Gypsum, a mineral extracted from ancient seabeds, stands as a vital component in various applications due to its unique properties. Found naturally in white, grey, yellow, red, and brown shades, gypsum’s distinctive characteristic is its innate fire resistance.
In the intricate process of manufacturing cement, gypsum enters the stage after the formation of clinkers. These clinkers, having undergone cooling, are combined with a small quantity of gypsum before heading to the final grinding phase. For ordinary Portland cement, the gypsum content hovers between 3 to 4%, while quick-setting cement may see a reduction to 2.5%.
Controlling Cement Hydration
The primary function of gypsum in cement lies in slowing down the hydration process. Cement, upon contact with water, swiftly reacts with C3A, leading to rapid hardening. This quick pace hinders the essential stages of mixing, transporting, and placing. Gypsum’s intervention alters this process by instigating a reaction with C3A, resulting in the formation of ettringite. Initially, these fine-grained crystals create a coating on C3A particles, maintaining the plasticity and workability of the cement mix.
Prevention of Flash Setting: Gypsum averts the occurrence of flash setting during cement manufacturing.
Setting Time Regulation: It serves to delay the setting time of cement, extending the duration available for mixing, transporting, and placing.
Enhanced Workability: The addition of gypsum ensures a more prolonged working time, influencing the strength, composition, and workability of concrete.
Heat Reduction: Gypsum acts as a coolant, mitigating the heat generated during the reaction between water, aluminates, and sulfates in cement.
Increased Strength: Gypsum-based cements exhibit higher strength and hardness compared to those without gypsum.
Reduced Water Requirement: Gypsum-based cement demands less water for the hydration process, contributing to its efficient utilization.
In conclusion, gypsum emerges as a crucial player in the cement production process, exerting control over the setting time and enhancing the overall performance of cement-based materials. Its multifaceted impact on the manufacturing and properties of cement positions gypsum as an indispensable element in the construction industry.
