Concrete is found almost everywhere we live, work, and play. But as commonplace as concrete might seem, it’s a complex material whose use dates back more than 2,000 years to Roman times.
Early forms of concrete-like materials were first used in ancient Egypt, where Egyptians mixed lime and gypsum as a mortar to build the Great Pyramids.
The Romans would later invent “pozzuolana”, a mixture of slaked lime and volcanic ash. Mixed with stones and sand, pozzuolana created a material that resembles today’s modern concrete. This material can still be seen today in the ruins of ancient Rome.
The concrete we use today is a mixture of coarse aggregates (rock and stones), fine aggregates (sand), and a binder paste composed of Portland cement and water.
Concrete starts out as a thick, viscous material that hardens when the binder paste reacts with water, a process called “hydration.” This reaction starts out rapidly after the concrete is placed, but how quickly concrete sets can be controlled by continuous mixing or through the addition of chemical additives known as admixtures.
Concrete hardens by hydration for years after placement, and gains strength as it ages. A concrete’s strength measurement is based on its “28-day” strength, which is deemed by engineering authorities as a suitable length of time for curing before testing a concrete’s strength.
Although the “recipe” for concrete might appear straightforward, a virtually infinite variety of concrete mixes is possible by carefully controlling the amount and type of aggregate, cement, water, and chemical additives used in its production.
Some examples of these variations include:
- Using fly-ash instead of cement powder to slow hydration, often used in massive pours
- Adding water reducers to preserve concrete’s workability while increasing its strength
- Introducing retardants that delay setting of the concrete, sometimes necessary on very hot days
- Adding colourants to tint the concrete to meet architectural design specifications
For more information about concrete
Concrete is suitable in a surprisingly wide range of industrial and residential applications. For more information about concrete, visit our Frequently Asked Questions page, or contact our dispatcher directly.