Which material can inhibit rusting of reinforcement steel when added to concrete mix?

Calcium nitrate is an effective material for inhibiting rusting of reinforcement steel when added to concrete mix due to its ability to serve as a corrosion inhibitor. When incorporated into the concrete, calcium nitrate reacts to form a protective passive layer on the surface of the steel. This layer can significantly reduce the diffusion of chloride ions and moisture, which are factors that contribute to the corrosion of steel reinforcement. Additionally, calcium nitrate has the added benefit of helping to mitigate the effects of alkali-silica reaction in concrete, further contributing to the durability of structures.

The other materials listed do not provide the same level of protection against corrosion. Gypsum primarily acts as a set retarder in cement and does not have properties that inhibit corrosion. Calcium chloride, while it may provide some benefits as an accelerator in concrete mixes, can actually increase the risk of corrosion in steel due to the introduction of chlorides. Tricalcium silicate is a major component of cement responsible for strength development, but does not function as a corrosion inhibitor. Thus, when focusing on enhancing the longevity and protective qualities of reinforcement steel in concrete, calcium nitrate stands out as the most effective choice.