LABORATORY EVALUATION OF FLY ASH CENOSPHERE-MODIFIED ASPHALT BINDERS AND ASPHALT MIXTURE THERMAL RESPONSE UNDER CONTROLLED IRRADIATION

Abstract

Asphalt binders are highly temperature-sensitive materials, and excessive heat accumulation can accelerate softening and reduce pavement service performance in hot climatic regions. This study evaluates the use of fly ash cenospheres (FAC), an industrial by-product with lightweight hollow morphology, as a potential waste-derived modifier for asphalt binders and examines its influence on laboratory-scale thermal response under controlled irradiation. Four binder formulations were prepared: virgin 60/70 penetration-grade binder and binders modified with 5%, 10%, and 15% FAC by binder weight. Conventional binder properties were assessed through penetration, softening point, ductility, flash point, fire point, specific gravity, and rotational viscosity tests. Asphalt mixture slabs prepared with the corresponding binders were then exposed to a controlled irradiation system, and peak temperature and time to peak temperature were recorded. The results showed that FAC modification progressively reduced penetration and ductility while increasing softening point, viscosity, flash point, and fire point, indicating a stiffer and more binder system with improved high-temperature consistency. Under irradiation, the peak temperature decreased from 67.0°C for the control mixture to 59.8°C at 15% FAC, corresponding to a 10.75% reduction. The time to peak temperature increased from 3588 s to 3700 s, indicating delayed heat buildup. These findings suggest that FAC can improve the laboratory thermal response of asphalt mixtures while providing a potential waste-utilization pathway. However, field validation is required before pavement-scale heat-mitigation claims can be made.