Final answer:
Applying a membrane-curing compound when there is free water on the surface of concrete is not recommended as it can prevent water from evaporating and being absorbed by the concrete. This can lead to reduced strength and increased cracking of the concrete.
Step-by-step explanation:
When there is free water on the surface of concrete, it means that the water is not yet absorbed by the concrete. Applying a membrane-curing compound in this situation is not recommended because the membrane will prevent the water from evaporating and being absorbed by the concrete. This can lead to issues such as reduced strength and increased cracking of the concrete.
Membrane-curing compounds are typically used on concrete surfaces that are already dry, as they provide a barrier to moisture evaporation. This helps the concrete to properly cure and develop its strength. However, if there is free water on the surface, the membrane can trap this moisture and prevent it from evaporating, causing potential problems.
It is important to ensure that the concrete surface is free of free water before applying a membrane-curing compound. This can be done by allowing the water to naturally evaporate or using other methods such as using a vacuum or absorbent materials to remove the excess water.