Research Projects

• Background: Among different recycling methods, cold recycling is notable for its potential to incorporate a high reclaimed asphalt pavement (RAP) content, up to 100%, while being produced at ambient temperatures. The cold recycled mixture is composed of RAP, virgin aggregate, emulsion, cement, and water. The presence of multiple constituents and their interactions results in an evolving microstructure. Major interactions include cement hydration and emulsion breaking, which occur at different rates during the service life. The current understanding of how emulsion, cement, RAP filler, and water interact to influence the mechanical properties of the cold recycled mixture is limited. Mixture characterization often overlooks the interactions, such as the breaking of emulsion and cement hydration, highlighting the need for characterization at the smaller scale length that is the mastic scale. The mastic scale, which includes material passing 0.075 mm, influences the overall mechanical response. • Research gap: Despite recent advances highlighting the influence of emulsion type, filler mineralogy, and hydration kinetics on the mechanical response of cold recycled asphalt mastic (CRAM), there is a notable lack of systematic studies focusing on the use of RAP fillers in these formulations. The roles of each component in microstructure evolution and mechanical properties remain poorly defined. To advance knowledge, comprehensive methods such as calorimetry, advanced rheology, and morphological analysis are collectively needed to examine emulsion breaking, hydration kinetics, and microstructural evolution. • Current project focus: This project aims to systematically investigate how each constituent affects the emulsion breaking, hydration reactions, microstructural development, and rheological evolution of CRAM. Special focus will be placed on the interactions among the component materials. Three controlled CRAM formulations will be developed: (1) Filler + Emulsion, (2) Filler + Cement + Emulsion and (3) Filler + Cement + Water + Emulsion. Two types of filler will be used: a RAP filler and a fresh aggregate filler. Experimental variables will include three levels: filler-to-binder ratio, filler-to-cement ratio, and water-to-cement ratio. Rheological properties will be assessed using a Dynamic Shear Rheometer (DSR), and the hydration kinetics will be analysed using isothermal calorimetry. Further, the evolution of microstructure will be analysed using a scanning electron microscope. • The expected outcome of this project is to establish a comprehensive, mechanistic understanding of how CRAM constituents interact during curing. This involves quantifying the effects of cement hydration and emulsion breaking, evaluating the role of RAP fillers in these processes, and connecting these changes to measurable rheological behaviour. With favorable outcomes from this research, better cold recycled mixtures can be designed with proper construction strategies.