Prof. Rajib B. Mallick and Prof. A. Veeraragavan
Roads are a necessity for the modern life – and more specifically, good roads are essential for an efficient transportation system. Quite often roads deteriorate not because of the poor quality of the surface layer alone, but because of problems in the underlying layers, which are typically referred to as base, subbase and subgrade, as one goes down the pavement structure. Such problems can be due to poor choice of materials in the lower layers, inadequate compaction of lower layers, moisture/inadequate sub-surface drainage in the layers, poor gradation, or simply layers that have deteriorated over the service life of the pavement. The problems can manifest themselves as rutting, cracking, potholes and, severe roughness and deformations. A road with any of such problems is very uncomfortable to ride, can be dangerous because of potential harmful effects on the stability of vehicles, and will have significantly reduced speed and capacity. Furthermore, a thin overlay of Hot Mix Asphalt (HMA) or cheaper layers such as chip seals (surface dressing) will definitely not solve this type of structural problems, and if done, will lead to waste of materials, money, labour and time. An option that might come in the mind is: why don’t we excavate the pavement upto the layer that is causing the problem, and get rid of the problematic materials and start the construction of the pavement from that layer upwards with virgin materials? Yes, that is an option, but a terribly costly, from the point of view of both men/materials and money, and time. Also, the materials that are excavated need to be transported to a landfill or a different area, which has to bear the burden of this construction waste, and then there is the additional energy (diesel) need for the trucks that are used for the removal of the materials.
Is there a better option? YES, fortunately, thanks to the advent of modern sophisticated road recycling machines, there is the technology of Full Depth Reclamation (FDR) that can be used in such cases to improve the road, by utilizing the existing material, and save money!
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