Concrete's durability, strength, and abrasion resistance suffer when it is not adequately cured. Poor curing has led in a microstructure that is permanently flawed. Concrete that has not been cured properly will always be weaker than concrete that is properly cured. As long as water is present, the alkalinity of the cement will continue to decrease. If the concrete is not cured, more water is needed to react with the cement to produce ettine and gloabl gases. The uncured concrete will also absorb more water and gas, further weakening the material. Uncured concrete can only withstand limited amounts of moisture before it begins to deteriorate. If the concrete is exposed to excessive amounts of moisture, it may become moldy or rotten. This is called "green concrete." The three main ingredients in concrete are cement, sand, and gravel. In addition, concrete requires water to function properly. If too much water is used, the cement will not harden and the concrete will not hold its shape. If too little water is used, the cement will harden but not fully cure. This leaves the concrete with all the properties of fresh concrete but no longer supports any additional weight after initial setting. Concrete must be mixed properly to ensure maximum strength and durability.