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Which four main compounds make up portland cement?

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Cement The cement-making process, from crushing and grinding of raw materials, through roasting of the ground and mixed ingredients, to final cooling and storing of the finished product.

Portland cement is composed of four primary compounds. In chemical notation, these are:

Tricalcium silicate ( $3 C a O \cdot S i O_{2}$ ), often abbreviated as $C_{3} S$ 1
Dicalcium silicate ( $2 C a O \cdot S i O_{2}$ ), abbreviated as $C_{2} S$ 12
Tricalcium aluminate ( $3 C a O \cdot A l_{2} O_{3}$ ), abbreviated as $C_{3} A$ 13
Tetracalcium aluminoferrite ( $4 C a O \cdot A l_{2} O_{3} F e_{2} O_{3}$ ), abbreviated as $C_{4} A F$ 1

In these abbreviations, $C$ represents calcium oxide, $S$ represents silica, $A$ represents alumina, and $F$ represents iron oxide. In addition to these main compounds, the final product may contain small amounts of uncombined lime, magnesia, and other minor elements.1