Mechanical properties and constitutive model of steel fiber-reinforced rubberized concrete

This study aims to assess the mechanical behavior of steel fiber-reinforced rubberized concrete (SFR-RuC) with and without mix optimization through experimental investigations, and eighteen concrete mixtures were manufactured for test specimens. Through mix optimization, SFR-RuC with a steel fiber volume fraction no more than 1.5% and a rubber particle volume substitution as high as 20% could successfully achieve a compressive strength of 49 MPa-56 MPa. Cubic and uniaxial compressive tests, direct shear tests and four-point flexure tests were conducted on all specimens. The results showed that optimized SFR-RuC had overall improved mechanical properties and more ductile failure than nature concrete, and the elastic modulus and compressive, flexural and shear strength were enhanced by 13%, 16%, 25% and 50% respectively, when 10% rubber particles and 1.5% steel fibers were added. The peak strain, toughness and post-peak deformation of optimized SFR-RuC under compression increased with the steel fiber volume fraction as well as the rubber particle volume substitution, while the peak deflection, toughness and ductility under flexure and shear increased mainly with the steel fiber volume fraction. An obvious synergistic action was shown between the rubber particles and the steel fibers, through Scanning Electron Microscope (SEM) analyses on the microstructure, as well as test observations on the failure mechanism of specimens. Based on uniaxial compressive test results, formulas were proposed for the compressive strength, elastic modulus and peak strain of optimized SFR-RuC, and a modified stress–strain model was developed based on the classical concrete stress–strain model in the Chinese code (GB50010-2010), for a detailed assessment of the complete stress–strain response.