What is the main reason for covering concrete with straw after pouring?

Covering concrete with straw after pouring primarily serves the purpose of preventing excessive evaporation of water from the surface of the concrete. When concrete is freshly poured, it contains a significant amount of water. This water is critical for the curing process, which is the chemical reaction that allows the concrete to harden and gain strength. If this water evaporates too quickly, it can lead to problems such as surface cracking, reduced strength, and overall poor performance of the concrete. By using straw as a covering, it provides a barrier that keeps moisture in, while also allowing for some airflow, which helps in managing the hydration process effectively.

Other methods, such as using plastic sheeting, can also be employed, but straw is a natural and effective option for mitigating water loss and ensuring that the concrete cures properly under optimal conditions. The straw does not add thermal insulation or significantly promote faster curing on its own; its main role is moisture retention during the crucial initial curing phase.