History
Concrete has been used for thousands of years, and may have even been used to build the pyramids! The ancient Romans also used concrete in their buildings, and some of their structures still stand today.
Lifespan
Concrete is known for its durability and longevity, with properly constructed concrete structures lasting for decades or even centuries. However, concrete can also deteriorate over time due to factors such as weather, environmental conditions, and poor maintenance. This can lead to issues such as cracking, spalling, and corrosion of reinforcing steel.
The most common issue with modern concrete structures is rusting rebar. Metal can expand up to 10x its original size as it rusts. Concrete is porous which means that oxygen and moisture can still reach the steel embedded in it. When the rusting metal expands, it cracks the concrete.
Ingredients
Concrete is made up of a combination of cement, water, and aggregates such as sand and gravel. Cement is the binding agent that holds the mixture together, while water is added to activate the cement and make the mixture workable. Aggregates provide the bulk of the material and give the concrete its strength.
Massive Carbon Emissions
The manufacturing process for concrete involves heating limestone and other materials in a kiln to produce cement, which is then combined with water and aggregates to create the final product. This process is extremely energy-intensive (often done by burning heavy fuel oil or natural gas) and releases a significant amount of carbon dioxide into the atmosphere. According to the Global Cement and Concrete Association, the cement industry is responsible for around 8% of global carbon emissions.
If the concrete industry were a country, it would be the third largest CO2 emitter in the world - after the US and China.
The World is Running Out of Sand
The other major issue with the sustainability of concrete is the sourcing of materials such as sand. We use about 50 billion tons of aggregate per year - enough to blanket the entire United Kingdom. But, "isn't sand everywhere?" you ask? Yes, but the type of sand and gravel that make good concrete come mostly from river beds and beaches. Desert sand is the wrong shape and size, making it nearly useless, and manufactured sand is expensive to produce, and does not have the same durability. Shortages of sand across many industries (including hotels and resorts) have lead to illegal sand mining and extraction, like that time in 2008 when thieves stole an entire Jamaican beach overnight.
Future
Despite these challenges, concrete is likely to remain a key building material for the foreseeable future, thanks to its durability and versatility. However, there is growing interest in alternative materials such as mass timber and hempcrete, which offer potential environmental benefits such as lower carbon emissions and more sustainable sourcing.
Key Points:
Concrete is made up of cement, water, and aggregates such as sand and gravel.
The manufacturing process is energy-intensive and releases a significant amount of carbon dioxide.
Concrete is responsible for around 8% of global carbon emissions.
Material sourcing is a significant sustainability issue - we are running out of sand.
Alternative materials such as mass timber and hempcrete offer potential environmental benefits and are gaining traction in the construction industry.