Innovative Application and Performance Exploration of Liquid Accelerator in Calcium Aluminate Cement Refractory Castable

Drawing on the construction technology of wet spraying cement-based materials, the construction method of bonding calcium aluminate cement refractory castable to high-temperature kiln equipment through wet spraying could improve work efficiency. The addition of liquid accelerator could significantly promote the setting and hardening of calcium aluminate cement (CA50-II, with Al 2 O 3 content between 50% and 60%, a relatively slow setting time, and excellent refractory performance and high-temperature volume stability), which was one of the important factors determining the construction performance of refractory castable. This research innovatively investigated the influences of alkaline liquid accelerator (A-LA), mainly composed of sodium aluminate, and alkali-free liquid accelerator (AF-LA), mainly made of aluminum sulfate, on the coagulation, hydration process, mechanical strength, and microscopic properties of CA50-II hydration products. The results indicated that adding different liquid accelerators could effectively promote the CA50-II solidification. After adding 2.0% A-LA and AF-LA, the initial setting time of CA50-II mortar was shortened by 70.2% and 46.8%, while the final setting time was shortened by about 76.7% and 66.8%, respectively. In addition, the compressive strength of CA50-II mortar with 2.0% A-LA was significant at 6.0 h. In the hydration later stages, adding 2.0% A-LA and AF-LA would reduce CA50-II mortar mechanical strength. In comparison, the addition of 2.0% A-LA had a more prominent effect on promoting CA50-II coagulation, while the compressive strength loss of CA50-II mortar with 2.0% AF-LA was relatively weak. The main reason may be attributed to the fact that the addition of 2.0% A-LA and AF-LA reduced the AH3 gel formation in the CA50-II hydration product and decreased the compactness of the hydration product structure, which led to the inversion of CA50-II mechanical strength in later periods. In comparison, there was a greater influence of A-LA on the composition and content of the CA50-II hydration product.