Influence of steel fiber distribution on splitting damage and transport properties of ultra-high performance concrete

The purpose of this paper is to study the influence of the steel fiber distribution on transport properties before and after UHPC specimens are damaged. By adjusting the dosage of superplasticizer, UHPC cylindrical specimens with steel fibers non-uniform distribution along the pouring direction were obtained. The fiber distribution coefficient was used to characterize the distribution of steel fibers. The damage caused by splitting load is characterized by crack characteristics, crack opening displacement (COD), and penetrable porosity. Gas permeability and sorptivity were carried out to evaluate the transport properties of UHPC specimens before and after pre-cracking. The results showed that with the increase of steel fiber content, the splitting tensile strength of UHPC gradually increased, and penetrable porosity, gas permeability, and sorptivity all showed a decreasing trend. When UHPC was damaged, the total crack area had an obvious correlation with the steel fiber content. The transport properties were closely related to residual COD(CODres) and steel fiber content. Both sorptivity and gas permeability could characterize the transport properties of UHPC, but the former is more sensitive to low deformation damage, and the latter is a better indicator to describe the degradation of UHPC durability under high deformation levels. The non-uniform distribution of steel fibers had an adverse effect on the overall damage indicator of UHPC, but it was beneficial to the impermeability indicator.