Cold Milling: A construction service in high demand
Published on 01/27/2009
For decades, cold milling (also referred to as cold planing) has been a construction service in high demand with little supply of available contractors. With state and local governments searching for cost-effective and environmentally responsible methods of maintaining their aging road infrastructures, they have relied on the technique of cold milling.
What is the cold milling process?
Cold milling is the mechanical removal of deteriorated asphalt pavement in the process of road rehabilitation. The cold milling process involves the removal of asphalt surfaces with a machine fitted with a rotomill. The cutting machine moves the milled material to an interior drum which transfers the material to a conveyor belt. The conveyor belt then dispenses the material in trucks or on the shoulder of the roadway. If the placed in the trucks, the milled asphalt can be transferred to an agent where it can be reused in a process known as hot plant recycling; or it can be stored and later reprocessed. The reprocessed material, termed hot mix, is then placed back on the milled roadway as new asphalt. In instances where the milled asphalt is unsuitable to be reprocessed, it can be used as shoulder backing material or base material.
Generally, this cold milling work can be classified into five general categories: fixing existing conditions; grade control; grade and slope control; full depth; and variable depth. Each of these categories refers to the depth, grade, and slope at which the asphalt is removed in the cold milling process. Fixing existed conditions, as in removing the surface irregularities, is the least invasive and full depth, referring to the removal of the pavement to the base, is the most invasive. In the instance of variable depth, the work that is to be done depends on the specification as noted by the individual project plans.
What are the benefits of cold milling?
Cold milling is attractive for a number of reasons. First, the focus on recycling the milled material is environmentally friendly and cost-effective. Cold milling helps to conserve resources. Asphalt is a petroleum product, and supplies are rapidly dwindling worldwide, and are increasingly more expensive to procure. Hence, the recycling of asphalt helps contractors and government agencies save money. Moreover, excess milled material from one site can be used on other projects ? helping to cut project costs elsewhere. Essentially, firms that perform cold milling have an opportunity to get free materials. In addition, contractors with a cold milling operation can increase profit margins because they do not have to subcontract the work and be concerned the fixed costs involved in that process. Not to mention that once a firm gains a cold milling capacity they take a step towards becoming an ?all-in-one? contractor to which state and local procurement agencies are attracted. Cold milling?s cost effectiveness and profit maximizing potential is certainly attractive to both agencies and contractors. Hence, firms capable of performing cold milling are more likely to sell lower bids on public works projects.
Other positive aspects of the cold milling method relate to its practical use as means through which roadways can be kept safe. For example, it keeps the proper flow of surface run-off and keeps roadways free of potholes. In a superficial sense, cold milling enhances the longevity of streets, thus keeping streets looking well maintained. Additionally, cold milling is relatively less time-consuming than other modes of asphalt relaying. Thus, it has a less detrimental effect on the flow of traffic.
Cold milling also allows for easier installation of underground services such as water, sewer, electrical and communications. With many cities removing services from overhead power lines and telephone poles and placing them under city streets, it is easy to see that this is an area of exponential growth for many years to come.
Low supply of contractors with high demand
Every agency, from the State and Federal DOT to counties and municipalities rely on cold milling to repair and resurface their roads. Much of the roadway infrastructure in the US is stretched beyond its 30-year lifespan. There is a backlog of rehabilitation projects for many of these agencies, and resurfacing rather than replacement will be the choice for many of their projects.
Despite the high demand for cold milling on construction projects, few contractors have the capacity to perform the service. According to the AGC, only 20 percent of paving contractors in the US currently own and operate cold milling machines. That leaves the other 80 percent of them to look for subcontractors to perform this work. Some subcontractors who have chosen to work in this field are doing quite well. Witness the success of ABSL Inc., a DBE certified firm located in the San Francisco Bay Area and Sacramento. They operate primarily in Northern and Central California, but also take on projects in Southern California and Nevada. Started in 1991, as a concrete work and traffic control company, they now own a fleet of Wirtgen milling machines capable of working on many construction projects simultaneously. Milling is now over 90% of the work they do. They may be contacted in Hayward at (510) 727-0900 or in Sacramento at (916) 379-0442.
If contractors are looking to get into cold milling, they may wish to contact Nixon-Egle Equipment Co located in both Northern and Southern California. Tracy, CA: (209) 830-8600 or Ontario, CA: (909) 1822. Also contact the Wirtgen America Inc. offices about Cold Milling machines at (615) 501-0600 or visit them on the web at www.wirtgenamerica.com.
