Performance of bituminous paving mixtures containing recycled concrete aggregate, fly ash and rice husk ash: A probabilistic approach

Due to the rapid increase in construction activities, the depletion of natural resources is accelerating. Extensive research has focused on finding alternative materials to conserve resources and minimize costs. This study explores the utilization of recycled concrete aggregate (RCA) as a substitute for coarse aggregate, along with waste materials like fly ash (FA) and rice husk ash (RHA) as fillers in bituminous paving mixtures. The aim is to address environmental concerns and waste disposal issues. The research evaluates the performance of different filler types in non-conventional bituminous mixtures using VG 30 grade bitumen as a binder, specifically for lower bituminous layers. A typical bitumen concentration of 5% by weight of dense bituminous macadam (DBM) mixtures is chosen based on existing literature. The study assesses various performance characteristics, including Marshall parameters, indirect tensile strength, and moisture susceptibility. A probabilistic approach is employed to determine the most suitable distribution model, focusing on retained stability (RS) as a measure of moisture susceptibility. For this, fifteen distribution functions were considered with three Goodness-of-fit (GOF) tests. To identify the best suitable function, 50 numbers of samples were prepared to find RS with two types of fillers and two types of coarse aggregate. Experimental results indicate that mixtures with natural aggregate exhibit slightly superior performance, but those with RCA meet all the requirements specified in relevant Indian codes and specifications. The probability analysis confirms that the Burr distribution best fits the experimental data, particularly for moisture susceptibility characteristics.