External Injection Method for Improvement of Concrete Pumpability (2021-09)¶

In this study, a new method was proposed to improve concrete pumpability. The friction between concrete and the internal surface of the pipe can be reduced by externally injecting a small amount of a chemical agent called a friction-reducing agent (FRA) into the pipe. The new idea was experimentally implemented with real-scale concrete pumping of 112, 137, and 518 m (367, 449, and 1700 ft) long pipelines. The experiments were performed with three different concrete mixtures and with the injection rate of the agent varying from 0.077 to 0.284% of concrete volume. It was found that the pumping pressure decreases from 26.6 to 60.2%. In addition, the rheological properties of concrete and the lubricating layer, and the viscosity of wet-screened mortar according to the dosage of FRA were measured. Based on analysis of these measurements, a method was proposed to quantitatively predict pressure reduction due to the external injection of the FRA.