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Stresses in the concrete surrounding dowel bars is a major factor that contributes to transverse joint distress in jointed plain concrete pavement (JPCP). In this study, a distribution of stresses around dowel bars was analyzed with special attention to compressive and tensile stresses, which are responsible for cracks' initiation and propagation. Calculations considering diameter, spacing, and length of dowels in JPCP were made using the finite-element method (FEM). Sliding interfaces with friction that permit separation between dowels and surface concrete were modeled using the full cylindrical surface between each dowel and the surrounding concrete. Practical functional relationships among the studied parameters may be useful in the calculation of maximal stresses in concrete around a dowel bar in dependence on its characteristics. Knowledge about the mechanical behavior of dowel bars at their contact with concrete is important to develop effective doweled joints and to improve the load transfer efficiency (LTE). It was also shown that permissible tensile stresses in concrete may be exceeded for dowel diameters <0.04 m, length 0.5 m, and distances >0.30 m. Based on derived empirical equations and relationships, it is possible to calculate stresses around dowels for different diameters, length, and spacing for a selected concrete pavement. They may be useful in a design of the pavement. [ABSTRACT FROM AUTHOR]

The procedure for the design of military rigid airfield pavements contained in the Unified Facilities Criteria 3-260-02 gives the minimum thickness of airfield concrete pavements as 152 mm (6 in.). The introduction of the C-17 aircraft and the requirement of dowel bars as a joint load transfer mechanism bring into question the validity of the 152-mm (6-in.) minimum thickness. With the objective of updating such minimum thickness criteria, a full-scale test section was constructed and trafficked with loads simulating F-15, B-52, and C-17 aircraft landing gear. Evaluation of the test section performance and analysis of the strain data supported a U.S. Army Engineer Research and Development Center team recommendations that the minimum pavement thickness be increased to 203 mm (8 in.) for any doweled airfield pavement and that the minimum thickness of 279 mm (11 in.) should be required for those pavements supporting C-17 aircraft. [ABSTRACT FROM AUTHOR]

Concrete block pavements (CBP) are increasingly used in pedestrian roads and low-volume highways. Concrete block pavements experience various failure modes, including shifting, cracking, spalling, and erosion of jointing sand. One of the most important causes of failure is the interlocking with high force between weak blocks. Laying patterns affect the global and local behaviors of different block types. A simple and efficient testing program was introduced and conducted for evaluating the interlocking performance of complex block shapes and different block patterns under horizontal loading conditions. An image technique, video capturing and block movement plots, was also applied to consider the individual movement of laid blocks on a test setup. A displacement-moment (D-moment) concept was suggested to interpret the local and global behavior of different block types and patterns. Typical rectangular and shaped block types with three different laying patterns such as stretcher, basket weave, and herringbone were compared in executed experimental results and interpreted parameters, i.e., maximum force, energy, and D-moment. [ABSTRACT FROM AUTHOR]

Pavement performance models exist in various forms to cater to the pavement management agencies' needs and resources. Well-calibrated models are needed to accurately predict future pavement conditions and to forecast and prioritize confidently the future rehabilitation and maintenance expenditures. Statistical tools are commonly used to develop the performance models. These statistical models may be impractical or misleading if they do not consider experts' opinions. This paper presents a hybrid technique where statistical tools and expert knowledge are combined for the calibration of pavement performance models. This technique was validated using historical pavement condition data for continuously reinforced concrete pavements (CRCP) from the Texas Department of Transportation's pavement management information system (TxDOT-PMIS). The recalibrated CRCP performance models obtained with the hybrid technique represent an improvement when compared to the current models since they merge expert opinion and statistical analysis, which better reflect field observations regarding distress initiation, distress evolution rate, and maximum allowable amount of distress growth. [ABSTRACT FROM AUTHOR]

This paper focuses on modeling of the shrinkage stress in concrete pavements that experience nonlinear shrinkage strain through the depth of the slab. A closed form of an analytical solution of shrinkage stress is developed. In the modeling, the nonlinear shrinkage strain through the depth of the slab is divided into three components, as follows: (1) uniform, (2) linear, and (3) nonlinear shrinkage. Afterwards, the shrinkage stress resulting from each component is calculated separately. The total shrinkage stress is then obtained by summing the three stress components together. Using the model, the distribution of the shrinkage stress in concrete pavements at an early age from concrete casting is calculated and analyzed. The model results show that the developed law of shrinkage stress in pavement is consistent with the development of shrinkage strain. Within the stage of the shrinkage strain uniformly developed, a uniform shrinkage stress is expected throughout the slab. In the stage with a shrinkage strain gradient, a stress gradient is also expected. With respect to the condition that the slab top experiences drying, the distribution of the shrinkage stress along the pavement depth is apparently nonlinear and the nonlinearity is stronger in the area close to the drying surface. The maximum and minimum tensile shrinkage stresses occur at the top and bottom, respectively, of the middle section of the slab in this case. Concrete strength can significantly influence the magnitude of the shrinkage stress and its distribution in the slab. For a given age and location, a higher concrete strength corresponds with a larger shrinkage stress and stress gradient. [ABSTRACT FROM AUTHOR]

This paper focuses on modeling of the distribution of shrinkage strain in early-age concrete pavements. In the modeling, an integrative model for autogenous and drying shrinkage predictions of concrete at an early age is introduced first. Second, a model taking both cement hydration and moisture diffusion into account synchronously is used to calculate the distribution of the interior humidity in concrete. The previous two models are experimentally verified independently by a series of shrinkage and interior humidity tests on three types of concretes with different compressive strengths. Using the models, the distribution of shrinkage strain in early-age concrete pavement (with respect to drying of the pavement surface) is calculated. The model results show the development of interior humidity inside of the pavement because the concrete cast obeys a two-stage mode, i.e., a vapor-saturated stage with 100% relative humidity (Stage 1) and a stage with the relative humidity gradually decreasing (Stage 2). The duration of Stage 1 increases with respect to the location, i.e., from the slab top to bottom. Within Stage 1, a uniform shrinkage strain is expected throughout the slab. By contrast, the shrinkage gradient along the slab depth is obvious in Stage 2. The maximum and minimum shrinkages occur at the slab top and bottom, respectively. The distribution of the shrinkage strain along the pavement depth is nonlinear and the nonlinearity is strong where it is close to the drying face. Concrete strength can significantly influence the magnitude of the shrinkage strain within the slab. For a given age and location, an increased concrete strength corresponds with an increased shrinkage strain and shrinkage gradient. [ABSTRACT FROM AUTHOR]

The evaluation of the pavement preservation interventions is the most important component of a pavement management system. There is a need for a rational methodology to evaluate pavement preservation alternatives to maximize both project- and network-level benefits. Lack of adequate guidance on the timing of preventive maintenance treatments was the main motivation for this study. On the basis of different effectiveness criteria, mathematical models to estimate optimum timing (OT) of maintenance treatments are developed to alleviate surface rutting. The developed model based on the long-term benefits was found to be a rational and a practical tool to estimate OT for various maintenance treatments by adjusting its parameters. The sensitivity and practical usage of the models are demonstrated by using the SPS-3 pavement sections in the paper. Although the modeling approach uses the existing understanding, the model can estimate OT of a fix on the basis of the pretreatment pavement rutting performance, jump, and slope adjustment factors for various treatment types. The required data for various treatments can be obtained from historical performance data collected for pavement management purposes. The results show that slurry and chip seals can be applied on younger pavements when rutting is minimal. However, thin overlay applications on older pavements with higher rutting levels will maximize the long-term benefits. [ABSTRACT FROM AUTHOR]

An adequate evaluation of stress developments in concrete is essential to ensure well-performing and long-lasting portland cement concrete (PCC) pavement designs and construction. In this study, the effects of creep and built-in curling (BIC) on the stress history of PCC pavements under environmental loadings were investigated primarily through a series of field tests and numerical data interpretations. To identify the stress-dependent strain component within the in situ measured total strain, a nonstress cylinder (NC) was employed in the field tests. The identified stress-dependent strains from the field tests were converted to stresses using a step-by-step numerical method. To investigate the effect of creep on stress developments, stress histories were computed in two different ways-one with elastic analysis and the other with viscoelastic analysis-and then their difference (stress relaxation) over time was evaluated. The finding indicated that creep may be a key element in the evaluation of long-term stresses and, in turn, the design and analysis of PCC pavements. Furthermore, this study examined the impacts of BIC on the residual stresses of PCC pavements. The result showed that BIC may affect the early-age stress development, but it has little influence on the long-term environmental stress state. [ABSTRACT FROM AUTHOR]

Faulting has traditionally been collected by using manual methods, which are labor intensive, time-consuming, and hazardous to workers and drivers. Therefore, alternative methods for effectively and safely collecting faulting data are needed. With emerging laser technology originally designed for crack detection, high-resolution, full lane-width coverage, three-dimensional (3D) continuous pavement profile data can now be acquired. This paper critically assesses the feasibility of using this 3D continuous pavement profile data for measuring faulting with a special focus on accuracy and repeatability. Controlled field tests were conducted to evaluate the accuracy for faulting in different ranges. Field tests were conducted at highway speeds on I-16 in Georgia to evaluate the repeatability and feasibility of the proposed method. Results show the proposed method can estimate faulting with an average error of less than 1 mm compared with those measured using the Georgia fault meter, and it can achieve reasonable repeatability with a standard deviation less than 1 mm in repeated runs at different highway speeds. Two tests have demonstrated that it is feasible to collect faulting data using 3D continuous pavement profile data. Recommendations for future research are also discussed. [ABSTRACT FROM AUTHOR]

Pervious concrete pavement (PCP) is of significant importance in the field of stormwater management in terms of reducing runoff volume. Stormwater managers should initially ensure that PCP adequately performs over time to be able to implement it in a stormwater management system. Performance models are intended to predict the performance of an asset over its service life. To develop a performance model commonly long-term performance data are essential. No performance model has been developed for PCP to date because PCP long-term performance data are rarely available. In such a case, expert knowledge is an alternative method to collect data for developing a performance model. This research aims to develop performance models for PCP for the first time by using an integrated Markov chain technique (combination of homogenous and non-homogenous techniques) through incorporation of expert knowledge. Both deterministic and stochastic approaches are applied to build up Markov models by using expected values and the Latin hypercube simulation technique, respectively. Both approaches provide consistent results although the stochastic Markov model provides more detailed results. Short-term experimental field data are also incorporated to validate the Markov performance models. [ABSTRACT FROM AUTHOR]

Because pervious concrete pavement (PCP) has a porous structure and can percolate water to an underground layer, it has been proposed as a stormwater best management practice (BMP), an environmentally friendly product, and sustainable paving materials. This porosity makes PCP susceptible to freeze-thaw damage in cold climates. Therefore, PCP has not been widely applied and investigated in such a climate. Long-term performance data are rarely available, and no performance model has been developed for PCP to date. The main objective of this research is to integrate expert knowledge (using the Markov-chain process) and experimental data (PCP field investigations) to build a performance model for PCP through incorporation of the Bayesian technique. The combination of these sources of data is an efficient and effective approach to build a performance model for a new type of pavement, such as PCP, which has not had a long-term performance database. As a result, a robust linear performance model is developed and applied to predict the service life of PCP. The service life of PCP is estimated to be approximately nine years using the developed performance model. In general, the expert knowledge leads to more conservative results rather than experimental data. [ABSTRACT FROM AUTHOR]

Modeling of the pavement image formation process by using reflection properties of macrotexture showed that digital images of concrete pavements can be used to monitor pavement wear. The specific optical characteristics of images and the optimum camera settings that can be used for this purpose were determined by theoretically formulating the Bidirectional Reflection Distribution Function (BRDF) of surface texture with uniform color. In the analytical phase of the study, desired levels of pavement texture were generated by combining a series of 3D sine surfaces of varying wavelengths and amplitudes. The optimum specular settings of the overhead point light source and the digital area-scan camera for effective highlighting of the imaged wheel path macrotexture were determined with an analytical formulation on the basis of a simplistic and physically meaningful BRDF model. It was also shown that the images obtained by the theoretical formulation closely resemble those captured from a similarly textured experimental surface under identical lighting and imaging conditions. In particular, the pavement image formation model revealed that quantifiable changes in the brightness of images do occur because of changes in texture depth and spacing (wavelength). In the next phase of the study, the traffic-induced pavement wearing process was simulated by gradual smoothening of the modeled surfaces, and then images corresponding to each wearing stage were generated. The theoretically predicted variation of the image brightness resulting from wear was experimentally verified by using images from a gradually worn-out concrete specimen. Finally, it was illustrated how the brightness evaluation of wheel path images has the potential to be a screening tool to monitor the degradation of macrotexture and, hence, the skid-resistance of pavements at the network-level. [ABSTRACT FROM AUTHOR]

Pervious concrete pavement (PCP) has the potential to provide significant technical, economical, and environmental benefits. To better understand the beneficial impacts of PCP, its performance must be comprehensively evaluated and quantified. To evaluate the PCP performance, its pavement condition should be assessed. The primary aim of this research is to evaluate the PCP condition through incorporation of an adequate panel rating method. Two panel rating methods are evaluated for this purpose: visual digital inspection and in situ inspection. Field investigations are also conducted to record the surface distresses by describing their severity and density using the Ministry of Transportation of Ontario protocol. Finally, a model is developed and validated which relates mean panel rating (i.e., surface distress rating) to a pavement distress. It is concluded that the only significant variable (i.e., distress) in this model is raveling. [ABSTRACT FROM AUTHOR]

In traffic characterization, axle load spectra (ALS) are one of the most critical inputs in the new Mechanistic-Empirical Pavement Design Guide (MEPDG). Axle load spectra have a significant effect on predicted pavement performance and, thus, the design life. Typically, axle load spectra as measured by weigh-in-motion (WIM) systems are assumed to have adequate data quality and accuracy. In fact, the quality of WIM-based data has inherent uncertainties attributable to inaccuracy and systematic bias. Whereas WIM data accuracy depends on the sensor technology, calibration errors and drift over time may introduce a systematic bias. This technical note investigates the effect of axle load measurement bias on pavement design for flexible and rigid pavements. The results show that negative bias in axle load measurements significantly affects cracking performance for both pavement types. The bias is more critical for rigid pavements with thinner slabs. Therefore, a measurement bias limit of less than ±5% should be required to ensure that both flexible and rigid pavements have adequate design reliability against cracking. That the WIM scales be calibrated periodically to prevent a high negative bias is strongly recommended. [ABSTRACT FROM AUTHOR]

Pavement overlay is the most efficient form of material sustainability in road rehabilitation. In the United Kingdom and, perhaps, in most countries there is no standard approach for calculating the residual life of an existing pavement that can then be used to calculate the required overlay thickness to cope with future traffic loading. This paper will discuss the process for determining most of the important parameters used in overlay design. These parameters are traffic loading, layer thickness, stiffness modulus, interface condition, and fatigue properties. The discussion is aimed at critiquing the practice in the evaluation of these parameters by many designers. The paper draws attention to the common practices and methodology in the United Kingdom. It may not present a full rational approach but will certainly enhance the thinking in the field. [ABSTRACT FROM AUTHOR]

In practice, it has been observed that the method of pervious concrete void maintenance depends on which machines or vehicles the owners have available. This research compares the abilities of three common municipal utility vehicles-a vacuum truck with a flexible, 200-mm (8-in.) hose; a vacuum street sweeper; and a regenerative air street sweeper-to remove clogging material from the voids of in-service pervious concrete pavements. By using optical microscopy, it was found that clogging materials rarely migrate into voids deeper than 12.7 mm (1/2 in.) from the surface. Furthermore, all three machines were able to remove clogging materials that were located within 3.18 mm (1/8 in.) of the surface. The clogging material that was located deeper than 3.18 mm (1/8 in.) remained within the voids but was likely disturbed by either the suction or the forced air of the maintenance vehicles. [ABSTRACT FROM AUTHOR]

To expand the applications of pervious concrete, additional research and testing must be conducted as to its structural performance. Distress surveys were performed on two field installations of pervious concrete subjected to equivalent traffic stresses as some collector streets in use for 20 years. The results of the distress survey were then used to calculate the pavement condition index (PCI) using the procedure from ASTM D6433. The PCI rating was considered to be a quantification of structural performance. The high PCI ratings of the thicker pervious concrete sections indicated that pervious concrete, when properly designed, is capable of being used for most residential streets and many collector streets for typical design life durations (20-30 years) while exhibiting satisfactory structural performance. [ABSTRACT FROM AUTHOR]

Steel-fiber reinforced concrete (SFRC) brings favorable properties to concrete pavements. The use of the material is limited by the lack of an appropriate analysis method. This paper is the second in a series of two aimed at providing a modeling approach, which can be used to model the behavior of SFRC concrete and SFRC ground slabs. In this paper, a finite-element model, capable of simulating the nonlinear behavior of the SFRC slab, is proposed and compared with the slab's experimental response. An approximate model describing the behavior of the support layers is developed using results from a plate-bearing test. The same support model is adopted for the analysis of the combined structure of the slab and the support. The material model developed and tested in the first paper, for the SFRC containing 15 kg/m3 of steel fiber, is adopted for the analysis of the SFRC slabs. In addition, a parameter study is conducted to investigate the influence of concrete strength, steel-fiber content, and the support stiffness on the load displacement (P-Δ) response of SFRC ground slabs. [ABSTRACT FROM AUTHOR]

Although pervious concrete material properties, mix design, and storm water applications are well documented in the literature, the structural behavior of pervious concrete pavement systems has not been investigated. A parking lot was constructed in which traditional impervious concrete was used on half of the parking lot and pervious concrete was used on the other half. The traditional concrete layer was placed on natural subgrade. The pervious concrete portion was divided into two sections with two pervious concrete mixtures and aggregate base thicknesses of 300 and 450 mm. To better understand the behavior of traditional and pervious concrete pavement systems of the parking lot, the subgrade soil properties were characterized by using plate load testing and nuclear density gauge. Furthermore, the aggregate base layers used in the pervious concrete systems were characterized by using plate load testing. After constructing the parking lot, falling weight deflectometer (FWD) testing was performed on the traditional concrete and the two pervious concrete pavement systems. In addition to summarizing the subgrade and base material properties, this paper compares the response of the three pavement systems during FWD tests. Furthermore, artificial neural network-based backcalculation models were used to better understand the response of the three pavement systems. FWD results show that a pervious concrete pavement system with 450-mm aggregate base experiences smaller measured deflections and better uniform support than the traditional concrete pavement system. [ABSTRACT FROM AUTHOR]

Curling stresses of concrete pavement can be very damaging, and reducing the temperature swings would be very beneficial. This study includes a field instrumentation effort with pavement temperature sensors to quantify the thermal behavior of concrete pavement with and without an open-graded asphalt rubber friction course. The study shows a nonlinear temperature profile across slab thickness, with a large change in temperature between day and night at the top of the concrete slab, and little change at the bottom of the slab. Adding an open-graded friction course over the concrete pavement reduces the temperature fluctuation between day and night as a result of the aeration effect, which is increased by traffic. A three-dimensional (3D) finite-element analysis with a nonlinear temperature gradient shows that adding the friction course reduces the curling stresses in the summer. Furthermore, since traffic increases the aeration effect, sections without traffic show lower effect of friction course on reducing the temperature differentials between the top and bottom of the slab. [ABSTRACT FROM AUTHOR]

Slab curvature, which represents the response of concrete pavement slabs to environmental loads, influences the location and magnitude of critical slab stresses and affects long-term pavement performance. The purpose of this study was to measure the changes in temperature and moisture profiles in a newly constructed concrete pavement and to determine both the overall deformed shapes of the slabs as well as the relative contributions of built-in and transient environmental effects over time. Data were collected from an instrumented jointed plain concrete pavement (JPCP) over a 2-year period. Slab curvatures were computed or predicted using measurements of temperature and moisture conditions in the slab, static strain measurements, and pavement surface profile measurements. It was found that the additional restraint provided by the dowel and tie bars does not appear to significantly reduce slab curvature resulting from daily temperature fluctuations or from reversible drying shrinkage. It does have a substantial effect on reducing slab curvature attributable to long-term drying shrinkage. It was also found that the Mechanistic-Empirical Pavement Design Guide default value is close to that measured in this study for the restrained slab but does not appear to be appropriate for unrestrained (i.e., undoweled) slabs. [ABSTRACT FROM AUTHOR]

State highway agencies have been experimenting with new concrete mixtures and pavement design features for improving the behavior and performance of concrete pavements. This paper presents the results of a field study undertaken in Maryland with alternative concrete mixtures. The objective of the study was to evaluate the in-place material properties for three concrete mixtures: a control, a fiber-reinforced, and a low-shrinkage concrete mix. Field instrumentation was used for monitoring the deflections and strains of the concrete slabs built with these concrete mixtures. Nondestructive testing (NDT) and back-calculation analysis were then used to evaluate the in situ material properties immediately after construction. Although traditional back-calculation analysis is based primarily on deflection measurements, in this study an iterative approach using NDT methods and measured strain and deflection data was employed for estimating the in situ modulus of subgrade reaction, k. This analysis provided a base model for future comparisons of the behavior and performance of the pavement test sections after prolonged exposure to in-service loading conditions. [ABSTRACT FROM AUTHOR]

The assumption of a linear temperature change through the slab depth has been overwhelmingly used in pavement analysis since Westergaard proposed a curling solution for rigid pavements. However, the actual temperature profiles through the slab thickness are primarily nonlinear. These nonlinear temperature profiles produce stresses that can be divided into three components: a uniform temperature stress, an equivalent linear curling stress, and a nonlinear self-equilibrating stress. It is the self-equilibrating stress component that often goes unaccounted for in concrete pavement stress prediction and can significantly affect the tensile stress magnitude and critical location. This paper presents a solution for a piecewise method and proposes a simplified method termed NOLA, or nonlinear area, that easily captures the effect of temperature nonlinearity on rigid pavement responses. The proposed NOLA method enables the use of a three-dimensional temperature frequency distribution that allows simple postprocessing of rigid pavement curling stress solutions derived from a linear temperature assumption. The impact of accounting for self-equilibrating stresses in terms of projected fatigue damage levels and critical cracking locations is also explored using a mechanistic-based rigid pavement analysis program called RadiCAL. [ABSTRACT FROM AUTHOR]

Two specific three-dimensional finite-element models are presented for making an evaluation of the maximum stresses at critical locations in concrete slabs (i.e., at the interior and edge) that is superior to the classic approach of the approximate methods. Concrete airport pavements with square-shaped slabs are studied. A homogeneous, isotropic elastic half-space is assumed as a subgrade (foundation) model so that the influence of variation in Young’s modulus is examined in contrast with Winkler’s reaction modulus. The effects of two aircrafts (A380 and B747), different subgrade bearing capabilities and temperature gradients (Δt), are investigated. Combined stresses due to aircraft load and temperature gradient (Δt) are accurately estimated by means of a finite-element software and compared to their separate actions. As a consequence the incorrect applicability of the principle of effects superposition, which is due to the support soil that is nonresistant to tensile stress, is quantified. Moreover, the difference in the values of the stresses due to the two different aforementioned aircrafts is calculated. A simplified method for predicting maximum stresses is also derived from the results of the finite-element software. This predictive method represents a useful tool for a faster estimation of stresses at a preliminarily design level. The proposed equations make adjustments to Westergaard’s load stress model and Eisenmann’s temperature stress model necessary, as they also do for the separate actions of load and Δt. The procedure makes use of dimensionless variables so that it may also be extended to different square-slab dimensions. [ABSTRACT FROM AUTHOR]

Digital image-based automated pavement crack detection and classification technology has seen vast improvements in the recent years. Although crack lengths and widths can be evaluated using state-of-the-art software with a reasonable accuracy, no reported evidence is found in extending this technology to evaluate crack depths. As a supplement to the existing technology, additional information relevant to pavement crack severity could be revealed by the optical modeling of the image formation process and the subsequent analysis of the variation in pixel intensity profiles within images. A preliminary study was carried out to model the digital image formation of cracked concrete pavements based on the bidirectional reflection distribution function. This study was specifically focused on the optical modeling of shallow longitudinal and transverse cracks as well as joints of concrete pavements using the variation of reflection properties at surface discontinuities. Surface discontinuities were considered to be of regular geometrical shapes for simplification. The new image formation model revealed a definitive relationship among the crack widths and depths and the maximum pixel intensity contrasts seen in the images of the cracks. The model calibration involved the selection of reflection properties to match the pixel intensity contrasts across model generated images of cracks and joints against those of identical cracks formed in concrete pavements. The model predictions of crack depths were also verified using actual crack data not used in the calibration. Finally the usefulness of the calibrated model in evaluating the depths of shallow cracks and differentiating cracks from joints and other surface irregularities in concrete pavements is illustrated. [ABSTRACT FROM AUTHOR]

This paper presents a finite-element model of a jointed concrete pavement with aggregate interlocking load transfer system. Interlocking mechanism has been modeled by a set of discrete springs. A new parameter “modulus of interlocking joint (Kj)” has been introduced to represent the load transfer characteristics of the interlocked joint. Guidelines have been proposed for the selection of the modulus of interlocking joint as a function of aggregate size and joint opening. Stiffness values for the linear springs can be selected using the modulus value Kj. The numerical model, with the joint spring stiffness values selected from the present guidelines, has been validated with experimental results available in literature. [ABSTRACT FROM AUTHOR]

In a jointed concrete pavement, the dowel bar system and the aggregate interlock are two mechanisms for transferring wheel loads from one panel to the adjacent panel. The aggregate interlocking load transfer mechanism is effective for narrow joints while the dowel bar system works well for both narrow and wider joints. This paper examines the effects of different parameters on load transfer efficiency of a joint with the help of a three-dimensional finite-element model for the analysis of a dowel-jointed concrete pavement. The model was compared using experimental data available in the literature. The group action of the dowel bar system was also examined and useful relationships have been developed for estimation of the relative load shared by the individual dowel bars. These relationships will be useful in the design and evaluation of dowel jointed concrete pavements. [ABSTRACT FROM AUTHOR]

Porous pavements are asphalt or concrete pavement surfaces designed to allow moisture to flow through the surface into an underlying reservoir or into the subgrade soil. Porous pavements prevent pollutants from entering into the water table and therefore, are considered sustainable construction. However, porous pavements eventually fill with debris and get clogged, preventing water infiltration. Thus, the greatest barrier to the use of porous pavements is susceptibility to clogging. Therefore, a major maintenance objective for porous pavements is to prevent clogging of the void spaces within the pavement. This paper describes a potential process of removing particles trapped in the pores of the pavement by flushing water from the bottom to the top of the pavement. Four variables were evaluated in this laboratory experiment to determine effects on particle removal. These were: (1) water pressure; (2) clogging material; (3) pavement porosity; and (4) number of flushes. Results indicate the reverse flush process was effective on both types of clogging material evaluated, was independent of the pavement porosity, and worked for the lowest pressure tested. [ABSTRACT FROM AUTHOR]

Development of an adequate performance model based on an appropriate condition index has been a major challenge for engineers particularly in case of a new type of design such as pervious concrete pavement structures (PCPSs) which suffer from limited long term performance data sets especially in colder climates. Soft computing techniques are significantly efficient at dealing with subjective, incomplete, and limited data. This paper proposes three most effective soft computing methods: fuzzy sets, the Latin Hypercube Simulation technique, and the Markov Chain process. A novel comprehensive condition index based on severity, density, and weighting factors of distresses occurring on PCPS has been developed incorporating fuzzy sets. A combination of homogeneous and nonhomogeneous Markov Chain has been applied to develop performance models. Transition probability matrices are presented using probability distribution functions rather than single values. A simulation technique is then used to incorporate the probability distribution function operations to compute the future condition of the pavements. The future performance of the pavements is expressed by both single expected values and suitable probability distribution functions. Ultimately, a probabilistic versus deterministic performance curve is presented. [ABSTRACT FROM AUTHOR]

Two types of analysis were conducted to examine the impacts of midcentury scenarios of anthropogenic climate change on flexible pavement infrastructure in southern Canada. An analysis of deterioration-relevant climate indicators at 17 southern Canadian sites revealed that over the next 50 years low temperature cracking will become less problematic, structures will freeze later and thaw earlier with correspondingly shorter freeze season lengths, and higher extreme in-service pavement temperatures will raise the potential for rutting. Pavement performance simulations conducted using the mechanistic-empirical pavement design guide and data from the Canadian long term pavement performance program for six of these sites also suggest that rutting issues will be exacerbated by climate change and that maintenance, rehabilitation, or reconstruction will be required earlier in the design life. While the simulated effect of climate change was found to be modest, both in absolute terms and relative to variability in pavement structure and baseline traffic loads, pavement engineers would benefit by incorporating longer time series of weather and climate in their designs. Although the analysis was conducted for southern Canada, many of the findings and impacts may be similar for the northern United States. [ABSTRACT FROM AUTHOR]

Accurately predicting the stiffness of asphalt pavements is difficult due to the complex behavior of materials under various loading, pavement structure, and environmental conditions. This study explores the utilization of the artificial neural network (ANN) in predicting the stiffness behavior of rubberized asphalt concrete mixtures with reclaimed asphalt pavement (RAP). A total of 296 asphalt mixture beams were constructed from two different rubber types (ambient and cryogenic), two different RAP sources, and four rubber contents (0, 5, 10, and 15%). All samples were tested at two different testing temperatures of 5 and 20°C. The regression statistical method was used to predict the stiffness behavior of these mixtures via the 7 input variables covering the material engineering properties of the asphalt beams. In addition, the data were organized into 5 independent variables and one dependent variable (the stiffness values of the modified mixture beams) in ANN models. Results showed the ANN techniques to be more effective in predicting the fatigue life of the modified mixture than traditional regression-based prediction models. [ABSTRACT FROM AUTHOR]

Gravel aggregates have been used extensively in the Houston District for continuously reinforced concrete (CRC) pavements construction for many years. However, some of these pavements have been subject to early-age delamination and eventual spalling damage. A series of studies since the early 1990's have been conducted to gain a better understanding of mechanisms, material properties, and construction practices related to delamination and spalling. This paper describes a systematic and methodical approach for selecting construction measures to counter the negative effects of using gravel aggregates in concrete paving as it pertains to minimizing early-age delamination distress. The approach was developed based on laboratory measures and practices, numerical approaches for assessing delamination potential, and test sections established in the Houston District, Texas. The testing programs in the laboratory and the field, as well as the analytical results, are presented in this paper. The analysis of the results leads to a step-by-step approach for evaluating and selecting construction measures. [ABSTRACT FROM AUTHOR]

Initiatives are underway to implement the new mechanistic-empirical pavement design guide (MEPDG) in Iowa. This paper focuses on the sensitivity study of jointed plain concrete pavements (JPCP) and continuously reinforced concrete pavements (CRCP) in Iowa using the MEPDG software. In this comprehensive study, the effect of MEPDG input parameters on the rigid pavement performance is evaluated using the different versions of the MEPDG software (0.7, 0.9, and 1.0) available to date. Representative JPCP and CRCP sections in Iowa were selected for analysis. Based on the sensitivity plots obtained from the MEPDG runs, the design input parameters were categorized as being most sensitive, moderately sensitive, or least sensitive in terms of their relative effect on distresses. In this study, the curl/warp effective temperature difference, the PCC coefficient of thermal expansion, and PCC thermal conductivity had the greatest impact on the JPCP and CRCP distresses. Compared to the original version of MEPDG software (Version 0.7), the updated versions (Versions 0.9 and 1.0) are more sensitive to inputs, which shows the evolution of engineering reasonableness. [ABSTRACT FROM AUTHOR]

In cement concrete pavements, a separation membrane is usually placed between the base and the concrete slab to make the interface condition smooth. A smoother interface condition offers less resistance to the movement of the slab caused by variation in temperature and moisture. However, a rough interface is useful in reducing load associated stresses. As the degree of bonding between the slab and the foundation influences the friction mobilized at the interface, a realistic assessment of interface friction is necessary for rational design of concrete pavements. In the present study, the interface friction of typical concrete pavements was evaluated by performing a number of push-off tests. For this purpose, concrete slabs were laid over different types of bases with smooth as well as rough interface condition. A parametric analytical study was conducted using finite-element method to evaluate the effect of different interface conditions on the critical responses of pavement subjected to the combined action of axle load and temperature variation. [ABSTRACT FROM AUTHOR]

Most rigid-pavement design methods in use today adopt the Westergaard’s approach that characterizes pavement foundation by k, the modulus of subgrade reaction. k is measured by a standard plate loading test conducted in the field. However, since this test is elaborate, expensive, and time consuming, the k value of a subgrade soil is usually estimated from other soil properties. In this regard, the relationship between k and the modulus of elasticity E of the soil is of special interest. This is because E is a fundamental engineering property and that there exists various test methods for determining E either in the field or in the laboratory. This paper proposes a procedure to estimate k from E by establishing an equivalency between two theoretical pavement models, a model of pavement slab supported by an elastic solid foundation (termed the E model) and a model of pavement slab supported by a dense liquid foundation (termed the k model). Instead of matching the k and E models directly as is done in currently available k-E relationship models, this study proposes to define an equivalent k model and an equivalent E model, separately, with respect to actual rigid pavements. The equivalency is established using back-calculation analysis based on load-deflection considerations. Using the deflection test data of the long-term pavement performance database, it is found that there exists a relationship between the radii of relative stiffness of the two theoretical systems, and this relationship can be used to estimate k from a given E value. [ABSTRACT FROM AUTHOR]

Since reflective cracking is related to both the existing pavement condition and the overlay material, appropriate tools are needed to characterize both properties. The rolling dynamic deflectometer (RDD) was employed to measure the continuous deflection profiles that relate to vertical movements of the underlying joints and cracks. An overlay tester (OT) was utilized to characterize the asphalt mix’s ability to resist reflective cracking. The reported threshold values were employed in the study that include: (1) W1–W3=6.5 milsfor composite pavement with old asphalt concrete (AC) overlay; (2) W1–W3=5.5 mils for exposed concrete pavement; and (3) 700 cycles of the OT were employed to evaluate six field rehabilitation projects (SH12, IH20, US96, SH73, SH225, and IH44). It was found that although there were severe transverse cracks and spalling on US96, all W1–W3 deflections were less than 5.5 mils, indicating low risk for reflective cracking. A stone-mastic asphalt (SMA) layer was placed 3 years ago and the performance is excellent. There are no visible cracks or distresses. The SMA was tested with the OT and exceeded 700 cycles (excellent property on resisting reflective cracking). For comparison, there were severe reflective cracks within 4 years on SH225 even with good underlying support and low vertical movements (all W1–W3 deflections less than 6.5 mils) on the jointed concrete pavement (JCP). The reflective cracks were due to a stiff/brittle mix (with OT life of 2 cycles) used on top of the JCP. Dowel bar retrofit (DBR) and full depth repair did improve load transfer and lowered W1–W3 deflections on the SH73 project. After 10 years of service, those locations had minor cracks, as opposed to severe reflective cracks in sections without DBR or full depth repair. Based on the results obtained, the RDD, OT, and the three threshold values provide an objective evaluation that correlates to field performance data. It is strongly recommended that both tools be used for the rehabilitation of concrete pavement with an AC overlay to evaluate the potential for reflective cracking. [ABSTRACT FROM AUTHOR]

While there has been a great deal of research conducted on concrete pavement performance and deterioration under static loads, only very limited research has been carried out on its dynamic response. Furthermore, opinions differ as to which type of loading (static or dynamic) results in greater values of slab deflection or flexural stress. In the present study, a test section consisting of two jointed reinforced concrete pavement and two jointed plain (unreinforced) concrete pavement was constructed and tested under both quasistatic and dynamic truck loads. Truck load was allowed to wander at predetermined locations on the instrumented pavement at speeds from 5 to 55 km/h. Strain gauges and displacement transducers were installed along the test section to monitor the pavement responses. Time history responses of the test section were recorded and used to validate a finite-element model developed in the ANSYS platform for further sensitivity study on those parameters affecting the dynamic response of concrete pavements. Results indicate the significance of dynamic amplification in concrete pavement design. [ABSTRACT FROM AUTHOR]

This paper presents an investigation of the subsurface drainage features of the test pavement at the U.S. 50 joint sealant experiment near Athens, Ohio. The concrete pavement incorporates a 100 mm(4 in.) thick open-graded base, whose drainage capabilities are assessed using the software DRIP 2.0, distributed by the Federal Highway Administration. It is found that the specified base thickness and permeability combination do not meet federal guidelines, evidently because no design calculations had been performed prior to construction. A field inspection of the test pavement drainage features revealed that these had received very scant to no maintenance. Drainage outlets were unmarked, overgrown by vegetation, difficult to find or sometimes missing, often clogged, and occasionally damaged. A literature review indicated that such problems are endemic in many states and point to an under appreciation of proper drainage in concrete pavements. [ABSTRACT FROM AUTHOR]

Reflection cracking is a common distress in asphalt overlays on cracked concrete pavements. Rubblization, which can minimize reflection cracks, has been used as an efficient rehabilitation method for aged concrete pavements in the United States. When applying the rubblization method, it is typical for the upper layer of aged concrete pavement to be rubblized to 40–70 mm in size, while the lower layer of the aged concrete pavement remains at a larger size, often over 300 mm. For thick concrete slabs, it is difficult to rubblize the entire depth of thick concrete slabs in terms of both construction and cost. The high impact energy necessary to rubblize the entire depth may cause degradation of the structural capacity of the pavement substructure. Korean highways are typically paved with thick concrete pavement slabs (30–33 cm concrete slabs with 15 cm lean concrete bases on granular subbases). This study conducted in Korea determined the minimum depth of effective 40–70 mm size rubblization to deter a reflection crack. An indoor simulation experiment was designed to assess the effects of the depth of the 40–70 mm rubblized layer on the prevention of reflection cracks. The experiment simulated two modes of reflection crack initiation: Mode I (bending failure) and Mode II (shear failure). Modes I and II tests were carried out for rubblization depths of 0, 10, and 20 cm. Reflection cracking did not occur with the simulated rubblization depths of 10 cm or 20 cm. [ABSTRACT FROM AUTHOR]

An experimental analysis of response data from actual aircraft passes at Denver International Airport was conducted to determine the effect of the slab-base interaction on concrete pavement responses. This analysis was divided into three parts: gap analysis from deflection data, interface analysis from paired strain data, and comparison between predicted and measured strains. The gap analysis showed that gaps exist between the slab and base, depending on the temperature differential and slab location. The gap analysis also indicated the existence of an effective built-in temperature difference. Despite the indication of gaps beneath the slab, the paired strain data analysis indicated contact friction or bonding action under wheel loading. The greatest contact friction occurred at the slab interior, followed by doweled transverse joints and transverse dummy joints, whereas an unexpected full-slip condition was found at tied longitudinal joints. The comparison between measured and predicted strain confirmed contact friction is developed under aircraft gear loading. [ABSTRACT FROM AUTHOR]

Reflective cracking through jointed concrete pavement overlays has been a persistent problem. Several different rehabilitation strategies have been used in Texas. This paper is a summary of the performance of strategies used in the past 10 years. The performance of the crack-retarding grid has been disappointing as it has been related to several premature failures. Only one project has realized a benefit of the crack-retarding grid, where the reflective cracking was delayed by about 1 year. The writers believe the small openings in the crack-retarding grid and the lack of an effective bond may be the causes of the layer separation. A proprietary crack-retarding asphalt material has been performing well over two years of monitoring. In one experimental project, 100% of the cracks reflected through conventional overlay material in the first year. Both Petromat fabric underseal and crack-retarding asphalt material have been performing satisfactorily to retard reflective cracking. However, there is a large cost difference between these two treatments. Seven experimental treatments on a major section of US 59 were evaluated. The worst-performing section on the US 59 project was the break-and-seat method, which failed due to weak subgrade support. The weak subgrade is unable to support cracked concrete, which leads to a rocking action under traffic loads. It is concluded that for future projects, the break-and-seat method should not be applied on subgrade with a dynamic cone penetrometer penetration rate exceeding 25 mm per blow. A flexible base overlay with thin asphalt surfacing and the Arkansas (large stone) mix have performed well. Flexible base overlays were able to absorb the joint movement and eliminate the reflective cracking. The flexible base should be of top quality with very low moisture susceptibility. In Texas, this involves specifying a Texas triaxial Class 1 material with classification of “good” in suction/dielectric tests. It is also critical to provide an effective seal for the flexible base. A chip seal followed by a thin 75-mm hot mix layer is recommended. [ABSTRACT FROM AUTHOR]

This paper introduces an integrated approach to the development of construction and traffic management plans for the reconstruction of high-volume urban freeways. The Devore project, which rebuilds a 4.2 km stretch of the deteriorated concrete pavement (truck lanes) on Interstate-15 (I-15) in San Bernardino County in southern California, is used as a case study. Alternative closure timing, closure duration, and number of closed lanes were compared to identify the best rehabilitation strategy for the Devore reconstruction project. The perspectives of construction schedule, traffic inconvenience (road user cost and maximum delay), and agency costs were considered. The analysis concluded that full closure of one roadbed with counter-flow traffic during repeated three or four continuous weekdays, utilizing round-the-clock reconstruction operations, was the best strategy for both the public and the sponsoring agency. A delay in the start of construction from Spring to Fall 2004 is expected to cause a 5% seasonal traffic increase, which will result in a $4.5 million increase in road user cost and a 20% increase in maximum queue delay per closure. [ABSTRACT FROM AUTHOR]

This paper describes the findings of a study carried out for evaluating the performance of cast in situ concrete block pavements for low volume roads. Concrete is filled up into a formwork of cells 150 mm×150 mm×100 mm made up of thin plastic sheets and compacted to form flexible interlocked concrete blocks. Details of a laboratory investigation on the proportioning of mixes and the evaluation of the strength of different mixes are presented. Cast in situ block pavements were constructed and tested in an accelerated pavement test facility. It was found that the blocks became interlocked and that the block pavement displayed a very little amount of rutting along the wheel path. A falling weight deflectometer test indicated that the equivalent elastic modulus of cast in situ concrete blocks was over 2,500 MPa. An example of pavement design using cast in situ concrete blocks is presented. [ABSTRACT FROM AUTHOR]

Crack width is a key pavement performance parameter in continuously reinforced concrete pavements (CRCP) because it controls the shear transfer between adjacent slabs. Several full-scale experimental sections were instrumented and tested to determine the crack width (CW) by means of observing variation in crack closing caused by combined load and temperature changes. The mechanical loads were applied to the CRCP section with an accelerated pavement testing machine while horizontal crack movement was acquired at various depths along the vertical edge of the slab. The load and temperature spectra tests found that the CW varied along the depth of the slab and was significantly affected by changes in the average pavement temperature and the temperature differential through the depth of the slab. Since the CW is dependent on the slab’s temperature profile and vertical depth from the surface, the measured CW was reported at the level of the steel and at a standard temperature condition. [ABSTRACT FROM AUTHOR]

In an attempt to better understand and predict rigid pavement behavior, the incorporation of material and climatic factors in mechanistic-empirical design methods are fast becoming standard in the United States. With the wide variety of climatic regions found in California, the inclusion of localized factors can have a profound effect on the critical distresses and life of the pavement. Permanent built-in curling from construction temperature gradients and differential shrinkage can have a considerable effect on the location and magnitude of concrete fatigue damage. A mechanistic analysis was developed employing an influence line approach in conjunction with Miner’s Hypothesis to calculate the fatigue damage at numerous locations in the concrete pavement slab for typical California rigid pavement sections. Concrete fatigue transfer functions which account for stress range or maximum stress, were used to predict the location and magnitude of critical damage. Results show that the critical cumulative damage levels and locations are highly influenced by factors such as effective built-in temperature difference, steer-drive axle spacing, load transfer level, lateral wheel wander distribution, and climatic region. For slabs with built-in curling and a combination of the aforementioned variables, top-down and bottom-up transverse, longitudinal, and corner cracking can occur. These predicted fatigue failure modes correspond well to the wide variety of observed fatigue cracking on existing California rigid pavements. [ABSTRACT FROM AUTHOR]

Instrumented concrete slabs were constructed in Palmdale, Calif., in order to fail the slab sections under accelerated pavement testing. Prior to fatigue failure testing, these slabs were monitored over 24 h cycles without load, and under a slow-moving 40 kN rolling wheel load. Slab temperature profiles, edge and corner deflections, and interior vertical deflections were collected at 2 h intervals. A finite element program was used to analyze the deflection data and calculate an effective built-in temperature difference (EBITD) through the slab, which represented the combined effects of nonlinear “built-in” temperature gradients, irreversible shrinkage, and creep. Differences in restraints (from adjacent slabs, shoulder, and base friction) and variability in material and structural properties resulted in wide variation in the measured EBITD. High EBITD values (-20 to -35°C) were observed for sections with low restraint, and low to moderate EBITD values (0 to -20°C) observed for sections with higher restraint. [ABSTRACT FROM AUTHOR]

A concrete slab was constructed at Texas A&M University to investigate environmental effects in terms of temperature and moisture effects on the behavior of jointed plain concrete pavements. The slab behavior was delineated relative to equivalent linear temperature and humidity differences as a function of time. As expected, the trends of these differences were found to relate with the trends of ambient temperature and relative humidity. The slab had daily periods of tensile and compressive strain corresponding to the daily changes in the ambient temperature and relative humidity. Furthermore, the trends in the slab displacements were clearly dependent upon the changes in ambient temperature and slab temperature gradients. Drying shrinkage and creep strains primarily in the vicinity of the top surface appeared to cause an overall shift in the slab movements. This shift manifest in both the strain and vertical displacement of the slab was determined from data collected up to 2 years after placement of the concrete. [ABSTRACT FROM AUTHOR]

Field data from a section of heavily instrumented concrete pavement on the Gene Snyder Freeway (I-265), Louisville, Kentucky were closely examined. To predict the mechanical behavior of the rigid pavement, a three-dimensional (3D) finite element pavement model was developed using the ANSYS program. The 3D finite element model was successfully implemented for predicting the stresses and strains in the concrete slabs. An important conclusion of this study was that temperature-induced pavement responses were more significant than traffic-induced responses. This is a very important finding, and can potentially have serious design implications. Applications of this work may include the development of a more scientifically based rigid pavement design and analysis systems for Kentucky conditions. Results of this study will serve as background information for the implementation of new pavement design procedures in Kentucky. [ABSTRACT FROM AUTHOR]

Seal coating is a preventive maintenance technique typically applied to low volume asphaltic concrete pavements to defer the need for major rehabilitation. Past research on seal coating effectiveness has generally indicated that both short- and medium-term benefits are associated with this treatment. Regarding the relationship between short-term effectiveness and initial pavement condition, results of past studies have been equivocal: some studies found that lower levels of initial pavement condition are associated with lower effectiveness after seal coating treatment, while results of other studies were to the contrary. This paper, in developing seal coating effectiveness models, explains the findings of both schools of thought. The paper finds that the direction of seal coating effectiveness in relation to the initial pavement condition depends on the measure of effectiveness used: pavements in relatively poor condition were generally associated with higher performance jumps but lower reductions in their rates of deterioration. This implies that the greater benefits of seal coating on relatively good pavements, compared to relatively poor pavements, are observed particularly when considered over an extended period of time. On the other hand, pavements in relatively good condition were generally associated with lower performance jumps but greater reductions in their deterioration rates. In the course of the study, the paper selects appropriate measures of seal coating effectiveness, calculates values of each measure using data on Indiana pavements that received this treatment, determines the statistical significance of such effectiveness values, and finally estimates seal coating effectiveness as a function of pavement and/or treatment attributes. In the computation of effectiveness values, due cognizance is given to the critical issue of relative timing between the application of the seal coating treatments and annual performance monitoring. [ABSTRACT FROM AUTHOR]

Practically all current design for and analysis of thermally induced stresses in rigid pavements are based on an assumed linear temperature distribution across the thickness of the pavement slab. Actual temperature distributions across the thickness of a pavement slab are not linear, and studies have shown that the errors in the computed maximum warping stresses caused by the assumption of linear temperature distribution could be as high as 30% or more. Finite-element models have been developed to analyze the effects of nonlinear temperature distribution. These are numerical methods and are generally not user friendly, as they require skills to design the finite-element mesh and good judgment to ascertain convergence of the solutions. This paper describes a closed-form theoretical model to compute the warping stresses caused by a nonlinear temperature distribution. The model is derived based on the Reissner thick-plate theory for a concrete pavement slab with four free edges resting on either a Pasternak or a Winkler foundation. The nonlinear temperature distribution across the slab thickness is divided into three components that are analyzed separately. The final solutions are obtained by superposition of the stresses caused by the three components of temperature distribution. [ABSTRACT FROM AUTHOR]