607-1 DESCRIPTION
Milling of asphalt pavement is the process of removing the pavement at locations, depths, widths, and typical sections indicated in the contract documents or as directed by the Engineer. The work also includes removing, transporting, and disposing of the milled material and cleaning the milled pavement surface.
The milled material normally becomes the property of the Contractor unless indicated otherwise in the Special Provisions. All milled material must be disposed of by the Contractor in areas provided by him that are outside the right-of-way, except where the milled material is required to be used in the work by the Special Provisions.
There are many advantages of milling versus other pavement removal methods. The pavement can be removed relatively quickly with minimal interruption to traffic flow, and in some cases the restored pavement can be opened to traffic immediately. The removal of asphalt pavement by milling is not limited to interstate or primary highways, but may also be utilized on rural secondary routes and urban projects. This process may also be effectively utilized in spot pavement maintenance operations. The milling procedure consumes substantially less energy than other methods of pavement removal and the removed material can usually be used again without further processing in a hot recycled asphalt pavement or possibly in an aggregate base course.
Milling can correct several pavement problems while saving time and money by not having to adjust adjacent structures or geometric designs. Some problems which can be corrected by milling are rutting, washboarding, pushing, shoving, and bleeding. Milling improves the texture for bonding of additional asphalt pavements and retains guardrail heights and bridge clearances. On multi-lane highways, the distressed lane can be milled with limited inconvenience to the traveling public. Also, the desired profile and cross-sections of roadways can be restored so that drainage systems can function properly.
It is important to understand that milling (pavement removal) is a separate entity from hot mix recycled pavements. Milling may or may not be done in conjunction with the production of a recycled mixture. Also, milled pavements may or may not be overlaid with a recycled hot mix. The connection of the
two is that the RAP from the milling operation may be used in a recycled mix. The purpose of milling, though, is not necessarily that of producing RAP for use in recycled pavements. The purpose(s) of milling should be that as discussed above.
607-2 EQUIPMENT
The Technician should always verify the equipment meets the specifications and is in good operating condition such that it will leave a reasonably smooth surface profile and texture. When the milling teeth are excessively worn, lost, broken, improperly replaced or out of adjustment, the machine will not be capable of leaving a surface free of excessive variations, ridges, and/or irregular texture.
When existing asphalt pavement is to be milled, the removal must be done by cold milling with equipment (“milling machine”) that has been designed and built exclusively for pavement milling operations and with sufficient power, traction, and stability to accurately maintain depth of cut and slope.
The milling machine must be equipped with an electronic control system which will automatically control the longitudinal profile and cross slope of the milled pavement surface through the use of either a mobile grade reference(s), an erected string line(s), joint matching shoe(s), slope control systems, or other methods or combination of approved methods. Locate the position of the grade control system such that the grade sensor is at the approximate midpoint of the mobile reference system.
607-3 CONSTRUCTION METHODS
The Engineer may waive the requirement for automatic grade and cross-slope controls where conditions warrant. However, the automatic controls should be used whenever possible to ensure a smooth longitudinal profile.
The Engineer may require re-milling of any area exhibiting laminations or other defects.
607-5 MEASUREMENT AND PAYMENT
Removal of the existing pavement shall be to the depth required by the plans or Special Provisions. The Engineer may direct the Contractor to vary the depth of milling by as much as
one inch. This provision is not intended to arbitrarily change the depth of milling for a
full inch throughout an entire project. The intent is to allow the depth to be modified to meet the variable conditions sometimes encountered on a given project. For example, if increasing or decreasing the depth is needed to remove the existing pavement at the interface between two previously placed layers, the Engineer could direct the depth change up to
one inch without a modification in the price. As stated, this provision can and should be used when necessary, but should not be abused.
When the directed depth of milling per cut is altered by the Engineer more than one inch, either the Department or the Contractor may request an adjustment in unit price under the provisions of
Article 104-3.
In administering the requirements of
Article 104-3, the Department gives no consideration to value of the reclaimed asphalt material due to the deletion or reduction in quantity of milling. For example, if the typical sections detail milling through an intersection and the Department determines it is in the best interest of the public to delete this milling, the contractor is barred from claiming higher costs to produce the asphalt mix due to the deletion of an anticipated amount of material to be used in a recycled asphalt mix. The Contractor should not have treated the anticipated millings as a commodity.
Incidental milling occurs when the Contractor is required by the plans to mill irregular areas and intersections or is directed to re-mill areas whose length is less than
100 feet. Incidental milling can be thought of as non-production milling. For example, a project has milling throughout an intersection. The milling machine will most likely cut the travel lanes through the intersection initially. Then they will back up and catch the irregular portions of the intersection, so that it could be paved in one operation. In this simple case, the technician should measure the travel lane milling through the intersection and beyond as “Milled Asphalt Pavement ___", and the irregular areas and adjoining intersection travel lanes would be measured as “Incidental Milling".
Measurement will be made for each cut the Contractor is directed to perform. Should the Contractor elect to make multiple cuts to achieve the final depth, no additional measurement will be made beyond the initial measurement.
ADDITIONAL RESOURCES
