Study on the optimum rice husk ash content added in asphalt binder and its modification with bio-oil

Abstract By-products and waste materials have become the main cause of environment contamination. In this study, Rice Husk Ash (RHA) was used as modifier to improve the high temperature property of asphalt binder. Bio-oil (BO) was selected as viscosity reducer to enhance the low-temperature and anti-fatigue properties of RHA Modified Asphalt (RHA-MA). Physical and rheological indexes were measured to determine the optimal RHA and BO content. The Scanning Electron Micrographs (SEM) and Energy Dispersive Spectrometer (EDS) analysis were adopted to reveal the modification mechanism of RHA and BO. Results show that RHA-MA possessed desirable high-temperature but unsatisfactory low-temperature performance compared with base asphalt and Limestone Filler Mixed Asphalt (LA). However, asphalt binder with 1% RHA and 20% BO (RB-MA) obtained ductility (15 °C) nearly 50% higher and loss modulus approximately 20% lower than those of RHA-MA. Meanwhile, the softening point is 4.2 °C more and G ∗ /Sinδ at all temperatures is higher than those of BO Modified Asphalt (BA). Furthermore, SEM observation illustrates that BO is able to reduce RHA agglomeration and increase the uniformity of RHA-MA mix system, contributing greatly to the excellent comprehensive performance of RB-MA. Consequently, the joint modification of base asphalt with RHA and BO could obtain desirable high temperature, low temperature and anti-fatigue performance. Therefore, it is likely that the development of RB-MA could be helpful to make conventional asphalt qualified for complex service ambient, as well as improve the recycling rate of agricultural waste to reduce environmental pollution and reduce the life cycle cost of asphalt pavement.