PERFORMANCE OF STONE MASTIC ASPHALT MIX USING SELECTED FIBRES

Abstract

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.