Cement hydration chemistry: which set of cement compounds react with water to drive the hydration reactions that produce strength and paste structure in ordinary Portland cement?

Introduction / Context:
Cement hydration involves several clinker phases reacting with water to form binding products (C-S-H gel, calcium hydroxide, ettringite, etc.). Understanding which compounds hydrate clarifies early versus later strength development.

Given Data / Assumptions:

• C_3S (tricalcium silicate), C_2S (dicalcium silicate), C_3A (tricalcium aluminate), C_4AF (tricalcium alumino-ferrite).
• Ordinary Portland cement with gypsum as set regulator.

Concept / Approach:
All four primary clinker minerals hydrate. C_3S hydrates rapidly, giving early strength; C_2S hydrates slower, contributing to later strength. C_3A reacts vigorously, especially with gypsum to form ettringite then monosulfate. C_4AF hydrates more slowly, contributing modestly to strength and color.

Step-by-Step Solution:
List reactive phases: C_3S, C_2S, C_3A, C_4AF.Recognize that each undergoes hydration reactions with water.Therefore, “All the above” is correct.

Verification / Alternative check:
Heat of hydration curves and XRD/SEM studies confirm all phases participate in hydration chemistry.

Why Other Options Are Wrong:

• Picking only a subset ignores the reactivity of the remaining phases.

Common Pitfalls:

• Assuming only silicates hydrate; aluminates are crucial for setting and early reactions.

Final Answer:
All the above