Mechanical Properties of Low-carbon Ultra-high Performance Concrete under Uniaxial Compression

To tackle the high carbon emissions issue resulting from doubling the cement dosage in ultra-high performance concrete (UHPC), a low-carbon ultra-high performance concrete (LC-UHPC) was developed by replacing a large proportion of Portland cement with granulated blast furnace slag, fly ash, and silica fume. Eleven groups in a total of 154 specimens were fabricated with three factors, namely, cement replace ratio, steel fiber volume content, and water-binder ratio taken into account. Through cube compression tests at different ages, flexural tests, and uniaxial compression tests, the mechanical properties of LC-UHPC, including failure patterns, basic strength, and deformation capacity, were analyzed. Based on the test results, a mathematical equation for the stress-strain curve under uniaxial compression was derived. Results indicated that the LC-UHPC displays shear failure mode under uniaxial compression. Moreover, the addition of steel fibers significantly enhances the mechanical properties of LC-UHPC. Compared with conventional UHPC, up to 70% of the cement in LC-UHPC can be replaced, and its 28-day compressive strength can reach 149.09 MPa. The established axial stress-strain equation can accurately predict the mechanical responses of LC-UHPC under uniaxial compression. This equation provides valuable insights for studying the mechanical properties of LC-UHPC and the design of related structural components.