Os solos das regiões arrozeiras apresentam características geotécnicas inadequadas para uso como revestimentos primários de estradas. Isto força o transporte de materiais de jazidas distantes, o que, além de onerar o custo de construção, nem sempre é uma solução durável. Nesta tese relata-se uma pesquisa que apresenta uma solução para esse problema: a pavimentação de estradas de baixo volume de tráfego com solo local modificado com cal. Foram realizados estudos laboratoriais e de campo, e os resultados analisados através de uma abordagem mecanístico-empírica. Dois pavimentos experimentais com revestimentos de solo-cal foram construídos e monitorados próximo a Cebollatí, leste do Uruguai. Foram realizados ensaios de caracterização e comportamento mecânico do solo e de misturas de solo e cal, variando-se o teor de cal, o tempo de cura e a energia de compactação. Realizaram-se ensaios de módulo de resiliência, para o qual foi projetado, montado e operado o primeiro equipamento de ensaios de carga repetida na compressão triaxial do Uruguai. Também foram realizados ensaios de fadiga na compressão diametral para o solo modificado com 3% e 5% de cal, curado por 28 e 150 dias. Para entender o comportamento das camadas de solo modificado com cal submetidas ao tráfego, realizou-se uma análise conjunta dos resultados laboratoriais e do monitoramento dos trechos experimentais, com uso de modelos computacionais. Apesar das limitações construtivas, de terem sido liberados ao tráfego em plena safra e das más condições de drenagem da região, após 5 anos de trafego, os pavimentos não mostram trincas de fadiga ou afundamentos nas trilhas de roda. Assim, a pavimentação de estradas de baixo volume de tráfego em regiões arrozeiras com revestimentos de solo local modificado com cal provou ser uma alternativa economicamente vantajosa, por reduzir custos de construção e manutenção, e sustentável, por preservar materiais não-renováveis, como solos e rochas. / Soils in rice plantation areas generally present geotechnical characteristics unsuitable for use as primary wearing course of roads. Because of that, it is necessary to import materials from distant sites, a solution that, besides increasing construction cost, is rarely long-lasting. In this thesis a research on paving low volume roads with lime modified local soils is reported, in order to present an alternative solution to that problem. Both laboratory and field studies were carried out and the results were analyzed by means of a mechanistic-empirical approach. Two test sections with wearing courses made of lime modified soil were built and monitored close to Cebollatí, a village in the east of Uruguay. Previously, laboratory characterization and mechanical tests on samples of the sedimentary soil were carried out. Lime contents for mixtures were determined and the stress-strain-strength behavior of mixes with different levels of lime content, curing time and compaction energy was studied. In order to analyze the elastic behavior of the lime modified soil under traffic, resilient modulus tests were carried out. This motivated the design, assembly and use of the first equipment for triaxial compression repeated loading tests in Uruguay. Besides, stress controlled fatigue tests were performed on cylindrical specimens of soil modified with 3% and 5% of lime, cured for 28 and 150 days. The results of laboratory tests and field monitoring were analyzed using computational models. In spite of the difficulties faced during pavements construction, including heavy traffic in early days, and the poor drainage, after 5 years of service no cracks or ruts are seen on top of the test pavements. Therefore, paving low volume roads in rice plantation areas with lime modified wearing courses has proved to be a cost-effective alternative, reducing construction and maintenance costs, and a sustainable practice, preserving non-renewable materials such as rocks and soils.

The Mechanistic-Empirical Pavement Design Guide (MEPDG) which is widely used for the rational design of pavements has three different design levels (i.e., Level 1, Level 2, and Level 3) that are typically based on the resources and the level of risk associated for a given project. Specifically, Level 2 design requires the estimation of the resilient modulus, MR (which is the key parameter in the mechanistic design procedures) from simple experiments such as the California Bearing Ratio (CBR), Unconfined Compressive Strength (UCS) and R-value tests. In this study, a technique is proposed for estimation of MR from CBR that can be used in Level 2 designs of pavements. The California Bearing Ratio (CBR) is a relatively inexpensive laboratory test which provides a measure of the strength of a soil. The CBR test can easily be performed as the experimental procedure is relatively straightforward to execute. The CBR test procedure widely used and is simple, however the fundamental engineering principles governing CBR tests do not realistically describe the mechanical behavior of pavements. Due to this reason, there has been a significant interest to design pavements using a mechanistic approach such as the resilient modulus (MR). The MR test method provides an indication of the stiffness of pavement materials under cyclic loads, which closely represents the typical loading conditions that are experienced by pavements. MR is a reliable method as it considers the cyclic loading (i.e., resilient response) of pavements. However, it has one major drawback as the triaxial testing equipment used for measurement of the MR is relatively costly, testing is complex and requires trained professional to perform them. The CBR and MR are both used in present day practice to evaluate the strength of pavement materials. However, the CBR is widely used because of its relatively low cost and the vast experience with its use in the design of pavements. The common trend in today’s practice is to estimate the MR from CBR as evident in most pavement design procedures used around the world. For instance, the Mechanistic-Empirical Pavement Design Guide (AASHTO 2008) suggests that the MR may be estimated from standard tests like the CBR for design of Level 2 pavements. Numerous studies in the literature propose relationships between CBR and MR, but only a hand full of these studies takes account of the effect of matric suction, 𝜓 which is a key stress state variable that describes the rational behavior of unsaturated soils. This thesis document includes the explanation of a modified CBR test equipment capable of measuring unsaturated properties (𝜓 and water content) of specimens subjected to wetting and drying. In addition, some correlations were developed using the measured CBR data and the data of MR from other studies. The results provide useful information for Level 2 mechanistic-empirical design of pavement structures for various soils in the province of Ontario.

No description available.

The modulus of aggregate base layers in pavement structures can potentially be increased through the use of geogrid. However, methods for determining how much structural benefit can be expected from a given geogrid product have not been standardized. A laboratory testing protocol is therefore needed to enable evaluation, in terms of modulus or California bearing ratio (CBR), for example, of the degree of improvement that may be achieved by a given geogrid. Consequently, the objective of this research was to identify a laboratory test method that can be used to quantify improvements in structural capacity of aggregate base materials reinforced with geogrid. For this research, National Cooperative Highway Research Program Report 598 repeated load triaxial, American Association of State Highway and Transportation Officials (AASHTO) T 307 quick shear, and CBR testing protocols were used to test unreinforced and geogrid-reinforced aggregate base materials from northern Utah. Biaxial and triaxial geogrid were investigated in multiple reinforcement configurations. Several statistical analyses were performed on the results of each test method to identify the test that is most likely to consistently show an improvement in the structural capacity of aggregate base materials reinforced with geogrid. The results of this research indicate that, for the methods and materials evaluated in this study, calculation of the modulus at 2 percent strain from the AASHTO T 307 quick shear data is the test method most likely to consistently show an improvement in structural capacity associated with geogrid reinforcement. Of the three configurations investigated as part of this research, placing the geogrid at an upper position within a specimen is preferred. Given that the end goal of the use of geogrid reinforcement is to improve pavement performance, additional research is needed to compare the results of the AASHTO T 307 quick shear test obtained in the laboratory with the structural capacity of geogrid-reinforced aggregate base materials measured in the field. In addition, correlations between the results of the AASHTO T 307 quick shear test and resilient modulus need to be investigated in order to incorporate the findings of the AASHTO T 307 quick shear test on reinforced base materials into mechanistic-empirical pavement design.

Virgin aggregate is being used faster than it is being made available creating a foreseeable shortage in the future. Despite this trend, the availability of demolished concrete for use as recycled concrete aggregate (RCA) is increasing. Using this waste concrete as RCA conserves virgin aggregate, reduces the impact on landfills, decreases energy consumption and can provide cost savings. However, there are still many unanswered questions on the beneficial use of RCA in concrete pavements. This research addresses the many technical and cost-effective concerns regarding the use of RCA in concrete pavements by identifying concrete mixture and proportioning designs suitable for jointed plain concrete pavements; constructing test sections using varying amounts of RCA; monitoring performance through testing, condition surveys and sensor data; modeling RCA pavement performance; and predicting life cycle costs. The research was carried out as a partnership between the Centre for Pavement and Transportation Technology (CPATT) at the University of Waterloo, the Cement Association of Canada, Dufferin Construction, and the Natural Sciences and Engineering Research Council of Canada. The literature review provides an overview of sustainability and key performance indicators, the material properties of RCA both as an aggregate and in concrete, concrete mixture and proportioning designs with RCA, performance of existing RCA pavements, and the implementation of RCA highlighting some examples where RCA has been used successfully. Twelve preliminary mixes were developed using three total cementitious contents amounts of 315 kg/m3, 330 kg/m3, and 345 kg/m3 to determine four suitable mixes with varying coarse RCA contents (0%, 15%, 30% and 50%) to place at the CPATT test track. At 28-days, all of the twelve mixes exceed the 30 MPa design strength. Four test sections containing 0%, 15%, 30% and 50% coarse RCA were constructed in June 2007. The test sections had identical cross sections consisting of 250 mm portland cement concrete (PCC), 100 mm asphalt-stabilized OGDL and a 450 mm granular base. For each coarse RCA content, one slab was instrumented with six vibrating wire concrete embedment strain gages to measure long-term longitudinal and transverse strain due to environmental changes, two vibrating wire vertical extensometers to monitor slab curling and warping, two vibrating wire inter-panel extensometers to monitor joint movement, and two maturity meters to measure maturity and temperature. Quality assurance and quality control (QA/QC) testing showed that the mixes containing RCA exhibited similar or improved performance when compared to the conventional concrete for compressive and flexural strength, freeze-thaw durability and coefficient of thermal expansion. Pavement performance of the four test sections was evaluated using visual surveys following the Ontario Ministry of Transportation’s Manual for Condition rating of Rigid Pavements. Nine pavement evaluations have been performed every two to four months since construction. All test sections are in excellent condition with pavement condition index (PCI) values greater than 85 after two years in-service and approximately three hundred thousand Equivalent Single Axle Loads. Sensor data from the strain gauges, and vertical and inter-panel extensometers are providing consistent results between the test sections. Long-term performance modeling using the Mechanistic-Empirical Pavement Design Guide (ME-PDG) showed improved performance with respect to cracked slabs, joint faulting, and pavement roughness as the RCA content increased. Multivariable sensitivity analysis showed that the performance results were sensitive to CTE, unit weight, joint spacing, edge support, surface absorption, and dowel bar diameter. Life cycle cost analysis (LCCA) illustrated the savings that can be expected using RCA as a replacement aggregate source as the cost of virgin aggregate increase as the sources becomes depleted. Multivariable sensitivity analysis showed that the LCCA results were sensitive to construction costs, discount rate, and maintenance and rehabilitation quantities.

Virgin aggregate is being used faster than it is being made available creating a foreseeable shortage in the future. Despite this trend, the availability of demolished concrete for use as recycled concrete aggregate (RCA) is increasing. Using this waste concrete as RCA conserves virgin aggregate, reduces the impact on landfills, decreases energy consumption and can provide cost savings. However, there are still many unanswered questions on the beneficial use of RCA in concrete pavements. This research addresses the many technical and cost-effective concerns regarding the use of RCA in concrete pavements by identifying concrete mixture and proportioning designs suitable for jointed plain concrete pavements; constructing test sections using varying amounts of RCA; monitoring performance through testing, condition surveys and sensor data; modeling RCA pavement performance; and predicting life cycle costs. The research was carried out as a partnership between the Centre for Pavement and Transportation Technology (CPATT) at the University of Waterloo, the Cement Association of Canada, Dufferin Construction, and the Natural Sciences and Engineering Research Council of Canada. The literature review provides an overview of sustainability and key performance indicators, the material properties of RCA both as an aggregate and in concrete, concrete mixture and proportioning designs with RCA, performance of existing RCA pavements, and the implementation of RCA highlighting some examples where RCA has been used successfully. Twelve preliminary mixes were developed using three total cementitious contents amounts of 315 kg/m3, 330 kg/m3, and 345 kg/m3 to determine four suitable mixes with varying coarse RCA contents (0%, 15%, 30% and 50%) to place at the CPATT test track. At 28-days, all of the twelve mixes exceed the 30 MPa design strength. Four test sections containing 0%, 15%, 30% and 50% coarse RCA were constructed in June 2007. The test sections had identical cross sections consisting of 250 mm portland cement concrete (PCC), 100 mm asphalt-stabilized OGDL and a 450 mm granular base. For each coarse RCA content, one slab was instrumented with six vibrating wire concrete embedment strain gages to measure long-term longitudinal and transverse strain due to environmental changes, two vibrating wire vertical extensometers to monitor slab curling and warping, two vibrating wire inter-panel extensometers to monitor joint movement, and two maturity meters to measure maturity and temperature. Quality assurance and quality control (QA/QC) testing showed that the mixes containing RCA exhibited similar or improved performance when compared to the conventional concrete for compressive and flexural strength, freeze-thaw durability and coefficient of thermal expansion. Pavement performance of the four test sections was evaluated using visual surveys following the Ontario Ministry of Transportation’s Manual for Condition rating of Rigid Pavements. Nine pavement evaluations have been performed every two to four months since construction. All test sections are in excellent condition with pavement condition index (PCI) values greater than 85 after two years in-service and approximately three hundred thousand Equivalent Single Axle Loads. Sensor data from the strain gauges, and vertical and inter-panel extensometers are providing consistent results between the test sections. Long-term performance modeling using the Mechanistic-Empirical Pavement Design Guide (ME-PDG) showed improved performance with respect to cracked slabs, joint faulting, and pavement roughness as the RCA content increased. Multivariable sensitivity analysis showed that the performance results were sensitive to CTE, unit weight, joint spacing, edge support, surface absorption, and dowel bar diameter. Life cycle cost analysis (LCCA) illustrated the savings that can be expected using RCA as a replacement aggregate source as the cost of virgin aggregate increase as the sources becomes depleted. Multivariable sensitivity analysis showed that the LCCA results were sensitive to construction costs, discount rate, and maintenance and rehabilitation quantities.

Soil-cement is an integral part of pavement design, especially in areas that are aggregate deprived, such as Mississippi. Current designs are reliant on the relationship of unconfined compressive strength (UCS) to other mechanical properties. The other properties discussed in this dissertation are Modulus of Elasticity (E), Indirect Tensile Strength (St), and Modulus of Rupture (MOR). This dissertation includes a comprehensive review of past design methods and mechanical property relationships. While some mechanical property relationships were shown to be well understood (i.e. St to UCS), others were not as accurate, especially for the later life mechanical properties (i.e. MOR to UCS and E to UCS). This dissertation investigates the Plastic Mold (PM) Compaction (PM) Device and its ability to measure mechanical property relationships (UCS, E, St) for soil-cement as well as different materials, such as lime stabilized subgrade and Cold in Place Recycling (CIR) stabilized with cement. These mechanical property relationships were compared to soil-cement beam specimens, which are capable of being tested for the four previously mentioned mechanical properties from an individual specimen. Finally to have a better understanding of the later life mechanical properties and their relationships, PM and beam specimens were exposed to elevated temperatures to forecast out how these properties interrelate over time. These mechanical property values and relationship were then compared to Mississippi field cores ranging from 10 to 54 years old. These protocols, beam and elevated curing, were able to replicate what was seen for pavement cores that were extracted after decades of service. Over 1300 specimens were testing showing how these mechanical properties interacted from early ages and throughout a pavement’s life.

No description available.

Stochastic analysis provides a rationale for the treatment of uncertainties, founded on the principles of probability theory and statistics, and is concerned with a quantifiable measure of the confidence or the reliability associated with any design process. In this thesis, a stochastic approach is employed in the design of flexible pavement structures, to facilitate the development of safe and reliable pavement structures. The important aspects that have been explored in sufficient detail include the system reliability and global sensitivity analysis, and the spatial and temporal uncertainties that pervade the life of pavements. Chapter 1 of the thesis provides an introduction to the stochastic modelling of flexible pavements and its significance in the present day. Highlighting the need for this study, this chapter also enumerates its objectives and presents an overview of the organization of the thesis. Chapter 2 provides a review of the existing literature of the design of flexible pavements and the approaches adopted to deal with the various sources of uncertainties in a probabilistic setting. The estimation of the uncertainties in fundamental pavement design inputs and their integration into the general performance prediction procedures has become a required component of the modern Mechanistic-Empirical pavement design methodology, which has been described in detail. This chapter also provides the scope of the thesis by identifying the areas of stochastic analysis that have received little attention in the flexible pavement design, which include the effect of spatial variability on the pavement structural responses and the techniques of global sensitivity analysis. Chapter 3 provides a detailed overview of the various methodologies adopted in this thesis to carry out the stochastic modelling of flexible pavements. The fundamental technique adopted for the analysis of reliability is the Monte Carlo Simulation (MCS), which relies upon a numerical/analytical model of the physical system, i.e. the pavement model and a probabilistic description of the design parameters represented by random variables or random fields. The high computational expense associated with the MCS, particularly in the case of random fields, is tackled by the use of meta-models based on the stochastic response surface methodology. The chapter outlines the steps followed to develop the meta-models in the form of Polynomial Chaos Equations (PCEs) and its extension to the Sparse PCE that can conveniently represent the spatial variability of the pavement fields. Chapter 4 deals with the probabilistic modelling of flexible pavements, where the design parameter and model uncertainties are quantified based on the available literature studies. The global sensitivity analysis, which aims to study the impact of the input uncertainty on the variation of a model output (critical pavement responses) through uncertainty propagation, is achieved by the construction of the Polynomial Chaos Equations (PCEs). To implement the global sensitivity analysis in a system reliability framework, a generalized approach based on Bayes’ theorem and the concept of entropy as a sensitivity measure, has been proposed in this chapter. Chapter 5 deals with the characterization of the spatial variability inherent in the pavement layer by employing random fields and analyzing the effect on the pavement responses. The discretization of the random field into a vector of random variables is achieved through the simple Midpoint Discretization and the efficient Expansion Optimal Linear Estimation method. Since the computational effort in stochastic problems is proportional to the number of random variables involved, it is desirable to use a small number of random variables to represent the random field. To achieve this, the principle of transformation of the original random variables into a set of uncorrelated random variables through an eigenvalue orthogonalization procedure is adopted. To further increase the computational efficiency of generating random fields for Monte Carlo Simulation, the variance reduction technique of Latin Hypercube Sampling and the meta-modelling technique using Sparse Polynomial Chaos Equations (SPCEs) are implemented. The primary focus of this chapter is to analyze the influence of the spatial variability of the pavement layer moduli, including its anisotropic characteristics on the pavement structural responses. Chapter 6 focuses on the time-dependent reliability of the pavement structures as they age in service, with due consideration given to degradation of strength with traffic loading. The study is concerned with the fatigue reliability and thereby only the decrease in the asphalt modulus with time is considered as a function of the accumulated damage due to repeated loading, whose uncertainty is determined by the uncertainties of material parameters and the traffic loading. The time-dependent model adopted in this chapter can be quite effortlessly embedded in the Mechanistic-Empirical design framework, and provides a tool to effectively schedule the maintenance of the pavement structure and ensure that the reliability level remains at the desired level for the entire design life of the structure. Chapter 7 summarizes the various studies reported in this thesis and highlights the important conclusions.

The primary objective of this research was to quantify the improvement in service life of a flexible pavement constructed using full-depth reclamation (FDR) in conjunction with cement stabilization when specified reductions in the spatial variability of specific construction-related parameters are achieved. This study analyzed pavement data obtained through field and laboratory testing of a reconstruction project in northern Utah. Data analyses included multivariate regression, Monte Carlo simulation, and mechanistic-empirical analyses of a model pavement structure. The results of the research show a steadily increasing trend in 28-day unconfined compressive strength of the cement-treated base (CTB) layer with increasing reductions in variability for cement content, moisture content, and reclaimed asphalt pavement (RAP) content across each of five different reliability levels. The most significant increases in CTB strength occurred with reductions in the standard deviations of moisture content and RAP content. Decreasing the variability of cement content did not provide significant additional strength to the CTB layer. Therefore, when involved on FDR projects, members of the pavement industry should focus energy on reducing the variability of both moisture content and RAP content, which both significantly impact pavement life, to achieve high-quality, long-lasting pavements.