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RAIL TRACKBED TECHNOLOGY

1999 
The treatment of soils with lime has become a viable and cost-effective method of improving the engineering properties of inadequate materials. It adds small quantities of quicklime (CaO) or hydrated lime (Ca(OH)2) to suitably reactive cohesive soils. With quicklime additions, three mechanisms act on the natural soil. In 1995, after several years of research, the Transport Research Laboratory (TRL) produced its draft Advice Note HA 74/95 "Design and construction of lime-stabilised capping", which was published by the Department of the Environment, Transport and the Regions (DETR). This Note has become established as best practice for the lime stabilisation of road capping layers. As a result of the proven effectiveness of lime improvement for highways, Railtrack, the UK rail infrastructure operator, commissioned the TRL to investigate the possibility of using lime treatment to improve rail track bed during track possessions, when very little time would be available. HA 79/95 requires a mellowing time (between adding lime and final compaction) of 24 to 72 hours, whereas the time available for mellowing during a track possession may be as short as four hours. The research aimed to find whether the required strength improvement could be achieved within this time, but validation trials are still needed.
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