Browsing by Subject "Fatigue resistance"
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Item Application of Direct Tension Testing to Laboratory Samples to Investigate the Effects of Hot Mix Asphalt Aging(2012-12-07) Padigala, Meghana 1989-While the oxidation of binders in hot mix asphalt (HMA) pavements and its subsequent detrimental effects on pavement life have been well recognized in the last few years, many important issues have not yet been investigated. Understanding how best to design mixtures taking this phenomenon into account and achieving maximum durability is an important and complex issue. This study was aimed at characterizing the effects of oxidative aging on durability in terms of mixture fatigue resistance of laboratory mixed-laboratory compacted (LMLC) samples. Direct tension tests were conducted on HMA samples to measure mixture stiffness and a Modified Calibrated Mechanistic with Surface Energy (CMSE*) analysis method was used to predict fatigue life. The effect of various mix design parameters was evaluated to understand their importance with respect to the aging phenomena and mixture fatigue resistance. Analysis of the results showed that aging has a significant negative effect on mixture fatigue resistance. Considerable increase in the stiffness modulus (Eve) of the mixtures was observed with age for all three mixtures analyzed. Air voids (AV) played a substantial role in affecting the fatigue resistance with aging, but a difference of 0.5% in binder content near the optimum level did not statistically change mixture durability in terms of fatigue resistance with aging. For the three mixtures in Texas included in this study, when comparing Eve, one month of artificial aging in the laboratory was equivalent to 10.5 months of natural aging in the field. A good correlation was also found between the Eve of the mixture and the Carbonyl Area (CA) and Dynamic Shear Rheometer (DSR) function of the extracted binder. Thus, a connection exists between the properties of the extracted binder, laboratory mixtures and field mixtures. This relationship will facilitate development of a more mechanistic aging component in pavement performance prediction models.Item Optimization of the number of design gyrations using the superpave gyratory compactor(2007-05) Aguiar-Moya, Jose Pablo, 1981-; Prozzi, Jorge AlbertoThis thesis investigates the effect of the laboratory compactive effort on resistance to rutting and cracking of hot-mix asphalt mixtures in Texas. With the objective of improving fatigue resistance of Texas’ asphalt mixtures, two procedures, based on a performance-related approach geared towards determining revised N-design compaction levels to increase binder contents in asphalt mixtures without compromising rutting performance, have been developed: 1) weighted combinations of performance curves, and 2) reliability-based analysis of performance. The experimental design has been devised to investigate the performance characteristics of Texas’ asphalt mixtures designed using the revised N-design. The procedure found strong support for decreasing current N-design levels under most conditions, except for high-volume facilities in warm environments. The number of design gyrations for most condition in Texas could be lowered to 75 to 85 from improved fatigue performance, without significant loss of rutting resistance.