This change could lead to an environmental friendly solution in construction industry. Concrete is the most consumed material after fresh water as more than 20 billion tons are produced each year worldwide. The mixture of concrete consists of 30% of sand. By replacing about 10% of it with plastic material, over 800 million tons of sand could be saved annually.
In general, plastic materials weaken concrete as they don't bond to the cement mix in the same manner that sand does. Dr. Richard Ball, from Bath’s Department of Architecture & Civil Engineering points out that there needs to be a certain balance between the utilization of plastic and the concrete's strength reduction: “The key challenge here was to have a limit between a small reduction in strengths, which we achieved, and using an appropriate amount of plastic to make it worthwhile. It is really a viable material for use in some areas of construction that might help us to tackle issues of not being able to recycle the plastic and meeting a demand for sand.”
Researchers investigated the impact of 5 finely graded plastics on the structural strength of concrete. A compressive strength of 54 MPa, similar to structural concrete, was achieved by sand-sized PET (Polyethylene Terephthalate) particles deriving from recycled plastic bottles. Dr. Ball stated: “Properties such as the type of plastic and the particle size and shape will all have an influence on the strength of the concrete to which it is added. If we can identify the most favorable properties of the ‘plastic sand’ we may be able to increase the additions allowable without compromising the properties. There are also important factors such as the rheology of the wet mix, environmental durability and fire performance which can be further explored.”
Mr. Orr also said that the team is now investigating the utilization of sources from plastic material that is already graded to the required level.
The study received the Atlas Award for its potential contribution to society.