The Role of Gypsum in Cement Manufacturing

Gypsum is an essential component of cement manufacturing, although it represents only 3 to 5% of the final composition. Its main role is to regulate the setting time of the cement, without which the concrete would harden almost instantly upon contact with water, making any implementation impossible. Gypsum retards the hydration of tricalcium aluminate (C3A), the clinker compound responsible for rapid setting.

The dosage of gypsum must be precise: insufficient, the cement sets too quickly (flash set); excessive, it can cause abnormal swelling of the concrete and reduce mechanical strengths. The optimal quantity depends on the C3A content of the clinker, the grinding fineness and the ambient temperature. At Dakhla Aménagement, the dosage is rigorously controlled by our laboratory for each production batch.

Gypsum also influences the long-term properties of the cement. An appropriate dosage contributes to the optimal development of mechanical strengths at 7, 28 and 90 days. It also participates in the dimensional stability of the hardened concrete, preventing swelling reactions that could compromise the integrity of the structures.

There are different types of gypsum that can be used: natural gypsum (CaSO4·2H2O), hemihydrate (plaster) and anhydrite. The choice of type and purity of gypsum is an important parameter that the engineers at Dakhla Aménagement master to guarantee the consistency of the quality of our CPJ 45 and CPJ 55 cements.