Experimental investigation on leaching behavior of ultra-high performance concrete submitted to a flow environment

Abstract

Ultra-high performance concrete (UHPC) is a cementitious material with exceptional durability. Uncertain is, however, the leaching behavior of UHPC in a flow environment. To investigate the leaching behavior of UHPC under the influence of moving water, accelerated tests simulating various naturally flowing solution conditions were conducted. The effect of flow environment, steel fiber content, and superplasticizer content on the degradation of UHPC was investigated. There are three flow velocities: static (0 m/s), low (0.3 m/s), and high (2 m/s), as well as three leaching solutions: 6 mol/L ammonium chloride, 3 mol/L ammonium chloride, and natural groundwater. Mass loss, porosity, degradation depth, flexural strength, and compressive strength were measured. The result showed that the maximum degradation of UHPC was observed in a high-velocity flow environment containing 6 mol/L ammonium chloride. Porosity, mass loss, degradation depth, and compressive strength loss following deterioration declined as the steel fiber content rose, reaching a minimum at 2% steel fiber in the same flow environment. The loss of flexural strength decreases and subsequently increases as the steel fiber content increases. The largest reduction in compressive strength was 16.4%, and the maximum reduction in flexural strength was 48.2%. At the same degraded ratio, the compressive strength loss of UHPC is significantly less than that of ordinary concrete. A predicted model for the loss of UHPC's cubic compressive strength is established.