Development of a specification for flexible base construction.

The Texas Department of Transportation (TxDOT) currently uses Item 247 “Flexible Base” to specify a pavement foundation course. The goal of this project was to evaluate the current method of base course acceptance and investigate methods to replace materials approval based on stockpile sampling and testing with a mixture design methodology and quality control procedure. Researchers gathered existing information that would assist in defining the types of tests to be used, specification acceptance criteria, and acceptance limits. Researchers then gathered data to identify tests that should be considered for inclusion in the specification and defined property variability of base course materials from nine pits/quarries in Texas. They also conducted other activities concerning precision and bias statement development, production/placement variability, technician certification, laboratory accreditation, and the development of relationships that allow test property parameters to predict pavement performance. The project developed draft flexible base course specifications in a quality control/quality assurance and quality monitoring program format. Researchers recommend an implementation project to determine the accuracy of the developed pavement performance prediction techniques and the suitability of the specification, including the types and limits of the test parameters in the specification.