Concrete is an engineering material that simulates the properties of rock and is a combination of particles closely bound together.
Concrete is made up of three main components:
- Binder (Cement)
In addition to the three main components, concrete admixtures and additives are also used in concretes with higher performance specifications again both fresh and hardened.
Sika began developing the first admixtures for cementitious mixes in 1910, the year in which it was founded. At that time the main aims were to shorten the setting time of mortar mixes, make them waterproof and increase their strength. Some of these early and successful Sika products are still in use today.
Water is necessary in concrete for consistence and hydration of the cement, but too much water is unfavourable for properties of the hardened concrete, so Sika products were also developed to reduce the water content while maintaining or even improving the workability.
Because of its general characteristics, concrete is sometimes referred to as artificial rock. It’s the most widely used construction material and is very strong in resisting compression. In use where tensile stresses have to be accommodated, reinforcement is incorporated into the concrete to absorb tension. It allows flexibility in structural form as it can be moulded into a multiplicity of shapes.
|Natural and industrial pozzolans||P or Q|
|Silica-rich fly ashes||V|
|Lime-rich fly ashes||W|
|Burnt shales (e.g. oil shale)||T|
|Limestone||L or LL|
Due to continually increasing demands for the concrete quality (mainly durability) and huge advances in admixture and concrete technology, it is now possible to produce many different kinds of concrete
- Standard concrete – Concrete with a maximum particle diameter > 8 mm Density (kiln dried) > 2’000 kg/m3, < 2’600 kg/m3
- Heavyweight concrete – Density (kiln dried) > 2’600 kg/m3
- Lightweight concrete – Density (kiln dried) > 800 kg/m3 and < 2’000 kg/m3
- Fresh concrete – Concrete, mixed, while it can still be worked and compacted
- Hardened concrete – Concrete when set, with measurable strength
- Green’ concrete – Newly placed and compacted, stable, before the start of detectable setting (green concrete is a precasting industry term)
Other terms in use are shotcrete, pumped concrete, craned concrete etc. they define the placement into the formwork, working and/or handling to the point of installation
Did you know…
- Concrete is the second most used material on earth after water
- Concrete in the middle of the Hoover Dam, opened in 1936, is still drying out!
- The largest ever unreinforced concrete dome construction is the Pantheon in Rome, which is over 2000 years old
- Cement, if sealed in a thermos flask with water, will reach boiling point
- 99% of all ‘cracked’ concrete is associated with other construction factors and not the material as delivered
- Concrete is an extremely inexpensive material when you consider what it does. For example: 1m3 of concrete = 1000 litres of product. If you were to buy the same volume of paint, you would pay a lot more and it wouldn’t be as durable
- Concrete sets and hardens under water
- Concrete actually has elastic properties
- A ready-mixed concrete plant can have in excess of 2000 mix recipes available