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.

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.