Q1: Initial setting of cement is caused due to

ANS:C - Tri-calcium aluminate

1. C3S - The hydrolysis of C3S is mainly responsible for 7-day strength and hardness.

2. C2S - At early ages, less than a month, C2S has little influence on strength and hardness. While after one year, its contribution to the strength and hardness is proportionately almost equal to C3S.

3. C3A - Tricalciumaluminate is responsible for the initial set, high heat of hydration and has a greater tendency to volume changes causing cracking.

4. C4AF - It is responsible for the flash set but generates less heat. It has the poorest cementing value.