Performance Evaluation of Different Rheometric Shearing Techniques to Disperse Concentrated Cement Suspension

Abstract

Build-up of cement-based suspensions is a complex phenomenon affected by the mixture concentration and testing parameters as well as the shear history. Accurate measurements of build-up rely on the efficiency of the applied pre-shear regime to achieve an initial defined and dispersed structure to eliminate the shear history. This can therefore enable understanding mechanisms of build-up and quantifying the structuration of cement suspension from a reproducible dispersed state. Dispersing efficiency of various disruptive shear techniques, including rotational, oscillatory, and combination of both was evaluated. The initial and final states of suspension’s structure were determined by applying small-amplitude oscillatory shear (SAOS). Test results showed that oscillatory shear has a greater effect on dispersing concentrated cement suspension than the rotational shear. Furthermore, the increase in shear strain in oscillatory technique enhanced the breakdown of suspension’s structure until a critical point, after which thickening effects dominate. An effective dispersing method is then proposed. This consists in applying a rotational shear around the transitional value between shear-thinning and shear-thickening followed by an oscillatory shear at the crossover shear strain and high angular frequency of 100 rad/s.

Keywords

• build-up
• concentrated cement suspension
• dispersion
• disruptive oscillatory shear
• small amplitude oscillatory shear