What is the primary function of cement in concrete?

• A. To hydrate with water and bind aggregates together to form a solid matrix.
• B. To act as a decorative finish
• C. To replace aggregates in concrete
• D. To be a filler with no chemical reaction

Answer: (C)

The primary function of cement in concrete is to act as a hydraulic binder that chemically reacts with water to form binding phases. When water is added, cement hydrates and produces binding products like calcium-silicate-hydrate that fill the spaces between aggregates and create a cohesive solid matrix. This matrix glues the sand and gravel together, giving concrete its strength and durability. It’s not just a decorative layer, it doesn’t replace aggregates, and it certainly isn’t a simple filler with no chemical reaction—the hydration process is what turns the mix into a solid, structural material.