Gypsum, a naturally occurring mineral, is a key player in various industrial applications, particularly in the construction realm. Derived from ancient seabeds, it consists of calcium sulfate and water, displaying a range of colors from white and grey to yellow, red, and brown. One of its standout features is its innate fire-resistant property.
In the intricate manufacturing dance of cement, clinkers take center stage. These clinkers, post-cooling, receive a dash of gypsum before the final grinding process. The amount of gypsum added varies, hovering between 3 to 4% for ordinary Portland cement and potentially reduced to 2.5% for quick-setting cement.
The primary mission of gypsum in cement is to pump the brakes on the hydration process that kicks into gear when water enters the cement mixture. Hydration involves a swift reaction with C3A, leading to rapid hardening. This quick pace poses challenges in transporting, mixing, and placing the cement.
Gypsum intervenes in this high-speed drama by fostering the creation of ettringite during the hydration process. These initial fine-grained crystals form a protective layer on the C3A particles, too tiny to bridge the gaps between cement particles. This keeps the cement mix malleable and pliable, allowing ample time for the critical steps of mixing, transporting, and placing.
The ability of gypsum to act as a retarding agent significantly impacts the strength, composition, and workability of the concrete.
Gypsum acts as a guardian, preventing the premature flash setting of cement during the manufacturing process.
Gypsum puts the brakes on the setting time of cement, extending the window for mixing, transporting, and placing.
When water joins the cement party, the reaction between aluminates and sulfates generates heat. Gypsum steps in as a cooling agent, curbing the heat of hydration.
Gypsum-infused cements boast superior strength and hardness compared to their non-gypsum counterparts.
Gypsum-based cement requires less water in the hydration process, contributing to a more efficient and sustainable construction process.
In conclusion, the unassuming mineral, gypsum, emerges as a silent hero in the realm of cement, regulating its behavior and enhancing its properties, ultimately shaping the structures that stand tall in our built environment.