Our friends at Wimbledon Design and Build the number one builders in Wimbledon and Morden, have produced the following information on the building materials of concrete. Concrete consists of four basic components- water, gravel, sand a Portland cement. When these four mix together, they create concrete, but not in the way that you might think. Many people mistakenly believe that the concrete mixture has to dry and the water must evaporate for the mixture to harden, but an entirely different reaction actually takes place. What to components within the mixture do is react chemically with the rest of the mixture in a process known as hydration.
During hydration, the water and the cement turn into new substances. They become compounds made up of calcium silicate hydrate. The new compounds keep the entire mixture bound together, acting as a sort of super-strong glue. When hydration occurs, these new compounds are created, forming concrete, but they are not what give the concrete its strength.
That comes from a process called curing. This process is the name for how moisture levels are maintained within concrete. Once those moisture levels are where they need to be, hydration keeps on going. Concrete can gain more and more strength as curing continues. If there is some free moisture and some un-hydrated cement within the concrete mixture, then the concrete will just become stronger.
The stronger concrete becomes, the less porous it is. It actually becomes denser. In the initial stages of concrete formation, the concrete is quite porous and not very dense. In those early stages, moisture can escape. What that does is decrease the moisture levels and cause the hydration process to stop. When concrete starts to lose moisture and manages to dry out, it won’t keep becoming stronger. That’s why most people who work with concrete will cover it as it is curing. They don’t want it to dry out and lose its hydration.
If the concrete were to dry out, it would become brittle and lose its strength. Many times, concrete workers will add more water to the mixture to ensure it stays hydrated and continues to trap moisture inside. They want that curing process to take place and the concrete to gain more strength. Once it dries up completely, no more curing can take place. The components of the concrete will have already solidified. If there is too much water, then the particles inside the concrete cannot knit together and form a strong bond. Just like having too little water present, if there is too much water in the mixture, it won’t be very strong.