Influence of alternative rice husk ash filler on bitumen emulsion-based recycled asphalt

The influence of rice husk ash (RHA) as an alternative active filler on the mechanical properties of bitumen emulsion-based recycled asphalt specimens in high- and low-temperature domains was investigated. The experimental methodology was comprised of static indirect tensile and wheel-tracking testing, as well as scanning electron microscopy using secondary electrons and energy dispersive X-ray spectroscopy. The results showed that the increase in the mass fraction of RHA gradually improved the water sensitivity and the high-temperature performance of specimens, but also negatively affected their low-temperature performance. The mass fraction of RHA above 1.5%, resulted in a tensile strength ratio after freeze-thaw and immersion of more than 80%, and in the dynamic stability in rutting test above 4500 mm(-1), but also the low-temperature indirect tensile strength below 2.0 MPa. Considering the relevant regulations, the mass fraction of RHA should be in the range of 1-1.5%.