The Rub’ al Khali, Saudi Arabia’s Empty Quarter, holds enough sand to bury France, and hardly a grain of it can hold up a building.

United Nations trade data compiled by TrendEconomy show Saudi Arabia spent roughly US$140,000 on natural sand from Australia in 2023, a small slice of the $6.45 million it spent on that category overall, most of it going to China. Set against a national trade account, that Australian entry is a rounding error, about the price of a decent ute. Its existence is the interesting part.

A desert kingdom keeps a budget line for imported sand.

What the wind does to a grain

Concrete is mostly aggregate bound by a thin film of cement paste, and the paste only earns its keep if the grains bite into one another. River sand and crushed quarry rock manage that because they have been freshly fractured and still carry sharp edges. Sand in a dune has spent millennia being lifted, dropped and rubbed together by wind, a process geologists call aeolian transport.

A 2025 review in the journal Materials, led by Bo Nan of Shenyang Agricultural University, describes desert grains as generally rounded and short of sharp edges, with smaller particle sizes, higher sphericity and smoother surfaces than river sand. Smooth spheres slide past each other. Angular ones lock.

Size compounds the trouble. That review puts about 60 per cent of desert sand particles between 0.15 and 0.30 millimetres, a band narrow enough to breach the grading limits that ASTM C33, the American standard for concrete aggregate, sets for fine material. A good mix wants a spread of sizes, so the small grains can fill the gaps left by the big ones.

Finding the workable ratio

How much desert sand can go into a concrete mix before strength starts to fall?

The same review concludes that substituting about 40 per cent of the fine aggregate can actually lift compressive strength, since the tiny grains fill microvoids and cut water demand, while heavier substitution raises porosity and drags strength and durability back down. Dhanik Vikrant, Abdullah Saand and colleagues, testing sand from the Tharparkar desert for the Mehran University Research Journal of Engineering and Technology, put the workable ceiling much higher, at 75 per cent, with results falling away past that because the grains were simply too fine. Different sands, different cements, different answers, and no single paper settles the figure.

Which is where the shipping comes in. A building programme on the scale of Vision 2030, NEOM included, needs structural concrete in the millions of cubic metres. A mix designed to tolerate 40 per cent dune material still has to source the other 60 per cent from a riverbed, a quarry or a boat.

Australia tests its own dunes

Australia exports sand by the shipload and sits on a great deal of desert of its own, which makes recent work at Western Sydney University quietly funny. A team including R. S. Krishna and Zhong Tao tested Australian desert sand as a partial replacement for river sand, reporting that a 50 per cent swap slightly reduced compressive strength while improving tensile behaviour, an effect they attribute to a denser matrix with smaller pores.

Wrapped in fibre-reinforced polymer, the samples behaved much like ordinary concrete under the same confinement, suggesting engineers wouldn’t need a new set of design models to use the material.

Why the line item will grow

“Sand is sometimes referred as the unrecognized hero of development,” said Pascal Peduzzi, who directs the GRID-Geneva unit of the UN Environment Programme. His agency’s third Sand and Sustainability report, published in May 2026, puts global sand use at around 50 billion tonnes a year, more than any other solid material on Earth, and projects that demand for buildings alone could climb by as much as 45 per cent by 2060.

Extraction already runs ahead of the geological processes that produce the material, a shortfall the report calls the sand gap. Rivers, coasts and seabeds supply the angular grain that concrete wants, and those are exactly the places where dredging erodes shorelines, salts up aquifers and wrecks fisheries.

Materials scientists have a decent shot at engineering around the shape of a grain. Nobody has worked out how to engineer around a number that large.