Delaying the hydration of Portland cement by sodium silicate: Setting time and retarding mechanism

Abstract

Sodium silicate is widely used as a coagulation accelerator for oil-well cement. However, the existing experimental results show that the addition of sodium silicate can significantly delay the setting of cement paste with retarder. This study investigated the effects of addition of sodium silicate on the setting time of oil-well cement. For oil-well cement with no retarder, the addition of sodium silicate shortened the setting time. In contrast, for oil-well cement with retarder, the addition of sodium silicate prolonged the setting time and served as a type of retarder. Moreover, the mechanisms involved in retarding the hydration of cement by adding sodium silicate were also examined in detail by XRD, BET nitrogen adsorption, and total organic carbon analysis. The results show that the addition of sodium silicate delayed the hydration of tricalcium aluminate and thus prolonged the setting process of oil-well cement.