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Ancient sayings relating to sand generally highlight its abundance. In the Bible for example: ‘I will…make thy seed as the sand of the sea, which cannot be numbered for multitude.’ But despite estimates that Earth contains roughly seven quintillion, 500 quadrillion grains of sand, world stocks are running dangerously low.
Chemically, sand is mostly silicon dioxide, and is non-renewable. It is essential for manufacturing bricks, plaster, glass, microchips, and above all concrete; the most popular and versatile modern building material. Concrete accounts for 75 per cent of our demand for sand with around 20 billion tons produced globally each year. Even so, surely there’s an almost infinite sand supply from deserts.
Unfortunately not. Sand grains come in different shapes and sizes, and while desert sand has small, smooth grains, concrete requires large, coarse-grained sand. This is generally mined from rivers, beaches and the sea bed. And because international control of sand mining is well-nigh impossible, sand piracy is rife, causing huge ecological damage.
Recently, 24 Indonesian islands were mined to extinction, with most of the sand used for land reclamation in Singapore, the world’s largest sand importer.
Our dependence on concrete is not just for new builds. Concrete’s life expectancy is just 50-60 years, after which so-called ‘concrete creep’ allows water seepage that corrodes supporting metal structures. So more concrete is required to repair or replace old buildings.
Now engineers are coming up with ingenious ideas for repairing cracked concrete, including using bacteria and fungi that produce calcium carbonate.
This could heal micro-cracks but the process will be years in development, while right now the US spend around $79 billion annually on bridge and highway maintenance and there are an estimated 188 million daily trips across ‘at risk’ bridges.
Many UK bridges are similarly at risk, so do we have a solution? The short answer is ‘no’, but right now the race is on to find new, more durable building materials to replace the need for sand and in so-doing preserve marine ecosystems.