Pumping influence on fresh properties of self-consolidating concrete

Pumped concrete has been widely used for repair and rehabilitation of many concrete structures. The flow ability, passing ability, and self densification of Self-Consolidating concrete are beneficial when repair is needed for tight and heavily-reinforced situations. The research investigation presented herein was intended to study the influence of pumping on the fresh properties of self-consolidating Concretes (SCC). The selected SCCs were made with a constant water-to-cementitious materials ratio of 0.40, a uniform cement content of 390.38 kg/m3 and a constant coarse-to-fine aggregate ratio of 1.083. Both polycarboxylate-based High Rank Water-Reducing Admixture (HRWRA) and Viscosity Modifying Admixture (VMA) were used to produce self-consolidating concretes with a slump flow of 635 ± 25 mm, VSI of 0, and T50, of 2 to 5 seconds. A pumping distances of 60 m was used to evaluate the flow ability, passing ability, stability, rheology (yield stress and plastic viscosity), air content and air void characteristics of the selected self-consolidating concretes. Test results revealed that the pumping adversely affected the fresh performance of the self-consolidating concrete by decreasing the unconfined workability, flow rate, and passing ability; and by increasing the dynamic segregation resistance. The impact of pumping on the rheological properties of self-consolidating concrete was manifested by a moderate increase in relative yield stress and a significant decrease in relative plastic viscosity. The air content remained unaffected by the pumping action, whereas the air voids characteristic was altered through size increases of the air bubbles