During concrete day… errr … week … errr … verging on two weeks this time, I’ve explored a lot of carbon emissions solutions for the full value chain of the gray glue that ensures our buildings don’t collapse, our bridges stay up, and our underground working chambers don’t pancake. We have to solve this problem, as it’s about 10% of global carbon dioxide emissions, and a bit of the methane emissions as well..
In a typical concrete mix, the proportions are approximately 25-30% sand and 40-45% gravel by volume. Given the total estimated usage of 28 billion tons of concrete across the major geographies, this translates to roughly 7 to 8.4 billion tons of sand and 11.2 to 12.6 billion tons of gravel. Coastal and marine sand mining involves extracting sand from beaches, dunes, and the seabed. This method can have severe consequences for coastal ecosystems, leading to beach erosion, loss of habitat for coastal and marine species, and increased vulnerability of coastal areas to storm surges and sea-level rise. Marine dredging, in particular, disrupts the seabed, affecting marine life and water quality.
As I was unsurprised to find in my exploration of SCMs, it’s about what’s cheapest and closest in concrete. When 28 billion tons are involved, every extra penny per ton ends up with a lot of zeros behind it. As the world moves forward, population growth ends somewhere between 2050 and 2070, and major geographies like China and India start recycling concrete more, it’s likely that a steady state of about 10% of aggregate coming from recycled concrete will become the norm. That’s good, but recycling concrete requires energy too.