Grant Quasha, Eco Materials Technologies, reveals how the innovative use of coal ash and other supplementary cementitious materials is helping the concrete industry reduce its carbon footprint and improve performance.
Much of the world’s infrastructure – highways, bridges, dams, tunnels, and buildings – is built with concrete. Comprised of aggregate, water, and cement, concrete is economical, strong, and durable. These traits have made concrete the most-used substance in the world after water and, by far, the most popular construction material.
From an environmental perspective, however, concrete has a significant drawback: its carbon footprint. Cement – the binding ingredient in most concrete mixes – accounts for about 8% of all man-made greenhouse gas emissions worldwide. Every tonne of cement manufactured, produces nearly the same amount of CO2, and global cement production is expected to top 6 billion metric t by 2050. With the climate change threat tied to increasing levels of carbon-dioxide emissions in the atmosphere, governments, researchers, and cement manufacturers are looking for solutions to help decarbonise the concrete industry.
For decades, builders have replaced a portion of the portland cement used to produce concrete with coal ash – chiefly for the performance characteristics it imparts to both fresh and finished concrete. Such benefits include increased strength, workability, and durability, as well as lower permeability and heat of hydration. As climate concerns have come to the forefront, however, coal ash is increasingly being specified for its ability to lower concrete’s carbon footprint. Each t of coal ash used to replace portland cement in concrete production saves almost 1 t of CO2 from entering the earth’s atmosphere. In 2022 alone, beneficial use of coal ash in concrete delivered approximately 11 million t of CO2 reduction.
Coal ash in abundant supply
Coal ash has traditionally been sourced directly from operating coal plants. However, as coal generators continue to be retired, previously disposed ash – now stored in landfills and surface impoundments throughout the country – has become an increasingly important supply of this material. The American Coal Ash Association estimates that there are approximately 2 billion t of coal ash stored in this manner.
Eco Material Technologies, the largest supplier of coal ash and other advanced supplementary cementitious materials (SCMs) in the US, is at the forefront of decarbonising the built environment. The company has developed multiple green cement products that can be manufactured with significantly lower carbon emissions than portland cement, and which can substitute for cement in even higher proportions than traditional SCMs. Researchers, chemists, and R&D experts at Eco’s Georgia-based Materials Testing and Research Facility (MTRF) work behind the scenes to develop these low-carbon cement alternatives from coal ash as well as natural and other industrial-based pozzolans.
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