Effects of Mixing Energy on Placing Properties of Injection Grouts in Formed In Place Pipes (FIPP)

In recent years, a number of trenchless techniques have been developed to rehabilitate ageing underground pipes and drains. Some rehabilitation methods employ flowable cement-based grouts to fill and reinforce the gap between new and old pipe. For this process to be effective, grouts need to have good fluidity and stable hardening characteristics to ensure optimum placement and integral of construction. Factors affecting fluidity and hardening characteristics include slurry preparation and pumping conditions. Deterioration of fluidity and hardening will cause filling problems and subsequent structural defects. Little research conducted on the effects of the mixing energy during slurry preparation has focused on the reasons or mechanisms for changes in characteristic properties. This paper describes and measures the effects of several mixing parameters on placing properties of grouts, such as fluidity, hardening characteristics and shrinkage of grouts. The results indicate that long mixing processes cause deterioration of flow and setting properties. These observations can be explained by changes in hydration kinetics and microstructure due to different mixing durations.