Effect of incorporating rubber aggregates and fiber reinforcement on the durability of thin bonded cement-based overlays

Abstract

After certain period of time, the degradation of concrete structures is unavoidable. For large concrete areas, thin bonded cement-based overlay is a suitable rehabilitation technique. Previous research demonstrated that durability of such applications is always a problem and one of its main reason is debonding at interface. Laboratory and field researches show that fiber reinforcement in repair material can be a solution for controlling crack opening and also to enhance the durability of thin bonded cement-based overlays. In other respect, previous researches also show that by addition of rubber aggregates obtained from grinding of used tyres is also a suitable solution for improving strain capacity of cement based materials. This present research mainly focuses on synergetic effect of using rubber aggregates and fiber reinforcement in mortar as a composite for the repair work. For this study four mortar compositions to be used as overlay material were prepared: one control mortar, second with fibers at dosage of 30 kg/m3, third containing rubber aggregates replacing 30 % sand by equivalent volume and fourth one containing fibers and rubber aggregates. Direct tension tests were conducted in order to obtain the tensile strength, strain capacity, residual post peak behaviour of the repair material and bond tensile strength of the repair-substrate interface. Results showed that although by incorporating rubber aggregates in mortar reduce compressive strength and modulus of elasticity but improvement in straining capacity is observed. Moreover, fiber reinforcement in repair significantly improves residual post peak tensile strength.