The shortcut: putting another layer of linoleum over a damaged floor, tacking more shingles over the old ones, painting a car before preparing the surface; these and many more corner-cutting tricks save time in the short-term. With budget and weather concerns, time pressure, and the ire of motorists, road surfaces often get this kind of once-over; another layer of asphalt on top of the damaged old layer.
After years of this treatment, the road surface may not be suitable for yet another layer, yet another quick fix. The damage from underneath can come through the new layer, and the rain control may no longer function as originally designed. Several options are available, including milling to take a layer from the surface in the hope that there is something better underneath.
In cases where the road is not in a condition to be repaired, it can be broken up with loaders and hauled away, and some of the old material can be recycled and brought back. The alternative is to use a recycling machine, such as the new Bomag MPH125, which saves time and resources by churning up the old asphalt in place, ready for compaction and reuse.
“Right now with the high price of oil and asphalt, a lot of municipalities and government agencies are looking at full depth reclamation as a way to save money,” said Doug Zoerb, Manager of Marketing Communications for Bomag America.
A rotor that is 56-in (1422-mm) diameter and 92-in (2337-mm) wide with 224 carbide cutting teeth spins below the cab to grind up old materials. The rotor is hydrostatically powered, spins between 90 and 130 rpm, and has overload protection to prevent damage. Concrete surfaces, although not a typical application, can also be reclaimed in this way as long as they do not contain rebar.
The power to pulverize roads comes from a 590-hp (440-kW) turbocharged Deutz diesel V8, driving the wheels through hydrostatic systems that also power the steering and rotor. This setup powers all four wheels, allowing for maximum traction as well as the ability to push a water tanker at the same time.
Water is added in both of the 125’s functions, asphalt recycling and soil stabilization. Water helps the churned asphalt to achieve a proper density, while with soil stabilization before construction, water helps to achieve the proper load bearing capacity. The 125 has also been designed to evenly mix lime, fly ash, or portland cement into the surface being prepared.
Despite a length of 393-in (9982-mm), the 125 is maneuverable thanks to an articulated structure backed up by rear-wheel steering. The 146-in (3708-mm) height could present a problem during transport, and so the 125 was designed with a height-adjustable cab, allowing for a transport height of 122 in (3100 mm) and far easier ingress/egress as the cab steps can be lowered to ground level. When in a raised position, the cab allows visibility to the machine's four corners for precise work.
Servicing is made easier through the use of a central lubrication system and easily accessible maintenance points. The rotor segments can be individually replaced, and the teeth are designed for easy changes with air tools through the use of the onboard air compressor.
With a mass of 54,014 lb (24,500 kg), the 125 is no lightweight, but the weight is needed when cutting through up to 21.7 in (551 mm) of material. The teeth must come into contact with the substrate below to aid in cooling, but generally only about 15 in (381 mm) of the material being shredded is asphalt.
With between 150 and 175 recyclers sold annually in the U.S. by various manufacturers, road construction projects have to be creative to maximize profitability. "These machines are typically rented for a period of time. A county may rent it for a month, do as many roads as they have budgeted, and then bring it back to the dealer," said Zoerb.
"We've also had situations where a county will go in and purchase one and they'll become the rental agency and actually rent it out to surrounding municipalities and regions to help offset the cost," added Dave Dennison, Bomag Soil Products Manager.