Sustainable and Cost-Effective Pavement Preservation Method: Micromilling and Thin Overlay

To respond to funding shortages and sustainably preserve their aged pavements, transportation agencies are forced to go beyond conventional thinking to develop innovative, cost-effective pavement preservation methods to stretch their limited funding. In 2007, the Georgia Department of Transportation (GDOT) developed a new pavement preservation method using micromilling in conjunction with a thin overlay to cost-effectively replace a porous asphalt layer without replacing or damaging the underlying dense-graded or gap-graded asphalt layer. The new method was applied on two large-scale projects, one in 2007 on I-75 that was approximately 150.6 lane-km, and another in 2011 on I-95 that was approximately 135 lane-km. These projects saved more than $10 million (approximately $37,092 per lane-km). Because of the successful implementation of the new pavement preservation method, GDOT has worked with Georgia Institute of Technology and contractors to standardize the new procedures, including applying pretreatment of the areas with distresses deeper than micromilling depth, determining the specifications for using variable micromilling depth to remove the porous layer completely and ensure the quality of the milled surface, developing a stringent requirement using a new performance indicator [ridge-to-valley depth (RVD)] to quantitatively measure the micromilled pavement texture to ensure its quality, and developing an automatic quality control method using a road laser profiler retrofitted to provide timely feedback to the contractors immediately after micromilling. This requires a contractor to adjust the milling operation if necessary, including the milling machine speed and the milling drum rotation frequency, and to conduct an inspection of machinery teeth, among other things, to achieve a productive milling speed while meeting the RVD requirement. This paper provides the details of this new method, including the challenges, the construction procedures, and the lessons learned in the course of the projects, which are especially valuable for transportation agencies to explore as they consider alternative pavement preservation methods that can cost-effectively preserve their aged pavements.