A blog about concrete? Surely that’s going to be as interesting as – well – watching concrete dry? Not at all! Read on, because concrete is the most widely used substance in the world after water, and we’d find it extremely difficult to manage without it.
If you think of concrete, what’s the first thing that comes to mind? The Barbican in London? Perhaps a Frank Lloyd Wright building, the 163 storeys of the Burj Khalifa skyscraper in Dubai, or the University of East Anglia in Norwich, whose student newsletter is called ‘Concrete’? Whatever your first thought, the chances are that it’s a relatively modern development.
However, the history of concrete goes back a long way. The earliest known examples include floors at Yiftahel, near Galilee, from around 7000 BCE, and in Serbia, from around 5600 BCE. These were made from a substance called lime concrete, which is made by burning limestone to produce quicklime and then mixing this with aggregate and water. This effective new material gradually became more widely known, spreading through Egypt and Ancient Greece to the Romans. In fact, the name concrete comes from the Latin ‘concretus’, meaning coagulating and solidifying.
The Romans used concrete in the development of some of their most iconic structures, including the Pantheon and the Colosseum, but after the fall of the Roman empire, its use died out and it doesn’t appear again until the 18th century.
In 1793 during the construction of the Eddystone Lighthouse in the UK, engineer John Smeaton pioneered a type of concrete which cured while under water, and in 1816 the Millbank Penitentiary, prone to subsidence on the marshy banks of the Thames, became the first known building since the Roman Empire to be underpinned with concrete foundations.
In 1824, Joseph Aspdin invented Portland cement by igniting a powder made of chalk and clay until the carbon dioxide was removed. The cement was named ‘Portland’ because it looked like the Portland stone which was quarried in Dorset.
Many people think the terms ‘concrete’ and ‘cement’ are interchangeable, but cement is in fact one of the ingredients of concrete. Today, concrete is made by mixing dry Portland cement (usually made from limestone) with water and aggregate, forming a liquid slurry which can then be poured into whatever shape is needed. The cement reacts with the water and gradually hardens via concrete hydration, the speed of the process being heavily dependent on the ambient temperature. Additives can be introduced to the mixture for different purposes, such as bitumen for asphalt concrete used on roads, and reinforcing materials to provide strength such as steel reinforcing bars or ‘rebar’.
One type of concrete which has been in the news lately is reinforced autoclaved aerated concrete or RAAC, a lightweight type of concrete which contains no coarse aggregate and was used in walls, roofs, floors and cladding from the mid-1950s to the mid-1980s. Its porous composition allowed the ingress of water, leading to structural damage which is currently causing serious issues in schools, hospitals and other buildings. Its use was abandoned in 1996.
On a more positive note, our roads, dams, tunnels, bridges, car parks, university campuses and developments from new homes to skyscrapers are all made possible because of concrete’s incredible properties. However, in the 21st century there’s another crucial element to consider in the use of building materials, and that’s sustainability. So how environmentally friendly is concrete?
It’s durable, robust and versatile; it can withstand fire, adverse weather conditions and erosion, and requires little maintenance. Despite that, the manufacture of cement for concrete is responsible for around 8% of global CO2 emissions per year, and it’s also responsible for approaching 10% of global industrial water use. Research into greener alternatives to concrete has produced a number of possible substitutes:
Green concrete uses waste from sources such as incinerator residue, quarrying, mining and power plants instead of cement; these use less energy during manufacture and produce less carbon dioxide.
Ashcrete also utilises waste material, in this case fly ash which is a by-product from the combustion of coal. Around 93% of it is made from recycled material. It increases the strength and durability of the material but requires a longer setting time which could be problematic during a building project.
Mycelium has been proclaimed as one of the most exciting concrete substitutes to emerge in recent years. It’s sourced from the tiny threads in fungi which, when mixed with other organic matter, forms an easily mouldable, dense and organically fire-resistant material. Its development is still in the early stages as its strength is considerably less than concrete, but work is ongoing.
Micro silica, recycled plastic waste and aggregate replacement are also possible concrete alternatives undergoing research as the construction industry becomes more aware of its responsibility to the environment. Any serious alternative must be produced from sustainable resources, use considerably less energy in production and create the minimum amount of waste.
In the meantime, measures to improve the sustainability of concrete itself are under investigation. There are improvements – over the last thirty years, the use of waste materials in place of fossil fuels has led to a reduction of 18% in the average CO2 intensity of cement production.
Concrete does have some environmental benefits. Its thermal efficiency means that it can help moderate temperature conditions within a building. Air leakage is a major culprit in energy loss from a building; by storing and then releasing the energy needed for heating or cooling, concrete reduces temperature swings, thereby cutting costs. Energy-efficient buildings can be constructed with the latest concrete wall systems which use external insulation and thermal mass.
Here at Oakwhite there’s nothing we don’t know about concrete as part of our commercial fit out and refurbishment work throughout the UK. Sustainability, reuse and recycling are cornerstones of the way we work, and we pride ourselves on completing projects on time and on budget.
If you’re interested in having a chat about a fit out or refurbishment, contact us via email, or give us a call on 01403 586062 and one of our friendly and experienced team members will be happy to help.