Twice as much concrete is used in construction around the world than all other building materials combined.
Concrete, the most versatile construction material of all, is a mixture of cement paste and aggregates such as sand, gravel and crushed stone. The paste, composed of portland cement and water, coats the surface of the aggregate particles. Through a chemical reaction called hydration, the paste hardens and gains strength to form the rock-like mass known as concrete.
Within this process lies the key to a remarkable property of concrete: it is plastic and malleable when newly mixed yet strong and durable when hardened. These qualities explain why one material, concrete, can be used to build skyscrapers, bridges, sidewalks, highways, houses and dams.
Concrete's many useful properties contribute to sustainable design and construction. The concrete industry in Canada is committed to contributing to sustainability in the construction industry through the development and delivery of materials and systems that provide a durable foundation for our communities.
Concrete is an essential enabling product for GHG emissions reduction in many sectors including agriculture, housing, transportation and buildings.
Concrete is Green
- Low CO2 intensity - the production of concrete, which consists of 10% - 15% cement, results in emission of about 0.13 tonne of CO2 per tonne of concrete. Thus, concrete manufacturing results in less CO2 per unit than almost all other construction materials.
- Resource Efficient - the ingredients for concrete; sand, gravel and limestone are abundant worldwide. Quarries are readily reclaimed for recreation, residential or commercial development. They may also be restored to their natural state.
- Less Construction Waste - as concrete is manufactured to specifications, only the product that is required is delivered to the site. This means that there is less material sent to landfill upon project completion.
- Local Resource - because the ingredients of concrete exist almost everywhere, concrete can be manufactured near a job site, requiring minimal energy for transportation. At least 60% of all concrete is made within 160 km of the job site. Wood and steel products, on the other hand, typically travel hundreds or even thousands of kilometres.
- Reuse - many concrete products can be reused, such as concrete pavers and precast wall panels. Concrete sidewalk slabs are reused to build "dry stone" retaining walls.
- Recycle - Waste products made useful - concrete is ideal as a medium for the inclusion of recycling waste or industrial byproducts such as blast-furnace slag (steel making) and fly ash (coal-burning electric plants). About a third of the fly ash produced annually in the U.S. is used in concrete.
- New Life for Old Concrete - used concrete can be recycled as aggregate for new concrete mixtures. Concrete yields 45% to 80% usable coarse aggregate and can be crushed and re-used in new concrete or as a base material.
Types of Concrete
Concrete is produced in four basic forms, each with unique applications and properties:
- Ready mix accounts for nearly three quarters of all concrete. It is prepared at local plants for delivery in the familiar trucks with revolving drums.
- Precast concrete products are cast at the factory. These products benefit from the tight quality control achievable at a production plant. Precast products range from concrete bricks and paving stones to bridge girders, structural components and panels for cladding.
- Concrete masonry, another type of manufactured concrete, is best known in its conventional 8 x 8 x 16-inch blocks. Masonry units can be molded into a variety of shapes, configurations, colors and textures for a wide range of building applications and architectural needs.
- Cement-based materials represent products that defy the label of "concrete," yet share many of its qualities. Conventional materials in this category include mortar, grout, and terrazzo. Soil-cement and roller-compacted "cousins" of concrete are used for pavements and dams. Other products in this category include flowable fill and cement-treated bases. A new generation of advanced products incorporates fibers and special aggregate to create roofing tiles, shake shingles, lap siding and countertops.
Below is a sample concrete mix. Different proportions of materials are used depending upon the requirements of the concrete solution.