Some will sing concrete’s praises due to its recyclability and longevity. Others are more cautious because of the by-products produced by concrete plants – amongst other things. Let’s dive in and see if there is a clear-cut answer to the question: is concrete eco-friendly?
The Most Common Building Material
Concrete is typically made up of Portland cement, water, and various aggregates. Additives are often included, such as accelerants or retardants, that could increase the toxicity of the concrete. As the most common building material in the world, it’s ubiquitous in urban environments.
The Big Problems
The biggest problem comes from the production of Portland cement – the main binding material. Cement production is one of the top sources of carbon dioxide pollution – up to 8% of the carbon dioxide produced worldwide. Calcium carbonate is decomposed into lime and carbon dioxide to create Portland cement. The lime is used, but the carbon dioxide is released as waste.
Carbon dioxide is also produced through the burning of fossil fuels to provide the large amounts of power the cement plant requires. The process to make cement includes heating the raw materials to around 1,500 °C – not an energy efficient endeavor.
Concrete is not porous, meaning it creates surface runoff that can increase the amount of erosion, water pollution, and flooding that happens. Concrete also plays a big role in the urban heat effect, where the urban environment produces significantly more heat than a rural setting.
Concrete Has a Lot Going for It
While the cement can be a big problem, the aggregate is often much less environmentally damaging. Gravel mining does have an impact, but the impact is relatively small and can be easily mitigated. Aggregate is often a readily available material and the ability to use recycled material – even recycled concrete – reduces the impact even more.
Unfortunately, without cement you wouldn’t have concrete. Many are looking for alternative binders in concrete to get around this issue. Some of the materials currently being researched include spent coffee grounds and rice husk ash.
Even though concrete can cause runoff issues that result in pollution and flooding, concrete works well for controlling water flow and flooding, through dams, and similar diversion structures. And studies have found that using lighter colored concrete significantly reduces the urban heat effect.
Just How Long Lasting is it?
One of the biggest arguments for the sustainability of concrete is it’s longevity. Estimated to last around 100 years, concrete lasts much longer than other materials, like wood.
Interestingly, modern concrete doesn’t last nearly as long as engineering originally thought it would last. Made from concrete, the Pantheon in Rome has been standing for close to 2,000 years. The main culprit of modern concrete’s relatively short life seems to be the steel reinforcement. We have traded the durability of ancient roman times for the strength steel reinforcement brings – enabling us to build thinner, taller structures.
Around the world we see concrete replacing traditional mud brick or rammed earth structures – options that might be more durable than concrete.
Like most things in life, the answer to the question “is concrete a sustainable option” isn’t one size-fits-all. Is it better to use a material that places a heavier burden on the environment during production but will last several lifetimes of another material?
If we see significant advances in the search for a new binder to replace cement, concrete could enjoy a spot at the top. For now, it’s a good option, but not the best. The question is: does the best exist yet?