Brian D Prowell

Validating the Fatigue Endurance Limit for Hot Mix Asphalt

This report presents the findings of research performed to investigate the existence of a fatigue endurance limit for hot mix asphalt (HMA) mixtures, the effect of HMA mixture characteristics on the endurance limit, and the potential for the limits incorporation in structural design methods for flexible pavements. The report describes the research performed and includes proposed standard practices using various experimental and analytical procedures for determining the endurance limit of HMA mixtures. Thus, the report will be of immediate interest to materials and structural design engineers in state highway agencies and engineers in the HMA construction industry.

NDT Technology for Quality Assurance of HMA Pavement Construction

This report contains the findings of research performed to investigate the application of nondestructive testing (NDT) technologies in the quality assurance of hot mix asphalt (HMA) pavement construction. The report contains the results and analyses of the research performed and presents several key products, notably a recommended manual of practice with guidelines for implementing selected NDT technologies in an agencys routine quality assurance (QA) program for HMA pavement construction and detailed test methods for the recommended NDT technologies. Thus, the report will be of immediate interest to construction and materials engineers in state highway agencies and the private sector.

EVALUATION OF INFRARED IGNITION FURNACE FOR DETERMINATION OF ASPHALT CONTENT

The Troxler Model 4730 infrared ignition furnace was compared with a standard Thermolyne ignition furnace. Comparisons conducted with a single unit of each furnace type were based on the correction factor for aggregate loss during ignition, accuracy, and the variability of the measured asphalt content and aggregate degradation during ignition. Forty-eight samples representing two nominal maximum aggregate sizes (9.5 and 19.0 mm), four aggregate types (granite, crushed gravel, limestone, and dolomite), and two asphalt contents (optimum and optimum plus 0.5% asphalt content) were tested in each furnace. The results indicated that the correction factors for aggregate loss during ignition were significantly different for each type of furnace, thus requiring a separate calibration for each type of furnace. In practical terms, the differences for all but the 9.5-mm nominal maximum aggregate size (NMAS) limestone and both dolomite mixtures were less than 0.1%. The samples with the optimum plus 0.5% asphalt content were tested by using the calibration factors developed for a particular mix–furnace combination. The results were analyzed in terms of accuracy (bias) and variability (standard deviation). Neither the measured biases nor the standard deviations for the two types of furnaces were significantly different. The results obtained with four sieve sizes (NMAS and 4.75, 2.36, and 0.075 mm) were evaluated for aggregate breakdown. A comparison of the aggregate gradations recovered from both furnaces indicated no significant difference in the degree of aggregate degradation. A round-robin investigation should be conducted to confirm that the precision of the infrared furnace is similar to the precision of the standard furnace.