Jacob E. Hiller

Simplified nonlinear temperature curling analysis for jointed concrete pavements

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.

Sensitivity of flexible pavement design to Michigan’s climatic inputs using pavement ME design

Abstract Climate condition is an important factor that affects the performance of pavements and distress predictions using mechanistic-empirical analyses. This study aims to analyse the sensitivity of flexible pavement distress predictions to climatic inputs using the AASHTOWare Pavement ME Design software in the state of Michigan. Typical traffic parameters, pavement structures and material properties for the state of Michigan were used as inputs for the analysis of flexible pavement performance. Six representative sites geographically distributed throughout Michigan and two typical traffic levels (high and medium) were incorporated in a comprehensive analysis of the effects of climate on flexible pavement performance predictions. A normalised sensitivity index was adopted to quantitatively evaluate the sensitivity of distress predictions to the five individual climatic variables: temperature, wind speed, precipitation, percent sunshine and relative humidity. The results of this study showed that the prediction of flexible pavement performance in Michigan is most sensitive to changes in temperature with other climatic factors such as wind speed, percent sunshine, precipitation and relative humidity impacting predictions to a lesser extent. Higher temperature and percent sunshine at a given location increased rutting and International Roughness Index (IRI) predictions, but reduced the likelihood of fatigue cracking. An increase in wind speed or precipitation reduced rutting and IRI predictions, but increased fatigue cracking predictions. Ambient relative humidity had a negligible effect on all flexible pavement distress predictions. These findings provide insights into the sensitivity of flexible pavement designs under different climate conditions. The sensitivity results are also beneficial for the Michigan Department of Transportation as they seek to improve the existing climatic files in PMED through evaluation of new climatic data sources.

Effects of mean annual temperature and mean annual precipitation on the performance of flexible pavement using ME design

The purposes of this study were to establish the difference between empirical and mechanistic–empirical approaches in the flexible pavement design and to quantify the effects of mean annual precipitation and temperature on the flexible pavement distresses using the Mechanistic-Empirical Pavement Design Guide (MEPDG) software. Seventy-six specific locations from 13 states throughout the USA were selected based on different climate conditions using virtual climate stations based on the interpolation from the nearest weather stations prior to meeting the objectives. Subsequently, analysis was conducted based on the predicted distresses, including longitudinal cracking, transverse cracking, alligator cracking, asphalt concrete rutting and total pavement permanent deformation. Generally, the pavement structure and materials have been set as constant to control the effects of material on the results. On the basis of the MEPDG analysis, the longitudinal cracking of flexible pavement is significantly affected by both factors (temperature and precipitation), particularly in wet climatic regions. The mean annual temperature has a great influence on the alligator cracking, transverse cracking and permanent deformation of flexible pavement. However, neither factors demonstrated a significant impact on the predicted International Roughness Index of flexible pavement surfaces.

Updating and augmenting weather data for pavement mechanistic-empirical design using ASOS/AWOS database in Michigan

Abstract Climatic files are an important input in the recently released pavement design software Pavement ME Design (PMED). Currently there are 24 climatic files embedded in the PMED for various locations within the state of Michigan, USA. However, the distribution of existing weather stations is not geographically uniform, with noticeable gap regions among these stations. The existing climatic files have only 5 to 9 years of hourly data and have not been updated since 2006. This study aims to add new weather stations to fill the gap regions and to update existing climatic files to the end of the year 2014 using historical climatic data from the Automated Surface/Weather Observation System (ASOS/AWOS). To achieve this goal, the climatic files from other locations in ASOS/AWOS were edited to meet the requirements of the PMED. The new climatic data were compared with existing data in detail to verify the data source consistency. A quantity and quality check was conducted for the new climatic files. Procedures were proposed for filling missing and correcting erroneous data. After thorough quality checks, the filling and correction procedures proposed in this study were shown to be viable for both the flexible and rigid pavement designs in Michigan using PMED. Finally, 15 new weather stations were added for Michigan with the average climatic data length being extended from 7.6 to 15.2 years. The approach and procedures developed in this study can be adopted for the improvement of climatic files in other states or regions.

Sensitivity of thermal parameters affecting cold-region ground-temperature predictions

This study formulates a heat-flux upper boundary to model ground temperatures in the Qinghai-Tibet plateau. This model considers the impacts of the environmental conditions, e.g., air temperature, ground-surface albedo, wind speed, and solar radiation on the ground-surface heat flux and on subsequent subsurface temperature profiles. It speculates that in arid regions, neglecting the evaporation-induced heat flux does not compromise the ground-temperature predictions notably. The predicted results are validated by the observed temperature profiles at a test station on the Qinghai-Tibet plateau. A temperature-controlled upper boundary model is also utilized to simulate the ground-temperature profile and is compared to the same field-observed temperature profiles. A sensitivity study is conducted to characterize the influence of local weather conditions on the ground-temperature development. Conditions considered include mean annual air temperature, seasonal air temperature amplitude, daily air temperature variation, mean annual wind speed, seasonal wind-speed variation, and daily wind-speed fluctuation. The sensitivity study also considers effects of variations the ground-surface albedo on the ground-temperature development and on the ground thermal re-equilibrium. It finally presents the implication of this re-equilibrium on the specified initial ground-temperature profile.

Volumetric Stability of Concrete Using Recycled Concrete Aggregates

Recent studies show that many pavements built in the United States of America using recycled concrete aggregate (RCA)-based concretes have experienced high amount of shrinkage cracking. Fresh and hardened concrete properties of RCA-based concretes are linked to the porosity and absorption capacity of the RCA aggregate. In this study, detailed evaluation of the porosity and absorption capacity using petrographic techniques of the selected aggregates was performed. This paper presents a study performed to evaluate the volumetric stability of RCA-based concretes using two types of locally manufactured RCA and one virgin aggregate type to assess the effect of recycling operations on the concrete performance. Concrete mixtures with water to cement ratio ( w/c of 0.42 were prepared using the selected virgin aggregates and RCA. Fresh concrete properties such as slump and air content were assessed in addition to hardened concrete properties at 28 days such as compressive strength, flexural strength, and elastic modulus. One-dimensional shrinkage of the virgin aggregate and RCA-based concretes was also measured using sealed and unsealed specimens stored at 50% RH to assess drying and total shrinkage respectively. The difference between the sealed and unsealed prisms gave an indication of the drying shrinkage potential of both the RCA-based and virgin aggregate concretes. Restrained shrinkage behavior and its associated cracking susceptibility was evaluated using the ring test as per AASHTO PP 34.

Correlation Analysis between Temperature Indices and Flexible Pavement Distress Predictions Using Mechanistic-Empirical Design

AbstractTemperature is the most influential climatic variable for flexible pavement design using a mechanistic-empirical approach. While the effect of climatic variables on pavement designs has bee...

Reversible Shrinkage of Concrete Made with Recycled Concrete Aggregate and Other Aggregate Types

Drying shrinkage gradients through the depth of a concrete slab can be divided into permanent and transient components because a portion of shrinkage is reversible. As there has only been a small amount of research on this topic in the past 60 years, the goal of this study was to characterize the amount of reversible shrinkage for standard paving concrete made with virgin, recycled concrete, and lightweight aggregates. This research found that approximately 30% of shrinkage was reversible for standard paving mixtures exposed to cyclic wetting and drying, regardless of the type of aggregate used. However, the level of reversible shrinkage increased significantly under long-term initial moisture curing. This research also corroborates the long-held assumption that the length change of concrete specimens is proportional to their weight change due to moisture movements.

New Warping and Differential Drying Shrinkage Models for Jointed Plain Concrete Pavements Derived with Nonlinear Shrinkage Distribution

Warping can be quantified by the equivalent temperature difference required to deform a theoretically flat slab to the same shape as the actual slab. In the Mechanistic–Empirical Pavement Design Guide (MEPDG), the current warping model for jointed concrete pavements uses a triangular shrinkage distribution within the shrinkage zone near the surface of the slab as well as modification factors to account for ambient relative humidity (RH) and the amount of total shrinkage that is expected to be reversible. The current warping model was evaluated and found to predict improbable values. A new warping model based on an assumed nonlinear shrinkage distribution that followed the curve described by one-quarter of an ellipse was proposed. The elliptical shrinkage distribution was found to agree well with predicted moisture distributions through the depth of the slab at various locations around the United States. A new factor accounted for the fact that only drying shrinkage contributed to warping, and changes were made to the RH adjustment factor. The proposed model was derived from plate theory, rather than beam theory, to account for the two-way bending behavior of a slab. Only parameters that were currently inputs in the MEPDG were required for the new proposed warping model. With slight modification, the model could be used to predict differential drying shrinkage levels in jointed concrete pavements.

Performance Prediction of the Dowel Bar Retrofit Technique Using Statistical Modelling

ABSTRACT Dowel Bar Retrofitting (DBR) is a pavement rehabilitation technique commonly adopted to increase the service life of pavements in the United States. This method involves either preventative or corrective maintenance of structural cracks or joints in jointed concrete pavement structures. The performance of DBR installations is typically measured using the Load Transfer Efficiency (LTE) parameter based on deflections. In this study, DBR was modeled using finite element analysis considering geometric, material, and support parameters. Statistical analyses were used to develop equations to predict performance of DBR in terms of stress transfer across joints or cracks. The use of stress-based load transfer provides engineers a more direct ability to determine what effect the load transfer mechanism has on reducing bending stress in the slab. This allows for proper retrofit strategies to be adopted thereby reducing fatigue mechanisms and extending the service life of rigid pavement systems.