Soil Stabilisation

With the increased emphasis on recycling, reducing waste going to landfill and reducing energy costs the use of stabilised materials in construction projects becomes more and more important. Using stabilised soils can also help to reduce the consumption of raw materials and the energy costs of transport.

Depending on the end use, the design of suitable stabilisation solutions can be a complex process requiring a number of trial mixes at various moisture contents and at various levels of binder. Mixes have to be cured and tested, typically after 28 days. Stabilisation binders include lime, cement, granulated blast furnace slag, PFA, fuel bottom ash and foamed bitumen. All of these have advantages and disadvantages and the selection of the most appropriate binder depends on the material being stabilised and the end use.

Design regimes are laid out in Highways Agency documents, HA74/07 and the Specification for Highway Works. The Britpave website www.soilstabilisation.org.uk also contains a lot of useful information. ESG is UKAS accredited for most of the tests required by these documents including IBI (Immediate Bearing Index), MCV, Proctor compaction, and swell testing. Carrying out the testing successfully requires expertise and the timing of each operation is crucial so that each trial mix has to be prepared at different moisture contents to allow the relationship testing (compaction and MCV) to be completed in one day.