Pavement Preservation Journal - Spring 2012 - (Page 27)

Fine-Mill Pavements for Smooth Thin Overlays by Dan Brown A s shrinking state road budgets continue to favor pavement preservation techniques, an increasing number of states are choosing fine milling, or micro milling, to prepare asphalt pavements for surface treatments. The cutter drum used for micro milling carries three to four times as many teeth as a conventional cutter, so the teeth are more closely spaced. The result is a finer surface texture on the pavement. Micro milling is poised for rapid, nationwide growth over the next five years, said Jeff Rule Sr., of Roadtec Cutter Drums. Micro milling offers several advantages that conventional milling does not. For one, a micro milled surface will not reflect upward into a thin overlay, as an aggressive, conventionallymilled surface can do. For another benefit, micro milling is less expensive. The milling machine usually makes a shallow cut of 1 in. or less, so there is less recycled asphalt to haul away. Rule says that states with specifications for micro milling include New York, Massachusetts, Rhode Island, Connecticut, Georgia, Alabama, Virginia, California, Indiana and South Carolina. “Tennessee is using micro milling now, and so is Georgia,” he said. “Alabama has a spec and has done some micro milling. Washington State is doing a lot of micro work.” A common specification for micro milling smoothness uses the glass bead test. A technician pours a premeasured amount of glass beads in one place on the surface. The technician then uses a hockey puck to apply a circular motion to the beads to spread them until they come to rest. The smoother the surface is, the further out the beads will spread, says Frank Corrao, a deputy chief engineer in the Rhode Island Department of Transportation. Then the technician measures the diameter of the circle covered by the spread-out beads. “If that circle is PHOTO CREDIT: Roadtec Corp. Werner Construction uses Roadtec milling machine to micro mill a section of I-80 in Nebraska. The machine is named ‘Big Red’ in support of the football program at University of Nebraska. greater than 6 in., then you have a fine corduroy micro milled surface that meets our specs,” said Corrao. “But if you spread the beads out and the bead circle average becomes less than 6 in., that is not considered an acceptable micro milled surface.” REPLACING OGFCs Massachusetts has a number of roadways with opengraded friction courses that have outlived their useful lives, said Ed Naras, pavement management engineer with the Massachusetts Department of Transportation. The pavement distresses include raveling and some delamination of the surface course. “We require fine milling on a lot of our thin overlay projects,” Naras said. “It gives you a fairly smooth pavement, and the final ride quality is better than with conventional milling. It’s smoother for road users during construction, seems audibly quieter at the roadside, and doesn’t impact traffic as much.” Naras says MassDOT has reduced pavement repair costs by performing micro milling in the fall, leaving An increasing number of states are choosing fine milling, or micro milling, to prepare asphalt pavements for surface treatments. Spring 2012 pavement preservation journal 27

Table of Contents for the Digital Edition of Pavement Preservation Journal - Spring 2012

President’s Message
National Preservation Conference: Make Plans Now
Pavement Preservation is ‘Sustainable’ Choice
Deck Micro Surfacing Cuts Accidents, Wins Award
Enhanced Fog Seals Boost Chip Retention
Sophisticated ‘Seal Coats’ Enhance Texas DOT Pavement Preservation
Rejuvenating Treatment Preserves Runway, Grooving
Fine-Mill Pavements for Smooth Thin Overlays
Puerto Rico, Southeast States Focus on Preservation
Maryland Identifies Right Fix for Right Road, Right Time
‘Thin is In’ for New Texas Center Courses
Why to Cut Back on Cutback Asphalt
Test Sections Constructed at Virginia Smart Road
Ground Penetrating Radar Fills Gaps in PMS

Pavement Preservation Journal - Spring 2012