Cement and concrete are terms that are often used interchangeably. Cement is an ingredient of concrete, while concrete is a mixture of aggregates, cement, and water. The most common aggregates used in concrete are sand and gravel or crushed stone.
Basically, concrete is a mixture of cement and water, also called paste, and aggregates. When this mixture binds together into a hard rock-like mass you have concrete.
Concrete, whether it is ready-mix concrete supplied by a company like Pretora Ready Mix, or a small batch mixed up in your backyard, can be moulded and formed into any shape when it’s just mixed. It becomes strong and durable when it hardens and continues to do so as the concrete ages, making concrete a preferred building material in various structures including sidewalks, skyscrapers, houses, and bridges.
Ready-mix concrete makes it easy to complete building jobs because it decreases the amount of mixing time need on site.
The ratio and mixing of ingredients are crucial when aiming for strong, durable concrete. Without enough paste the concrete is rough and porous, while too much paste makes the concrete more likely to crack, resulting in the need to replace it often.
Generally, a concrete mixture is by volume about 10 to 15% cement, 60 to 75% aggregates and 15 to 20% water. The remaining 5 to 8% may be made up of trapped air bubbles in the mixture.
When combined with water, cement undergoes a chemical reaction called hydration. This allows the paste to harden as it surrounds and binds to the sand and stone aggregates.
The strength of paste depends on the water to cement ratio and the better quality the paste is, the better quality the concrete is. By lowering the water-cement ratio, high-quality concrete can be achieved without sacrificing the workability of the fresh concrete. In general, using less water produces a higher quality concrete, as long as the concrete is properly placed, consolidated and cured.
Pretoria Ready Mix supplies ready-mix concrete for houses and civil projects. Get in touch with us today.