Research Projects

Depletion of good quality virgin aggregates, an increasing amount of asphalt coated aggregates (e.g., RAP) stockpiles, and restricted allowable RAP usage in hot mix asphalt motivates the use of RAP in cement-based systems (e.g., portland cement concrete or PCC) mixes. A major hindrance for high-volume RAP utilization in PCC is the significant mechanical strength reduction due to the weak interfacial bonding between the organic asphalt-coated aggregates and inorganic cementitious matrix. This results in insufficient friction between non-colloidal particles (mechanical interlocking between aggregates) and less cohesion provided by the colloidal particles (cement hydration involving Van der Waals forces and electrostatic forces), leading to reduced strength and durability of the concrete. In addition, the leaching of organic compounds from the asphalt-coated aggregates can retard the cement hydration due to high pH pore solution of the cementitious matrix, drastically affecting the concrete performance. A fundamental study is proposed to understand the effect of leaching compounds on the hydration kinetics and interfacial bonding of organic asphalt-coated aggregates with inorganic cementitious matrix. To achieve this overarching goal, the leaching compounds will be determined by a novel method which will be proposed in this research. The pH, electrical conductivity, total organic compounds, elemental composition, and polycyclic aromatic hydrocarbon content will be analyzed at different time intervals, and their influence of the cement hydration kinetics and interfacial bonding will be investigated. The findings from this research will provide a framework for high-volume RAP utilization in cement concrete pavements, thereby promoting a cost-effective and environmentally friendly solution.