Is it true that the world is running out of sand to produce concrete, and if so, why is that?
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Concrete needs “sharp” sand. The grains are angular with sharp edges. This is different to desert sand or deep sea sand, which tends to be round.
When you make concrete you are essentially using cement to glue together sand and rocks. If the grains are rounded, then the smooth surface can allow a bit of movement and slippage against the cement. Irregular shaped, angular sharp gains end up getting locked in place against each other as well as the cement, so the structure is stronger.
Sharp sand and angular gravel basically come from recently eroded or crushed rocks. Old sand and gravel gets smoothed out.
Sharp sand typically comes from rivers, so you need a river with a sandy bed close to where you want to build, and which doesn’t have rare fish or other sensitive ecosystems. In certain parts of the world, where a lot of building is taking place, there can be limited availability.
One option is to artificially crush gravel and grit with machines. The freshly crushed grains have sharp edges, so work well. This process is often used for preparing gravel for concrete,
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