Influence of splitting load on transport properties of ultra-high performance concrete

This paper presents an experimental investigation on the influence of splitting load on transport properties (air permeability and sorptivity) of UHPC incorporating different dosages of steel fibers (0%, 1%, 2% and 3%). ϕ100 mm × 50 mm specimens were subjected to splitting loads with stress levels varying from 50% to 80% of the ultimate splitting tensile strength. The splitting load induced damage was characterized by the crack pattern, crack opening displacement (COD) and penetrable porosity. Gas permeability and water sorptivity tests were carried out to evaluate the transport property of UHPC specimens after exposure to different levels of splitting load. The correlation among splitting tensile stress level, COD and transport property degradation of UHPC was analyzed. The results indicate that gas permeability and sorptivity of UHPC before loading are much better than that of normal concrete. The splitting tensile strength of UHPC is almost doubled by the addition of 1 ∼ 3% steel fibers in volume and the peak lateral deformation is increased by more than 10 times. Both the maximum value of COD (CODmax) under loading and the residual COD (CODres) after unloading of UHPC specimen increase with the more addition of steel fibers when exposed to the same stress level of splitting load. Both gas permeability and sorptivity of UHPC increase with the splitting load induced CODres. The higher dosage of steel fibers plays a positive effect on improving the transport properties of UHPC with the same CODres value. The sorptivity is more sensitive under a low deformation damage and the gas permeability is a better indicator to describe the durability degradation of UHPC under a high level of deformation.