Evaluating fresh state, hardened State, thermal expansion and bond properties of geopolymers for the repairing of concrete pavements under restrained conditions

Abstract

In this study, slag-based geopolymer concretes, including partial dosages of pumice and silica fume, are employed as repair materials for deteriorated concrete pavements. Pumice and Silica fume were used to improve the fresh properties of geopolymer concrete, specifically the setting time. In this regard, a series of mixtures were prepared with 0%, 5%, 10%, and 15% replacements of pumice and silica fume by weight of total binder in slag-based geopolymers concrete, while maintaining the percentage of other parameters. Then, the characteristics of fresh and hardened states of concretes constructed using these geopolymers were investigated. The parameters studied include setting time, slump, fresh density, mechanical strength (compressive, tensile, and flexural), bonding behavior, drying shrinkage (free and restrained), coefficient of thermal expansion, water absorption, and porosity. In addition, the effect of the roughness of the substrate layer on the shrinkage of the repair layer was evaluated. The results showed that the addition of pumice and silica fume increased the setting time and workability of fresh concrete, reduced the compressive, tensile, and flexural strength, and maintained the bond strength with no significant effect. It also increased the thermal expansion coefficient and shrinkage. Moreover, water absorption and porosity increased due to the increase in the amount of pumice and silica fume. Finally, the results confirmed that the roughness of the substrate layer has a significant effect on the shrinkage cracking of the repair layer.