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This report summarizes the results of determining the moisture susceptibility by the primary test methods: (a) Original Lottman Method. (b) Modified Lottman Method (Tex-531-C); (c) Tunniclif f-Root Method; and (d) Boiling Test (Tex-530-C). Comparisons were made between the laboratory mixtures, plant mixtures, and cores obtained from the field test sections to determine the effectiveness of the various antistripping additives and to evaluate the various methods for measuring that effectiveness.
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 synthesis will be of interest to pavement designers, construction engineers, maintenance engineers, and others interested in avoiding or limiting moisture damage in asphalt concrete. Information is provided on physical and chemical explanations for moisture damage in asphalt concrete, along with a discussion of current practices and test methods for determining or reducing the susceptibility of various asphalt concrete components and mixtures to such damage. Moisture damage in asphalt concrete is a nationwide problem which often necessitates premature replacement of highway pavement surfaces. This report of the Transportation Research Board describes the underlying physical and chemical phenomena responsible for such damage. Current test methods used to determine the susceptibility of asphalt concretes, or their constituents, to moisture damage are described and evaluated. Additionally, current practices for minimizing the potential for moisture damage are examined.
Moisture damage of asphalt mixes, better known as stripping, is a major distress affecting pavement performance. AASHTO T 283 (KT-56) has been used by many agencies over the past decade to detect moisture susceptible pavements through the determination of a tensile strength ratio (TSR). Results from AASHTO T 283 (KT-56) have been inconsistent. As a result, there has been increased interest in finding an alternative test method. Preliminary indications reveal that loaded wheel rut testers, such as the Asphalt Pavement Analyzer (APA), have the potential to detect moisture susceptible mixtures. To date no standard test methodology has been developed. The objective of this project was to evaluate the effects of sample preconditioning on APA rut depths and to further evaluate the APA's suitability for predicting moisture susceptible mixtures. Eight different mixes from seven project sites were evaluated with the APA. Samples were tested at 40 deg C using four different preconditioning procedures: dry, soaked, saturated, and saturated with a freeze cycle. The results were compared with TSR values, methylene blue values and sand equivalent. The APA was able to identify every mix with a failing TSR.
The purpose of this literature review is to search the literature in the area of chemical and mineral agents used to promote adhesion of asphalt-aggregate mixes. In addition, tests performed to measure the effectiveness of these agents were reviewed. The information gained through this literature search and review provides background information for the research being performed in the SHRP A-003B contract. This literature search was performed using on-line chemical abstracts for documents in the time period of 1967 to present.
This book presents new studies dealing with the attempts made by the scientists and practitioners to address contemporary issues in pavement engineering such as aging and modification of asphalt binders, performance evaluation of warm mix asphalt, and mechanical-based pavement structure analysis, etc.. Asphalt binder and mixture have been widely used to construct flexible pavements. Mechanical and Chemical characterizations of asphalt materials and integration of these properties into pavement structures and distresses analysis are of great importance to design a sustainable flexible pavement. This book includes discusses and new results dealing with these issues. Papers were selected from the 5th GeoChina International Conference 2018 – Civil Infrastructures Confronting Severe Weathers and Climate Changes: From Failure to Sustainability, held on July 23 to 25, 2018 in HangZhou, China.
A technical review of moisture damage of asphalt pavements and antistripping additives has beencompleted as part of a review and testing study for the Transportation Association of Canada that has the objective of developing a Canadian manual on the assessment of moisture susceptibility and selection of antistripping additives. The review is based on practical asphalt technology experience, questionnaires to agencies and asphalt cement suppliers, and the technical literature on moisture damage of asphalt pavements. Methods of mitigating moisture damage in asphalt pavement structures, in addition to the use of antistripping additives, such as drainage, compaction, aggregates selection, mix designs and quality control, were reviewed in terms of stripping mechanisms and causes. The Strategic Highway Research Program has involved considerable research on the moisture susceptibility of asphalt concrete and appropriate laboratory procedures to assess moisture damage. Qualitative and quantitative (strength) tests for assessing the moisture susceptibility of hot-mix asphalt mixes are reviewed. There is strong technical support for the Tunnicliff-Root (ASTM D 4867), Modified Lottman (AASHTO T 283) and Ontario MTO Immersion Marshall (LS-283) tests. The use of liquid (amines generally) and hydrated lime antistripping additives is considered. There is considerable technical information on the comparative efficacy of hydrated lime as an antistripping additive. An important area of research need is appropriate quality control/quality assurance to monitor the field effectiveness of antistripping additives. For the covering abstract of this conference see IRRD number 872978.