Civil Engineering - Building Materials - Discussion

Properties of cement compounds These compounds contribute to the properties of cement in different ways

Tricalcium silicate, C3S:- This compound hydrates and hardens rapidly. It is largely responsible for portland cement's initial set and early strength gain.

Dicalcium silicate, C2S:- C2S hydrates and hardens slowly. It is largely responsible for strength gain after one week.

Tricalcium aluminate, C3A:- It liberates a lot of heat during the early stages of hydration, but has little strength contribution. Gypsum slows down the hydration rate of C3A. Cement low in C3A is sulphate resistant.

Tetracalcium alumino Ferrite, C4AF:- This is a fluxing agent which reduces the melting temperature of the raw materials in the kiln (from 1650o C to 1450o C). It hydrates rapidly but does not contribute much to the strength of the cement paste. By mixing these compounds appropriately, manufacturers can produce different types of cement to suit several construction environments.

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.

Answer is right, When water is mixed with cement to form a paste, reaction starts. In its pure form, the finely ground cement is extremely sensitive to water. Out of the three main compounds, viz. C3A, C3S, and C2S, reacts quickly with water to produce a jelly-like compound which starts solidifying. The action of changing from a fluid state to a solid state is called 'setting' and should not be confused with 'hardening'.

The Answer is right because it is asking the for the early setting time of cement which is due to tricalcium aluminate but for the early strength of cement, tricalcium silicate and ultimate strength or final strength is due to dicalcium silicate. So don't be confused be clear.

Both C3A and C4AF are responsible for flash setting. As the proportion and rate of hydration of C4AF are more than that of C3A, C4AF is responsible for the initial setting time.

Hello guys, the answer is right, because C2S is responsible for early STRENGTH of cement in the INITIAL stage, in this question ask the initial setting time of cement.

Answer is wrong C3S (Tricalcium Silicate) is responsible for initial setting and Di Calcium silicate (c2s) contributes strength after 7 days.

C3S - early strength.
C2S - ultimate strength.
C3A - the initial setting of cement.

Heat of hydration C3A > C3S > C4AF > C2S.

When water is added in cement, first tricalcium aluminate is reacted with water and it is responsible for initial setting of cement.

Give ans is right.

Here asked about initial setting, not asked speeds the setting. Kindly read the que again.