Sand in short supply

After water, sand is the most important raw material in the world. But the freely available reserves of these miniscule grains are gradually becoming scarce. How are scientists planning to change that?

“It’s not so easy to find good-quality sand anymore,” says Professor Dietmar Stephan, Head of the Department of Building Materials and Construction Chemistry at TU Berlin, Germany. This is primarily due to the construction boom. “When it comes to concrete production, roughly 3 metric tons of sand are needed per metric ton of cement,” explains Stephan. In 2014, the UNEP estimated that between 26 and 30 billion metric tons of sand are poured into cement mixers every year worldwide.

Since then, these numbers will have only increased. The demand for this raw material in expanding metropolises such as Singapore, Shanghai, or Dubai is always growing. Mega construction projects in these cities are already devouring vast quantities of sand, as we see with the numerous major projects in Dubai. The raw material is not only needed to erect huge skyscrapers like the Burj Khalifa. The foundation for Dubai’s Palm Jumeirah artificial island in the Persian Gulf is also formed from a massive deposit of these fine grains. According to media reports, more than 150 million tons of sand were delivered from Australia.

Desert countries rely on sand imports

Meanwhile, the sand from the surrounding deserts remained untouched. “Desert sand simply cannot be used as a building material,” says Oliver Mazanec, head of Product Management at BASF Construction Solutions. The wind sweeps it up and blows it away. The grains become small, smooth, and uniform. The result: “The grains of sand do not mesh and cavities form in the fresh concrete. This significantly increases the amount of water needed when mixing cement, which adversely affects the strength of the concrete.”

Extremely rough edges are required for construction work. But this type of sand can only be found in quarries, riverbeds, and the ocean – with negative consequences for the environment. According to UNEP estimates, three out of four beaches could simply vanish in the future. This is due to the raw material being mined directly on beaches, which is often illegal, and because beaches are slipping as sand is being drawn off the seabed. Entire islands in Indonesia, for example, have already fallen victim to this phenomenon. The power of the waves also makes sure that sand drifts away. But there are also shortages inland. Easily accessible deposits of high-silicon quartz sand are slowly being depleted.

“The MasterSuna sand blocker from BASF improves the properties of these challenging sands. It ensures that water and superplasticizer are not absorbed by the sand, and instead the concrete is generously liquefied,” says Mazanec. Sands that were previously unsuitable can now be used, and existing deposits can be more intensively exploited. This new admixture is currently available in France, Spain, Germany, the United Kingdom and Australia. These countries are particularly affected by sand contaminated with clay.

5 things you didn’t know about sand

Laboratories around the world are also looking into ways to exploit the abundance of fine desert sand. One idea, for example, is to enrich it with fly ash, so the cement adheres to the finely ground sand grains more effectively during concrete mixing. Another idea is to use plastics, such as polyester resins from crude oil, as a binder instead of cement. “This basically resolves the issue, but it isn’t feasible on a large scale. Or isn’t a permanent solution, as with the fly ash. This is because it involves coal combustion, which will be an increasingly rare method of power generation in the future,” says building materials expert Stephan.
 

A far more promising solution than desert sand is old concrete. If building rubble is pollutant-free, it can be recycled relatively effectively in a process involving separation, shredding, and fine grinding. This mineral rubble sand needs to contain at least 25 percent concrete to bear the label “recycled concrete.” To date, recycled concrete has primarily been used to form sublayers in road construction. Recycled concrete is still the exception when it comes to house construction. “It’s technically feasible, but its success will be determined by price,” Stephan says. The price is generally higher, although it fluctuates considerably from region to region. And because rubble sand does not have the same ideal grain size as fresh sand, it is more difficult to process.