Concrete

Concrete is one of the important and most widely used construction materials in the world. Concrete is environmentally friendly in a variety of ways. Once set it does not leak harmful chemicals into the surrounding environment. Also it has great compressive strength and thermal properties. Concrete is a composite material made up of Portland cement, water, and aggregate. The cement and water are mixed into a paste which becomes a binder and is mixed with an aggregate, commonly sand and blue metal rock.

Concrete Mix

In a given quantity of concrete the aggregate takes up about 75% of the volume while the remaining volume is cement paste and small air voids. Ready-mix concrete is a common type of concrete that is manufactured in a factory or batching plant, according to a set recipe, and then delivered to a worksite, while being continually mixed in transit mixers (cement trucks). There are many different types of mixes available for houses and the mixture depends on the use and properties needed.

Concrete Setting

The setting or hardening of concrete takes place through a chemical reaction call Hydration which is a reaction between water and cement. Concrete has a limited time span between mixing and setting and this means that ready-mix should be placed within 2 hours of it being mixed at the batching plant. It is very important to have the concrete form work in place before the concrete is ordered.

There are a number of different types of concrete available that depend on the use and strength and working time required. However for building a house, general purpose Portland cement is the main cement used. Concrete, like bricks, has very strong compressive strength; however it is relatively weak under tension. This means it is has excellent properties on holding and supporting weight but it is not very good at flexing or bending. This is the reason that reinforcing steel is added to concrete slabs.

Tips

• When ordering know your purpose, for example, concrete slab for a house, concrete driveway, concrete path, etc.
• General purpose for house slabs and driveways is 20 MPA (Mpa is the strength rating)
• On Hot Days do not let the concrete dry out. A spray of water may be necessary during the curing process. Or if the concrete is set pond water on the top to stop it drying out.