Design of crack free, durable and ductile concrete for sustainable highway rigid pavement overlays

The superior ductility with high strength and improved durability characteristics suggest that the Engineered Cementitious Composites (ECC) could be used as an alternative to conventional concrete overlay materials. In this thesis, the research program was divided into two phases. In the first phase, an experimental program was performed to understand the dependence of the composite properties on its mixture composition governed by mineral admixture types and maximum aggregate size and amount. In the second phase, two different ECC-overlay mixture designs were selected from the first phase: one with high strength and moderate ductility, and the other with moderate strength and high ductility. The performance of two selected ECC mixture as an overlay material was investigated by laboratory experiments. Micro-silica concrete (MSC) was also prepared as a reference mixture. The layered composite specimens? flexural strength, reflective cracking characteristics and bond properties were investigated as performance criteria. The test results show that, layered ECC beams have significantly increased both load carrying capacity and deformability and shows better crack width control in comparison with MSC composite beam. Also, ECC increases bond strength, eliminates the reflective cracking and delamination failure in repaired systems and ECC overlay with 35 mm thickness is superior to MSC overlay with 50 mm thickness for rehabilitating concrete pavements. The superior performance of ultra-thin ECC overlay system under mechanical loading will be expected to prolong the service life of the structure under traffic loading and to reduce the costs in the rehabilitation work.