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原文传递 Development of Small Specimen Geometry for Asphalt Mixture Performance Testing.

题名：	Development of Small Specimen Geometry for Asphalt Mixture Performance Testing.
作者：	Castorena, C.; Kim, Y. R.; Pape, S.; Lee, K.
关键词：	Highways, Materials, Pavements
摘要：	This project sought to develop equipment to enable small specimen testing in the Asphalt Mixture Performance Tester (AMPT), evaluate the effects of specimen geometry on dynamic modulus and direct tension fatigue tests and pavement performance prediction, and optimize the laboratory fabrication of small specimens extracted from gyratory-compacted specimens. Two small specimen geometries were evaluated for dynamic modulus and direct tension fatigue testing. The two small specimen geometries were compared against the standard 100-mm diameter cylindrical specimens using five mixtures with nominal maximum aggregate size (NMAS) values ranging from 9.5-mm to 25.0-mm. With the exception of a 9.5-mm mixture, the dynamic modulus and phase angle master curves at low and intermediate temperatures acquired from the large and small specimen geometries are statistically equivalent for all of the mixtures. At high temperature, the small specimen dynamic modulus values are higher and the phase angle values are lower than those of the large specimens. Therefore it is recommended to limit small specimen testing to the temperatures outlined in AASHTO PP 61. The specimen-to-specimen variability for the large and small specimen dynamic modulus tests are comparable. The cyclic fatigue test results of the small and large specimens are very similar for the mixtures evaluated. Pavement performance was predicted by the Pavement ME program and the FlexPAVE™ program using the small and large specimen test results. The results suggest that specimen geometry does not significantly affect pavement fatigue damage predictions, which indicates promise for the use of small specimen geometries in practice. To optimize the laboratory fabrication of small specimens from gyratory-compacted samples, the effect of coring direction in small cylindrical specimens was analyzed. Findings indicate that vertical coring is recommended for obtaining small specimens from gyratory-compacted samples for both fatigue and dynamic modulus testing. Four small specimens can be cored vertically from the inner 100 mm of gyratory-compacted samples, which is the proposed procedure for the laboratory fabrication of small specimens. The specimen-to-specimen variability of four plant-produced mixtures with varying NMAS was evaluated using the optimized extraction procedure. Small specimen performance test results generally demonstrate an increase in specimen-to-specimen variability with increasing NMAS. The results show no clear linkage between the small specimen air void content and the performance test results within the observed specimen air void content range of ± 0.7% from the target. Therefore, it is recommended that initial small specimen provisional standards include an air void content tolerance of ± 0.7% from the target, to be refined upon future ruggedness testing.
报告类型：	科技报告