During the last two decades, environmental awareness and climate change concerns have encouraged and supported the implementation of recycled techniques in the Transportation Infrastructure Industry for rehabilitating and constructing pavements in the United States. Besides that, pavement roads are public goods that bring economic and social benefits to all countries. Therefore, assessing the pavement structural condition is essential to understand the performance of new materials and determine actions for conservation, maintenance, or rehabilitation. In-situ Pavement monitoring through embedded instrumentation is a type of monitoring technique, which uses several sensors installed within the pavement to obtain the structural responses used in Mechanical-Empirical design to control the performance and define asset management plans. This thesis presents the instrumented response of a Recycled Pavement Section on the Interstate 64 (located in Virginia, USA) to analyze the actual pavement responses (strain and stress) under real traffic and environmental conditions. Several sensors were installed during the construction (including strain gauges, pressure cells, thermocouples, and TDR probes), and two recycling techniques were used (CCPR and Full Depth Reclamation (FDR)) in this project. The Instrumented Recycled Pavement Section analyzed in this research was tested during five months in 2019 to evaluate the effect of temperature, sensor location, and load configuration on the pavement responses collected in the field. During the tests, three loaded trucks ran over the instrumented section. The results showed that the pavement structure is working properly, the stress responses decreased with depth, the maximum strain over the months was compared, and the temperature effect was addressed. Nevertheless, the stress and strain data obtained in each test presented a large variability because it is difficult to control the position where the trucks are passing during this type of experiment. Furthermore, the measured strains were useful to develop a calibrated pavement structural model, which showed that the pavement is expected to have a long structural service life. / M.S. / During the last two decades, different Departments of Transportation have been studying the implementation of recycled materials in pavement structure to provide better economic, environmental, and social benefits by addressing environmental challenges within the Transportation Infrastructure Industry. Among the emerging recycled techniques, Cold-Central Plant Recycling (CCPR) and Full Depth Reclamation (FDR) are included. Both procedures recollect and use the existing asphalt in the rehabilitation or reconstruction of the new pavement structure. The main benefits of pavement recycled materials include reduction of raw materials required and gas emissions. Nevertheless, recycled techniques are not commonly implemented due to the lack of information about long-term performance under real traffic and environmental conditions. In addition, since 2004, when the new Pavement Design Guide was released, the evaluation and validation of new materials require the understanding of the interaction between material properties, traffic, and climate. To address this concern, this thesis analyzed the pavement response measurements obtained in the Interstate 64 Widening Project (Virginia, USA), where two recycling techniques were used (CCPR and FDR). In this project, several sensors were installed during the construction to obtain information regarding the current environment condition (temperature and moisture) and pavement performance (stress and strain). The recycled pavement section was tested during five months of 2019 and trucks with known load configurations were implemented in the field tests. The results showed that the pavement structure is properly working, there is an acceptable stress distribution within the pavement layers, and the overall thickness is expected to have a long structural service life. Besides that, measured strain values obtained through the field experiment were compared with the theoretical ones obtained with computational tools.

This thesis investigates the application of In-Situ Recycling and provides guidelines for localities to aid in the selection of recycling methods, as well as documents a local government's experience with Cold In-Place Recycling. The recycling methods discussed in this study include Cold In-Place Recycling (CIR), Hot In-Place Recycling (HIR), and Full Depth Reclamation (FDR). These methods are performed onsite and in-place in a continuous process of milling, mixing, and placement. The In-Situ Recycling guidelines include suggestions based on: traffic characteristics, existing road condition, distress types, road access, local climate, road geometry, and other road characteristics. The guidelines are based on information from sources including NCHRP Synthesis 421, American Recycling and Reclamation Association (ARRA), FHWA, and state agencies with recycling experience. This study also resulted in documenting obstacles that localities may face when in-situ recycling, as well as the impact of limited experience with recycling. The study also evaluated the construction of Cold In-Place Recycled pavement sections in Christiansburg, VA, using Falling Weight Deflectometer (FWD) and Ground Penetrating Radar (GPR). Additionally, using the FWD and GPR data, alternate recycled designs were proposed in addition to a cost comparison to a conventional design. / Master of Science

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.

Full-depth reclamation (FDR) in conjunction with cement stabilization is an established practice for rehabilitating deteriorating asphalt roads. Conventionally, FDR uses dry cement powder applied with a pneumatic spreader, creating undesirable fugitive cement dust. The cement dust poses a nuisance and, when inhaled, a health threat. Consequently, FDR in conjunction with conventional cement stabilization cannot generally be used in urban areas. To solve the problem of fugitive cement dust, the use of cement slurry, prepared by combining cement powder and water, has been proposed to allow cement stabilization to be utilized in urban areas. However, using cement slurry introduces several factors not associated with using dry cement that may affect road base strength, dry density (DD), and moisture content (MC). The objectives of this research were to 1) identify construction-related factors that influence the strength of road base treated with cement slurry in conjunction with FDR and quantify the effects of these factors and 2) compare the strength of road base treated with cement slurry with that of road base treated with dry cement. To achieve the research objectives, road base taken from an FDR project was subjected to extensive full-factorial laboratory testing. The 7-day unconfined compressive strength (UCS), DD, and MC were measured as dependent variables, while independent variables included cement content; slurry water batching temperature; cement slurry aging temperature; cement slurry aging time; presence of a set-retarding, water-reducing admixture; and aggregate-slurry mixing time. This research suggests that, when road base is stabilized with cement slurry in conjunction with FDR, the slurry water batching temperature; haul time; environmental temperature; and presence of a set-retarding, water-reducing admixture will not significantly affect the strength of CTB, provided that those factors fall within the limits explored in this research and are applied to a road base with similar properties. Cement content and cement-aggregate mixing time are positively correlated with the strength of CTB regardless of cement form. Additionally, using cement slurry will result in slightly lower strength values than using dry cement.