Tensile strength and failure of ultra-high performance concrete (UHPC) composition over a wide range of strain rates

Abstract

In the fibre reinforced concrete, the geometry, density, distribution and orientation of micro-steel fibres can have a significant effect on mechanical performance. In this study, five different compositions of ultra-high performance concrete (UHPC) with steel fibres were designed and developed for improving the mechanical properties over conventional control concrete. An improvement of around 300% in tensile strength was observed with the addition of micro-steel fibres during quasi-static loading in tension. High strain rate behaviour was also studied using Kolsky bar experiments in tension, which was combined with in-situ imaging to capture failure initiation and progression during loading. From the experimental results, it was found that the binary composition of the UHPC matrix is more rate sensitive than the ternary and quaternary compositions. In addition, the dynamic increase factor (DIF) was found to be lower for specimens with micro-steel fibres in contrast to control with only matrix material. From the fracture and failure analysis of UHPC specimens, it was observed that the micro-steel fibres in the UHPC matrix prevent the splitting failure, and maintain the structural integrity of the specimen beyond peak stress.