Performance Characteristics of Calcium Sulfoaluminate Cement

What is CSA Cement

CSA cement is the abbreviation for calcium sulfoaluminate cement. It uses bauxite, limestone, and gypsum as the main raw materials and, through a low-temperature calcination process at 1300~1350℃, forms clinker with calcium sulfoaluminate and dicalcium silicate as the main components. Ground together with an appropriate amount of gypsum, this hydraulic cementitious material exhibits characteristics such as short setting time, high early strength, and low alkalinity.

Performance Characteristics of Calcium Sulfoaluminate Cement

Faster Setting Time

According to the GB175-2007 standard, the initial setting time for Portland cement should not be less than 45 minutes, and the final setting time should not exceed 10 hours. In comparison, the initial setting time for CSA cement is typically between 30 to 40 minutes, and the final setting time is between 55 to 75 minutes, demonstrating its faster setting properties.

Remarkable Early Strength

Compared to ordinary Portland cement, CSA cement exhibits a more rapid strength gain. Its 1-day strength is notable, and the strength at 3 days can reach over 85% of the 28-day strength of Portland cement. Additionally, because CSA cement clinker contains a certain amount of C₂S, its later strength can steadily increase, thereby avoiding the late strength decline problem that may occur with some fast-setting, quick-hardening, early-strength cements.

Moderate Free Expansion Rate

During the hydration of CSA cement, ettringite is generated, which can cause volume expansion due to its growth. Consequently, CSA cement exhibits a certain degree of free expansion. Data shows that under the condition of a lime-sand ratio of 1:0.5, the 28-day free expansion rate of low-alkali CSA cement ranges from 0.00% to 0.10%, while that of fast-hardening CSA cement ranges from 0.00% to 0.07%. This indicates that although CSA cement possesses some expansion characteristics, the expansion rate is controlled at a low level, ensuring its safety in practical applications.

Lower Liquid Phase Alkalinity

Compared to the hydration liquid phase pH of Portland cement, which is about 13, the hydration liquid phase pH of CSA cement is maintained in the range of 11.5 to 12.0. This lower alkalinity characteristic makes low-alkali CSA cement ideal for preparing glass fiber composites. Especially when an appropriate amount of admixture, such as limestone, fly ash, or slag powder, is added to CSA cement, its alkalinity can be further reduced, making it more suitable for the production of glass fiber products.

Excellent Freeze-Thaw Resistance

CSA cement also performs well in freeze-thaw resistance. Due to its fast-hardening and early-strength properties, its strength is less affected when subjected to freezing in the early stages. In contrast, ordinary Portland cement, when frozen early and subsequently returned to normal temperature, loses about 50% of its strength, while CSA cement loses only about 9%. Additionally, under low-temperature conditions from 0 to 10℃, the early strength of CSA cement is 5 to 8 times that of ordinary Portland cement. If used in even lower temperatures of -20℃ and combined with a small amount of antifreeze to keep the casting temperature above 5℃, the concrete can achieve 70% to 80% of its design strength within 3 to 7 days.