PAVEMENT SURFACE PREPARATION
Posted by Jesse Willoughby on Tue, May 05, 2009 @ 04:13 PM
Preparing Existing Pavement (Tack Coat)
Pavements deteriorate with time. Air, water, traffic and temperature cycles all shorten pavement life. Existing pavements are overlaid to correct surface irregularities, to strengthen the pavement structure and to seal out air and water.
Preparation for a pavement overlay includes cleaning dirt and debris off the old pavement and applying a tack coat. Tack is an asphalt product (usually an emulsion), which is sprayed on existing pavement in a thin film.
It provides a bond between old and new pavement.
If the old pavement has severe dips or ruts, it may require leveling with asphalt concrete prior to the overlay.
It may also be necessary to raise manhole covers, storm water inlets and similar objects.
Leveling
If a need for filling dips and ruts is anticipated, it will generally be indicated on the typical section in the plans for the project. Small holes and cracks are filled by hand with a shovel and a rake. Larger dips will require leveling with a motor grader (blade) or with a paving machine.
Normal procedure is for the inspector to stretch a string line across the dip to determine its depth and then mark the edges of dip with orange paint. Depth in the dip is marked in tenths of feet of asphalt fill required.
The Contractor then fills it to the depth and dimensions indicated. Deep dips must be filled in successive layers, starting at the deepest point and working radially outward. Each lift must be compacted separately with the rubber-tired roller.
All old pavement surfaces must be cleaned and tacked prior to leveling.