Construction World November 2018

ADMIXTURES/CONSTRUCTION CHEMICALS

UNMATCHED STRUCTURAL INTEGRITY Structural integrity, durability, energy efficiency and fire resistance are just a few of the benefits concrete construction offers for the creation of infrastructure, says Bryan Perrie, MD of The Concrete Institute (TCI).

can be placed close to the areas of demand thereby reducing the energy required for transport. “The materials used in concrete furthermore make efficient use of natural resources and again the potential for recycling at life-end saves quarrying of finite resources. Concrete mixes for ready-mix plants and precast yards are designed specifically to use aggregates sourced from local quarries – and more recently also from recycled concrete – which reduces fuel costs for transporting these materials. “The embodied energy in the construction of a structure is usually minimal compared with the energy likely to be consumed during the life or use phase of a structure. Perrie says another benefit of concrete structures is that concrete does not burn or emit any toxic substances during a fire. It will not produce smoke or drip molten particles and therefore concrete can be described as ‘fire resistant’. The concrete in structures, unlike in other construction materials, generally does not require fire-proofing or protection if appropriately designed. Concrete’s inherent fire resistance will restrict smoke from spreading and will largely maintain a building’s strength during a fire. After a fire, the continuing structural strength and reduction in smoke damage also reduce the magnitude of insurance claims. “Fire-damaged concrete buildings usually do not require demolishing or rebuilding so concrete structures protect life and preserve property, contributing to enhanced social and economic performance of the built environment – an important consideration for all property owners such as municipalities. “When aesthetic qualities such as design flexibility and variety of finishes are added to the sustainability benefits of concrete, it is easy to see why it is the preferred choice of building material for property owners, developers, designers and contractors,” Perrie adds. 

P errie says the strength of concrete elements in buildings is well understood by structural engineers, architects and contractors. This includes in-situ reinforced concrete, precast concrete, tilt-up, hybrid construction, and post-tensioned concrete elements. “South African design and construction codes regulate the structural requirements of concrete buildings which ensure that concrete structures are safe, with the capacity to cope with any permanent, imposed, wind and earthquake actions,” Perrie states. Concrete is renowned as one of the most durable materials on earth so well-designed, well-constructed concrete ensures long life in any structure. This results not only in

lower expenditure of energy in building new infrastructure or housing but also in reduced maintenance and impact on the use of finite resources. “The first line of defence against deterioration is good quality, impermeable concrete. In the case of reinforced concrete, the quality of the cover concrete is extremely important in protecting the steel reinforcement against aggressive agents and fire. This zone of concrete is intended to act as the barrier between the reinforcing steel and external aggressive environments and its quality is of primary importance in durability considerations. Good material choice, mix proportioning, and sound construction practice are essential to ensure durable concrete,” Perrie emphasises. Concrete’s energy efficiency is shown in many ways. The use of local materials in production of concrete minimises fuel costs for handling and transportation and, once in place, structure. Most of the primary materials used in concrete are produced locally. Cement extenders and slag aggregates used are secondary industrial products that would otherwise have required dumping. While the cement factories are generally located close to the location of the necessary raw materials, sources of aggregates and ready-mix plants concrete offers significant energy savings over the lifetime of the

The flexibility of concrete as building material – both externally and in interiors – has provided inspiration for designers the world over.