Desert pavements consist of a one- to two-layer thick surface armory of stones overlying finer, virtually stone-free material which often adopts the appearance of a meticulously tiled mosaic. They cover half of the arid land surface in North America and are usually concentrated on low-sloping alluvial fans and desert piedmont surfaces. McFadden et al. (1987) suggested the accretionary mantle model of desert pavement formation, following research on pavements atop the Cima volcanic complex in the Mojave Desert. However, the wide-spread applicability of this model to diverse lithologies and geomorphic environments remains to be seen. No research has been conducted on desert pavement at Big Bend National Park (BBNP), Texas, despite the occurrence of well-developed pavements in the park and surrounding regions of the Chihuahuan Desert. This research highlights three diverse desert pavement sites at BBNP through a detailed geomorphic assessment including location of desert pavement distribution, classification into surface mosaic units, examination of sediment and soil characteristics, and determination of lithology of the pavement clasts. At each BBNP study area, values for desert pavement clast size, sorting, and percent ground cover were compared to the parameters set forth in Wood et al. (2002) to classify the desert pavements into surface mosaics based on degree of development. Sediment analysis and soil profile photographs were used to characterize the surface sediments and subsurface soil horizons. To determine geologic origin, dominant lithologies of the pavement clasts were compared to outcrop and bedrock samples and to published geologic maps of BBNP. Desert pavements in this study differ significantly in surface texture, soil characteristics, geologic origin, and degree of development compared to the typical pavements of the Mojave Desert used in much of the fundamental research. Results indicate that the desert pavements at BBNP may not have been derived from bedrock and evolved in-situ, as suggested by the accretionary mantle model. Primarily, a combination of fluvial processes and weathering appears more influential to desert pavements in the semi-arid environment of BBNP. This study presents a new perspective on desert pavement geomorphology in Big Bend National Park and serves as a baseline for continued research.

Most paved roads in the United States are surfaced with asphalt. These asphalt pavements suffer from fatigue cracking and thermal cracking, aggravated by the oxidation and hardening of asphalt. This negative impact of asphalt oxidation on pavement performance has not been considered adequately in pavement design. Part of the reason is that the process of asphalt oxidation in pavement is not well understood. This work focused on understanding the asphalt oxidation kinetics and on developing pavement oxidation model that predicts asphalt oxidation and hardening in pavement under environmental conditions. A number of asphalts were studied in laboratory condition. Based on kinetics data, a fast-rate ? constant-rate asphalt oxidation kinetics model was developed to describe the early nonlinear fast-rate aging period and the later constant-rate period of asphalt oxidation. Furthermore, reaction kinetics parameters for the fast-rate and constant-rate reactions were empirically correlated, leading to a simplified model. And the experimental effort and time to obtain these kinetics parameters were significantly reduced. Furthermore, to investigate the mechanism of asphalt oxidation, two antioxidants were studied on their effectiveness. Asphalt oxidation was not significantly affected. It was found that evaluation of antioxidant effectiveness based on viscosity only is not reliable. The asphalt oxidation kinetics model was incorporated into the pavement oxidation model that predicts asphalt oxidation in pavement. The pavement oxidation model mimics the oxidation process of asphalt in real mixture at pavement temperatures. A new parameter, diffusion depth, defined the oxygen diffusion region in the mastic. A field calibration factor accounted for the factors not considered in the model such as the effect of small aggregate particles on oxygen diffusion. Carbonyl area and viscosity of binders recovered from field cores of three pavements in Texas were measured and were used for model calibration and validation. Results demonstrated that the proposed model estimates carbonyl growth over time in pavement, layer-by-layer, quite well. Finally, this work can be useful for incorporating asphalt oxidation into a pavement design method that can predict pavement performance with time and for making strategic decisions such as optimal time for maintenance treatments.

Pavement Management Systems (PMS) are widely used by transportation agencies to maintain safe, durable and economic road networks. PMS prioritize the maintenance and rehabilitation of pavement sections by evaluating pavement performance at the network level. There are many PMS software packages that have been developed over the past decades for provincial/state road agencies. However, sometimes due to lack of budget and experience, adopting the existing PMS for a road agency is not cost effective. Thus, it is important to introduce a simple, effective, and affordable PMS for a local agency and municipality. This research is carried out in partnership between the City of Markham and the Centre for Pavement and Transportation Technology (CPATT) located at the University of Waterloo. For the purpose of developing a PMS for local agencies, an extensive literature review on PMS components was carried out, with emphasizing data inventory, data collection, and performance evaluation. In addition, the literature review also concentrated on the overall pavement condition assessment. In July 2011, a study on “Evaluation of Pavement Distress Measurement Survey” was conducted as a part of this research and was distributed to cities and municipalities across Canada. The study focused on the current state-of-the-practice in pavement distress and condition evaluation methods used by local agencies to compare the results from the literature review. The components of the proposed PMS framework are also developed based on the literature review with some modifications and technical requirements. The City of Markham is selected as a case study, since it represents a local agency and provides all the data, to illustrate the validation of the proposed PMS framework.

Desert pavements consist of a one- to two-layer thick surface armory of stones overlying finer, virtually stone-free material which often adopts the appearance of a meticulously tiled mosaic. They cover half of the arid land surface in North America and are usually concentrated on low-sloping alluvial fans and desert piedmont surfaces. McFadden et al. (1987) suggested the accretionary mantle model of desert pavement formation, following research on pavements atop the Cima volcanic complex in the Mojave Desert. However, the wide-spread applicability of this model to diverse lithologies and geomorphic environments remains to be seen. No research has been conducted on desert pavement at Big Bend National Park (BBNP), Texas, despite the occurrence of well-developed pavements in the park and surrounding regions of the Chihuahuan Desert. This research highlights three diverse desert pavement sites at BBNP through a detailed geomorphic assessment including location of desert pavement distribution, classification into surface mosaic units, examination of sediment and soil characteristics, and determination of lithology of the pavement clasts. At each BBNP study area, values for desert pavement clast size, sorting, and percent ground cover were compared to the parameters set forth in Wood et al. (2002) to classify the desert pavements into surface mosaics based on degree of development. Sediment analysis and soil profile photographs were used to characterize the surface sediments and subsurface soil horizons. To determine geologic origin, dominant lithologies of the pavement clasts were compared to outcrop and bedrock samples and to published geologic maps of BBNP. Desert pavements in this study differ significantly in surface texture, soil characteristics, geologic origin, and degree of development compared to the typical pavements of the Mojave Desert used in much of the fundamental research. Results indicate that the desert pavements at BBNP may not have been derived from bedrock and evolved in-situ, as suggested by the accretionary mantle model. Primarily, a combination of fluvial processes and weathering appears more influential to desert pavements in the semi-arid environment of BBNP. This study presents a new perspective on desert pavement geomorphology in Big Bend National Park and serves as a baseline for continued research.

The volumetric strains induced in the subgrade of a pavement or light foundation by the swelling and shrinking of expansive soils routinely cause distress, and ultimately failure of the structure. Additionally, shallow embankment slope failures have also been shown to cause damage to pavements throughout Central Texas. As such, the main objective of this project was to correlate observed field pavement distresses, attributed to expansive soil movement, to results obtained from laboratory forced ventilated swell-shrink tests. Additionally, the author wished to analyze if edge distresses could be attributed to shallow slope stability failures. This research was conducted with the cooperation of the Capital Area Pavement Engineering Council (CAPEC); a multi-agency entity with the goal of mitigating or eliminating historical pavement distresses with roadways constructed over highly expansive soils. Forced ventilated swell-shrink tests were conducted on specimens from six specific test section locations. In general, the magnitude of shrinkage strains measured in the laboratory were larger for specimens obtained from severely distressed roadway sections. / text

Methodical maintenance and renewal of infrastructure systems is critical due to the rapid deterioration of infrastructure assets under increasing loads and environmental effects and the scarcity of resources allocated for their preservation. A crucial step in pavement management is the formation and prioritization of maintenance and rehabilitation (M&R) projects that compete for limited funding for inclusion in the agency’s multiyear pavement management plan (PMPs). In general, many highway agencies perform this task subjectively, and thus a more rational and objective approach is desired to produce sound and justifiable PMPs. Specifically, such methodology should take into account the multiple factors that are considered by engineers in prioritizing M&R projects. This research addresses this need by developing a methodology for use by the Texas Department of Transportation (TxDOT) in preparing their four-year PMPs. Several key decision factors were considered and TxDOT decision makers were surveyed to weigh these factors as to their influence on prioritizing M&R projects. These were then used to develop a priority score for each candidate M&R project. Since TxDOT collects and stores data for individual 0.5-mile pavement sections, these sections must be grouped in a logical scheme to form realistic candidate M&R projects. The incremental benefit-cost analysis was performed on the candidate M&R projects to identify a set of M&R projects that maximizes network’s priority score under budgetary constraint. Future pavement condition was projected using performance prediction models and the process is repeated throughout the planning horizon to produce a multi-year pavement management plan. Data from Bryan district, which consists of 7,075 lane-miles of roadway, were used to develop and validate the PMP methodology. Comparison with the actual PMP (produced by TxDOT) shows some disagreements with the PMP generated by the methodology though the latter was shown to produce more cost-effective and defendable pavement management plans. Since the methodology is founded on TxDOT engineers’ decision criteria and preferences, they can be assured that the PMPs produced by this methodology are in line with their goals and priorities.

Rural roads play a crucial role in the economic and social development of societies, linking rural communities to education, health services and markets. During the last decade, considerable efforts have been made to evaluate the benefits of rural road investment in developing countries. Although outputs of these studies have led to a global rethinking of traditional road appraisal methods, limited attempts have been made to integrate these findings to the rural road management process. For the sustainable management of rural roads, social, institutional, technical, economic and environmental aspects should be considered under a long term perspective. The current practice in developing countries is that only some of these key sustainable aspects are being considered in the management process. In addition, rural roads maintenance management is commonly performed under a short term basis, not considering the life cycle costs and benefits in the economic analysis and project prioritization. Available management tools and studies have essentially focused their efforts on improving technical and economic aspects of low-volume roads. Whereas, the common practice observed in face of limited resources and lack of technical skills is that decisions are made under a political short term perspective. This research is directed at the development of an applied and practical system for the sustainable management of rural road networks in developing countries. The approach considers the development of all components required by the proposed management system and their integration into a practical and easy-to-use computer tool. To achieve this goal a sustainable framework for rural roads management was first developed, where system components and modules were defined. A network level condition evaluation methodology was selected and validated. Long term condition performance models were calibrated from the probabilistic analysis of field data. Optimal maintenance standards were developed under a cost-effectiveness approach. A long term prioritization procedure was developed to account for sustainable aspects of rural roads in the management process. A computer tool was finally developed to integrate the system components and display them in a friendly interface for potential users. The tool was programed in Visual Basic, considering Microsoft Excel interface. The computer tool considers the four system components: Input Data, System Modules, Network Analysis Interface and Output Data. System Modules include Condition Performance Module, Network Maintenance Module and Long Term Prioritization Module. For each of the system components and modules a separate worksheet has been included in the computer tool. The tool is centered on the Network Analysis Interface, which interacts with the other three system components. The user enters network data in the Input Data interface and may adjust information in System Modules considered if the network under study has differences to predefined conditions of. Adjustments to System Modules can be performed by the user, however it is advised that prior calibration is required for the successful analysis of the network. The management system was applied and validated in two rural road networks in developing countries located in Chile and Paraguay. Sensitivity analysis was carried out to assess the impacts of input parameters in the performance of developed system. As a result of the research an adaptable and adoptable sustainable management system for rural networks was developed to assist local road agencies in developing countries.

Pavement Management Systems (PMS) are widely used by transportation agencies to maintain safe, durable and economic road networks. PMS prioritize the maintenance and rehabilitation of pavement sections by evaluating pavement performance at the network level. There are many PMS software packages that have been developed over the past decades for provincial/state road agencies. However, sometimes due to lack of budget and experience, adopting the existing PMS for a road agency is not cost effective. Thus, it is important to introduce a simple, effective, and affordable PMS for a local agency and municipality. This research is carried out in partnership between the City of Markham and the Centre for Pavement and Transportation Technology (CPATT) located at the University of Waterloo. For the purpose of developing a PMS for local agencies, an extensive literature review on PMS components was carried out, with emphasizing data inventory, data collection, and performance evaluation. In addition, the literature review also concentrated on the overall pavement condition assessment. In July 2011, a study on “Evaluation of Pavement Distress Measurement Survey” was conducted as a part of this research and was distributed to cities and municipalities across Canada. The study focused on the current state-of-the-practice in pavement distress and condition evaluation methods used by local agencies to compare the results from the literature review. The components of the proposed PMS framework are also developed based on the literature review with some modifications and technical requirements. The City of Markham is selected as a case study, since it represents a local agency and provides all the data, to illustrate the validation of the proposed PMS framework.

The work presented in this thesis is aimed at improving the accuracy of one of the components of a flexible pavement design procedure commonly used in South Africa, namely the South African Mechanistic- Empirical Design Method. This is achieved through the development of a new design approach and permanent deformation model for the pavement subgrade. The new distress model for the pavement subgrade was developed from a comprehensive Accelerated Pavement Testing (APT) database on subgrade behaviour and permanent deformation that was generated by a fleet of Heavy Vehicle Simulators (HVSs) over 20 years of testing in South Africa. A literature review of the origin of the current subgrade design model that is used by the South African Mechanistic-Empirical Design Method revealed that that model is based on very little actual subgrade performance data. The model was also developed from the AASHO road test data and adjusted for South African conditions, based on general observations of subgrade behaviour without any calibration. Previous researchers have illustrated the potential of using Heavy Vehicle Simulator data to develop structural pavement design models and it was decided to apply a similar process to the permanent deformation of the pavement subgrade. The present investigation consisted of two components, namely, the evaluation of the resilient and the permanent deformation response of the pavement subgrade, the emphasis in this thesis being more on the permanent deformation response. A general, multi-dimensional empirical model was formulated for the permanent subgrade deformation and the characteristics of the model investigated based on previously published permanent deformation data and mathematical assessment. A set of 35 HVS tests for which suitable data were available was identified and additional field and laboratory tests were done on selected sites to improve the classification of the subgrade materials at these sites. Standard procedures were developed to present the pavement, instrumentation and load sequence data of each HVS test. A process for doing the initial analysis of the deflection and permanent MDD displacement data and presenting the data was also developed. In terms of the resilient response of the subgrade, it was shown that the vertical depth deflection and vertical strain could be modelled accurately if an appropriate set of resilient modulus values was selected for the pavement layers. A detailed investigation of the resilient response of selected HVS sections did, however, clearly illustrate the stress-dependent behaviour of subgrade material, resulting in resilient modulus values being determined, which were well outside the range that would normally be expected for natural gravel subgrade material. This research needs to be continued to enable the development of a comprehensive set of stress-dependent resilient modulus models for South African subgrade materials. The selection of an appropriate critical parameter that can be used as a predictor of permanent subgrade deformation was done by an investigation of the relationship between potential critical parameters and several permanent deformation parameters. It was found that the subgrade elastic deflection showed the best correlation with the subgrade bearing capacity (the number of load repetitions that can be sustained before a terminal rut condition is reached). The vertical subgrade strain that is currently used in the South African Mechanistic-Empirical Design Method in fact correlates poorly with subgrade bearing capacity and has to be replaced with subgrade elastic deflection. A set of subgrade bearing capacity or design models was developed for different levels of permanent subgrade deformation. These models are referred to as S-N models and form contour lines on the general permanent deformation model that was formulated. The subgrade design model accommodates loading conditions ranging from a 40 kN dual wheel load to a 100 kN dual wheel load as well as subgrade materials ranging from a material quality one class better than that which would normally be used for a subgrade, to the lowest possible material class. The model is therefore very flexible in terms of its application. / Prof. P. Pretorius

abstract: United States Air Force airfield PAVER pavement management system enterprise data was reviewed for 67 networks. The distress survey extents and severity fields were joined with treatment costs estimated using RSMeans to determine the costliest distress. In asphalt surfaced pavements Longitudinal/transverse cracking, weathering, and block cracking resulted in the most pavement condition index (PCI) deducts while the costliest distresses are weathering, block cracking and longitudinal cracking. In portland cement concrete surfaced pavements linear cracking, joint seal damage, and joint spalling resulted in the most PCI deducts while the costliest distresses are joint seal damage, linear cracking, and corner spalling. The results of this data were then compared to airfield attributes: Pavement Temperature Group, Dominant American Association of State Highway and Transportation Officials (AASHTO) Soil Classification, Pavement- Transportation Computer Assisted Structural Engineering (PCASE) Climate Zone, and years since last maintenance. Maps showing the Pavement Temperature Group, Dominant AASHTO Soil Classification, and PCASE Climate Zone are included in Appendix A. Alligator cracking is most prevalent at the airfields with PTG 64-34 (Ellsworth, Fairchild, Hill, and Offutt) and 58-22 (Niagara and Vandenberg). Rutting is most prevalent at PTG 64-34 (Ellsworth, Fairchild, Hill, and Offutt). An increasing trend of joint spalling, corner spalling, and corner break with decreasing soil quality (AASHOTO A-1 to A-8 soils). The PCASE Climate Zone Cost Indices the cost index for weathering is approximately double in the moist region over the dry region. The cost index for block cracking is approximately double in the cold region over the hot region. It is recommended that the agency review its pavement performance modeling in the pavement management system to increase the recommendation of pavement preservation treatments and review the use of higher quality materials for pavement maintenance treatments. / Dissertation/Thesis / Masters Thesis Civil, Environmental and Sustainable Engineering 2020