Indirect tensile strength of UHSC reinforced with steel fibres and its correlation with compressive strength

Ultra-high-strength (UHS) fibre-reinforced concrete (FRC) has a much larger tensile strength than normal concrete and engineers should thus consider the tensile strength as a design parameter. However, in the current design codes, the tensile strength of concrete is not considered a major design parameter. It is therefore difficult to design UHS FRC structures using the current design codes. In this study, the indirect tensile strength of UHS FRC was investigated by tests and statistical evaluations. The tensile strength of UHS FRC was found to have a correlation with compressive strength and the content of fibre reinforcement. The indirect tensile strength, splitting strength and flexural strength were influenced by the compressive strength of concrete in an exponential form and also increased with increasing fibre contents. Using this observation and test data from the literature, the effects of compressive strength and fibre content on the indirect tensile strength increase ratio was investigated. Using regression analysis, prediction equations for calculating the indirect tensile strength of UHS FRC were developed, considering the concrete compressive strength and fibre content simultaneously.