What is Concrete
Concrete is easily and readily prepared and fabricated in all sorts of shapes and structural systems. Its great simplicity lies in the fact that its constituents are ubiquitous and are readily available almost anywhere in the world. As a result of its ubiquity, functionality and flexibility it has become by far the most popular and widely used construction material in the world.
The material concrete is often confused with the material cement. Cement is one of the many constituents of concrete, part of the glue that holds the other materials together. Concrete is made by mixing cement, supplementary cementitious materials, water, fine aggregate (sand/crushed rock fines), coarse aggregate (gravel or crushed rock) with or without admixtures, reinforcement, fibres or pigments.
The ingredients are proportioned and engineered to produce a concrete of a specific strength and durability, so it is 'fit for purpose' for the job for which it is intended. It can be produced in the form of precast products or as ready-mixed concrete, which is delivered in the familiar rotating concrete lorry.
There are literally thousands of sites throughout the UK from which concrete can be sourced. One of the major sustainability benefits of concrete is that it is almost entirely sourced from within the UK, with the average delivery distance for all concrete being 46km.
Admixtures are used to improve the performance of fresh and hardened concrete and in both cases there are potential sustainability benefits. The amount of admixture required is small compared to the amount of concrete enhanced by their use.
Aggregates are inert granular materials such as sand, gravel or crushed rock that are used in construction as a product in their own right, as well as being an essential ingredient in concrete.
Concrete has a number of performance characteristics that can improve the sustainability performance of a building or structure.
There are essentially two types of concrete block: aggregate blocks and aircrete blocks. From an environmental perspective, they are locally produced and can have a high recycled content, giving them low embodied CO2.
'Cement’ generally refers to the powder component of concrete which, when mixed with water, becomes the glue-like material, or binder, that allows concrete to set, harden and strengthen. These materials include Portland cement, fly ash, ground granulated blastfurnace slag (GGBS), limestone fines and silica fume.
Mortar is a material used in masonry construction to fill the gaps between the bricks and blocks. Mortar is a mixture of sand, a binder such as cement or lime, and water and is applied as a paste which then sets hard.
Precast concrete refers to any concrete products formed in factory conditions and then provided to site. This includes concrete blocks, precast concrete elements for buildings and infrastructure, as well as whole building systems.
Ready-mixed refers to concrete that is batched for delivery from a central plant, instead of being mixed on the job site. Each batch of ready-mixed concrete is tailor-made according to the specifics of the contractor.
Rebar (reinforcing bar) is an important component of reinforced concrete. The steel used in UK reinforced concrete utilises 100% recycled scrap steel. At the end of its life, all reinforcing steel can be recovered, recycled and used again.
Water is a finite resource. The UK concrete sector is very aware of the importance of water, especially when considered alongside the likely impacts of global warming and climate change.