Rehabilitation of roads to overcome the existing problems, by cold milling technology, is the most cost-effective, suitable and eco-friendly solution at hand.Growing volumes of traffic and increasing axle loads leave the pavement wearing course severely damaged and unusable for the traffic in city roads and highways. To make these roads reusable, repair work must be carried out diligently. Further, repeated overlaying of old asphalt surface leads to increased levels of the road. Rehabilitation of roads to overcome these problems by cold milling technology is the most cost-effective, suitable and eco-friendly solution. For this purpose, Wirtgen has range of 21 cold milling machines with working widths ranging from 350 mm to 4,200 mm and working depths of up to 320 mm.The Process The milling machine is designed to remove the carriage-way pavements, asphalt as well as concrete, with the help of a milling drum, which is the heart of this machine. Optimum wear carbide cutting tools are inserted into the tool holders, which in turn are welded on to the body of milling drum in a spiral fashion. The milling drum rotates against the feed at a speed of about 100-200 rpm (depending on the type of machine) to cut the existing pavement.The cutting tools, tipped with tungsten carbide, rip up and granulate the pavement. The milled material is lifted and conveyed into a tipper through an integrated discharge conveyor system. The reclaimed asphalt pavement (RAP) to a large extent can be reused and recycled for producing new asphalt depending on its actual condition. The RAP is transported to the hot mixing plant site where new bitumen and aggregate are added and also processed for reusing in granular base course material such as GSB and WMM.CSR benefit The land use on either side of the road section comprises predominantly agricultural, plantation (fields, plantations, etc) and forest, except near settlements where it is residential/commercial establishments in the urban areas. The contractor is a responsible corporate entity towards corporate social responsibility (CSR) and dumping the excavated pavements in someone's cultivable fields will not add value to its obligation towards society at large. Green TechnologyReusing in situ material and hence every available opportunity of reducing waste, is planned by recycling the reclaimed asphalt pavement and the underneath pavement layers. These measures require enhanced efforts to bring in new technology milling machines to protect the environment. By reusing RAP and suitable sub-grade material, we save on energy for crushing and transporting fresh aggregates. This can be documented to earn carbon credits.Time AdvantageOne major benefit which many project authorities should consider is the time advantage due to this process. Here, we save a full PCC laying process by 60 per cent which gives an immense advantage to the concessionaire to start early tolling and marginalisation of resources in manpower and machine utilisation which are unquantifiable at any stage of this project.Wirtgen in Various ProjectsMilling bituminous pavement: The milling machine will cut an average thickness of 320 mm in a single pass. If the bituminous layer exceeds 200 mm, then it is recommended to cut in two passes to optimise the use of milling machine and give the best cost-per-tonne calculations for the contractor.Milling WMM/WBM/Stone soling layer: This layer comprises mainly of single sized aggregate compacted to an average thickness of 200 mm. The top layer of 25 mm of WBM/stone soling coated with emulsion/tack coat can be milled with the bituminous pavement. Balance layer can be milled separately and transported to site to be stacked for further use in GSB, cement layers as per the characteristics of the milled material.RAP reuse solutions: The RAP generated can be blended with fresh aggregate and reused as GSB, WMM, aggregate for increasing the CBR of base soil and constructing the approach roads etc. With this method, we can first ascertain the gradation of milled asphalt pavement and then use it in proportional mix with new aggregate to form an acceptable design mix as per MORTH specifications. Wirtgen India is well versed with the required procedures to convince the authorities to allow the reuse of RAP and can help its esteemed customers avail this benefit.Milled material RAP: The milled material is stacked at site for further reuse. The speed and depth of the milling machine can be adjusted to get the desired size of the milled product.RAP in sub-base soil stabilisation: An excavator is used for mixing RAP with soil from borough area at site. The soil CBR is increased to the required level with this method.RAP in granular sub-base: GSB with RAP mixed in a local mixing plant. The blended GSB was used in new pavement wherever possible.RAP in wet mix macadam: The standard WMM plant available with all our contractors throughout India is used to mix RAP with stone dust and 40 mm down aggregate.RAP in diversion road: Diversion roads laid out with RAP material have the best load bearing capacity since they are laid with milled material of density 2.35 kg/sq cm. Once compacted, they can be immediately opened for traffic.