Experimental study on crack width control ability of ultra-high performance concrete

Abstract:

The axial tensile stress-strain curves and crack width control ability of three types of ultra-high performance concrete (UHPC) were investigated, including high strain-hardening UHPC, low strain-hardening UHPC and strain-softening UHPC, respectively. The tensile stress-strain curves and crack width-strain curves of the UHPC were attained from tests on dog-bone shape specimens. The results show that the tensile stress-strain curves of high strain-hardening UHPC and low strain-hardening UHPC include three stages (elastic, strain hardening, strain softening), while the strain softening UHPC has only elastic stage and softening stage. The turning point of strain hardening stage and strain-softening stage is the critical point of slow propagation and rapid expansion of the cracks. The ultimate tensile strain improvement of UHPC can improve the crack width control ability. When the tensile strain of high strain-hardening UHPC is below 0.42 %, the crack width is less than 0.05 mm. In comparison with C50 concrete (ultimate strain and ultimate tensile strength are 0.012% and 2.3 MPa, respectively), the impact of the crack width checking in serviceability limit state on high strain-hardening UHPC can be avoided by its excellent crack width control ability, and the high strain-hardening UHPC can work together with steel under tensile loading before steel yield. It is meaningful to use reinforced high strain-hardening UHPC in those structures with high demand of crack width control.