Quicklime and hydrated lime is often used in construction as a stabiliser and for drying wet and clay-bound soils. Lime application to these types of soils helps provide a sound base for the construction of roads, farm tracks, dairy pads, wind farms, pipe trenches, stop banks and numerous other applications.
Effective soil drying and soil stabilisation can occur almost all year round. In a roading context, the correct application of quicklime or hydrated lime can improve load bearing performance, pavement durability and assist to avoid costly delays in project timelines.
There are essentially two forms of improvement when using either quicklime or hydrated lime:
- soil modification
- soil stabilisation.
The use of lime can modify almost all fine-grained soils to some extent, but the most dramatic improvement occurs in clay soils of moderate to high plasticity.
Modification primarily occurs due to the exchange of calcium cations supplied by the hydrated lime. The clay surface mineralogy is altered as it reacts with the calcium ions to form cementitious products. This will result in a decrease in plasticity and a reduction in swelling and moisture-holding capacity, ultimately leading to improved stability.
Soil stabilisation occurs when the proper amount of lime is added to a reactive soil. Stabilisation differs from modification in that a significant increase in strength is developed over the longer term through an on-going pozzolanic reaction. This reaction results from the formation of calcium silicate hydrates and calcium aluminates as the calcium from the lime reacts with the aluminates and silicates solubilized from the clay mineral surface. This reaction can begin quickly and is responsible for some of the effects of modification. However, the full-term pozzolanic reaction can continue for a long period of time, often for many years. As a result, some soils can produce strength gains over time and durability when treated with lime.
Graymont quicklime is supplied in different size gradings from finely ground to coarser pebble quicklime material. Hydrated lime is available for other roading applications including foamed bitumen stabilisation.
Additional Resources - National Lime Association (North America):
- Lime treated Construction Manual – NLA
- Mixture Design and Testing Procedures for Lime Stabilized Soil – NLA
- Using Lime for Soil Stabilization and Modification – NLA
Additional Resources - AustStab – Pavement and Recycling and Stabilisation Association
- Lime stabilization practice – AusStab (Lime Stabilization Practice)
Acknowledgement
Graymont would like to acknowledge and thank the National Lime Association and AusStab Australia for access to web content and downloadable material.