Concrete is an integral part of modern society. From roads and bridges to the buildings in which we live and work, everywhere around you are structures and infrastructures comprised of concrete. Considering concrete is used to make vital parts of our everyday lives, you should know the science behind concrete that makes it so strong and reliable.
Composition of Concrete
Concrete is made from more than one type of material, making it a composite material. The composite material is formed with a filler, which is an aggregate used to make the texture of the concrete, and a binder or paste used to "glue" the filler together. Cement and water make up the binder. The mixture of aggregates, cement and water creates the useful composite we know as concrete.
Cement is made from clay, sand, iron ore and limestone burned together at extremely high temperatures. The limestone must be quarried and crushed into small pieces. A mixer combines the small pieces of limestone, iron ore, sand and clay to form a powder of all four components. A rotating cylinder-shaped kiln then burns this composition of materials for up to two hours.
When you mix water with cement, it forms a paste that binds all the components together. The process of hydration is a chemical reaction between the water and the components of the concrete that causes the concrete to harden. You must use pure water to ensure the chemicals react correctly and create strong cement. The ratio between the cement and the water is crucial to making useful cement. Too little or too much water could make the cement too weak or unworkable. Useful cement requires the perfect balance between cement and water.
Aggregates are another component used in making concrete. Aggregates are materials such as sand or rocks added to the cement and water mixture. Since cement is the most expensive part of making concrete, adding cheaper aggregates gives you more concrete for less price. The final product is about 70 to 80 percent aggregates. Choosing a type of aggregate depends on the type of concrete you want to produce. You can create dense, strong concrete by using dense aggregate. Likewise, using soft and porous aggregates like sand creates weaker concrete with less resistance to wear. Like water, good aggregates should be pure. Any impurities in the aggregate could interfere with the chemical reaction required to make concrete or make the concrete weaker.
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