Question

The primary binding compound responsible for strength development in cement is:

• A. Tricalcium aluminate
• B. Dicalcium silicate
• C. Tricalcium silicate
• D. Calcium sulfate

Hint:

Logic Tip: In cement chemistry, the "Silicates" provide the strength. $C_3S$ has "Three" calcium atoms, giving it a faster, more aggressive early reaction compared to the "Two" in $C_2S$, making it the primary early strength driver.

Answer 1

The Correct Option is C

Concept:
Portland cement consists of four main clinker minerals (Bogue's compounds) that hydrate at different rates. The timeline and magnitude of strength development depend entirely on which compound is hydrating.

Step 1: This compound reacts violently and quickly with water. It is responsible for the initial stiffening (flash set) but contributes almost nothing to the structural strength of the concrete.

Step 2: This compound hydrates very slowly. It is responsible for the progressive strength increase that occurs at later stages (from 7 days up to a year).

Step 3: This compound hydrates rapidly and generates a large amount of heat.

Step 4: Tricalcium silicate ($C_3S$) is the most critical compound because it is responsible for the initial and primary load-bearing strength development during the crucial first 1 to 7 days of curing.

Step 5: Calcium sulfate (Gypsum) is added to retard the flash set of $C_3A$, not to provide primary binding strength.