Research Projects

The low water-to-cement (w/c) ratios of stiff paving mixtures like roller-compacted concrete (RCC) often possesses significant challenges in moisture retention and proper curing, thereby leading to potential issues such as shrinkage cracking and poor durability. Conventional curing methods (e.g., external water curing) often prove insufficient due to RCC’s denser matrix and low permeability. This can result in uneven hydration profile where the surface may retain some moisture while the deeper sections of the concrete may remain dry and unhydrated. It is therefore crucial to implement effective curing strategies immediately after the fresh concrete is placed and compacted to achieve uniform hydration and thereby leading to improved long-term performance. The use of internal curing technology can be a solution to primarily reduce concrete shrinkage, and thus mitigate early cracking particularly in stiff mixtures like RCCs. Internal curing can provide a modern twist on good curing practice by providing water to the cementitious matrix after setting. It can improve the performance of concrete by increasing the reaction of the cementitious materials. However, unlike conventional curing that supplies water from the surface of concrete, internal curing provides curing water from the aggregates within the concrete. This is very beneficial since the depth that external water can penetrate is limited for any concrete, while internal curing is dispersed throughout the depth of the concrete. Lightweight aggregates (LWA) such as expanded clay/ shale aggregates, pumice, cenosphere (fly ash-based aggregates) are few candidate materials that can be used to partially replace coarse/ fine natural aggregates to promote internal curing in concrete. These materials are highly porous which has higher water absorption capacity and desorption (release) potential to promote internal curing in concrete. Contrary, these materials can be prone to breaking, segregation, and crushing due to compactive energy during rolling operation specifically when used in RCC pavements. There is very limited understanding of how LWAs post compaction would influence the internal curing mechanism of RCC pavements. Therefore, this research is a fundamental study to understand the dominating parameters affecting the mesostructural arrangement of LWA particles within the concrete skeleton when compacted with different mechanisms. To achieve this overarching goal, the compactive energy of field rollers will be simulated on the laboratory-produced LWA incorporated RCC specimens by different methods including modified proctor, vibratory hammer, vibratory table, and gyratory compactor. The influence of these parameters on governing fundamentals parameters (e.g., packing density, aggregate breakage, absorption and desorption, hydration kinetics, internal humidity, pore structure evaluation, microstructural stability) and subsequently to load carrying capacity of RCC pavements will be investigated.