Effects of Different Retarders on Thickening and Mechanical Properties of Calcium Sulfoaluminate Cement

Sulphoaluminate cement is a type of cement independently developed in China during the last century, primarily composed of calcium aluminate hydrate and dicalcium silicate. Owing to its rapid hydration rate and swift development of early mechanical properties, it is also known as early-strength cement. Sulphoaluminate cement has been widely used in the construction cement sector. However, due to its excellent performance in low-temperature environments and its potential for low-temperature cementing, it has garnered significant attention and gradually become a research hotspot. Nevertheless, the rapid early-stage hydration rate of sulphoaluminate cement makes its setting time difficult to meet the requirements of cementing operations, thereby limiting its application in cementing projects. To regulate the thickening properties of sulphoaluminate cement, this study investigates the regulatory effects and underlying mechanisms of three representative retarders (glucose, boric acid, and borax) on the thickening and mechanical properties of sulphoaluminate cement. The results show that: in terms of mechanical properties, all three retarders promote the increase in 1-day compressive strength of the cement paste without significantly affecting later-stage strength. Regarding retarding effects: boric acid > glucose > borax, and none of them alter the low-temperature right-angle thickening characteristics of sulphoaluminate cement. The addition of these three retarders does not alter the types of early-stage hydration products in sulfoaluminate cement but only affects the rate of their formation. At low dosages, they promote the formation and development of calcium aluminate hydrates (cahs), while at higher dosages, they inhibit the hydration reaction, leading to a significant decrease in the formation rate of cahs.