Moisture Susceptibility of Warm-Mix Asphalt (original) (raw)
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Performance Evolution of Hot-Mix and Warm-Mix Asphalt with Field and Laboratory Aging
Economic, environmental, and engineering benefits promoted the rapid implementation of Warm-Mix Asphalt (WMA) across the world during the past decade. While WMA technologies have been successfully used as a paving material, concerns remain about the difference in performance between WMA and Hot-Mix Asphalt (HMA) due to changes in the mixture production process. Previous laboratory testing results indicate that WMA is oftentimes more susceptible to rutting and moisture damage as compared to HMA, and that this difference in performance is minimized with mixture aging. However, the prevalent concern of increased moisture susceptibility of WMA has not been observed in the field. The objectives of this study are to evaluate the differences in stiffness and moisture susceptibility between WMA and HMA with time (i.e., field and laboratory aging). Stiffness was measured with the Resilient Modulus (M R) test, while the Indirect Tensile (IDT) strength test and Hamburg Wheel Tracking Test (HWTT) were used to quantify moisture susceptibility. Test results show that field and laboratory aging significantly increase the stiffness and improve the moisture resistance of the mixtures, and equivalent or better performance can be achieved by WMA versus HMA after a summer of field aging or significant laboratory Long-Term Oven Aging (LTOA). The correlation between field aging and laboratory LTOA in terms of mixture performance was also determined as part of this study.
The Effect of Short-Term Aging on Warm Mix Asphalt Moisture Performance
Civil Engineering Journal
Warm Mix Asphalt (WMA) is a good pavement option due to its environmental benefits. Short-term aging is one of the critical factors that the WMA should carefully study. This research aims to study the effect of short-term aging on the warm mix asphalt that has different percentages of rubber. In this study, three percentages of rubber (1, 1.5, and 2%) by weight of aggregate are considered to be added to the WMA. By use of the Indirect Tensile Strength test for HMA, WMA unmodified and modified with CR that is exposed to an aging protocol to assess the sensitivity of asphalt mixture to moisture damage. The results show that HMA is less sensitive to moisture than WMA, and the addition of crumb rubber to WMA generally improves the resistance to moisture compared with WMA with 0% of rubber. However, as the rubber content increases to 2%, the resistance starts to decrease. Finally, SEM images were taken of rubber particles, WMA with and without rubber to investigate the changes occurring ...
Moisture damage characterization of warm-mix asphalt mixtures based on laboratory-field evaluation
Construction and Building Materials, 2012
This study presents laboratory evaluation integrated with field performance to examine two widely used warm-mix asphalt (WMA) approaches-foaming and emulsion technology. For a more realistic evaluation of the WMA approaches, trial pavement sections of the WMA mixtures and their counterpart hot-mix asphalt (HMA) mixtures were implemented in Antelope County, Nebraska. Fieldmixed loose mixtures collected at the time of paving were transported to the laboratories to conduct various experimental evaluations of the individual mixtures. Among the laboratory tests, three (two conventional and one newly attempted) were performed to characterize moisture damage potential which is the primary focus of this study. From the laboratory test results, WMA mixtures showed greater susceptibility to moisture conditioning than the HMA mixtures, and this trend was identical from multiple moisture damage parameters including the strength ratio and the critical fracture energy ratio. Early-stage field performance data collected for three years after placement presented satisfactory rutting-cracking performance from both the WMA and HMA sections, which generally agrees with laboratory evaluations. Although the field performance data indicated that both the WMA and HMA show similar good performance, careful observation of field performance over a
Evaluation of the performance of warm mix asphalt in Washington state
International Journal of Pavement Engineering, 2015
Warm mix asphalt (WMA) is a relatively new and emerging technology for the asphalt industry. It offers potential construction and environmental advantages over traditional hot mix asphalt (HMA). However, WMA must perform at least as well as HMA before it can be used to replace HMA. This study evaluates the performance of HMA and WMA mixes obtained from various field sites in the state of Washington. Different WMA technologies are examined in four separate projects; these technologies include Sasobit ® and three water foaming technologies, Gencor ® Green Machine Ultrafoam GX ® , Aquablack ™ and water injection. Performance tests are conducted on the cores and extracted binders to evaluate the resistance of HMA and WMA samples to fatigue and thermal cracking, rutting and moisture susceptibility. Additionally, the early-age field performance of WMA and HMA control pavements is compared.
Transportation Research Record: Journal of the Transportation Research Board, 2012
Moisture can lead to serious damage and failures in hot-mix asphalt concrete pavements. This is an even greater concern for warm-mix asphalt because the much lower production temperatures may not completely dry the aggregates. In this Maine Department of Transportation study, the use of fracture energy parameters was evaluated to determine the influence of incomplete drying of mixes on their mechanical properties. Fracture energy–based parameters [energy ratio (ER); ratio of energy ratio (RER)] were determined from the following testing of mixes with fully and partially dried aggregates, some of which were subjected to moisture conditioning: resilient modulus, creep compliance, and indirect tensile strength (ITS) at 5°C. The results indicate that (a) resilient modulus, creep compliance, and ITS were all affected by the presence of moisture in mixes; (b) the trend and the degree of influence of moisture for different mechanical parameters were different; (c) the moisture conditioning...
Evaluation of the Performance of a Warm Mix Asphalt (WMA) Considering Aged and Unaged Specimens
Coatings
In the last decades, all technology production sectors reached a high level of development, without neglecting the attention to environmental aspects and safeguarding energy resources. Moreover, in the sector of pavement industry, some alternatives of bituminous mixtures were proposed to reduce the greenhouse gas emissions. One of these is the warm mix asphalt (WMA), a mixture produced and compacted at lower temperatures compared to traditional hot mix asphalt (HMA) (about 40 °C less), to allow a reduction of emissions into the atmosphere and the costs. Other operative benefits concern the health of workers during the whole road construction process, the reduction of distances to which the mixture can be transported, and therefore also the positioning of the plants. However, it is not all benefits, since reduced production temperatures can bring short- and long-term water sensitivity issues, which could threaten the pavement performance. This paper evaluated the performance (water s...
Laboratory investigation of moisture susceptibility of long-term saturated warm mix asphalt mixtures
International Journal of Pavement Engineering, 2012
Moisture damage in flexible pavements might cause stripping in asphalt pavements and ultimately result in premature failure. Warm mix asphalt (WMA) technology as a means to decrease the energy consumption and emissions associated with conventional hot mix asphalt production is broadly being used recently. However, the utilisation of the hydrated lime and liquid anti-strip additives in WMA mixtures makes these issues more complicated. The objective of this study was to investigate and evaluate the moisture susceptibility of mixtures containing anti-stripping agents (ASAs) and WMA additives after long-term saturated durations. The experimental design for this study included the utilisations of one binder source (PG 64-22), three ASA additives and control, two WMA additives and hot mix, and three aggregate sources. A total of 36 types of mixtures and 540 specimens were fabricated and tested in this study. The performed properties included indirect tensile strength (ITS), tensile strength ratio, flow and toughness. The results indicated that the aggregate source has an effect on dry ITS and flow values but had no effect on wet ITS, wet flow and toughness values. In addition, hot mixture generally had higher dry and wet ITS values, and there were significant differences in flow and toughness values between hot and warm mixtures. Moreover, the hydrated lime exhibited the best moisture resistance in WMA mixtures; the liquid ASA additives could increase the ITS values of mixtures but exhibited a weak moisture resistance in this study. Furthermore, the storage and saturated duration generally had no effect on ITS values, and statistical analysis results did not show any differences among these mixtures.
Laboratory Conditioning Protocols for Warm-Mix Asphalt
Economic, environmental, and engineering benefits have led to the rapid implementation of Warm-Mix Asphalt (WMA) across the world during the past decade. While WMA technologies have been successfully utilized as a paving material, standard mix design protocols remain under development. A study of the effect of laboratory conditioning protocols (prior to compaction) on the performance of HMA (Hot-Mix Asphalt) and WMA mixtures made with chemical additives, wax additives, or a foaming process was performed. Resilient Modulus (M R), Dynamic Shear Rheometer (DSR), and image analysis techniques were used to evaluate the properties of the extracted binders and mixtures conditioned with different protocols. Laboratory Mixed Laboratory Compacted (LMLC) specimens conditioned for 2 hours at 240°F (116°C) for WMA and 275°F (135°C) for HMA had stiffness similar to those of cores collected during the early life of field pavements. For off-site Plant Mixed Laboratory Compacted (PMLC) specimens, different conditioning protocols are recommended to simulate the stiffness of Plant Mixed Field Compacted (PMFC) cores at construction: reheat to 240°F (116°C) for WMA with additives and reheat to 275°F (135°C) for HMA and foamed WMA.
Construction and Building Materials, 2014
h i g h l i g h t s In case of ITS sat all first, second and interactive terms were significant. In case of ITS dry and TSR the interactive term of PPSS 4.75 mm-Sasobit was not significant. In saturated WMA specimens, hydrated lime acts positively both as a filler and as an anti-stripping agent. Lime content has the greatest effect on TSR increase, compared with other parameters.
Transportation and Development Institute Congress 2011, 2011
Moisture damage in flexible pavements might cause stripping in the asphalt pavement and ultimately lead to premature failure. In addition, rising energy prices, global warming, and more stringent environmental regulations have resulted in an interest in warm mix asphalt (WMA) technologies as a mean to decrease the energy consumption and emissions associated with conventional hot mix asphalt production. In this study, the objective was to conduct a laboratory investigation of long-term influence of anti-stripping additives on moisture damage in WMA mixtures. The test results indicated that the aggregate source did not show a remarkable effect on moisture susceptibility of mixture in this study. The addition of anti-stripping additives increased the ITS, TSR, and flow values; however, the differences were not statistically significant compared to the control mixtures. Mixtures containing Asphamin® did not perform as well as others. In addition, an increase of condition duration decreases the anti-stripping resistance regardless of mixture type.