Evaluation of Moisture Susceptibility of Asphalt Mixtures Using Dynamic Modulus


Book Description

A pothole is one of the distresses in asphalt pavement caused by the presence of water in the asphalt pavement and the presence of traffic passing over the affected area. Recently, lots of potholes were observed due to heavy rain in Korea. Thus, the indirect tensile strength ratio (TSR) is commonly used based on the AASHTO T 283 procedure to evaluate the moisture susceptibility of an asphalt mixture; however, TSR cannot be used as a representative index for the mechanical behavior of the moisture-conditioned asphalt mixture. In this study, the dynamic modulus |E*| laboratory test is applied as a replacement test for the TSR in order to assess the moisture susceptibility of four different asphalt mixtures. The dynamic modulus test is used to determine the % of retained stiffness, a term that was referred to as the dynamic modulus ratio (DMR). The results of both TSR and DMR conducted on the same mixtures are compared and statistically analyzed. The logistic regression model was used to evaluate the correlation between TSR and DMR. The correlation between TSR and DMR at 20°C is significant. However, there was no relation between TSR and DMR at other temperature ranges (5°C, 40°C, 54.4°C) because there was different viscoelastic behavior at different temperature.




Evaluation of Hot Mix Asphalt Moisture Sensitivity Using the Nottingham Asphalt Test Equipment


Book Description

Pavements are subjected to different stresses during their design lives. A properly designed pavement will perform adequately during its design life, and the distresses will not exceed the allowable limits; however, there are several factors that can lead to premature pavement failure. One such factor is moisture sensitivity. AASHTO T 283 is the standard test used in the moisture susceptibility evaluation of asphalt mixtures, but the results of the test are not very representative of the expected behavior of asphalt mixtures. The dynamic modulus test measures a fundamental property of the mixture. The results of the dynamic modulus test can be used directly in the Mechanistic-Empirical Pavement Design Guide (MEPDG) and are considered a very good representation of the expected field performance of the mixture. Further research is still needed to study how the dynamic modulus results are affected by moisture. The flow number test was studied in previous research as a candidate test for moisture-susceptibility evaluation, but the results of that research were not favorable. This research has four main objectives. The first objective of this research is to evaluate the usefulness of the dynamic modulus and flow number tests in moisture-susceptibility evaluation. The second objective is to compare the results to those achieved using the AASHTO T 283 test. The third objective is to study the effect of different methods of sample conditioning and testing conditions. The fourth objective of the research is to study the variability in the test results.




Comparative Evaluation of Moisture Susceptibility Test Methods for Routine Usage in Asphalt Mixture Design


Book Description

Asphalt materials experience substantial amounts of environmental damage throughout their lives as surface layers in pavements. One of the most prominent forms of environmental damage, moisture-induced damage, is caused by the weakening of internal bonds of the material because of the presence of moisture in the voids of asphalt mixtures and is a common problem for asphalt pavements in wet climates. Moisture-induced damage is typically accounted for during asphalt mixture design by conducting performance tests to ensure the material is not susceptible to severe damage from moisture, although many of these methods have seen mixed amounts of success historically. The main objective of this study is to evaluate the ability of multiple asphalt mixture moisture susceptibility tests to identify good and poor performing mixtures with respect to moisture-induced damage to replace current mix design testing requirements. Ten plant-produced hot mix asphalt materials with established good and poor field moisture performance were subjected to various moisture susceptibility test methods. The results from these procedures are assessed to determine which procedure is most effective and practical as a moisture susceptibility test for routine usage during asphalt mixture design for transportation agencies. Results from this study suggest that performance tests with stiffness-based measurements, such as dynamic modulus paired with moisture conditioning and the saturated aging tensile stiffness procedure, show better correlation to field performance than traditional test methods such as AASHTO T-283, Standard Method of Test for Resistance of Compacted Asphalt Mixtures to Moisture-Induced Damage, and that the Hamburg wheel tracker test is the most effective and practical test method to reliably identify mixtures prone to experiencing moisture-induced damage.







Suitability of Dynamic and Relaxation Tests for the Evaluation of Moisture Susceptibility of Asphalt Mixtures


Book Description

The presence of waIn ter in asphalt pavements deteriorates their condition and causes distresses that result in high maintenance costs to state and federal agencies. The objective of this research was to execute dynamic and relaxation tests and evaluate their effectiveness in assessing moisture susceptibility of asphalt mixture specimens with different air void structures determined using X-ray computed tomography (CT) and conditioned using the modified Lottman procedure. The dynamic test consisted of the application of a sinusoidal cyclic compressive load on the specimen while maintaining the strain within a specified range. The relaxation test, performed in both direct tension and compression, consisted of the application of a constant static strain. A statistical analysis was used to study the effectiveness of the tests in evaluating the moisture susceptibility of the asphalt mixtures. The results showed that none of the tests (dynamic or relaxation) were consistent in differentiating between the moisture conditioned and unconditioned specimens or between the responses of the different mixtures within each condition. In addition, the results of the dynamic and relaxation tests were compared after applying different methods to convert frequency-domain data to time-domain data.




Evaluation of Procedures Used to Predict Moisture Damage in Asphalt Mixtures


Book Description

Procedures for evaluating the moisture susceptibility of asphalt mixtures were compared by performing them on mixtures having a known history of susceptibility. Data included the retained ratios, visual stripping, mechanical values (tensile strength, stability, etc.), saturation, and swell. The most promising procedures appeared to be the NCHRP 246 and NCHRP 274.




Improved Conditioning and Testing Procedures for HMA Moisture Susceptibility


Book Description

Explores whether combining the environmental conditioning system with the simple performance test would provide a superior procedure for determining the moisture susceptibility of hot-mix asphalt (HMA).




Evaluation of the Moisture Susceptibility of WMA Technologies


Book Description

"TRB's National Cooperative Highway Research Program (NCHRP) Report 763: Evaluation of the Moisture Susceptibility of WMA Technologies presents proposed guidelines for identifying potential moisture susceptibility in warm mix asphalt (WMA). The report also suggests potential revisions to the Appendix to AASHTO R 35, "Special Mixture Design Considerations and Methods for WMA" as a means to implement the guidelines."--publisher's description




Moisture Damage in Asphalt Concrete


Book Description

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.




Evaluation of Moisture Damage in Warm Mix Asphalt Containing Recycled Asphalt Pavement


Book Description

Warm mix asphalt (WMA) has been used worldwide for many years, primarily in Europe. The National Asphalt Pavement Association first brought WMA to the United States in 2002. By using warm mix technology, the temperature of an asphalt mixture during production, transportation, and compaction decreases dramatically. Several concerns about WMA arise due to the reduced mixing temperature. One of the primary concerns in asphalt pavement is the moisture damage. The lower mixing temperature may not be high enough to vaporize all the moisture absorbed in the aggregate, and part of the moisture may be entrapped in the pavements during compaction. This thesis presents a laboratory study to evaluate the moisture susceptibility of warm mix asphalt (WMA) produced through plant foaming procedure. Two types of mixtures were evaluated. A base mixture meeting the state of Tennessee "BM-2" mix criteria was evaluated at 0, 30, 40, and 50 percent fractionated recycled asphalt pavement (RAP), and a surface mixture meeting the state of Tennessee "411-D" mix criteria was evaluated at 15, 20, 30, 40 percent fractionated RAP. WMA mixture specimens were obtained and compacted at the asphalt plant. The WMA specimens were compared to hot-mix asphalt (HMA) specimens through a set of laboratory mixture performance tests. In addition to traditional AASHTO T283 freeze and thaw (F-T) tensile strength ratio (TSR), Superpave indirect tensile test (IDT) with F-T and MIST conditioning, and Asphalt Pavement Analyzer (APA) Hamburg wheel tracking tests were utilized to evaluate asphalt mixtures. Moisture tests indicated that with the higher inclusions of RAP, specimens exhibited lower rut depths and higher tensile strength retention. Tensile strength ratio tests indicated that HMA specimens had higher tensile strength retention when freeze thaw conditioned. Dynamic modulus conditioned specimens indicated that simple performance tests can show the difference between conditioned and unconditioned specimens. HMA specimens showed lower susceptibility to moisture compared to WMA specimens for both BM-2 and 411-D mixtures. The higher percentages of RAP in WMA and HMA in both BM-2 and 411-D mixtures showed a reduction to moisture susceptibility.