CRACKING IN ASPHALT PAVEMENTS: IMPACT OF COMPONENT PROPERTIES AND AGING ON FATIGUE AND THERMAL CRACKING

Cracking in asphalt pavements is one of the most common and critical pavement distresses. Cracks let the water penetrate from the surface to underlying layers resulting in shorter pavement service life and poor riding quality. There are various factors that affect the cracking potential of asphalt mixtures including the properties of asphalt components, mix design factors, loading time and loading mode, temperature, stress state, and aging. While several researchers have conducted studies investigating the cracking of asphalt mixtures, the effective parameters are not all well understood to allow engineers to design and construct more resistant pavements against cracking. The work presented in this dissertation provides some additional insights into the effects of component properties and aging condition on asphalt cracking. The cracking susceptibility of hot mix asphalt (HMA) is evaluated through the experimental testing and numerical modeling on mixtures produced either in design (laboratory) or production (plant) stage. Various criteria and approaches for the prediction of cracking in asphalt binder and asphalt mixture are assessed and their correlation are discussed. Different levels of aging in laboratory are simulated, and the effects of long term oven aging (LTOA) on linear viscoelastic parameters, fatigue and fracture characteristics of asphalt mixtures are explored. The uniaxial tensile fatigue testing based on simplified viscoelastic continuum damage (SVECD) approach is conducted to characterize fatigue behavior, and semi circular bending (SCB), disc-shaped compact tension (DCT) testing and cohesive zone model are used to evaluate thermal cracking in asphalt mixtures. This dissertation makes a good contribution in improvement of available approaches for evaluation of cracking potential of asphalt pavements and allows for assessment of different mixtures at early stage of material selection. The results of this study can lead to develop a new parameter to predict fatigue and thermal cracking susceptibility of flexible pavements in performance-based specifications, resulting in a better ride quality and cost saving for contractors and taxpayers

Determining Asphalt Mixture Properties Using Imaging Techniques

This study introduces imaging technology to determine the bulk specific gravity (Gmb) of compacted asphalt mixture specimens. Using an advanced three-dimensional scanner, a fast, accurate technique for determining compacted asphalt mixture specimen Gmb was developed. The feasibility of this technique was evaluated by testing a collection of asphalt mixtures, including dense-graded and stone mastic asphalt mixtures. The results were compared with those obtained using the currently-specified Gmb measurement methods of AASHTO T166 and CoreLok. The proposed scanning technique was also used for both laboratory-prepared and field-cored specimens to determine its reliability and reproducibility. The study results suggest the proposed imaging technique is effective in decreasing Gmb measurement variation as well as in improving the accuracy and reproducibility. Additionally, the results indicate the proposed technique can be applied to any asphalt specimen, regardless of mixture type, aggregate sizes, or fabrication technique

Quality Control and Quality Assurance of Asphalt Mixtures Using Laboratory Rutting and Cracking Tests

The main objectives of this project were to review the available balanced-mix design (BMD) methodologies, understand the I-FIT and Hamburg Wheel Tracking Test (HWTT) test methods using INDOT asphalt mixtures, and to explore the application of these tests to both a BMD approach and as performance-related Quality Control (QC) and Quality Acceptance (QA) methods. Two QA mixture specimen types, plant-mixed laboratory-compacted (PMLC) and plant-mixed field-compacted (PMFC) were used in the determination of cracking and rutting parameters. Distribution functions for the flexibility index (FI) values and rutting parameters were determined for various mixture types. The effects of specimen geometry and air voids contents on the calculated Flexibility Index (FI) and rutting parameters were investigated. The fatigue characteristics of selected asphalt mixtures were determined using the S-VECD test according to different FI levels for different conditions. A typical full-depth pavement section was implemented in FlexPAVE to explore the cracking characteristics of INDOT asphalt mixtures by investigating the relationship between the FI values of QA samples with the FlexPAVE pavement performance predictions. The FI values obtained from PMFC specimens were consistently higher than their corresponding PMLC specimens. This study also found that FI values were affected significantly by variations in specimen thickness and air voids contents, having higher FI values with higher air voids contents and thinner specimens. These observations do not agree with the general material-performance expectations that better cracking resistance is achieved with lower air voids content and thicker layers. Additionally, PG 70-22 mixtures show the lowest mean FI values followed by the PG 76-22 and 64-22 mixtures. The same order was observed from the ΔTc (asphalt binder cracking index) of INDOT’s 2017 and 2018 projects. Finally, it was found that the HWTT showed reasonable sensitivity to the different characteristics (e.g., aggregate sizes, binder types, and air voids contents) of asphalt mixtures. Mixtures containing modified asphalt binders showed better rut resistance and higher Rutting Resistance Index (RRI) than those containing unmodified binders

First report of Klebsiella pneumonia carbapenemase-producing Pseudomonas aeruginosa isolated from burn patients in Iran: Phenotypic and genotypic methods

Wound infection associated with carbapenem-resistant Pseudomonas aeruginosa in burn patients is a growing problem. One of the main mechanisms of resistance to carbapenem antibiotics is the ability of P. aeruginosa to produce carbapenemase enzymes. Klebsiella pneumonia carbapemenase (KPC) is an important type of carbapenemase which can hydrolyze carbapenem antibiotics. The Modified Hodge Test (MHT) and boronic acid as a KPC inhibitor are two phenotypic methods used for detection of carbapenemase. The sensitivity and specificity of these two phenotypic tests for the identification of KPC can be measured by PCR. In this study, 241 P. aeruginosa strains were isolated from wounds of hospitalized burn patients. Carbapenem-resistant P. aeruginosa isolates were determined by the disk diffusion method. KPC-producing carbapenem-resistant strains were examined using the Modified Hodge Test, followed by boronic acid. Further, strains with positive responses to MHT and boronic acid tests were analyzed with the PCR molecular method. One hundred eighty-six of 241 isolates were resistant to carbapenems and 75 were positive in the MHT. Three exhibited an at least 5-mm diameter difference when meropenem was combined with boronic acid vs meropenem alone in the boronic acid test. Two strains had a specific band with primer No.1 after gel electrophoresis. This study showed that MHT, despite excellent sensitivity, has variable specificity independent of bacterial species. Further, the use of KPC inhibitors such as boronic acid did not yield favorable sensitivity and specificity among the specimens from Iranian patients. Thus, it seems that sequencing after PCR should be considered the gold standard for the detection of KPC-producing P. aeruginosa

Glutathione, cell proliferation and differentiation

All organisms require an equivalent source for living. Reduced glutathione is the most abundant thiol containing protein in mammalian cells and organs. Glutathione was discovered by Hopkins in 1924 who published his findings in JBC. It is a three peptide containing glutamic acid, cystein and glycin and is found in reduced and oxide forms in cell. High concentration of glutathione and its high reduced/oxide potential makes GSH a powerful antioxidant and the first defense line against free radicals. However, glutathione is the most efficient tool for detoxification of xenobiotic. In several studies, the effect of GSH on different cell types has been investigated and so, in this study, a review of the glutathione function, focusing on cell proliferation and differentiation would be carried out.Key words: Glutathione, proliferation, differentiatio

Demonstration Project for Asphalt Performance Engineered Mixture Design Testing

The asphalt industry is moving towards performance-based methods for asphalt mixture design. The Federal Highway Administration (FHWA) is supportive of state departments of transportations (DOT) adopting index and predictive performance tests, especially those making use of the Asphalt Mixture Performance Tester (AMPT). The FHWA is therefore encouraging state DOTs to gain experience with the requirements of the procedures and analysis tools for Balanced Mixture Design (BMD). The main objective of this study is to evaluate fatigue cracking on three INDOT mainline pavement projects that have asphalt mixtures designed by the Superpave 5 mixture design, and to better understand the fundamental engineering testing capabilities of the AMPT. A total of four Superpave 5 asphalt mixtures were collected and tested from the three projects. The viscoelastic characteristics and fatigue behavior of plant-mixed, laboratory compacted (PMLC), laboratory-mixed, laboratory compacted (LMLC), and plant-mixed, field compacted (PMFC) specimens were assessed according to the AASHTO TP-132 and AASHTO TP-133 test methods. Two AMPT machines (IPC Controls and PaveTest) were used to conduct the dynamic modulus tests, while all fatigue tests were performed using a PaveTest AMPT. The raw data were analyzed using the FlexMAT software. The dynamic modulus and cyclic fatigue test results indicate that AMPT testing can be used to effectively evaluate INDOT asphalt mixtures during the mixture design and production phases. However, to do so, detailed planning and effective training are needed to help ensure the successful completion of AMPT testing

Implementing the Superpave 5 Asphalt Mixture Design Method in Indiana

Recent research developments have indicated that asphalt mixture durability and pavement life can be increased by modifying the Superpave asphalt mixture design method to achieve an in-place density of 95%, approximately 2% higher than the density requirements of conventionally designed Superpave mixtures. Doing so requires increasing the design air voids content to 5% and making changes to the mixture aggregate gradation so that effective binder content is not lowered. After successful laboratory testing of this modified mixture design method, known as Superpave 5, two controlled field trials and one full scale demonstration project, the Indiana Department of Transportation (INDOT) let 12 trial projects across the six INDOT districts based on the design method. The Purdue University research team was tasked with observing the implementation of the Superpave 5 mixture design method, documenting the construction and completing an in-depth analysis of the quality control and quality assurance (QC/QA) data obtained from the projects. QC and QA data for each construction project were examined using various statistical metrics to determine construction performance with respect to INDOT Superpave 5 specifications. The data indicate that, on average, the contractors achieved 5% laboratory air voids, which coincides with the Superpave 5 recommendation of 5%. However, on average, the as-constructed mat density of 93.8% is roughly 1% less than the INDOT Superpave 5 specification. It is recommended that INDOT monitor performance of the Superpave 5 mixtures and implement some type of additional training for contractor personnel, in order to help them increase their understanding of Superpave 5 concepts and how best to implement the design method in their operation

Environmentally Tuning Asphalt Pavements Using Phase Change Materials

Environmental conditions are considered an important factor influencing asphalt pavement performance. The addition of modifiers, both to the asphalt binder and the asphalt mixture, has attracted considerable attention in potentially alleviating environmentally induced pavement performance issues. Although many solutions have been developed, and some deployed, many asphalt pavements continue to prematurely fail due to environmental loading. The research reported herein investigates the synthetization and characterization of biobased Phase Change Materials (PCMs) and inclusion of Microencapsulated PCM (μPCM) in asphalt binders and mixtures to help reduce environmental damage to asphalt pavements. In general, PCM substances are formulated to absorb and release thermal energy as the material liquify and solidify, depending on pavement temperature. As a result, PCMs can provide asphalt pavements with thermal energy storage capacities to reduce the impacts of drastic ambient temperature scenarios and minimize the appearance of critical temperatures within the pavement structure. By modifying asphalt pavement materials with PCMs, it may be possible to tune the pavement to the environment

Demonstration Project for Asphalt Performance Engineered Mixture Design Testing

SPR-4452The asphalt industry is moving towards performance-based methods for asphalt mixture design. The Federal Highway Administration (FHWA) is supportive of state departments of transportations (DOT) adopting index and predictive performance tests, especially those making use of the Asphalt Mixture Performance Tester (AMPT). The FHWA is therefore encouraging state DOTs to gain experience with the requirements of the procedures and analysis tools for Balanced Mixture Design (BMD). The main objective of this study is to evaluate fatigue cracking on three INDOT mainline pavement projects that have asphalt mixtures designed by the Superpave 5 mixture design, and to better understand the fundamental engineering testing capabilities of the AMPT. A total of four Superpave 5 asphalt mixtures were collected and tested from the three projects. The viscoelastic characteristics and fatigue behavior of plant-mixed, laboratory compacted (PMLC), laboratory-mixed, laboratory compacted (LMLC), and plant-mixed, field compacted (PMFC) specimens were assessed according to the AASHTO TP-132 and AASHTO TP-133 test methods. Two AMPT machines (IPC Controls and PaveTest) were used to conduct the dynamic modulus tests, while all fatigue tests were performed using a PaveTest AMPT. The raw data were analyzed using the FlexMAT software. The dynamic modulus and cyclic fatigue test results indicate that AMPT testing can be used to effectively evaluate INDOT asphalt mixtures during the mixture design and production phases. However, to do so, detailed planning and effective training are needed to help ensure the successful completion of AMPT testing

Determining Asphalt Mixture Properties Using Imaging Techniques

SPR-4415This study introduces imaging technology to determine the bulk specific gravity (Gmb) of compacted asphalt mixture specimens. Using an advanced three-dimensional scanner, a fast, accurate technique for determining compacted asphalt mixture specimen Gmb was developed. The feasibility of this technique was evaluated by testing a collection of asphalt mixtures, including dense-graded and stone mastic asphalt mixtures. The results were compared with those obtained using the currently-specified Gmb measurement methods of AASHTO T166 and CoreLok. The proposed scanning technique was also used for both laboratory-prepared and field-cored specimens to determine its reliability and reproducibility. The study results suggest the proposed imaging technique is effective in decreasing Gmb measurement variation as well as in improving the accuracy and reproducibility. Additionally, the results indicate the proposed technique can be applied to any asphalt specimen, regardless of mixture type, aggregate sizes, or fabrication technique