Effect of Fractured Aggregate Particles on Linear Stress Ratio of Aggregate and Resilience Properties of Asphalt Mixes—A Way Forward for Sustainable Pavements

The interlocking and packing of aggregate particles play a key role in achieving high level of linear viscoelastic properties and rutting resistance in asphalt mix for sustainable pavements. In this study, the quantitative effect of fractured aggregate particles (FAPs) on loading (i.e., 500 kPa normal stress), along with the resilience properties of asphalt mixes, was evaluated. Linear and nonlinear stress behaviors of aggregates (from direct shear test) and asphalt mixes (from resilient modulus test) were analyzed. A new quantitative parameter (linear stress ratio), i.e., linear stress (Pi)/maximum stress (Pmax), is proposed to be used in selection of aggregates for asphalt mixes. It was observed that 15.5% increase in FAPs caused 19.5% increase in ϕ and 70.7% increase in linear stress ratio (LSR). The same content of FAPs resulted in 29.4% and 36% increases in total resilient modulus (MRT) and 34.2% and 24.5% increases in instantaneous resilient modulus (MRI) for 0.1 and 0.3 s load durations, respectively. The proposed LSR is observed to be superior to conventionally used ϕ for aggregate resistance in design of flexible pavements

Effect of Particle Sizes and Dosages of Rubber Waste on the Mechanical Properties of Rubberized Concrete Composite

The utilization of waste rubber in concrete composites has gained more attention nowadays owing to its enhanced engineering properties and eco-friendly viability. This study explored the effect of waste rubber sizes and its contents on the mechanical properties of developed concrete composites. Rubber waste with various particle sizes (R1, R5 and R10) was replaced with 10%, 20% and 30% of aggregates by volume, and the workability, compressive, splitting tensile and flexural strengths and impact resistance of the developed composite were investigated. An increase in the waste rubber contents decreased the slump of the composite due to the rougher surface of the rubber particles. The reduction in the slump was more pronounced for mixtures with smaller rubber sizes. Similarly, an increase in rubber contents decreased the compressive strength, tensile strength and flexural strength because of the lower stiffness of the used rubber waste and the poor bond between the rubber particles and the matrix. For instance, an approximately 27% decrease in compressive strength was observed for the mixture incorporating 20% of R1 rubber compared to that of the control mixture without rubber. It was observed that the incorporation of rubber waste in the concrete composite led to an enhanced resilience toward impact loading due to the improved energy dissipation mechanism offered by the rubberized concrete composite. For example, 13 blows in the case of 30% of the rubber replacement were required for the final crack as compared to 5 blows for the control mixture without rubber. It can be concluded that the choice of the optimal replacement ratio and the size of the rubber yield the developed rubberized concrete composite with a desirable strength and impact resistance