Concrete is the world most widely used construction material. It is the second most consumed material after water. The annual consumption of concrete is around eight billion cubic meter per year, which can be translated to equivalent to more than one cubic meter per person each year. Concrete is made of three principal ingredients that comprised of cement, aggregates (both fine and coarse aggregates) and water. When all ingredients are mixed together, it would transform into a liquid state that can be poured into almost any shapes.
Cement or commonly known as Portland cement, when mixed with water acts as binding agent that bond the aggregates together. The use of water serves two purposes; first to chemically react with the cement and then assist in the hydration process, and secondly to enhance the workability of the concrete during pouring state. So the amount of water used in the concrete are one of the crucial elements to consider in the mix design. Too much of water might be good in term of workability but can have an adverse effect on the strength. In practice, concrete mix designer need to specify the water-to-cement (w/c) ratio. Typically the maximum w/c ratio for strength class C30/37 is somewhat between 0.45 and 0.55 depending on the exposure condition.
Concrete is relatively popular for many reasons. First, the materials used to make concrete are readily available anywhere in the world and secondly concrete is a low technology system. It does not required complicated equipment. Depending on the mixtures of cement, aggregates and water we used, we can produce materials with very different properties. Concrete is usually strong in compression, but weak in tension. For structural applications, it is normal practice to reinforce with steel bars to enhance the tensile resistance. Concrete is also durable in wide range of environment. Due to this reason, concrete is not just popular for use in buildings we live in, but also in many infrastructure such as bridges, nuclear power station, offshore structures, coastal structures, high temperature furnaces and so on.