Laboratory Evaluation of the Effect of using Rice Husk Ash (RHA) Filler on the Mechanical Characteristics of Stone Matrix Asphalt (SMA)

Asphalt mixtures with aggregate or stone mastic asphalt (SMA) are among the hot asphalt mixtures that have been used in different countries due to their special characteristics and in order to increase the load-bearing capacity of pavements and increase their surface friction. Excessive use of bitumen in these mixtures forms a relatively thick membrane of bitumen on aggregates, and creates special properties for these mixtures compared to asphalt concrete mixtures. Various methods have been used to strengthen of the asphalt mixture, such as the use of various additives. Rice Husk Ash (RHA) filler is one of the additives that has been proposed to improve the connection between asphalt bonding and materials used in addition to the environmental aspect. For this purpose, in this paper, a total of nine types of SMA in different percentages of bitumen 60/70 and with the percentage of replacement of filler stone materials with 0%, 25%, 50%, 75% and 100% filler of RHA, and experiment Marshall were done on them. The results of mechanical properties showed that the addition of rice husk filler improved the adhesion between bitumen and aggregates and increased the rutting resistance of SMA by increasing the Marshall Ratio. Increased unit weight and percentage of space filled with bitumen due to the increase in the thickness of the bituminous membrane around the aggregates and due to the presence of rice husk filler were other results of this study. Finally, it was concluded that the replacement of aggregates filler with RHA filler in different percentages and 6.5% bitumen resulted in better result.