3% of gypsum is added to cement to "prevent the rapid setting of cement"
Gypsum is added to cement to decrease the setting time.
Gypsum is added to portland cement to retard C3A hydration
Because the gypsum only needs 2 percent added to the mix
The construction industry uses both the natural and the synthetic forms of gypsum in Portland cement manufacturing. Although the amount of gypsum used in the mix represents a small percentage of the volume of all ingredients, gypsum has important functions.
gypsum increase the setting time of cement.
The primary minerals used to make cement are limestone, clay, and gypsum. Limestone provides calcium and clay provides silica and alumina, which are necessary for the chemical reactions that occur during cement production. Gypsum is added to regulate the setting time of the cement.
Gypsum is a mineral that contains up to 88% CaSO4.2H2O. this compound Calcium Sulphate dihydrate is responsible for retarding the setting time of cement. the action of Calcium Sulphate dihydrate is such that it inhibits the speed at which Calcite (C3S) molecules bind with water to set thus creating a cement that is workable.
gypsum
Gypsum is commonly used in construction as a building material. It is used to make drywall, plaster, and cement. It is also used in agriculture as a soil amendment to improve soil structure and fertility.
Gypsum board is mainly used for walls and ceilings and is known as drywall. Gypsum blocks are used similar to cement blocks in construction projects.
OPC is ordinary Portland cement and PPC is Portland pozolona cement. OPC is obtained by grinding clinker and gypsum whereas PPC is obtained by grinding clinker gypsum and high reactive silica. High reactive silica improves the quality of cement by reducing liberated lime.
We are a company that produces an additive capable to mix in perfec combination gypsum and cement in a proportion of (75% gypsum/25%cement) for the construction industry, producing a rendering mortar whith better qualities than any good mortar in the market (degradationb free, mildew free, corrosion free) as the additive carries a component to avoid all these pathologies. Question: when mixing gypsum and cement, is it convenient to raise the ph of the gypsum with another component to improve strenth and its lifetime? We would be glad to get an answer to: j.anru@emechinternational.com