<p>This thesis describes new methods for automatic crack detection in pavements. Cracks in pavements can be used as an early indication for the need of reparation. </p><p>Automatic crack detection is preferable compared to manual inventory; the repeatability can be better, the inventory can be done at a higher speed and can be done without interruption of the traffic. </p><p>The automatic and semi-automatic crack detection systems that exist today use Image Analysis methods. There are today powerful methods available in the area of Computer Vision. These methods work in higher dimensions with greater complexity and generate measures of local signal properties, while Image Analyses methods for crack detection use morphological operations on binary images. </p><p>Methods for digitalizing video data on VHS-cassettes and stitching images from nearby frames have been developed. </p><p>Four methods for crack detection have been evaluated, and two of them have been used to form a crack detection and classification program implemented in the calculation program Matlab. </p><p>One image set was used during the implementation and another image set was used for validation. The crack detection system did perform correct detection on 99.2 percent when analysing the images which were used during implementation. The result of the crack detection on the validation data was not very good. When the program is being used on data from other pavements than the one used during implementation, information about the surface texture is required to calibrate the crack detection.</p>

The performance of different pavement maintenance treatments were evaluated by investigating practical projects collected from Tennessee Pavement Management System (PMS) and Long Term Pavement Performance (LTPP) database. The influence of factors on the effectiveness, cost-effectiveness and cracking initiation of different treatment were evaluated by “Optime”, multiple linear regression and parametric survival analysis. Pavement roughness, pavement serviceability index (PSI) and the initiation time of cracking were used as pavement performance indicators. Investigation on the pavement maintenance projects in Tennessee by Optime and multiple linear regression analysis indicated that HMA overlay had the highest effectiveness, followed by mill & fill and micro surfacing. Due to the relatively low cost, micro surfacing was the most cost-effective treatment, followed by HMA overlay and mill & fill. The effectiveness and cost-effectiveness decreased with the increase of traffic level and pre-treatment pavement condition. Investigation on the LTPP resurfacing treatments indicated that thick overlay and milling reduced the roughness after rehabilitation. Thin overlay, high traffic level and poor pre-rehabilitation pavement condition increased the deterioration rate of new overlay. Using reclaimed asphalt material did not influence the treatment performance but was cost-effective in reducing the roughness of new overlay. For a certain deterioration rate, there was an optimized pre-rehabilitation roughness value or time for applying maintenance treatment. Survival analysis on the crack initiation of asphalt overlay indicated that high traffic level accelerated the initiation of cracking. Thick overlay delayed the initiation of cracking except for the non-wheel path longitudinal crack. Mill retarded the occurrence of the non-fatigue cracks, whereas severe freeze thaw condition accelerated the occurrence of the two types of cracking. Using 30% RAP accelerated the initiation of longitudinal fatigue crack on wheel path but did not cause serious fatigue problem. The performance curves of HMA resurfacing treatments used in Tennessee were calibrated by investigating the influence of different factors on the slopes and intercepts of post-treatment performance curves. The analysis indicated that pavement with high pre-treatment PSI, thick overlay and deep milling had low deterioration rate, whereas pavement with higher traffic level deteriorated faster.

Porous asphalt pavements offer an alternative technology for stormwater management. A porous asphalt pavement differs from traditional asphalt pavement designs in that the structure permits fluids to pass freely through it, reducing or controlling the amount of run-off from the surrounding area. By allowing precipitation and run-off to flow through the structure, this pavement type functions as an additional stormwater management technique. The overall benefits of porous asphalt pavements may include both environmental and safety benefits including improved stormwater management, improved skid resistance, reduction of spray to drivers and pedestrians, as well as a potential for noise reduction. With increasing environmental awareness and an evolving paradigm shift in stormwater management techniques, this research aims to provide guidance for Canadian engineers, contractors, and government agencies on the design of porous asphalt pavement structures. One of the keys to the success of this pavement type is in the design of the asphalt mix. The air void percentage, which is ultimately related to the effectiveness of the pavement to adequately control the runoff, is a critical component of the mix. However, special consideration is required in order to obtain higher air void percentages while maintaining strength and durability within a cold climate. The objectives of this study were to evaluate several laboratory porous asphalt mix designs for durability and strength in cold climate conditions. The porous asphalt mixes consisted of a porous asphalt Superpave mix design method whereby the asphalt binder type was varied. Performance testing of the porous asphalt including draindown susceptibility, moisture-induced damage susceptibility, dynamic modulus, and permeability testing were completed. Based on the preliminary laboratory results, an optimal porous asphalt mix was recommended for use in a Canadian climate. Initial design guidelines for porous asphalt were provided based on preliminary findings and hydrological analysis.

This thesis describes new methods for automatic crack detection in pavements. Cracks in pavements can be used as an early indication for the need of reparation. Automatic crack detection is preferable compared to manual inventory; the repeatability can be better, the inventory can be done at a higher speed and can be done without interruption of the traffic. The automatic and semi-automatic crack detection systems that exist today use Image Analysis methods. There are today powerful methods available in the area of Computer Vision. These methods work in higher dimensions with greater complexity and generate measures of local signal properties, while Image Analyses methods for crack detection use morphological operations on binary images. Methods for digitalizing video data on VHS-cassettes and stitching images from nearby frames have been developed. Four methods for crack detection have been evaluated, and two of them have been used to form a crack detection and classification program implemented in the calculation program Matlab. One image set was used during the implementation and another image set was used for validation. The crack detection system did perform correct detection on 99.2 percent when analysing the images which were used during implementation. The result of the crack detection on the validation data was not very good. When the program is being used on data from other pavements than the one used during implementation, information about the surface texture is required to calibrate the crack detection.

Porous asphalt pavements offer an alternative technology for stormwater management. A porous asphalt pavement differs from traditional asphalt pavement designs in that the structure permits fluids to pass freely through it, reducing or controlling the amount of run-off from the surrounding area. By allowing precipitation and run-off to flow through the structure, this pavement type functions as an additional stormwater management technique. The overall benefits of porous asphalt pavements may include both environmental and safety benefits including improved stormwater management, improved skid resistance, reduction of spray to drivers and pedestrians, as well as a potential for noise reduction. With increasing environmental awareness and an evolving paradigm shift in stormwater management techniques, this research aims to provide guidance for Canadian engineers, contractors, and government agencies on the design of porous asphalt pavement structures. One of the keys to the success of this pavement type is in the design of the asphalt mix. The air void percentage, which is ultimately related to the effectiveness of the pavement to adequately control the runoff, is a critical component of the mix. However, special consideration is required in order to obtain higher air void percentages while maintaining strength and durability within a cold climate. The objectives of this study were to evaluate several laboratory porous asphalt mix designs for durability and strength in cold climate conditions. The porous asphalt mixes consisted of a porous asphalt Superpave mix design method whereby the asphalt binder type was varied. Performance testing of the porous asphalt including draindown susceptibility, moisture-induced damage susceptibility, dynamic modulus, and permeability testing were completed. Based on the preliminary laboratory results, an optimal porous asphalt mix was recommended for use in a Canadian climate. Initial design guidelines for porous asphalt were provided based on preliminary findings and hydrological analysis.

Multiple objectives are often used by agencies trying to manage pavement networks. Often alternative investment strategies can accomplish the agencies’ target objectives. If the goal is to achieve the target objectives at the minimum cost, an approach is needed to assist agencies in identifying investment strategies capable of meeting the targets while minimizing costs. The approach used by the agency should not be limited to an analytical method to mathematically solve the funding allocation problem. Finding mechanisms to ensure the sustainability and efficiency of the investment strategy over time is a great challenge that needs to be addressed by the approach. The challenge is even greater for local agencies where resources are usually limited. This research develops a multi-objective strategic management approach oriented to improving decisions for pavement management practices in local agencies. In this approach, target objectives are tied to key pavement network parameters in the management process. A methodology to identify the best combination of projects to meet target objectives at the minimum cost while maximizing treatment effectiveness is provided as a result of the research. Concepts from the pavement management program (PMP) of the Metropolitan Transportation Commission (MTC) of the San Francisco Bay Area were used as a basis for developing the methodology. Four pavement network parameters are considered for setting the target objectives over the agency’s planning horizon: the average network pavement condition index (PCI), average network remaining life, percent of the pavement network in good condition, and percent of the pavement network in poor and very poor condition. Results from a case study show that funding allocation methods influence the allocation of preservation and rehabilitation funds among pavement network groups, affecting budget estimates and future condition of the pavement network. It is also concluded that the use of mechanisms that facilitate data integration and the flow of knowledge across management levels can contribute to making better informed decisions. Hence, the adoption of the multi-objective strategic pavement management approach developed in this dissertation should lead to identifying more efficient investment strategies for achieving the pavement network state desired by a local agency at a minimum cost.

Most engineering as well as pavement materials are composites composed of two or more components to obtain a variety of solid properties to support internal and external loading. The composite materials rely on physical or chemical properties and volume fraction of each component. While the properties can be identified easily, the volume fraction is hard to be estimated due to the volumetric variation during the performance in the field. Various test procedures have been developed to measure the volume fractions; however, they depend on subjective determination and judgment. As an alternative, electromagnetic technique using dielectric constant was developed to estimate the volume fraction. Empirical and mechanistic approaches were used to relate the dielectric constant and volume fraction. While the empirical models are not very accurate in all cases, the mechanistic models require assumptions of constituent dielectric constants. For those reasons, the existing approaches might produce less accurate estimate of volume fraction. In this study, a mechanistic-based approach using the self consistent scheme was developed to be applied to multiphase materials. The new approach was based on calibrated dielectric constant of components to improve results without any assumptions. Also, the system identification was used iteratively to solve for dielectric parameters and volume fraction at each step. As the validation performed to verify the viability of the new approach using soil mixture and portland cement concrete, it was found that the approach has produced a significant improvement in the accuracy of the estimated volume fraction.

Asphalt binder oxidation in pavements has been proven to be an ongoing process throughout a pavement's service life. Understanding the nature of the oxidation process is a critical step toward better pavement design to achieve greater pavement durability. The main component in asphalt binder oxidation in pavements is binder oxidative hardening. As the aromatic compounds in asphalt binders are oxidized, more polar carbonyl compounds are created, which results in stronger associations between asphalt components and eventually leads to an increase in asphalt elastic modulus and viscosity. Consequently, the performance of pavements is affected directly by asphalt binder hardening. Also, low levels of accessible air voids in pavements potentially relate to binder oxidation according to a recent research study. When the pavements have sufficiently high accessible air voids (4 percent or greater), the oxidation rate is largely determined by the temperature in the pavement. On the other hand, when the percentage of accessible air voids in the pavement is considerably lower (2 percent or less), the hardening rate of binders in pavements is reduced significantly. Field evidence is mounting that asphalt binder oxidization in pavements produces a binder that is more susceptible to thermal and fatigue cracking. While the fundamentals of this oxidation process are fairly well known, predicting quantitatively the rate of oxidation as a function of depth in the pavement, is not straightforward. A thermal and oxygen transport model, coupled with binder reaction kinetics, provides the basis for such calculations. A one-dimensional thermal transport model, coupled with site-specific model parameters and recent improvements in the availability of required input climate data, enables calculation of pavement temperatures throughout the year, which then is used in an asphalt binder oxidation and transport model to calculate binder properties in the pavement over time. Calculated binder property changes with depth and time are compared to measurements of binder oxidation in the field. The work in this study is aimed at understanding the oxidation kinetics of asphalt binders in pavements, determining the impact of accessible air void levels on asphalt hardening, and ultimately developing an improved model of asphalt binder oxidation in pavements.

Performance-based asset management provides a strategic framework for managing transportation infrastructure to improve existing procedures for resource allocation. The importance of comprehensive management of pavement marking assets not only results in monetary benefits to the agencies but also complements other management systems in providing safer driving conditions. A majority of research concerned with pavement markings addresses installation, performance, maintenance, and economic evaluation. Although agencies have developed guides and manuals on these subjects, they had difficulties in practical implementation. The purpose of this study was to address the issues that were identified in the practical implementation of analytical and information tools of asset management practice in the field of pavement markings. Problems of limited variable data, censored data and uncertainty in field evaluation and retroreflectivity based prediction were addressed by adopting statistical techniques. Sectional assessment and management methods were proposed as a part of a practical restriping methodology. An information tool was developed in a geographic information system (GIS) environment as an application. Retroreflectivity was the only performance measure on which the analysis and application was carried out. Two case studies were conducted, one for statistical techniques with retroreflectivity data collected by the National Transportation Product Evaluation Program (NTPEP) on U.S. Highway 78 westbound, Lee County, Mississippi. The other for application with retroreflectivity data collected using mobile retroreflectivity unit (MRU) on FM 57, Fisher County, Texas. This research effort provides a framework for an agency in developing a pavement marking management program to maintain good visibility of markings. It also provides a basis for further research in building an integrated asset management system based on other transportation assets.

Traditionally, destructive methods such as coring are used for the condition assessment of an existing concrete structure. Although these methods may yield valid data about the corresponding concrete section, they are quite expensive and time consuming. More important than these, destructive methods damage the structure being investigated and these points usually become focal points for further deterioration. For all these reasons, only a few samples can be collected from a structure and this results in a poor representation of the complete structure. The impact-echo technique is one of the most suitable non-destructive test methods that may be used on concrete for thickness determination or for investigation of possible delaminations in the internal parts of a concrete structure without damaging the surface. It has been observed that reliable results can be obtained quickly. Unlike pulse-echo tests which are commonly used on steel, testing a heterogeneous material like concrete requires the use of low frequency sound waves as in impact-echo, in order to mitigate the effects of paste-aggregate interfaces or small air voids. This method may be used to locate internal cracks or large air voids existing in concrete. It is known that impact-echo has been used successfully on structures with varying geometries and various purposes such as evaluation of concrete pavements, retaining walls and other reinforced concrete sections. Besides the investigation of the internal state, it may also be used when the other side of the section cannot be reached, as in the case of concrete pavements, in order to find the thickness of the section. This is especially important for quality control and for cost calculations. Research conducted in this thesis study was concentrated on the thickness determination of existing concrete pavement sections, produced in the laboratory with dimensions of 1500 x 2000 mm four and varying thicknesses, and the accuracy associated with these results. In order to correctly determine the sensitivity, several other parameters were investigated and optimum ranges were determined for these to be used while on a field test. Among these factors were the steel impactor size, accuracy related to the data acquisition, distance between the impact point and the transducer and the location of the test point. Finally, the accuracy of the impact-echo method for concrete pavement applications was studied. By observing the large number of data points collected, it was found out that an average error of 1.5% exists for a single impact-echo reading regardless of section thickness, but this value reduces to 0.6% when the average of all test results is used while determining pavement thickness. Results of this study show that the impact-echo technique is reliable and may be used with success for the thickness determination of concrete pavements and for locating internal voids.