TPWA Short Course Highlights Lime Stabilization Process

More than 150 participants convened in Waco to learn about the various approaches available to cities and counties when reconstructing and rehabilitating deteriorated pavements.
This year’s Texas Public Works Association “short course,” conducted Feb. 10-13, featured Richard Martinez from the city of San Antonio Streets Department and Larry Peirce of the Lime Association of Texas, who presented a detailed overview of the pavement selection criteria used during the APWA street reconstruction demonstration conducted during the National Congress for APWA held in San Antonio in September 2007.
One of the key techniques highlighted during this informative session included lime stabilization. Emphasis was placed on the importance of testing the soil to determine how much lime is needed as well as critical considerations for proper construction of a lime-stabilized layer. For instance, laboratory testing indicated the presence of organics in the clay, which can compete with the alumina and silica in the clay for the calcium in the lime, causing a need for additional lime. Without proper laboratory testing, this information would not have been known.
With regard to field construction, presenters discussed the need for plenty of water, thorough mixing at the proper depth to set the process in motion, along with mellowing, final mixing and compacting.
Attendees also were schooled on the benefit of using existing materials and “reclaiming” the base material by pulverizing the existing pavement and base and blending an asphalt emulsion into it to create a new material that was laid back down on top of the lime stabilized layer, providing a strong and durable base layer.
Finally, warm mix asphalt, a relatively new but very promising technology, was discussed. Warm mix asphalt technology basically allows asphalt mixtures to be produced at much lower temperatures than traditional hot mix asphalt. These reductions in plant production can sometimes be as much as 100 degrees Fahrenheit. The chemistry for this process was developed by Mead-Wesvaco, and is blended with liquid asphalt binder provided by Ergon Asphalt and Emulsions from their facility in Pleasanton.
During the construction phases, the city of San Antonio provided their own forces and equipment to carry out these three different processes. All and all, this project demonstrated how public and private entities worked successfully to create an innovative and educational opportunity.
Special thanks are extended to Austin White Lime, Chemical Lime, Texas Lime, Ergon Asphalt and Emulsion, Vulcan Materials, Fugro Consultants, Valero Asphalt, the Asphalt Institute, and the city of San Antonio.
For more information, please contact Larry Peirce at 512-633-1130.
By Larry Peirce