Waste materials in ground improvement applications

Sustainability is emerging as a key consideration in all branches of engineering. The construction industry is under growing pressure to play a part in sustainable development by minimising the amount of waste generated and maximising the quantities of materials that are recycled and reused.

Various ground improvement systems have evolved from the need to develop sites that were previously considered marginal; these are now being developed as a result of tightening construction regulations and increasing land prices. These ground improvement methods seek to improve the strength and stiffness properties of the soil so that a more cost effective foundation design may be adopted. One particular ground improvement method that is becoming increasingly popular is that of Vibro-Stone Columns. However, the substantial quantity of ‘inert’ crushed stone and gravel that is consumed by the technique is a major sustainability concern.

This paper investigates the viability of incorporating potentially renewable granular aggregate as a full or partial alternative to using ‘inert’ stone. Four common waste products that are often condemned to landfill sites have been identified as potential renewable sources. These include: (i) crushed concrete, (ii) cement paste, (iii) rubber ‘chips’, and (iv) polystyrene. A series of circular plate loading tests were conducted to assess each material’s performance in relation to standard inert aggregate columns. The results presented indicate that crushed concrete and rubber have potential for industrial applications, however further prototype full scale testing is required to validate these findings.