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The use of hydrated lime or other liquid anti stripping agents (ASA) is the most common method to improve the moisture susceptibility of asphalt mixes. However, most laboratory test conditions used to evaluate the moisture susceptibility of the mixes are only for a short duration of time. This might not be a good representation of the field conditions (i.e., several months or years of service). Thus, a study to evaluate the effects of conditioning the mixes for longer durations was initiated. Also, another problem with the use of the liquid anti stripping agents is their heat storage stability. This report addresses these two issues, by preparing and testing mixtures made with fresh binder for indirect tensile strength after conditioning the samples for 1, 7, 28, 90 and 180 days, and samples prepared from binder stored for three days at 160° C after conditioning them for 1, 28 and 90 days. The results of this study indicated that hydrated lime and the liquid anti stripping agents were equally effective for the mixes used in this research when conditioned beyond one day. In the case of samples prepared from stored binder, there was no significant difference in the effectiveness of hydrated lime and the liquid anti stripping agents even after conditioning for one day. Though it was observed that none of the ASA treatments performed better than others in the case of samples prepared with stored binder, it was also observed that almost all mixes gave significantly similar wet ITS and TSR values as samples prepared from fresh binder.
The use of hydrated lime or other liquid anti stripping agents (ASA) is the most common method to improve the moisture susceptibility of asphalt mixes. However, most laboratory test conditions used to evaluate the moisture susceptibility of the mixes are only for a short duration of time. This might not be a good representation of the field conditions (i.e., several months or years of service). Thus, a study to evaluate the effects of conditioning the mixes for longer durations was initiated. Also, another problem with the use of the liquid anti stripping agents is their heat storage stability. This report addresses these two issues, by preparing and testing mixtures made with fresh binder for indirect tensile strength after conditioning the samples for 1, 7, 28, 90 and 180 days, and samples prepared from binder stored for three days at 160° C after conditioning them for 1, 28 and 90 days. The results of this study indicated that hydrated lime and the liquid anti stripping agents were equally effective for the mixes used in this research when conditioned beyond one day. In the case of samples prepared from stored binder, there was no significant difference in the effectiveness of hydrated lime and the liquid anti stripping agents even after conditioning for one day. Though it was observed that none of the ASA treatments performed better than others in the case of samples prepared with stored binder, it was also observed that almost all mixes gave significantly similar wet ITS and TSR values as samples prepared from fresh binder.
This project evaluated the influence of anti-strip additives on the durability and moisture susceptibility of granite-based open-graded friction course, referred to as FC-5 asphalt mixtures. The laboratory testing involved two granite-based FC-5 mixtures containing 1% hydrated lime (by weight of aggregate), 1% hydrated lime plus 0.5% liquid anti-strip (LAS) additive (by weight of asphalt binder), 1.5% hydrated lime, and 1.5% hydrated lime plus 0.5% LAS additive. Two sources of granite aggregates were obtained: one from Junction City, Georgia and the other from a regional supplier with an original source from Nova Scotia, Canada. Four types of LAS additives were collected from Road Science ArrMaz, Inc. and Ingevity, Inc. The binder bond strength test was used to select the LAS agents that provided the best improvement in moisture resistance. The FC-5 mixtures were fabricated in the laboratory using two FC-5 mix designs provided by the Florida Department of Transportation. The specimens were conditioned by the asphalt pavement weathering system to simulate the long-term aging and moisture conditioning in the field. Mixture performance tests, including the Cantabro test, tensile strength ratio test, and Hamburg wheel tracking test, were used to comprehensively evaluate the durability and moisture susceptibility of FC-5 mixtures. Finally, a cost-benefit analysis was performed to determine the cost-effectiveness of the FC-5 mixtures with anti-strip additives. This project found that the addition of LAS additive, extra 0.5% hydrated lime, or both produced longer lasting FC-5 mixtures, and the additional anti-strip additives would improve the cost effectiveness of FC-5 mixtures.
Moisture susceptibility of hot mix asphalt (HMA) pavements continues to be a major pavement distress. Past research has primarily focused on HMA stripping prevention through material component evaluation/testing and addition of preventative additives. Stripping is caused by traffic, water, and high in-place service temperatures. Today, agencies use various methods to evaluate HMA moisture susceptibility with varying degrees of success. The study objective was to evaluate a prototype stripping simulator's ability to predict HMA moisture susceptibility. The simulator evaluates moisture susceptibility by measuring conditioning water turbidity. Boil test and indirect tensile strength testing were also conducted for comparison purposes. Stripping simulator results indicate further refinement is required before it can be used for moisture susceptibility prediction.
The intention of this research effort is to evaluate the use of warm mix additives with typical polymer-modified and terminal blend tire rubber asphalt mixtures from Nevada and California. The research effort is broken into three phases that are intended to evaluate the impacts of warm mix additives with typical polymer-modified and terminal blend tire rubber asphalt mixtures from Nevada and California: moisture damage, performance characteristics, and mechanistic analysis. In Phase I of this research effort, mixture resistance to moisture damage was evaluated using the indirect tensile test and the dynamic modulus at multiple freeze-thaw cycles. Laboratory testing was conducted to address the following: (1) the impact of warm mix additive and reduced production temperatures on the moisture damage resistance of asphalt mixtures, (2) the impact of residual aggregate moisture on the moisture damage resistance of WMA mixtures, (3) the impact of warm mix additives on the moisture damage resistance of anti-strip treated WMA mixtures, and (3) the impact of long-term aging on strength gain and the moisture damage resistance of WMA mixtures. A total of one aggregate source, four warm mix asphalt technologies (Advera, Sasobit, Revix and Foaming) and three asphalt binder types (neat, polymer-modified and terminal blend tire rubber modified asphalt binders) typically used in both Nevada and California are being evaluated in this study. This thesis will only summarize the test results and findings of the Phase I of the study for two warm-mix additives: Advera and Sasobit. The evaluation of the other two technologies (i.e. Revix and Foaming) as well as the Phase II testing are still in progress and have not been completed.
Warm mix asphalt (WMA) is a fairly recent technology developed primarily to address issues such as high vapor emissions and high energy costs associated with the traditional hot mix asphalt (HMA) paving. Although the WMA is becoming a popular paving technology through field and laboratory evaluations, many researchers and transportation personnel are concerned about its moisture resistance. The present study analyzes the free energy of adhesion or wetting ability between eight different aggregates and an asphalt binder modified with varying dosages of two warm mix additives, namely Sasobit and Aspha-Min. Sasobit showed a maximum of 20.9 % and an average of 12.8 % increase in the free energy of adhesion in dry condition. The adhesion in the presence of moisture, referred to as free energy of reduction, was also evaluated to understand the moisture susceptibility of the WMA. The lower the free energy of reduction, the lower the asphalt binder's tendency to de-bond from aggregates in the presence of moisture. A maximum of 20.5 % and an average of 13.2 % decrease in the free energy of reduction were observed for asphalt binder with 3 % Sasobit. However, Aspha-Min did not exhibit any significant effect on any of the surface properties. One amine-based anti-stripping agent, AD-here HP Plus, is studied to evaluate its effect on adhesion and moisture susceptibility of the WMA. While its performance as an anti-stripping agent was good on the plain asphalt binder, AD-here HP Plus did not improve the adhesion of the selected binder modified with WMA additives either in dry or wet condition. The free energy of adhesion in wet and dry conditions showed either detrimental or no effect with selected aggregates, suggesting a negative or no influence of AD-here HP Plus on the WMA additive-modified binder.