Manufactured sand – a solution to the global sand shortage?

Many challenges are associated with the use of natural sand

Sand is commonly used as a construction material because it’s affordable, easy to obtain and suitable for many purposes like producing asphalt, concrete or glass. Unfortunately, sand is often extracted illegally from rivers or marine environments. This has consequences, such as erosion in rivers and coastlines, and changes in the water’s PH levels. It also threatens marine fisheries, biodiversity and the availability of fresh water. When digging sand, the mud from the riverbed mixes with the water, which hinders animals’ food supply. As natural sand is exploited without concern for the wider environmental impacts, it has become a major global sustainability challenge.

Global aggregates demand is expected to increase to 60 billion tonnes per annum by 2030 because of megatrends like growing population, urbanization and economic growth. According to some forecasts, buildable sand may run out as early as the first half of this century. One might ask why we don’t use desert sand, which is plentiful. Desert sand doesn’t have the right shape: The grains are too round for industrial concrete purposes. In concrete, the grains must be sufficiently angular to better adhere to each other and make the material durable enough. What about sea sand? It’s possible, but sea sand must be washed first. Otherwise, salt rusts steel bar reinforce supports, making them brittle more quickly.

The numerous benefits of manufactured sand

Fortunately, sand can also be produced mechanically. The raw material for manufactured sand usually comes from bedrock and is produced in the same way as sand is formed naturally: The rocks are crushed and grinded into ever smaller pieces. With various types of crusher and the appropriate process design, depending on the application and the sand spec to be produced, cone crushers, HSI, VSI and HRC can be utilized to transform the stones into just the kind of aggregate required to meet the specified requirements.

In the manufactured sand process, customers can obtain much better grain proportions with the new HRC technology, as well as control in the manufactured sand gradation with a very good particle shape and less ultra-fines generation. With the Barmac VSI technology, an excellent particle shape can be achieved; with the NPXX HSI and the new cone crushers fine or EF configuration, high reduction ratios can be achieved. Finally, the ultra-fines generated under any process configuration can be treated with an air classifier via a dry process, or with MWS technology if a wet process is required.

The use of manufactured sand makes sense from various perspectives. First, manufactured sand is more uniform in structure compared with natural sand. It also has an advantage when it comes to concrete production, because manufactured sand is less needed in the concrete mix by a margin of 5 to 20% compared with natural sand to fill the voids volume between the particles. Even though the mechanical manufacturing of sand consumes energy, production can be done on-site, which reduces transportation costs and environmental impact.

Additionally, to produce their core products in accordance with market demand, many quarry operations may also generate other rock products that become waste materials for several reasons. Such products generate a high cost problem for the producer, because they occupy large storage spaces and require double handling equipment and fuel consumption but are very suitable as a raw material for manufactured sand production.

By combining the different crushing and screening technologies that we have available, one can reprocess these materials and transform them into high-quality, high-value products that meet the construction industry requirements of particle shape and grading proportions, with the advantage of being able to thread the fines below 0.074 mm (200 mesh), utilizing a dry or wet process.

New ways to make concrete are constantly being explored

It’s a fact that the need for manufactured sand will increase in the future. For example, an international administration has been proposed by scientists to control the distribution and use of sand. Sand use is already regulated in Europe and the United States, as well as in developing countries, but control is still weak in many other areas. In India, the possibility of replacing some of the sand in the concrete mix with waste plastic is being investigated. Alternative ideas for “green concrete” have also been tested like recycling waste concrete from waste pavements, reusing waste aggregates, or substituting sand and aggregates with other materials.

Yet high-quality concrete demands high-quality raw materials. Sand may constitute between 30 and 40% of the main components of concrete – or even higher, depending on the mix design – but is has a great influence on the amount of cement required to achieve the concrete properties demanded. Here, cement will represent an average 50% of the cost of the total mix. High-quality manufactured sand will therefore not only offer benefits by improving concrete quality; it will also offer high cost cutouts in prepare high-quality concrete.

*UNEP 2019. Sand and sustainability: Finding new solutions for environmental governance of global sand resources. GRID-Geneva, United Nations Environment Programme, Geneva, Switzerland. 
The report has been used as one source for this blog post.