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Construction & Civil Engineering

Although widely known as Soil Stabilisation, there are a number of distinct processes which can be carried out by the addition of quicklime to waterlogged, clay bearing or contaminated land. Improvement is the first process step, which is the drying out of water bearing material by the heat generating reaction with quicklime, this also converts some of the free water to hydrated lime. Using this process, it is possible to convert an unworkable site into a solid working platform providing a base for construction development, or alternatively as a potential area for agricultural use.

Hydrated lime can be used as an additive to hot mix asphalt used for road surfacing. The addition of lime increases the resistance of the asphalt to water stripping, allowing it to maintain strength and provide good resistance to heavy stress i.e. for road surfaces prone to regular traffic or congestion. Lime also acts as a mineral filler which increases the viscosity of the binder, increasing the stiffness, tensile strength, compressive strength and resistance to water stripping. Asphalt is currently used for the majority of road networks throughout the world. Infrastructure is often dependent on the quality of road surfaces, and without its superior materialistic properties, roads would be more hazardous and all types of vehicles would be prone to damages and accidents.

Quicklime is mixed with cement, sand, water and aluminium powder to give a slurry which rises and sets to form honeycomb structured blocks which have excellent thermal and sound insulation properties. The heat generated when quicklime reacts with water and the alkaline conditions combined with aluminium powder generates hydrogen bubbles which cause the blocks to rise. The heat generated subsequently causes the slurry to set. The blocks are then heated in an autoclave, which promotes reactions between calcium and silicates in the sand or PFA and gives extra strength. Dolomite lime and/or modified quicklime can be added to reduce excessive shrinkage or cracking, an issue which is increasingly useful for highly stressed materials, such as busy road junctions.

Buildings pre 1900 would not have been built with cement but with a lime mortar. Therefore in order to conserve these buildings it is essential to use similar materials when doing so. To introduce cement or cementitious mortar would cause decaying due to the difference in chemical composition of cement and inevitably result in irreversible damage. Hydraulic lime mortars, hydraulic lime plasters and renders and lime putty are therefore all used for the restoration of majority of Europe's built heritage. The restoration of these buildings is often important for surrounding communities, providing them with lasting historical and cultural heritage, prolonging the buildings use as a tourist attraction, and often even increasing the aesthetic appeal of the local area.