Sand – A resource in great demand

Prof. Dirk E. Hebel

Professorship of Sustainable Construction, Karlsruhe Institute of Technology

Sand is the most widely used solid raw material in our world. It is found as a concrete aggregate in building elements, in glass, in electrical components of our computers and telephones, in cleaning agents, and even in our toothpaste. Sand is the megastar of our industrial and electronic age.

Dirk Hebel
The construction industry demands the resource in grain sizes and shapes that only occur in water-dissolved sand in rivers, lakes and seas. Mountains and rock formations have been weathering into gravel, sand and dust for millions of years due to natural influences of temperature, radiation, wind and precipitation. Precipitation then carries them via watercourses into our oceans, the smaller particles remain in suspension, while grains with a size of 0.06mm to 4mm (commonly referred to as sand) are deposited mainly in coastal areas. This weathering product is diverse in shape and size.
Haptic properties: Water-bound sand

Sand particles of different sizes compact very dense, they build up a pressure matrix with a relatively large grain distribution curve and thus only small voids between the grains. It is precisely this property that makes sand in combination with gravel of different sizes so valuable for our construction industry, as little cement is needed to fill these voids. Sand is mostly made of quartz, a silicon dioxide. It is the most abundant material on the earth’s surface and is “harder” than steel. However, once it is bound as an aggregate in concrete, it could not be recovered to its original form until now.

Sand particles
© Pixabay
Sand particles © Pixabay
Haptic properties: Desert sand

Desert sand (but beware: there are great geological differences and variations worldwide), on the other hand, is generally rather unsuitable for the construction sector, the grain sizes are very uniformly small at 0.1 to 1mm, and exclusively round, all caused by permanent wind movements, which results in only a low packing density – which means many voids when used as an aggregate in concrete. This is an unsuitable basic condition, as higher cement admixtures and thus higher costs would be the consequence in order to fill the voids. This also results in poorer mechanical properties of the concrete: the shrinkage and creep behaviour deteriorates compared to the use of water-bound sand.

Sand is the megastar of our industrial and electronic age, we rely on it.
The global demand of sand

Due to its enormous demand – one remembers the figures published by the Bill Gates Foundation that China used as much concrete and thus sand in 2011-2013 as the USA did in the last 100 years [1] – water-bound marine or river sand is increasingly becoming a finite resource of our planet. According to John Milliman [2], humanity is currently mining twice as much sand as is carried by all the rivers on our planet. According to Swiss radio [3], this amounts to a gigantic 15 billion tonnes per year, with a trade volume of 70 billion US dollars. The United Nations Environment Program (UNEP) [4] even speaks of 30 billion tonnes, but the actual figure is probably even higher. Today, 50% of the sands that originally reached our oceans are already tapped on their way there in river courses. Whereas in this country, extraction is meticulously monitored by the authorities, other nations and groups help themselves unscrupulously and unsustainably.

Sand - a valuable resource
© pixabay
Sand - a valuable resource © pixabay
Ecological consequences

Thus, the gigantic extraction of the material cannot take place without serious consequences for our environment. More and more drastic forms of sand extraction are spreading around the world. Beaches on the north coast of Africa are being illegally eroded (in Morocco already 50%), rivers are being dredged uncontrollably and the seabed is being sucked out, leading to the sliding of land masses and the disappearance of entire islands. The consequences are felt far beyond the actual extraction area and leave far-reaching damage in their wake. Rivers in India, Thailand and Cambodia that are dredged too heavily lower their water levels dramatically, which in turn destroys traditional settlements and ways of life, much to the chagrin of the local population. Mafia-like structures exploit people and the environment to extract sand in developing countries. The suction of the seabed not only destroys the fragile foundation of entire ecosystems, the churned-up sediments are also carried by the currents to farflung areas. Oceans are inert systems whose behaviour can hardly be simulated. The consequences of sand mining will therefore affect generations after us and could be catastrophic.

The consequences of sand mining will therefore affect generations after us and could be catastrophic.
Illegal activities

The scarcity of the raw material is leading to an increase in illegal sand mining and trading. Martial slogans like “sand wars” [5] or “sand mafia” are doing the rounds. This mafia is particularly active in Singapore. Sand is needed in Singapore both for building construction and for large land reclamation projects. In just under 100 years, the island state has increased in area by about 25%. [6] However, the export balance of the neighbouring countries and the import balance of Singapore show large gaps: while Singapore speaks of an import of 517 million tonnes in the last 20 years, the neighbouring countries state an export of 637 million tonnes to Singapore in the same period. [7, 8] Singapore gave little thought to the origin of the material until the disappearance of Indonesian islands caused political tensions and an at least officially declared export stop by the neighbouring country. [9] Malaysia, Thailand and Vietnam followed this example. Since then, Cambodia has been the main supplier of illegally dredged sand from its rivers. [10] And Dubai, with its dreams of the Arabian Nights heaped up in the sea, is also increasingly importing its sand from South-East Asian regions with low ethical and legal standards, in addition to Australia, thus promoting the attractiveness of a market that is slipping into illegality.

Ocean sand fleet
© Designed by Freepik
Ocean sand fleet © Designed by Freepik
Sand is a finite resource

When we talk about future urban development and consider the rapid rates of urbanisation in Asia, Africa and South America, the question arises as to whether our current building methods and materials are still viable. In all these areas, gigantic construction tasks of cities with millions of inhabitants are still ahead. Already today, almost 90% of the world’s cement (and thus twice the amount of sand as concrete aggregate) and 70% of the world’s steel are used in developing areas. But if the most important raw material is missing, what alternatives are left? And what role can research institutes and universities play in exploring such alternatives?

Read on soon in the sequel “Sand – from linear to circular use”

[1] Gates Foundation, GatesNotes, The Blog of Bill Gates: “A stunning statistic about China and Concrete”, 2014, June 25,
[2] Milliman, John D, and Syvitski, James PM. “Geomorphic/tectonic Control of Sediment Discharge to the Ocean: The Importance of Small Mountainous Rivers.” The Journal of Geology, September 1, 1992, 525-44.
[3] ECO Special: Sand – a business worth billions. TV, Documentary. SFR, 2014.
[4] Peduzzi, Pascal. Sand, Rarer than One Thinks. Global Environmental Alert Service. UNEP, March 2014.
[5] See also: Delestrac, Denis. Sand, the new environmental time bomb. Documentary, 2014.
[6] Hassler, Uta, Milica Topalovic and Armin Grün. Constructed Land – Singapore 1924-2012. ETH Zurich, 2014.
[7] See also: Peduzzi, Pascal. Sand, Rarer than One Thinks. Global Environmental Alert Service. UNEP, March 2014.
[8] “United Nations Statistics Division – Commodity Trade Statistics Database (COMTRADE).” Accessed September 9, 2014.
[9] ECO Special: Sand – a business worth billions. TV, Documentary. SFR, 2014.
[10] Boden, George, and Oliver Courtney. “Shifting Sand Report – Supporting Documents.” Global Witness, May 2010.

In an older version, this article was published in 2014 at ETH Zürich, FCL.

Further information about the author

Prof. Dirk E. Hebel
Professor of Sustainable Construction and Dean of the Faculty of Architecture, KIT Karlsruhe