EVALUATION OF SELECTED LABORATORY PROCEDURES AND DEVELOPMENT OF DATABASES FOR HMA

The objectives of this research project were to develop and validate laboratory test protocols for measuring rut susceptibility of hot mix asphalt (HMA) mixtures; to identify the best available laboratory test protocol(s) for predicting moisture susceptibility of HMA paving mixtures; and to develop a TxDOT HMA test database to be used for evaluating and/or validating the proposed AASHTO mechanistic-empirical pavement design guide. Twelve field mixes and three lab mixes were tested using Asphalt Pavement Analyzer (APA), Hamburg, Dynamic Modulus, Flow Time, Flow Number, and Simple Shear at Constant Height for the evaluation of rutting tests. Mixture parameters resulting from different tests were ranked and compared with APA rut depth as a base. Rankings of the different parameters were analyzed using statistical techniques. Findings indicate that flow time and flow number tests capture fundamental material properties and should be considered for inclusion in the mixture design and selection processes. Caution must be exercised in interpreting rut susceptibility of mixes based on the E* parameters, especially when evaluating mixtures containing polymer-modified asphalts. Nine mixtures were tested using the Hamburg. Their individual aggregates and binders were tested for surface energy measurement using Universal Sorption Device and Wilhelmy plate method, respectively. Mixtures with and without antistripping agents like hydrated lime and commercially available liquid antistripping agents were tested. Within groups of controlled mixes, the calculated bond strength based on surface energy measurements relates well with the deformation data from the Hamburg test. About 30 plant-produced mixes and 50 lab-produced field mixes were tested using the Hamburg and dynamic modulus devices. Plant-produced mixes were tested for production verification and lab-produced mixes were tested to develop a mixture database for future use, especially for the AASHTO design guide.