Capital Equipment News January 2016

COVER STORY

COLD MILLING MACHINES HAVE REAL BITE The tools that cold milling machines use for removing road layers were originally developed for the mining industry. So- called point-attack cutting tools, fitted to a rotating milling drum on the underside of the machine, bite into the road at precisely the specified depth. No material is too hard for these tools. Cold milling machines are even capable of rehabilitating pavements, whether asphalt or concrete. The material is milled and then directly loaded on trucks to be transported from site, all in one single pass. As traffic is often slow-moving in the area of the job site, car drivers mock the massive cold milling machines by saying that they’re always first in the traffic jam. Few bear in mind, however, that rehabilitation projects using cold milling machines are mostly carried out as mobile roadworks. Alterna- tive methods would involve a much greater effort. Cold milling of road pavements is un- rivalled in terms of both logistics and speed of execution.

ROAD MILLING MACHINES ARE TEAM PLAYERS Not all cold milling machines are as big as a complete apartment. Some models are as small as a passenger car. On many job sites, machines of different sizes frequently work as a team, each one playing its own aces. The large milling machine removes the large surfaces, while the small one takes care of milling off the pavement around “nuisances”, such as manhole covers or kerbstones. Typical of rehabilitation methods using cold milling is that the damaged pavement layers are usually replaced with asphalt, – irrespective of whether the distressed pavement consisted of asphalt or concrete. The new surface course or asphalt road structure is paved by road pavers prior to conventional compaction by rollers. PAVING AND COMPACTING USING PAVERS AND ROLLERS

tie-in points and follows the edge of the road from there. The pavement is pressed home in a further pass. Dynamic compac- tion is mainly used for the main compac- tion process. The drums vibrate horizontally (oscillate) or vertically (vibrate), thus signifi- cantly increasing the effect of compaction. The operation is completed by a final roll- er pass that will “iron out” any remaining irregularities in the asphalt pavement or surface to produce a perfect surface finish. STRUCTURAL MAINTENANCE, REPAIR AND REHABILITATION Roads are exposed to tremendous loads that will sooner or later leave their marks on them. A time will come when every road will be in need of a general overhaul. But no two damage patterns are alike. Replacing the pavement is a standard procedure when repairing roads. The challenge is to ensure that only the damaged layers of the road structure are removed, and to avoid disruptions to traffic at the same time. Under these conditions, cold milling is the only viable option for many construction projects.

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