Concrete is the most versatile construction material.
It can be placed as a liquid into moulds of virtually any shape or size and, over a period of a few hours, will solidify in that form. The cement in concrete undergoes what is called an “hydration” reaction when it is mixed with water. This reaction, in basic terms, forms a gel around each cement particle and proceeds to bind the sand and gravel into an interlocking mass.
Concrete undergoes a setting process as well as a reduction in moisture content. As the interlocking crystalline structure grows and becomes interconnected the concrete has started to set. At this time, further mixing or agitating will greatly reduce the potential strength of the concrete, as the initial setting process only works over a short period of time.
The water in concrete serves two purposes. Firstly, water is required for the hydration process to begin. Secondly, and equally as important, water is required for adequate workability. The water that is added to the dry ingredients of concrete is weighed by the kilogram at the batch plant.
Excess water in concrete has a very detrimental effect on the finished product. It causes strength reduction, poor durability and shrinkage cracking, which, when combined, results in a very poor finished product. Therefore, water should not be added to concrete for a short term increase in workability as it has a detrimental effect on the short and long term quality of the concrete.
The amount of water added to each load at the batch plant is very precise and should not be altered by adding additional water on site to improve the workability of the concrete. Correctly batched concrete does not contain excess water and results in a superior final product.
The setting process of concrete is a precise event and great care goes into the preparation of your selected mix. To avoid any lowering of the concrete’s performance a few basic rules must be observed.
Firstly avoid adding extra water to the mix, or having an inefficient job site that unnecessarily extends the mixing time of the concrete. Hot or cold weather affects the laying and finishing time. If you require varied setting times, speak to our sales team, as we can design a mix to specifically meet your requirements.
Knowledge is power, so understanding this interesting and useful product gives you a professional advantage