What material is primarily responsible for the compressive strength of concrete?

Cement is the primary material responsible for the compressive strength of concrete because it acts as the binding agent that holds together the other components in the concrete mixture. When cement is mixed with water, it undergoes a chemical reaction called hydration, which leads to the formation of a hardened structure that provides strength. The quality, type, and amount of cement used significantly influence the final compressive strength of the concrete.

While water is essential for hydration and the overall workability of the mix, it is not the primary contributor to strength. Fine aggregates, which include sand, contribute to the bulk and packing of concrete but do not significantly enhance its compressive strength. Admixtures can modify certain properties of concrete, such as setting time or durability, but they do not serve as the main factor in strength development. Therefore, cement is crucial for establishing the structural integrity and strength of concrete as it cures and hardens.