Final answer:
Concrete is the product of heating limestone, sandstone, and shale in a kiln, which then hardens when mixed with water. As a Roman invention, it is celebrated for its durability, versatility, and ease of production compared to cut stone. The key chemical reaction for its hardening involves slaked lime reacting with CO2.
Step-by-step explanation:
The construction product formed by heating limestone, sandstone, and shale in a kiln, driving off CO2, and forming a material that hardens when mixed with water is concrete. Concrete was indeed a Roman invention and is composed of a mix of lime mortar, pebbles, sand, and water, which can be poured into molds. Once hardened, concrete functions similarly to stone and proves advantageous in construction due to its relative lightness, cost-effectiveness, and ease of production compared to traditional stone quarrying and shaping.
The chemical process of hardening involves the reaction of slaked lime, or Ca(OH)2, with CO2 to form calcium carbonate, contributing to the hardening of plaster and concrete. This process is shown by the reaction Ca(OH)2 + CO2 → CaCO3 + H2O. The role of calcium carbonate is also seen in nature, as limestone caves are primarily formed of this compound.