Sand is a scarce resource in the Danish underground. And absolutely indispensable in the production of the concrete that must be used in huge quantities in the many planned infrastructure projects. To make ends meet, the concrete and mortar manufacturer Saint-Gobain Weber, the waste management company RGS Nordic and the Danish Technological Institute have now joined forces in a project to replace the sand with crushed waste concrete.
Creates a material cycle
– Recycling of building materials is essential for the sustainability of future buildings, and here the collaboration between knowledge partners and industry creates long-lasting solutions. By using finely divided concrete waste as a replacement for some of the sand in mortar and concrete, we create a material cycle where waste is transformed into a resource. It is good for both the environment and the economy, says project manager Signe Strange Grønborg from the Danish Technological Institute in a press release.
Irreplaceable sand
As brilliant and flexible a material as concrete is, it is just as simple: you mix sand, stone, cement and water in the right ratio, and then you can start casting. It is already possible today to replace parts of the stone consumption in concrete with coarsely divided recycled concrete. On the other hand, today it is not possible to replace sand in concrete with finely divided concrete waste without compromising the quality of the concrete. Finely divided concrete fractions absorb water. This makes it difficult to control the concrete’s water balance, and thus its strength and durability.
Aims to develop profitable method
The aim of the project is therefore to develop a profitable method to process the fine concrete powder into a sand-like, uniform fraction that can replace natural sand in new concrete products. At the same time, the well-known cement-based recipes must be further developed so that concrete production can be adapted to the changed properties of split concrete as a partial replacement for natural sand.
– Our goal with the project is to be able to reduce the need for natural raw materials and make better use of concrete waste, which today typically ends up as filler in asphalt. With the project, we hope at the same time to learn more about how we can recycle a larger part of our products, and partly to be able to inspire other companies in the construction industry to work with the waste streams that end-of-life products generate, says Anja Sørensen, director for business development at Saint-Gobain Denmark.
Hoping to replace a third of the sand
The hope is that the project can form the basis for new concrete production, where a third of the sand in the concrete is replaced by crushed concrete. After the project, the ambition is to roll out the solution to the European market. The project will therefore be able to make a good contribution to future cement products with less waste and downcycling of concrete waste.
Great recycling potential
– Concrete waste is a fraction with great recycling potential, and the project here ensures further processing of the fine fraction from broken down concrete. Therefore, we envision that there may be an interesting market potential that supports the green transformation of construction and at the same time ensures that scarce natural materials such as sand are allowed to remain in the ground, says RGS Nordic COO Rasmus Brødsgaard Buch.
Facts:
- The project “Future cement products based on recycled building materials” lasts two years.
- The project is supported by MUDP (Environmental Development and Demonstration Program) under the Danish Ministry of the Environment.
- The project is a collaboration between the Technological Institute, Saint-Gobain Weber and RGS Nordic A/S.
- Source: Institute of Technology
