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A Rolling Dynamic Deflectometer (RDD) is a nondestructive testing device for determining continuous deflection profiles of pavements. Unlike discrete testing methods, the RDD performs continuous measurements. The ability to perform continuous measurements makes the RDD a powerful screening/evaluation tool for quickly characterizing large sections of pavement, with little danger of missing critical pavement features. RDD testing applications have involved pavement forensic investigations, delineations of areas to be repaired, selection of rehabilitation treatments, measurements of relative improvements due to the rehabilitation, and monitoring of changes with time (trafficking and environmental loading). However, the speed of RDD testing with the current rolling sensors is between 1 and 2 mph (1.6 to 3.2 km/hr). Improvements in testing speed and data analysis procedures would increase its usefulness in project-level studies as well as permit its used in some pavement network-level studies. A three-part study was carried out to further improve the RDD. The first part involved the development of speed-improved rolling sensors (referred as the third-generation rolling sensor). Key benefits of this new rolling sensor are: (1) increased testing speed up to 5 mph (8.0 km/hr), and (2) reduced level of rolling noise during RDD measurements. With this rolling sensor, the RDD can collect more deflection measurements at a speed of 3 to 5 mph (4.8 to 8.0 km/hr). Field trials using the first- and third-generation rolling sensors on both flexible and rigid pavements were performed to evaluate the performance of the third-generation rolling sensor. The second part of this study involved enhancements to the RDD data analysis procedure. An alternative data analysis method was developed for the third-generation rolling sensor. This new analysis method produces results at higher speeds that are comparable to the existing analysis method used for testing at 1 to 2 mph (1.6 to 3.2 km/hr). Key benefits of this analysis method that were not previously available are: (1) distance-based deflection profiles (report RDD deflections based on a selected distance interval), (2) improved-spatial resolution without sacrificing the filtering performance, and (3) analysis of the rolling noise characteristics and signal-to-noise and distortion ratios better characterize the deflection profiles and their accuracy. The third part of this study involved investigating the effects of parameters affecting RDD deflection measurements which include: (1) force level and operating frequency, (2) in-situ sensor calibration, (3) load-displacement curve, and (4) pavement temperature variations. These parameters need to be considered in testing and data analysis procedures of the RDD because small errors from these parameters can adversely influence calculations of the RDD deflections. Criteria are presented for selecting the best operating parameters for testing. / text

The Texas Department of Transportation (TxDOT) uses the Pavement Management Information Systems (PMIS) to store and analyze pavement data, and to summarize information needed to support pavement-related decisions. The information on overall condition of the pavement is stored in PMIS, measured with various scores based on visual distress and ride quality surveys. However, a direct measure of the pavement structural condition is currently not in use. A network-level index that can distinguish pavements that require Preventive Maintenance (PM) from those that require Rehabilitation (Rhb) is required, because, it is not cost-effective to apply PM treatments to pavements that are structurally inadequate. The necessity to use an index to improve pavement treatment selection process, especially under financial constraints has motivated this research. The objective of this research is to validate the pavement Structural Condition Index (SCI) developed under a previous Research Project 0-4322, and to develop guidelines for implementing the SCI at the network level. / text

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Petróleo Brasileiro S/A / It is unusual practice, in national projects of new pavements and restorations, the consideration of viscoelastic behavior and non-linear elastic of materials that compound or will compound the layers of pavement. However, the linear elastic response is a simplification of the actual behavior of the pavements layers, since the materials used in the structure have dependent stiffness of the stress state (granular layers and subgrades) or temperature and load application time (asphalt concrete). Therefore, it was aimed to study the behavior of the pavements structures of three monitored sections in the city of Santa Maria/RS. For this, tests were performed with the equipment FWD applying four different loads in each stake that compounds the extension of the three sections. It was found from deflection basins and backcalculated resilient moduli the nonlinear elastic behavior of granular layers (base and sub-base) of the sections 1 and 2, with resilient modulus directly proportional to the increase of the confining pressure. The subgrades of both sections exhibited varied behavior and can be simplified by the linear elasticity without considerable loss. The same happened to the asphalt concrete of section 1. On the other hand, the coating of the section 2 resulted in resilient modules dependent of the increase of vertical surface tension in the center of the load plate. In relation to section 3, the results related only to deflection measures indicated mostly behavior near of linearity in all evaluated reading distances, except for that carried out under the load application. Sequentially to load pulses, also were determined deflections with the Benkelman beam, aiming to find a local correlation between the results obtained from different equipments. The deflections basins indicated higher values, measured with the beam, in relation to those determined by FWD. Consequently, the resilient modules were higher when determined from the backcalculation of the readings taken with FWD, in relation to Benkelman beam. In parallel, it was verified and quantified the influence of bounding conditions between the layers and correction, total or partial, of deflections basins, depending on the temperature, in backcalculated resilient moduli. It was found that the assignment of total bounding in the interfaces between the layers reduces considerably the backcalculated resilient moduli of granular materials. Regarding to the temperature correction, it is appropriate the determination of the rigidity of the granular materials and the subgrade by performing backcalculation without any adjustment in the field basins. Taking these values as a basis, it was considered appropriate to repeat the iterative procedure, with adjustment of the deflections depending on the temperature in the initial readings, thereby determining the new asphalt concrete resilient moduli. / Não é prática usual, em projetos nacionais de pavimentos novos e restaurações, a consideração do comportamento viscoelástico e elástico não linear dos materiais que constituem, ou que irão constituir as camadas do pavimento. Todavia, a resposta elástica linear é uma simplificação do comportamento real das camadas dos pavimentos, já que os materiais empregados na estrutura possuem rigidez dependente do estado de tensões (camadas granulares e subleitos) ou da temperatura e tempo de aplicação de carga (concretos asfálticos). Em vista disso, buscou-se estudar o comportamento das estruturas dos pavimentos de três trechos monitorados, na cidade de Santa Maria/RS. Para isso, foram realizados ensaios com o equipamento FWD, aplicando quatro diferentes carregamentos em cada estaca que compõe a extensão dos três trechos. Verificou-se, a partir das bacias deflectométricas e dos módulos de resiliência retroanalisados, o comportamento elástico não linear das camadas granulares (base e sub-base) dos Trechos 1 e 2, com módulo de resiliência diretamente proporcional ao incremento da tensão confinante. Os subleitos de dois trechos exibiram comportamento variado, podendo ser simplificados pela elasticidade linear, sem prejuízo considerável. O mesmo aconteceu para o concreto asfáltico do Trecho 1. Já o revestimento do Trecho 2 resultou em módulos resilientes dependentes do incremento da tensão vertical na superfície no centro da placa de carga. Em relação ao Trecho 3, os resultados, referentes apenas às medidas deflectométricas, indicaram comportamento majoritariamente próximo da linearidade em todas as distâncias de leitura avaliadas, com exceção daquela medida abaixo do centro da placa de carga. Sequencialmente aos pulsos de carga, foram determinadas também as deflexões com a viga Benkelman, objetivando encontrar uma correlação local entre os resultados obtidos a partir dos diferentes equipamentos. As bacias deflectométricas indicaram valores superiores, medidos com a viga, em relação àqueles determinados pelo FWD. Consequentemente, os módulos de resiliência foram maiores quando determinados a partir da retroanálise de leituras efetuadas com o FWD, em relação à viga Benkelman. Em paralelo, foi verificada e quantificada a influência das condições de aderência entre as camadas e da correção, total ou parcial, das bacias deflectométricas, em função da temperatura, nos módulos de resiliência retroanalisados. Constatou-se que a atribuição de aderência total nas interfaces entre as camadas reduz consideravelmente os módulos de resiliência retroanalisados dos materiais granulares. Em relação à correção de temperatura, verificou-se adequada a determinação da rigidez dos materiais granulares e subleito mediante a realização da retroanálise sem nenhum ajuste nas bacias de campo. Tomando estes valores como base, julgou-se pertinente a repetição do procedimento iterativo, com ajuste das deflexões em função da temperatura nas leituras iniciais, determinando assim o novo módulo de resiliência do revestimento.

When evaluating low volume roads (LVRs), structural capacity emphasis is minimal since deterioration typically results from environmental factors. However, in cases where LVR’s experience rapidly increased traffic loading, structural condition becomes important. The research objective was to determine whether the Light Weight Deflectometer (LWD) can be used as a structural evaluation tool for LVRs in the aforementioned conditions. This study explored the capability of LWD equipment in evaluating major factors that influence flexible pavement structural capacity: load induced deterioration, soil moisture, and asphalt temperature. Falling Weight Deflectometer (FWD) and LWD tests were performed to measure pavement structural condition. LWD was shown applicable for LVRs experiencing accelerated traffic. The LWD is portable and efficient for LVRs when high rut depths are permitted. The LWD and FWD produced similar trends. The LWD, based on this thesis, can be recommended for use in lieu of FWD to assess structural condition of LVRs for rapidly increased traffic loading.

In order to avoid the occurrence of early-age damage, cement-treated base (CTB) materials must be allowed to cure for a period of time before the pavement can be opened to traffic. The purpose of this research was to evaluate the utility of the soil stiffness gauge (SSG), heavy Clegg impact soil tester (CIST), portable falling-weight deflectometer (PFWD), dynamic cone penetrometer, and falling-weight deflectometer for assessing early-age strength gain of cement-stabilized materials. Experimentation was performed at four sites on a pavement reconstruction project along Interstate 84 near Morgan, Utah, and three sites along Highway 91 near Richmond, Utah; cement stabilization was used to construct CTB layers at both locations. Each site was stationed to facilitate repeated measurements at the same locations with different devices and at different curing times. Because of the considerable attention they have received in the pavement construction industry for routine quality control and quality assurance programs, the SSG, CIST, and PFWD were the primary focus of the research. Statistical techniques were utilized to evaluate the sensitivity to curing time, repeatability, and efficiency of these devices. In addition, the ruggedness and ease of use of each device were evaluated. The test results indicate that the CIST data were more sensitive to curing time than the SSG and PFWD data at the majority of the cement-treated sites during the first 72 hours after construction. Furthermore, the results indicate that the CIST is superior to the other instruments with respect to repeatability, efficiency, ruggedness, and ease of use. Because the CIST is less expensive than the SSG and PFWD, it is more likely to be purchased by pavement engineers and contractors involved with construction of CTBs. For these reasons, this research suggests that the CIST offers greater overall utility than the SSG or PFWD for monitoring early-age strength gain of CTB. Further research is needed to identify appropriate threshold CIST values at which CTB layers develop sufficient strength to resist permanent deformation or marring under different types of trafficking.