Effects of Steel and Polypropylene Fiber Addition on Interface Bond Strength between Normal Concrete Substrate andSelf-Compacting Concrete Topping

Abstract

Based on facts that the composite action in semi-precast and strengthened structural system depends on the bond strength of the interface between concrete faces of different ages, this preliminary research is aimed to investigate effects of mixed polypropylene (PPF) and steel fiber (SF) addition on the hardened properties of Self-Compacting Concrete (SCC) and its bond strength when used as topping layer on normal concrete substrate. Effects of hybrid fiber addition on the hardened properties of SCC were investigated based on the compressive, splitting tensile and flexural strength of concrete specimens which is tested in 28 days of age. In the next step, the tensile and shear strength of the interface were evaluated using indirect splitting tensile and bi-surface shear test method. In this research, fiber addition were prepared using 1 kg/m PPF and various SF addition ranging from 15 kg/m3, 20 kg/m3, 25 kg/m3 and 30 kg/m3. Test results indicate that hybrid fiber addition does not affect the compressive strength significantly but it leads ositive improvement to the splitting tensile and flexural strength of hardened SCC and also improve the bond strength between SCC and normal concrete. Hybrid fiber addition of 1 kg/m3 PPF which is combined with 20 kg/m3 SF can be suggested as optimum composition for Hybrid Fiber Reinforced Self-Compacting Concrete (HyFRSCC) that will be used as topping or overlay material based on its hardened properties and interface strength.