Enhancing the strain-hardening performance of ultra-high performance concrete by tailoring matrix toughness and fiber parameters

Ultra-high performance concrete (UHPC) features high strength but a relatively low tensile strain capacity. Matrix, fiber parameters and their interaction are the controlling factors, which need careful designation to enhance the tensile performance of UHPC. In this research, different fiber parameters, e.g., fiber shapes, fiber aspect ratios, fiber hybridization and crumb rubber are utilized to tailor fiber parameters and matrix toughness to improve the tensile properties of UHPC. Systematic investigations were carried out to obtain the uniaxial tensile, compressive, fracture toughness and single-crack tension properties of UHPC. Results show that the tensile properties of UHPC could be largely improved by adjusting the fiber parameters and matrix toughness, in which the incorporation of crumb rubber demonstrates the most predominant effect in enhancing both tensile strength and strain capacity. The tensile strain capacity and crack number of developed UHPC reach 5585 mu epsilon and 18, respectively, which are almost twice as the values of referred UHPC. The fracture toughness of developed UHPC ranges from 4.01 to 6.17 MPa center dot m(1/2), approaching that of metals and alloys. The methods used in this work provide potential methods for more efficient improvement of the tensile performance of UHPC.