Pavement Preservation Journal - Spring 2012 - (Page 22)

PHOTO CREDITS: BASF Corp. Forces of TxDOT District 15 place chip seal utilizing CHFRS-2P asphalt emulsion in May 2011 Sophisticated ‘Seal Coats’ Enhance Texas DOT Pavement Preservation D rivers in the San Antonio District of the Texas Department of Transportation (TxDOT) are benefiting from the use of a new highperformance asphalt emulsion for seal coats that is providing longer-lasting chip seals and optimizing traffic flow through work zones. There are three “tools” from the “Pavement Preservation Toolbox” that the San Antonio District uses to prolong road life. They are thin asphalt overlays, micro surfacing, and seal coats. “You might call them chip seals, but we call them seal coats,” said John Bohuslav, P.E., director of maintenance, TxDOT San Antonio District 15. Some 99 percent of San Antonio District pavements are surfaced with either chip seals — called “seal coats” in the local lingo — or asphalt lifts. Seal coats are critical to keeping San Antonio District pavements in keeping with TxDOT goals of achieving 90 percent of roads in good or better condition. A pavement condition index (PCI) of 70 or greater is considered good or better. Today, a CHFRS-2P asphalt emulsion — a cationic, high-float, rapid-set emulsion in the No. 2 viscosity range with polymer added — is solving adhesion and slow break problems endemic to lower-performance emulsions that had been experienced by the district. “It’s from a local supplier, it’s easy to get, and it’s on our low-bid list of items to buy, as is the CRS-2P,” he 22 added. “The difference between the two is the high-float characteristic that grabs the rock better. The guys like it, it sets well, grabs the rock and holds it. The work I’ve seen them do is outstanding, I think our crew does some of the best seal coats in the state.” In addition to its better adhesion and durability attributes, the cationic emulsion allows the state to place seal coats on the hottest days, of which there are many in the San Antonio region. “On hot summer days, when it’s in the 100 deg F range and we are trying to shoot seal coat, the anionic emulsions won’t break and set quickly enough,” Bohuslav said. “They just sit there. But the cationic will break and set much faster, so we can get the work done, finish and move on.” The higher-performing emulsion now is getting too popular at the district. “It costs us a little bit more money but as it controls aggregate loss and sets up quickly in the heat, it’s been worth it for use on hot summer days and on long distance seal coats,” Bohuslav said. “Now everybody’s getting spoiled on the cationic and they want the cationic all the time! In response we’ve restricted use of the cationic emulsion to full-width, full-length seal coats and specific projects.” Traffic pressures dictate use of a fast-breaking emulsion, Bohuslav said. “When we are doing 10 miles of seal coat we have to have it break and set quickly,” he said. “For that length we have to keep moving down the road, and traffic will soon be driving on that seal coat we just shot. The CHFRS-2P lets us do that.” View past issues of the Pavement Preservation Journal online at

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