Rheological behavior of oil well cement pastes containing various types of dispersants at different hydration temperatures

Abstract

This research discusses the effects of different types of oil well dispersants and hydration temperatures on the rheological properties of cement pastes through rheometer. A polycondensate dispersant, AFS and three polycarboxylate dispersants, APC, PCES and MHS, were used at dosages ranging from 0.1% to 0.3% by weight of cement, and three hydration temperatures of 30, 45 and 60 ℃ were selected. The yield stress was calculated by modelling the flow curve through Herschel-Bulkley and Modified Bingham models. Furthermore, the thixotropy of the cement paste involving different dispersants and hydration temperatures was analyzed by hysteresis loop methods. Besides, the small amplitude oscillatory shear (SAOS) test was applied to evaluate rigidification rate of cementitious material, offering useful information for structuration process of cement paste. The results show that the influences of dispersants on rheological behavior are closely related to the molecular structure and the dosage of dispersant, as well as the temperature of hydration. Increasing the dosage of dispersant decreases the yield stress and apparent viscosity, but increases the hysteresis loop area, especially at the lower hydration temperature of 30 ℃. During SAOS measurement, the critical strain of cement paste with dispersants is higher than without dispersant. The storage modulus (G’) continuously increases with hydration time and temperature.