The correct answer is: B. Finer grinding
Cement is a powder that is made by heating limestone and clay to a high temperature. When water is added to cement, it reacts to form a hard material called concrete. The strength of concrete depends on the type of cement used, the amount of water added, and the curing conditions.
Rapid hardening cement is a type of cement that gains strength quickly. This is due to the finer grinding of the cement particles. The smaller the particles, the more surface area they have, and the faster they can react with water.
Gypsum is a mineral that is added to cement to control the setting time. It does not affect the strength of the concrete.
Tri-calcium silicate and tri-calcium aluminate are two of the main components of cement. They are responsible for the strength of the concrete. However, they do not affect the early attainment of strength.
In conclusion, the early attainment of strength in rapid hardening cement is mainly due to the finer grinding of the cement particles.