This paper has discussed the application of rice husk ash (RHA) and biochar (BC) as environmentally friendly additive in hot mix asphalt (HMA) to enhance their mechanical, thermal, and durability characteristics. There were seven asphalt mixtures prepared; one control mix and 6 modified mixes with 5, 10, and 15 % RHA or BC as partial replacements. The mixtures were tested in the form of marshal stability, dynamic modulus, fatigue life, thermal conductivity, specific heat capacity, tensile strength ratio (TSR) and aging resistance (RTFOT and PAV). The findings indicated great improvements as compared to the control mix. The uppermost values of the mixtures were RHA10% and BC10% with a Marshall stability value of 10.7 kN and 10.4 kN respectively compared to the control value of 12.6 and 9.5 respectively. RHA10% enhanced the dynamic modulus of fatigue life as much as 4.8 and 20% respectively. Thermal conductivity decreased to 0.743 W/m2.K in BC10% as compared to 0.872 W/m2.K (control), and specific heat capacity increased to 1024 J/kg K as compared to 923 J/kg K, indicating improved thermal insulation. The durability parameters were also improved with the TSR improving to 89.3% and long-term aging resistance (PAV) improving to 77.9%. These findings indicate that both RHA and BC are both environmentally friendly fillers that would help to strengthen and sustain asphalt pavements making them eco-friendly and reducing carbon emissions.
Ahmed et al. (Thu,) studied this question.