It’s everywhere around us (not unless you live in the forest, and even then your home will probably be built with it) and it is surrounding you now as you read this. No, not air, but that material which is heavily used for building called ‘concrete.’
What is the Difference between Concrete and Cement?
The main difference between concrete and cement is that concrete is a blended material made from a mixture of water, aggregate, and cement. Cement is a fine powder made of limestone and other minerals, which absorb water and acts as a binder to hold the concrete together. Concrete is often used with a reinforcing steel mesh, known as rebars. While cement is solely a construction material, concrete cannot be made without cement.
What is Cement Made From?
Cement is manufactured from limestone, calcium, silicon, iron, and aluminium, among other ingredients. This mixture is heated in large kilns to around 2,700°F (1,482°C) to form something known as ‘clinkers’, which closely resemble marbles. These are then ground into a powder and gypsum is added, creating the grey flour-like substance known as cement. When mixed with water, it starts a chemical process that allows it to harden.
What is Concrete Made From?
Concrete, in comparison, is a building material that uses cement to hold and bind together crushed stone, rock, and sand, also known as ‘aggregate.’ Cement makes up around 10% to 15% of the total mass of concrete; the exact proportions can vary depending on the type of concrete being made. The aggregate and cement are fully mixed with water, which starts the chemical reaction which then causes the cement to harden and set. Before this happens, the concrete mix is usually poured into a mould so that it will harden into a specific shape, in most cases a block or a slab.
How Much Time Does it Take to Set?
The length of time it takes for concrete to harden and set depends in part on how much gypsum is added to the mixture. This process can be sped up by adding calcium chloride or slowed down by adding of all things, sugar. These compounds work by altering the development of the hardening crystals that form as the concrete sets. Concrete that will be exposed to freezing and thawing conditions will have additional chemicals added to help avoid cracking. If interested in reinforced steel mesh and you happen to be in Australia, make sure to use a reputable and trusted company.
Aggregate is of vital importance, because it makes up more than 60% of a concrete mix, and up to 80% in other cases. Larger rocks require less concrete, so less water is needed, and a stronger end product is achieved. Aggregate is also cheaper than cement, so a higher percentage can bring costs down. In general terms, a good aggregate has a combination of rocks of many different sizes, with a specific average and maximum size; these stones must be clean and durable, and must not consist of clay or other minerals that can absorb water.
Concrete’s high rock content makes it extremely durable, and it often is used in swimming pool decking, skyscrapers, subways, and lamp posts, as well as pavements, driveways, and roads. Take a look around you and wonder at its use!