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Did you know that concrete has been used since before the Roman Empire? In fact, it is the second most consumed product in the world behind water. You will be hard-pressed to find a construction site nowadays that doesn’t utilize concrete in some way, shape, or form.
It is estimated that 8-10% of global CO2 emissions originate from the manufacture of cement. These are categorized as scope 3 emissions pertaining to embodied carbon which are the most challenging emissions to eliminate when on the path to carbon neutrality. Through the utilization of certain additives and green technology, you can greatly reduce the carbon footprint of your next project without sacrificing quality, cost, or schedule. Let’s take a look at a few options:
- Fly Ash – fly ash is a waste product created by burning coal. By diverting fly ash from landfills and adding lime and water, it becomes similar to conventional cement. Alternatively, using up to 30% fly ash in a cement mix can improve the strength and durability of hardened concrete. Because fly ash is a waste product, it is generally a cost-effective solution to reducing Portland cement in the aggregate mix.
- Blast Furnace Slag – similar to fly ash, blast furnace slag is a waste product that can be recycled to be added to concrete mixes as a more eco-friendly alternative. It can replace up to 70% - 80% cement while simultaneously improving the strength of the final product. Blast furnace slag also has the added benefit of emitting less heat during hydration, leading to a further carbon reduction benefit.
- Micro Silica – micro silica, or "silica fumes," are a powdery by-product of the silicon production process as silicon dioxide is condensed. It can displace up to 12% cement in concrete, while improving strength and decreasing permeability. Because of the reduced permeability, it is a particularly excellent material choice for concrete structures that are exposed to harsh chemicals as part of a manufacturing process.
- Other Methods – Besides the eco-friendly options listed above, you can make concrete by replacing aggregate with waste paper, glass, or even plastic. More recently, new forms of carbon-negative concrete are being invented that go so far as to absorb carbon dioxide from ambient conditions.
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