than the control mix (conventional hot mix asphalt). In addition, all the mixes investigated achieved the required minimum TSR of 80%. Measured rut depth using the Asphalt Pavement Analyser (APA) device and fatigue cycles to failure using beam specimen indicated that the mixes performed similar to or better than the control mix. The results showed that warm mix asphalt using sasobit-additive and containing high percentages of RAP could be a sustainable alternative to the conventional HMA mix.