High-Performance Emulsion Boosts Urban Chip Seals
Better Roads Staff
“Use of the new CHFRS-2P emulsion is part of our continuous effort to improve operations,” Vasquez said. “We did a pilot program two years ago and tried it on one pavement. It worked so well we decided to try it extensively this year and our foreman Joiner noticed a lot better chip retention right away.”
The emulsion handles in much the same way as the emulsion used previously, he said. “The CHFRS-2P handles the same as the CRS-2P,” Vasquez said. “Our guys have extensive experience in handling the emulsions and I did not see any difference in handling between the two.
The emulsion used by Bexar County combines the best attributes of anionic and cationic emulsions. “For years we have used both cationic and anionic emulsions, and we have used anionic high-float emulsions for some time,” said Cary Brownlee, regional sales manager, Ergon Asphalt & Emulsions, Inc. “They represent a value-added product. This product takes the best of the cationic and anionic products and marries them together so you have a cationic emulsion with a high-float attribute.”
The high float attribute makes the material less-susceptible to flow or movement under higher temperatures. It fights bleeding long after it’s been placed, which becomes a long term benefit over the years, Brownlee said. That results in a very rapid-setting material in terms of break time, allowing the county to have the best of both worlds in a product that can be used for chip sealing with a very fast break and good early strength.
Benefits include the ability to open a seal coat to traffic much earlier, and greatly reduced aggregate loss and windshield break claims.
Use of the Butonal NX 1122 polymer modifier is essential to Bexar County’s new asphalt emulsion, he said. “The polymer adds to the early build of strength, and retention of aggregate, that allows you to seal or pave the road and get traffic back on it as fast as possible,” Brownlee said. “Everybody is striving to seal the road while keeping the disruption to traffic flow as minimal as possible. When you have a good polymer it will grab hold of that aggregate – enhancing the adhesion characteristics – while allowing you to get traffic back on it as soon as possible by building early strength. These both are very beneficial things.”
The chip seal program exists within an overall pavement management program for Bexar County.
“In 2007 we implemented a Cartegraph asset management system,” Vasquez said. “A consultant did a pavement data inventory – measuring distress data such as cracking, rutting and ride indices – and used them to come up with an overall condition index (OCI). We try to do that every three years and in 2011 undertook our second round of data collection.”
A data collection van is used to gather the information at highway speeds. “Using the OCI we program different maintenance strategies into a software module, which gives us different budget scenarios for different treatments on different pavements,” Vasquez said. “You can create a plan for however long you want, but we plan for three years because that’s our evaluation cycle. Right now we are planning for the cycle from 2012 to 2015.”
And because the county has GIS capabilities the plan can be displayed on a county map as well, which greatly enhances planning capabilities and the ability to communicate the program to county administration and to citizens.
“Our overall condition rating is at 90.46, on a scale of zero to 100, up from the high 80s about three years ago,” Vasquez said. “My goal is to keep the OCI above 90 and focus on specific types of distress that we have. If there is rutting we will reconstruct the road or do something that will remove the cause of the rutting.”
With use of pavement preservation in the context of asset management – by which agencies protect their investment in their infrastructure – materials like Bexar County’s high-performance asphalt emulsion can help agencies preserve more miles, in the same amount of time.
“Everything happens faster,” Ergon’s Brownlee said. “Everyone works faster, whether they are contractors or in-house forces. They can get in, do the chip seal, and move on to the next project, confident that they’ve left a good, sound product behind them.”
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