Precision of the Moisture Susceptibility Test Method TEX-531-C: Research Report;Research rept. 1 Jul 99-1 Apr 00

摘要

Test Method Tex-531-C is the primary method of determining moisture damage susceptibility of hot mix in Texas. There are no known precision statements for this test method. Such a precision is required for reliable judgment of moisture susceptibility of the mixture. The repeatability and reproducibility of this test procedure were determined based on testing performed within a single laboratory and among several laboratories. This 10-month research began in August 1999 and was completed by June 2000. The limestone aggregates were treated with lime, as specified in the mix design, and the gravel aggregate was treated with a liquid anti-stripping agent. The mixtures with limestone aggregates had PG 64-22 binders while the gravel aggregate was mixed with a PG 70-22 binder according to the design procedure. Nine laboratories participated in the round-robin testing. On the average, the single-operator standard deviation of tensile strength for dry specimens was found to be 15 psi and that for moisture-conditioned specimens to be 12 psi. The reproducibility standard deviation of the tensile-strength ratio between different laboratories was found to be 10 percent on the average. The average coefficient of variation of the tensile-strength ratio was found to be approximately 8 percent for specimens compacted in one laboratory and tested in different laboratories. The average coefficient of variation of the tensile-strength ratio was found to be approximately 12 percent for specimens both compacted and tested in different laboratories. The differences noticed in the results from different laboratories could be influenced by many factors such as variability in compaction, conditioning, and indirect tensile testing. It is important to minimize the variability in these influencing factors in order to improve the precision of the test method.