Dissertation (Ph.D.)--Worcester Polytechnic Institute. / Keywords: Temperature; Asphalt Pavement; Thermal Conductivity; Heat Transfer. Includes bibliographical references (leaves 156-159).

The use of polymers in bituminous materials has been gaining popularity over the last decade. Despite their superiority in enhancing the performance of bituminous mixtures, problems have been experienced due to limitations on the applicability of currently available assessment techniques. This thesis is concerned with the mechanical behaviour of polymer modified bitumens and the performance of polymer modified bituminous mixtures. The first part of the thesis presents different pavement distresses and the importance of using polymer modified binders to improve the performance of bituminous mixtures. The second part deals with identification of properties of polymer modified binders and their mixtures by using dynamic mechanical analysis. The third part attempts to develop a novel technique for assessing resistance to permanent deformation of HRA mixtures using a dissipated energy method. Some polymer modified binders are susceptible to storage instability. However, this work has demonstrated that certain empirical tests are unsuitable for assessing the temperature susceptibility and storage stability of polymer modified binders. Viscoelastic behaviour of bituminous materials is better presented by dynamic mechanical analysis. The dynamic mechanical analysis provides a basis for explaining the unsuitability of some empirical tests on polymer modified binders. Determination of dissipated energy during creep testing enables more comprehensive and accurate assessment of the resistance to permanent deformation of Hot Rolled Asphalt (HRA) mixtures. This study reveals that assessment of the resistance to permanent deformation based upon permanent strain rate in the linear region is in good agreement with the dissipated energy method. The end of the linear region, N1, can be accurately determined by the dissipated energy method and provides a confidence that analysis will always be conducted in the linear region. As expected, polymer modified mixtures are superior to the unmodified ones in their resistance to permanent deformation which confirm by the wheeltracking test, but was not evident from the Marshall tests.

Master of Science / Department of Civil Engineering / Stefan A. Romanoschi / The primary objective of this research project was to evaluate the shear behavior of three asphalt-to-asphalt mix interfaces. To accomplish this objective, a special attachment and loading mechanism was designed and built to facilitate the measurement of the dynamic shear reaction modulus and shear strength of the asphalt-to-asphalt interfaces when shear and normal forces are acting simultaneously and they are proportional. Two tests were conducted on 4-inch diameter cylindrical samples cored from an asphalt concrete pad where three types of asphalt-to- asphalt interfaces were built. For each interface, four tack-coat quantities were sprayed. On each sample, the Dynamic Shear Reaction Modulus test was conducted first. Then the Shear Strength test was conducted until the sample failed in shear at the interface. The experiments suggest that the shear strength of the interface is affected neither by the interface type nor by the tack-coat application rate. However, the dynamic shear reaction modulus was affected by both interface type and by the tack-coat application rate. The lowest moduli were recorded for the interface between two fine graded asphalt mixes. With very few exceptions, the highest moduli were obtained for the tack-coat application rate recommended by the construction specification.

Sustainability presents a pathway for future generations to have a better life. Cradle to cradle methodology is the essence of sustainability. In cradle to cradle approach, we aim to reuti-lize a given waste instead of disposing or landfilling it. Each year, millions of waste tires are dis-posed of in landfills. This poses a major challenge environmentally and economically. Environ-mentally, those tires become prone to fire hazards as well as being a place for rodents and mos-quitos to reside at. Economically, on the other hand, each tire has an average of about 50% valu-able polymers as well as oily components. One of the methods to utilize the valuable raw materi-als in waste tires is to recycle it in the form of ground tire rubber also known as crumb rubber modifier (CRM). Although CRM has been widely used as an asphalt modifier, however, due to the complexity of asphalt as well as the waste nature of CRM, the full understanding of the CRM modification mechanism with asphalt has not been fully understood. Understanding of the modi-fication mechanisms involved in the CRM interaction with asphalt would enable us to produce a crumb rubber modified asphalt (CRMA) with enhanced properties. In the current research work, an attempt is made to better understand the mechanism of interaction between CRM and asphalt and the nature of components from asphalt and CRM that take part in the interaction between them. In addition, we investigate the effectiveness of CRM as a modifier for asphalt on the mac-ro and microscale aspects. Another part of the current research work deals with a second waste material; used motor oil. Used motor oil (UMO) presents yet another challenge to environment. With the ever increas-ing motor vehicles produced with advanced technologies and increased advanced motor oil de-mand. This presents a burden on the environment, with the continuous production of UMO. In the current research work, we investigated the feasibility of utilizing UMO as a modifier for asphalt and CRMA. We also investigated the effect of UMO on the micro and macroscale aspects of asphalt.

Recycling of millions of scrap tires produced everyday is crucial challenge encountered by waste management systems. Recycling tire rubbers in form of ground tire rubber, known as crumb rubber modifier (CRM), in asphalt industry was introduced in early 1960's and is proved as an effective recycling method. Interaction between CRM and asphalt is physical in nature which happens mainly due to exchange of components between CRM and asphalt and enhances the time temperature dependant properties of asphalt. In this work, the interaction between CRM and asphalt was evaluated through monitoring the evolutions of CRM in asphalt in macro and micro-level. The mechanism and extent of CRM dissolution were monitored under several interaction conditions. The composition of materials released from CRM was investigated using thermo-gravimetric analysis (TGA). The molecular status of the released components were studied using gel permeation chromatography (GPC) analysis. The composition analysis indicated that the CRM start releasing its polymeric components into the asphalt matrix at dissolutions higher than 20%. The released polymeric component of CRM alters the microstructure of the asphalt and creates an internal network at certain interaction temperatures according to viscoelastic analysis. At these temperatures, the released polymeric components are at their highest molecular weight based on GPC results. The effect of released components of CRM on the time temperature dependent properties of asphalt and its glass transition kinetic was monitored using dynamic shear rheometer (DSR) and differential scanning calorimetry (DSC), respectively. The DSC results showed that the intensity of glass transition of the asphalt binder which is mainly defined by the aromatic components in asphalt reduced by absorption of these components by CRM. The evolution of CRM was investigated during short-term aging of the modified asphalt binder. In addition, the effect of presence of CRM and release of its component on oxidization of asphalt binder was evaluated using Fourier transform infrared spectroscopy (FTIR). The results revealed that CRM continue absorbing the aromatic components of asphalt during aging which stiffen the asphalt binder. Also, it was observed that release of oily components of the CRM, which contain antioxidant, reduces oxidization rate of asphalt significantly. / National Science Foundatio (Grant No. 0846861)

Moisture induced damage in Hot Mix Asphalt (HMA) mixture is a prevalent problem all over the world. It is one of the leading causes of premature failures in asphalt pavements and a significant concern to the paving industry. It is, therefore, necessary to identify mixes that are susceptible to moisture damage during the mix design process. Extensive research has been carried out by several researchers over the years to develop a reliable and practical laboratory test procedure that can simulate field moisture damage conditions and that can make predictions that are likely to correlate to field performance. However, it is inferred from literature that no single laboratory test method can accurately predict the moisture induced damage performance HMA mixtures. The objectives of the present study are to: Develop a framework that considers different test methods to predict the moisture induced damage of Hot Mix Asphalt (HMA); Develop a suitable machine learning method to achieve significantly high accuracy in predicting the moisture damage potential of Hot Mix Asphalt (HMA); and develop a tool (App) for use by practicing engineers to identify HMA mixes that are likely to be susceptible to moisture induced damage. A total of 35 in-plant produced asphalt mixtures with known field performance were sampled, and compacted in the laboratory, and the compacted samples were subjected to mechanical tests before and after moisture conditioning with the Moisture Induced Stress Tester (MiST). In addition, the effluent from the MiST was checked for Dissolved Organic Carbon (DOC) content and gradation of dislodged aggregates. Fourier-Transform Infrared Spectroscopy (FTIR) analysis of the asphalt extracted from HMA samples was performed to observe changes in the functional groups before and after the MiST test. Statistical analysis showed that seismic modulus and indirect tensile strength were effective in distinguishing poor-performing mixes from the well-performing mixes. Principal component analysis was conducted on the test data, and a reduced set of dimensions that were capable of explaining significant variance in the data was identified. The significant test properties were used to develop machine-learning models with two supervised classification approaches. The k-nearest neighbor model was found to be very accurate in differentiating the mixes. The use of MiST conditioning, specified physical tests, and machine learning methods are recommended for the identification of moisture-susceptible hot mix asphalt. Contribution of this Work The major contribution of this work is the creation of a framework or a system that combines appropriate test methods and suitable machine learning models to achieve high accuracy (84%) in predicting the moisture damage potential of Hot Mix Asphalt (HMA). A secondary contribution is that this study, for the first time, combines the principles of Artificial Intelligence (AI), in the form of Machine Learning (ML), with the field of pavement performance, specifically for the evaluation of mixes that are subjected to moisture damage. Finally, the work provides users with a highly accurate ML model as well as an app, which can be used and further improved.

The introduction of chlorine into hydrocarbon compounds produces a product with properties markedly different from those of the original hydrocarbon. Methane, a gas at ordinary conditions, becomes methyl chloride, still a gas but having a higher condensation point than methane, upon the substitution of one chlorine atom in place of a hydrogen atom per molecule of methane. Upon the introduction of three atoms of chlorine per molecule of methane, chloroform, a very volatile liquid, is formed, and upon the introduction of four atoms of chlorine carbon tetrachloride, a less volatile liquid is produced. Chlorination takes place in a “saturated” hydrocarbon by substitution, while in an “unsaturated” hydrocarbon it may take place both by substitution and addition. Asphalt is composed largely of hydrocarbons with a small amount of compounds of sulfur, oxygen, and nitrogen. The hydrocarbons are principally naphthenes, cyclic compounds, which may be represented by the type formula CnH2n. The lowest member of the series, cyclopropane has the structural formula: [see PDF file for formula] This series is “saturated”, but “unsaturated compounds with a similar structure can occur. Such a compound would be cyclopropane, [see PDF file for formula]

Ideally, asphalt pavements are designed to achieve sufficient stiffness prior to the application of traffic to resist rutting while also maintaining enough flexibility after years of service to minimize the amount of durability/brittleness related distresses (e.g. cracking and weathering). Multiple factors have caused an industry transition to mixes which are much more susceptible to crack, and durability related distresses are often the primary mechanism by which pavements fail. To restore a balance between rutting and durability distresses in asphalt pavements, the industry has started investigating balanced mix designs (BMDs). While mitigating only rutting or cracking behaviors is a straightforward exercise based on the collection of knowledge, simultaneously considering the two types of distresses is challenging considering that rutting is an early life distress and durability distresses are not typically observed until longer term aging has occurred. Mixture conditioning protocols to simulate field aging in conjunction with tests to fairly evaluate mixture integrity after conditioning are needed to scrutinize asphalt mixtures for durability related distresses during the mixture design phase. The current longer term conditioning protocol (R30) adopted by the American Association of State Highway and Transportation Officials (AASHTO) is not as severe as suggested when considering durability/brittleness (Isola et al. 2014; Yin et al. 2016; Cox et al. 2017). This dissertation’s primary objective is to provide guidance on asphalt mixture aging by contributing in four areas: 1) ensuring proper density measurement of field aged cores, 2) provide guidance on increased short term aging time effects in asphalt mixtures, 3) suggest improved mixture conditioning protocols to simulate longer term field aging, and 4) make suggestions for improving binder conditioning protocols to simulate longer term field aging. To these ends, a series of mixture and extracted binder tests were conducted on materials that were used to construct a full-scale test section in Columbus, MS that was monitored for aging for up to 5 after construction. The overall work presented provides simple recommendations or protocols which have the potential to improve the level of scrutiny that can be given to paving materials during the mix design phase and thus improve overall pavement performance.

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