Material properties and characteristics for development of an expert system for coal-tar sealers
Shoenberger, James E.
Technical ReportAbstract: Coal-tar sealers are used to protect asphalt pavements from damage by fuel spillage. The useful life of coal-tar sealers has been limited by cracking in both trafficked and non-trafficked areas and in all climatic regions. Several coal-tar mixtures that varied with source of the coal-tar emulsion, amount of aggregate, and amount of polymer used in the mixtures were evaluated for their field performance and material properties. The material properties of these mixtures were determined through curing, thermal, bending, tensile, and stress-relaxation testing. The material properties were determined using testing and evaluation methods either adapted from previous work or developed for this research. The results of the evaluation showed that two coal-tar emulsion sealers meeting all current applicable specifications could have substantially different field performance. The amount of aggregate and polymer on the coal-tar mixtures will affect the sealer's performance. The sealer mixtures age or harden over time and cracking occurs through thermal movements resulting in a build up of stresses that the sealer cannot relax or dissipate. Generally, mixtures with higher amounts of aggregate and at least some polymer (acrylonitrile-butadiene) performed the best. The information gained during the field and laboratory evaluation of the various sealer mixtures was used to develop an expert system for specifying coal-tar sealers. The expert system provides a practical method for an engineer/designer to develop a systematic approach to selecting the type of sealer, material and design considerations, and construction methods. A guide specification that incorporates recommended test methods, materials, and application procedures are included as an appendix. The use of this system and guidelines is intended to provide an optimum coal-tar sealer mixture.
Geotechnical and Structures Laboratory (U.S.)Engineer Research and Development Center (U.S.)
Coal tar; Coal-tar emulsion; Coal-tar sealer; Expert system; Fuel-resistant sealer; Pavement sealer; Sealants; Asphalt pavements
ERDC/GSL TR ; 01-15.
Approved for public release; distribution is unlimited.