Concrete has changed little in its basic formation – mixing an aggregate with water and cement.
Thousands of years ago, the ancient Greeks used concrete. During the Roman Empire, builders constructing arches, cupolas and tombs used concrete, made from volcanic ash, crushed pumice and quicklime. This mixture set quickly and was extremely durable.
Notable examples of the use of concrete by the Romans survive today, including the Pont du Gard in Provence and the dome of the Pantheon. In these structures, concrete forms a core, which is topped with stone cladding.
Several differences exist between the concrete of the Romans and that used today. Early concrete was stiff and spread onto the surface. Modern concrete is mixed better and more fluid, allowing it to pour into forms. Invented in 1849, concrete reinforced with steel bars was used in the Hoover and Grand Coulee Dams.
The manufacture and quality of concrete, a mainstay of the construction industry, has improved greatly over the last decade and many sustainable benefits are derived from its use. Because concrete is strong, long-lasting, versatile and fire-resistant, it’s a great choice for environmentally-friendly construction.
• Recently, manufacturers of concrete products are recycling older concrete to use as the aggregate with asphalt paving, and the water used to wash out concrete trucks is now used to mix fresh concrete.
• Because concrete is produced close to building sites, transportation costs are low.
• Concrete structures are energy-efficient, because the thermal mass holds the heat there is little leakage So heating and cooling costs are less. Increased use of insulating concrete forms filled with reinforced concrete produce energy-efficient buildings.
• Reduction in the amount of waste material going to landfills, because greater use is made of plastic and metal forms.
• The form liners of elasticised polyurethane, which create an architectural finish, are now used 50–100 times. This practice increases the cost-effectiveness of construction projects and decreases waste.
• Portland cement, first made in the UK during the 18th century, requires much energy to produce and is responsible for high levels of carbon emissions into the atmosphere. Reducing carbon emissions and improving energy efficiency is essential. New types of cement mixtures ensure this.
• Concrete that reduces pollution is used on pavements in the Netherlands to clean the air.
Improvements to the production process
• Lightweight, pre-moistened aggregates are mixed into ordinary aggregate. Water from the special aggregate assists in the internal curing process, which lessens distortion, shrinkage and cracking of the concrete. Basements of homes can become living spaces free from moisture seepage through floors and walls.
• Created by nanotechnology, ultra-high-performance concrete is a new kind of material with greatly improved durability, strength and permanence. It’s particularly useful for bridge construction.
• Concrete that can repair itself seems like an impossible dream, but the addition of polymers, carbon nano-fibres and a catalyst to the mix ensures that any cracks appearing in the columns supporting bridges repair themselves.
• Translucent concrete is produced by adding fibres to the mixture to produce colours and patterns. This technique could be used for concrete floors and countertops.
Improvements in the production of concrete and growing interest in the environment ensure that concrete will remain an important element in the construction industry.