Case Study: Texas DOT Chip and Seal

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Case Study Overview

Project: Texas DOT Chip and Seal
Location: Grosbeck, TX, United States
Project Type: Roads
Application: Pavement Underlayer
ProductS Used: PETROMAT®

Photo showing PETROMAT paving fabric placed on the eastbound lane before the second tack coat and chip were to be applied.

Problem

The test site was one of four locations to lay Petromat® under a chip and seal overlay. The project involved both the east and west lanes of an .8-mile section of Highway 164, just east of Grosbeck, Texas. The pavement was swept clean with a street sweeper to remove any unwanted or loose materials from the surface. Any cracks in the pavement had been filled with an appropriate material, but the pavement appeared to be in relatively good condition. A distributor truck then spread .13 gpsy of pure asphalt tack on the westbound lane. It was determined that the .15 gpsy of tack was the optimum rate for this type of project.

Solution

The distributor sprayed the pavement 370 linear feet at the time prior to the placement of the Petromat 4599 fabric. The Petromat® was immediately placed in the hot coat to assure proper bonding. Petromat® was then installed using a tractor equipped with a front-end unit at the rate of about 11 rolls per hour. The brooms of the unit helped push the Ptromat® into the tack coat. The Petromat® was then rolled with rubber-tired rollers to enhance the bond between the Petromat® and the existing surface. The Petromat® was already bonded well to the surface, so the rolling was not necessary, but the contractor decided to do it anyway. When all of the eastbound Petromat® had been installed and rolled, the distributor truck then applied a topcoat of pure asphalt on the Petromat® at the rate of .36 gpsy. The chip spreader immediately followed the distributor. Again, the distributor did not get too far ahead of the chip spreader. The chips were a processed material. formed from a shale material then baked to form a .5-inch to .75-inch stone. The material was very consistent, with zero fines. The topcoat of chips was immediately rolled into the heavy asphalt tack, and then opened to traffic. The entire project took about five hours.

Photo showing PETROMAT paving fabric being rolled out along Highway 164 in Grosbeck, TX.
Photo showing comparison of the two sides of the road after a two year period, and the side which had PETROMAT applied was holding up far better than the one which did not.

Performance

After two years of weather and traffic, the section of roadway that used Petromat® (on the right) was holding up extremely well. The area that used chips alone (on the left) did not fare as well and needed additional application of chips. All parties involved were very pleased with the installation and the performance of Petromat®. A representative from the North Carolina Department of Transportation was in attendance with the intent of trying this in their state.


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