Concrete is simply a coalition of particles into one solid mass.
The Pyramids have the earliest semblance of concrete, more than 2,000 years before the birth of the Roman Empire in 31 B.C. The ancient Romans did not invent concrete but perfected the art of ‘opus caementicium’: Mixing lime, water and volcanic ash from Mount Vesuvius, to use as a building material.
Concrete is basically a mix of three ingredients – water, cement and aggregate (sand and/or gravel).
Modern concrete was invented in 1756 by English engineer John Smeaton. He added pebbles and powdered brick to the cement. Portland cement, the mass-produced cement used in concrete today, was invented in 1824 by English bricklayer Joseph Aspdin. He burnt ground-up limestone and clay together, a process that changed the chemical properties of these materials, creating stronger cement than crushed limestone.
Additives, a.k.a. admixtures, improve or modify concrete to set faster, or slower, or stronger, reduce corrosion, etc. Additives are used to make specialized concrete products.
During Roman times, it was apparently discovered that adding volcanic ash produced concrete that could set under water. Adding horse hair, which was plentiful then, would make concrete less liable to crack during the setting process. Adding blood made it more frost resistant.
The ingredients for concrete are mixed into a thick paste. The mix is poured through a cone-like instrument in a slump test. How smoothly it flows out, and how fast, shows whether the mix is right.
Concrete is used more than any other man-made material on the planet.
Once the proportion of ingredients is correctly set, batches of concrete are mixed. Large volumes are mixed in batching plants. For small amounts, e.g. In villages or towns where people build their own houses, manual mixers may be used.
Concrete structures are designed to last 100 years or more. Researchers have suggested that adding silica fume can increase durability to 16,000 years. Concrete is also resistant to fire and water.
The ready mixed concrete is poured into a frame for shape. It can also be sprayed, like shotcrete. The mix hardens to create a very strong stone-like building material.
The hardening process is a chemical reaction to air, known as hydration. The water reacts with the cement – the binding agent - which ‘glues’ the sand, aggregate, water and additives together.
Flour to cake is also the same for cement to concrete. The word ‘concrete’ comes from the Latin word 'concretus' which means to grow together.
The time taken for concrete to harden depends on its purpose. It can harden within a few minutes, a couple of hours, in the air, or under water. In cities like Singapore, massive amounts of concrete are needed to build, e.g. skyscrapers, expressways, subways and airport tarmacs.
Concrete connects the past to the future, and is everywhere you look. Without concrete, there would not be safe roads, safe traveling in general, comfortable homes or sturdy buildings to work in.
Useful Concrete Terms
Ready mixed concrete
is produced in a batching plant, precisely to a set recipe, and then delivered to a construction site by a mixer truck.
PanU supplied 6 million cubic metres of ready mixed concrete to public and private sector projects in Singapore in 2016. This equals filling up 2,400 Olympic-sized swimming pools to the brim.
(Assume a pool that is 50 m x 25 m x 2 m).
is concrete in which steel reinforcing bars (rebars) or rods are embedded to increase its tensile strength.
Reinforced concrete was invented by French gardener Joseph Monier in 1849.
is produced by casting concrete in a reusable mold or "form" then placed onsite. For example, expressway beams and pre-fabricated building components.
In Singapore, pre-cast concrete comprises less than 10% of the total concrete industry. It is used mostly in public housing projects.