There is more to making concrete than meets the eye. Ever wonder what the curing process means? This is an important part of the process for making strong, durable concrete but what does it involve and why does it need to happen?
When you add water to cement, a chemical reaction called hydration begins. Over time, this process of hydration of cement and water transforms into a calcium silicate hydrate compound. This is a fancy name for the glue that makes the cement stick together. It becomes a binding agent, holding the aggregate together and forming a hard, solid substance which we rely for our roads, walkways and buildings. Other compounds are also formed during this hydration process, but they do not increase the strength as calcium silicate compound does.
Curing is needed to keep this important process of hydration. It maintains moisture levels deep in the concrete to allow the hydration process to continue. You would not imagine so much happens after concrete has been laid! If moisture and hydrated cement are present in the concrete, it will continue to harden, stronger and more solid. In short, curing is a method of keeping the cast concrete moist, so that the hydration process can continue.
Concrete continues to hydrate and it becomes less porous as it gets stronger. The reason this is important is that newly laid concrete is much more porous than older concrete, which has had longer to hydrate. The higher porosity of new concrete, the more moisture evaporates from the surface. It lowers the level of humidity inside is so important for hydration to continue. If the concrete dries too quickly, it will not be strong. That’s why you shouldn’t cover freshly cast concrete.
Concrete is not fully cured until the majority of the cement has been hydrated. It really can take months, or even years! Normally, concrete is cured just long enough for it to achieve the desired strength. Therefore, the time to cure depends on the concrete purpose. Temperature, mix design and strength needed are all factors that must be decided when starting development with concrete. For Kent Ready Mix Concrete, visit a site like VMC Ltd, leading suppliers of Kent Ready Mix Concrete
Concrete that is needed more quickly will have a design mix adjusted to reflect this requirement. After all, the customer will not want to wait for months! Mix design can be adjusted to have a high initial strength, allowing the concrete to be cast, cured, processed and delivered within days. The construction grade concrete is designed to achieve a very high level of strength in less than a month. More sophisticated mixes can achieve the desired strength in just a few hours if necessary.
Temperature also has a significant impact on the cure time. Cold temperatures reach desired strength levels in a longer time than in warm conditions. Strength is very important in concrete as it is used to build some of our most important infrastructure. Weak concrete is dangerous because it can crack, soften or chip leaving structures vulnerable.