Kandhal Draft as of 14 April 2011
TENTATIVE GUIDE SPECIFICATION FOR COLD MILLING OF EXISTING ASPHALT PAVEMENT
[Notes in italics have been provided throughout the draft to clarify or to give the background for some specification requirements to the reviewer so that unnecessary comments are minimized. These notes in italics shall be deleted from the final draft once the draft specification is approved by the IRC Council.]
1. INTR INTRO ODUCTI UCTIO ON
Cold milling of existing asphalt pavement is required (a) to improve the rideability and cross slope of the existing pavement, (b) to lower the finished grade adjacent to existing curb or shoulder prior to resurfacing, and (c) to completely remove the existing asphalt pavement. pavement. There was need to develop a specification for cold milling of existing asphalt pavement to accomplish the preceding objectives in India. Such a specification would also encourage reuse of milled, reclaimed asphalt pavement (RAP) material through appropriate recycling processes. Prof. P.S. Kandhal developed this tentative guide specification on 14 April 2011 for consideration by the Flexible Pavement Committee of the Indian Roads congress. 2. SCOPE
This specification covers the work of milling an existing asphalt pavement. Cold milling may be necessitated to improve the rideability and cross slope of the existing pavement; pavement; to lower lower the finished finished grade grade adjacent adjacent to existing existing curb or shoulder shoulder prior to resurfacing; and to completely remove the existing asphalt pavement. The work specified herein also includes the transporting, stockpiling, or otherwise disposing of the removed pavement material. The removed material shall become the property of the Contractor unless otherwise specified. [Note to reviewer: It has been the experience of the developed countries that the government government cannot cannot manage manage RAP stockpiles stockpiles effectively, effectively, which which solidify solidify with time. It is is best to give the RAP to the contractor who can recycle it later on some paving project. The government still benefits indirectly because the contractor gives a lower price for the project in hand in exchange for the RAP which contains expensive bitumen.]
3. EQUIPMENT
The equipment for this operation shall be a milling machine capable of maintaining a depth of cut and cross slope which shall achieve the results specified herein. The machine shall have a minimum overall length (out to out excluding the conveyor) of 5 m and minimum cutting width of 2 m. The milling machine shall be equipped with automatic grade controls which operate by sensing from one or more skis, wheels, or
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other type of mechanism moving along the pavement surface and, if required, shall produce a skid resistant surface texture. The sensing device shall be of sufficient design to significantly improve the longitudinal profile of the pavement surface. A smaller milling machine may be used when milling adjacent to existing curb, around utilities, or other areas where it is not practical to use the larger machine. The machine shall be equipped with a means to effectively limit the amount of dust escaping from the removal operations.
4. CONSTRUCTION
The existing pavement shall be milled to varying depths in a manner which will restore the pavement surface to a uniform longitudinal profile and cross section as specified on the plans or as directed by the Engineer. The required milling depth at the centreline and at the edge of pavement may vary to obtain the required cross slope. The approximate depths of required milling are shown on the plans for the appropriate typical sections. In areas where the existing roadway does not have the required crown and/or super elevation rate, the milling depths shall vary to provide the desired cross slope and profile. The Contractor may elect to make multiple cuts to achieve the required pavement configuration or depth of cut. The milling machine shall be operated to effectively minimize the amount of dust being emitted from the machine. Prewetting of the pavement may be required. On resurfacing projects, the milling operations shall be limited to an area where the milled area will be covered with a bituminous surface treatment or paving, whichever applicable, within 24 hours after milling has begun, unless otherwise noted on the plans. A positive drainage of the milled surface and adjacent pavement shall be provided as soon as possible. Prior to resurfacing or opening a milled area to traffic, where permitted, the milled surface shall be thoroughly swept with a power broom or other approved equipment to remove, to the greatest extent practicable, fine material and dust particles. This operation shall be conducted in a manner so as to minimize the potential for creation of a traffic hazard and to minimize air pollution. Material removed by the milling machine, and materia l swept from the pavement, shall be disposed of in locations approved by the Engineer. If the reclaimed material is suitable for use in a recycled asphalt plant mix, and the Contractor elects to use the material in such fashion, then the height of the stockpiles at the asphalt plant should be limited to prevent moisture build-up or reconsolidation of the material.
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5. MILLED SURFACE
If the milled surface is to be the final surface of the pavement, it shall have either continuous or intermittent striations or any other pre-approved pattern which will provide an acceptable level of skid resistance. If pavement is to be constructed over the milled surface, it shall have a texture which will provide good bonding. The finished milled surface shall have a reasonably uniform texture and shall be within 6 mm of a true profile grade both in transverse and longitudinal directions, when measured with a 3-m long straightedge. Areas varying from a true surface in excess of the above stated tolerance may be accepted without correction if the Engineer determines that they were caused by a preexisting condition which could not have reasonably been corrected by the milling operation. Any unsuitable texture or profile, as determined by the Engineer, shall be corrected by the Contractor at no additional compensation. The Engineer may require remilling of any area where a surface delamination causes a non-uniform texture to occur. 6. METHOD OF MEASUREMENT
The area over which milling is completed to the desired depth and accepted shall be measured in square meters. 7. BASIS OF PAYMENT
The milling of pavement ordered and accepted, measured as noted above, will be paid for at the contract unit price bid which shall be full compensation for the milling of the pavement, the transporting and stockpiling of the removed surplus material, the removal and disposal of pavement markers, the removal of grinding residue and the satisfactory disposal thereof, and the cleaning of the pavement and for all materials, equipment, tools, labour, and incidentals necessary to complete the work.
8. REFERENCES
Kandhal, P.S. and R.B. Mallick. Pavement Recycling Guidelines for State and Local Governments. US Federal Highaway Administration Publication No. FHWA-SA-98042, December 1997. [Download Chapter 5 which addresses cold milling in detail at http://www.scribd.com/doc/47299513/Pavement-Recycling-Guidelines-for-State-andLocal-Governments-Federal-Highway-Administration-Publication-No-FHWA-SA-98042-December-1997] ************************************ [ Note to reviewers of this specification: The above specification was developed by consulting the specifications of three US states: Alabama, Florida and Pennsylvania, which have widely and successfully used cold milling over a period of several years. The specifications were then drafted considering Indian conditions.]
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