Demand for sand is rising, and illicit traders are moving in

Demand for sand and gravel is exploding around the word, fuelled by urbanisation of emerging economies, and prices are rising. Inevitably, an illicit market following close behind.

Sand and gravel used as aggregates for construction purposes actually have to meet fairly specific criteria in terms of size and angularity, and that generally means it has to be sourced from specific locations, such as rivers.

Sand from windswept deserts like the Sahara and the Arabian dessert are of little use, unfortunately, as the grains tend to be too rounded to bind well in concrete. Meanwhile, sand from the sea has to be cleaned of corrosive salt, and that is expensive.

That means with supplies limited, illegal mining in suitable source areas like riverbeds is being carried out to meet demand, sometimes with very damaging social and environmental impacts.

Zack Sickmann of the University of Texas at Austin – co-author of a study presented last week at the Geological Society of America (GSA) annual meeting – is working on a way to identify the source of sand and gravel used in construction projects using sediment provenance analysis.

Using the approach, it might even be possible to identify the source of the aggregates used in a concrete block taken from a completed construction project, right back to the river they came from.

Sand is second only to water as a natural material extracted by humans, with most destined for use in concrete. But it is also a strong forensic marker, according to Sickmann. It reflects the unique rocks within a drainage basin and keeps the record from extraction to construction.

“There's no reason why I couldn't go take a core of concrete of an existing skyscraper and take that same compositional signature and tie it back to a source,” he says. However, “the real crux of the issue is finding the most effective way to use the method in a regulatory capacity.”

The projected demand for sand and gravel is expected to jump from 35 gigatons per year at 2011 levels to 82 gigatons per year by 2060, driven by the growth of fast-developing economies like Southeast and South Asia.

Sickmann and co-author Aurora Torres of Michigan State University want to find the most cost-effective way to quickly and effectively fingerprint sand from different sources.

They plan to start a proof-of-concept test on US sand first, where the sources and processing locations are well known, collecting concrete from retail outlets to see if they can trace back the source of the sand. If successful, they will turn their attention to other regions, including Southeast and South Asia.

“I see this as a valuable tool that will be that will complement other strategies that are being put in place to track and monitor these illicit supply networks,” says Torres.