Concrete is a construction material composed of crushed rock or gravel and sand, bound together with a hardened paste of cement and water. A range of different cements and aggregates, chemical admixtures and additions can be used to make an array of concretes that have the required properties in both the fresh and hardened states for a wide range of applications.
Concrete was known to the Romans, Egyptians and to even earlier Neolithic civilisations. After the collapse of the Roman Empire its secrets were almost lost, to be rediscovered in more recent times. Its modern development spans less than 200 years - 1824 is the date on the patent for the manufacture of the first Portland cement, one of the important milestones in concrete's history. Since the middle of the 19th century, open sea has been spanned, huge buildings erected, mighty rivers dammed and extensive networks of roads constructed. In these and a thousand other ways the face of the world has been changed as a result of the discovery of concrete. Concrete has also been instrumental in improving the health of the world's inhabitants, through its use for sewage disposal and treatment, and for dams and pipes providing clean water for drinking and washing.
|The Pantheon in Rome: built in AD 127, using early lightweight|
concrete, it is still a major tourist attraction.
Uses of concrete
Concrete plays a major role, often unseen, in every aspect of our daily lives. Its strength and durability are exploited to the full by North Sea oil platforms and sea defences, while its thermal and acoustic insulation properties help make houses and flats more comfortable places to live. Concrete bases to motorways and runways provide a solid transport infrastructure, and the material's ability to span large rivers makes a useful and often striking addition to our landscapes.
Dams, ring mains and water towers use concrete's ability to contain water, and its resistance to chemicals make it an ideal choice for sewerage works, slurry pits and even wine vats. Not surprisingly, artists make full use of concrete, as its potential to take any shape, colour or texture is limited only by their imaginations.
The way forward for concrete construction will be largely influenced by the need to conserve the earth's resources, be they materials, land or energy. Concrete has a major role to play in sustainable construction, as it can be recycled after use, requires relatively little energy in its manufacture and provides thermal mass in buildings, thus reducing the need for air conditioning.
Skilled site labour is another resource that is likely to become scarce in the future. Innovative construction techniques can help overcome this. Self-compacting concrete is easier to place and unmanned equipment could be used to finish concrete floors. Transferring the construction process to a controlled operation in a factory is another way of coping with skills shortage. For example, whole bathroom pods can be assembled off-site, even down to the installation of the plumbing, and then slotted into place at the site.
Accompanying all these advances will be the development of concrete as a material. Continued improvements in cement and concrete production, alternative reinforcing materials and the use of computer-aided design will all have parts to play.
The developments will be complemented by the adoption of construction techniques that will cut out waste and reduce time taken on site, so shortening the period before a building or structure can be brought into use and begin to earn its keep. The success of all these endeavours, both now and in the future, will depend very much on sound concrete practice on site.