Answer:

Introduction:
Cement is a crucial material used in the construction industry. It is used as a binding material in the construction of buildings, bridges, dams, and other civil engineering structures. Cement is manufactured by heating a mixture of limestone and clay in a kiln. The resulting product is then ground into a fine powder. There are different types of cement available in the market, and each type has its unique properties and applications.

Tricalcium Silicate:
Tricalcium silicate, also known as alite, is the most abundant compound in cement. It is responsible for the early strength of cement. When water is added to cement, tricalcium silicate reacts with water to form calcium silicate hydrate (C-S-H) and calcium hydroxide (CH). This reaction is exothermic and releases a considerable amount of heat. The reaction between tricalcium silicate and water is responsible for the initial setting of cement.

Dicalcium Silicate:
Dicalcium silicate, also known as belite, is the second most abundant compound in cement. It reacts with water to form C-S-H and CH, but the reaction is slower than that of tricalcium silicate. Dicalcium silicate is responsible for the long-term strength of cement.

Tricalcium Aluminate:
Tricalcium aluminate, also known as aluminite, is the compound responsible for the rapid hardening of cement. It reacts with water to form calcium aluminate hydrate (C-A-H) and calcium hydroxide. The reaction between tricalcium aluminate and water is faster than that of tricalcium silicate, but it is also less exothermic. Tricalcium aluminate is responsible for the early strength gain of cement.

Conclusion:
In conclusion, tricalcium aluminate is the compound in cement that reacts immediately with water and sets first. It is responsible for the rapid hardening of cement and the early strength gain of cement. Tricalcium silicate and dicalcium silicate are also essential compounds in cement and contribute to the overall strength of cement.