Effect of Rice Husk Ash on the Performance of Hot Asphalt Mixes

Abstract

In this paper, using rice husk ash (RHA) in hot mix asphalt (HMA) as filler was evaluated. The main aim of replacing mineral filler is enhancing the performance of asphalt mixes and producing an economical asphalt mix. For this purpose, five different mixes were prepared; the first was a control mix (traditional mix) containing 100% Lime Stone Dust (LSD) as filler and 0% RHA. While, the other mixes contain 25%, 50%, 75% and 100% of RHA as a percentage of the filler weight. Optimum bitumen content (OBC) was determined using Marshall test, also all Marshall parameters (Stability, Air Voids, Voids in Mineral Aggregate, Unit Weight and Flow) were examined. Indirect Tensile Strength Test (ITST) and Wheel Tracking Test (WTT) were conducted and their results were analyzed. Dynamic modulus (│E*│) is considered an important parameter used in mechanistic-empirical pavement design. The │E*|is measured at different temperature/frequency combinations. Dynamic modulus (│E*│) and phase angle (δ) are used for the visco- elastic characterization of HMA. Thus, these properties were measured for mixes with and without RHA. The results indicate that RHA has the potential to be used as partial substitution of mineral filler LSD in pavement construction. Adding RHA enhances Marshall stiffness, reduces rut depth and increases indirect tensile strength values. Further, a significant change has been occurred in OBC for all mixes and the optimum replacement ratio is recorded as 50% RHA: 50% LSD. Finally, mixes containing RHA show higher dynamic modulus values and flow number.