Hot Weather Water Impacts on Thermal Profiles in Pervious Concrete
Alexandre Lorenzi, Federal University of Rio Grande do SolShow Abstract
Liv Haselbach, Lamar University
Luiz Carlos Silva Filho, Federal University of Rio Grande do Sol
Ângelo Pessutto, Federal University of Rio Grande do Sol
Gabrielle Bidinotto, Federal University of Rio Grande do Sol
Pervious concrete has many environmental benefits including the mitigation of heat island impacts. This mitigation is a complex combination of its insulating capability and its ability to store water which may provide evaporative cooling. However, the introduction of water may also bring heat into the system. This study involved three different mix design placements in southern Brazil on a hot sunny summer day. The experiment had a control section and two test spots where controlled artificial rain events were introduced at two times during the afternoon for each of the three placement types. The ‘rain’ initially brought heat from the surface into the pervious concrete layer. Subsequent evaporation cooled these interior spots to levels similar to the control locations. This introduction of water into pervious concrete with very hot surface temperatures in the heat of the day is expected to be the most severe condition for adding heat to the system through the flow of water. If water additions are made at different times such as nighttime rain, they would provide similar evaporative benefits with less heat transfer into the system via the water phase, and thus even more cooling of the system. These experiments reinforce the conclusion that pervious concrete is a cool pavement during summer conditions, even under extreme conditions when surface heated stormwater enters the system. The data may be further applied to complex models of the system, with convective, conductive and evaporative heat fluxes.
Winter Temperature Prediction for Near-Surface Depth of Pervious Concrete Pavement
Benjamin Nantasai, Washington State UniversityShow Abstract
Somayeh Nassiri, Washington State University
Pervious concrete pavement (PCP) consists of a highly porous concrete slab, placed on a permeable base layer. This permeable pavement system allows stormwater runoff to infiltrate through the pavement and percolate into the subdrainage system or directly into the subgrade soil. PCP is gaining popularity for many municipal applications across the United States, including the cold-climate regions. For winter maintenance purposes, it is critical that thermal behavior of PCP during the winter is understood and can be predicted. A PCP sidewalk was placed and instrumented on Washington State University’s campus in Pullman, Washington. Temperature measurements at various depths of the PCP sidewalk were presented and evaluated in this study for one winter. The Enhanced Integrated Climatic Model (EICM) software was used to simulate the PCP sidewalk and predict its temperature during the winter. EICM considers the heat transfer between the pavement and the surroundings, using each layer’s thermal properties. Heat conductivity and capacity were established for the PCP using the parallel model, based on the volumetric proportion of concrete constituents. Meteorological indices for the model were obtained from a local weather station and an on-site pyronometer for solar radiation. Comparison of the predicted temperature for the top three-inch (76-mm) depth of the pervious concrete layer showed agreements with the field data during the winter. A multiple linear regression model was developed to predict PCP temperature at 0.5-inch (13-mm) depth. This model can be used to identify freezing periods for PCP during the winter, thus enhance winter maintenance operations.
Development of Climatic Regions for Concrete Pavement Design in Florida Using Satellite Weather Data
Bruce Dietrich, Pavement Analytics, LLCShow Abstract
Rhonda Taylor, Florida Department of Transportation
Wiley Cunagin, Florida Department of Transportation
Local calibration studies in Florida using the Pavement ME design software have shown the performance of jointed plain concrete pavements (JPCP) to be sensitive to climatic inputs. These studies indicated significant performance differences among regions of the state. Weather station data were used for the study, but were limited by the non-uniform spacing of the stations, gaps in coverage, and questionable data from many of the stations. Satellite based weather data have recently become available through the FHWA and AASHTO. The FHWA data were developed by NASA and are called Modern-Era Retrospective Analysis for Research and Applications (MERRA). These data were uniformly spaced and of high quality with over 35 years of history. Florida is using these data to reanalyze the design regions used in the state. Design regions and thickness tables per region will aid pavement designers in rapidly checking the reasonableness of their Pavement ME designs. Due to the multitude of input variables required by the Pavement ME software, it is often difficult to get consistent designs due to minor input errors which are often tedious to find and correct. To develop the design regions, the 47 MERRA cells in Florida were processed through Pavement ME with standard design inputs, with only location, traffic and concrete thickness varied. Cells were then identified where thickness changes of 0.5 inches or more would occur. An interpolation process was then performed to further refine the climatic region borders and develop maps of the results for use by pavement designers.
Sensitivity of Rigid Pavement Performance Predictions to Individual Climate Variables Using PavementME Design
Xu Yang, Michigan Technological UniversityShow Abstract
Zhanping You, Michigan Technological University
Jacob Hiller, Michigan Technological University
Pavement ME Design (PMED) is a pavement design tool built based on the Mechanistic-Empirical Pavement Design Guide. Five individual climate variables are required as climatic inputs in a pavement design using PMED. While it is believed that all these five climatic variables affect the distress predictions in pavement design, the detailed effect of these factors on the design of jointed plain concrete pavement (JPCP) has not been well researched. This study aims to investigate the effect of the five individual climate variables on the performance predictions of JPCP using PMED. The one-at-a-time approach was used to change the individual climate variables. Four weather stations located in different climate zones (cold, warm, hot-humid, and hot-dry) in the United States were selected for the analysis. The effect of individual climatic variables on the JPCP distress predictions were analyzed first. Then a normalized sensitivity index (NSI) was adopted to analyze the sensitivity of performance predictions to individual climate variables. The effect results showed that with a 10% increase in the values of the climatic variables, the average temperature and daily temperature range have a positive effect on the values of the transverse cracking prediction. The effect of temperature on the IRI and faulting may not be consistent in different climate zones, and the wind speed has a negative effect on the values of all the three distresses. The percent sunshine and relative humidity have a positive effect on the values of all three distresses, and the effect of precipitation is negligible. The occurrence of probability of the temperature gradient within the concrete slab after the change in variables were also obtained and plotted to help interpret the findings. The sensitivity analysis showed that percent sunshine is the most influential climatic variable, followed by temperature, wind speed, relative humidity, and precipitation.
Evaluation of Dowel Bar Configuration on Structural Response Characteristics of Jointed Plain Concrete Pavement Using Finite Element Analysis
KUKJOO KIM, University of FloridaShow Abstract
Sanghyun Chun, Arkansas Department of Transportation
Mang Tia, University of Florida
James Greene, Florida Department of Transportation
This study primarily focused on evaluating the effect of two different dowel bar configurations (i.e. standard and special dowel bar configurations) on change in structural response characteristics and performance of Jointed Plain Concrete Pavement (JPCP). A 3-D finite element (FE) model was developed to evaluate the change in structural responses of the JPCP due to the different dowel bar configurations under the critical loading condition. Also, field performance evaluation was conducted using a demonstration project under real traffic and environmental conditions. The FE analysis results found no apparent changes were indicated for corner deflections, edge stresses, bearing stresses in the concrete slab, and dowel shear stresses, which may result in no significant difference in potential performance. To account for the asphalt layer as the base material used in this study, a parametric study was also conducted. The results from the parametric study indicate that change in base modulus significantly affects the dowel-joint behavior and stiffer base condition could significantly improve the dowel-joint performance. In addition, the field performance evaluation results exhibited that no significant performance difference was observed between the pavement sections with standard dowel and special dowel bar configurations which confirms the comparable results between the analytical FE model and experimental field evaluation. Based on these results, it can be concluded that if the base layer is stiff enough to appropriately support the slab deflection and resist erosion, the special dowel bar configuration appears to provide a similar performance as compared to a standard dowel bar configuration.
Development of Numerical Simulation Tool for Continuously Reinforced Concrete Pavements
Nancy Aguirre, University of Texas, El PasoShow Abstract
The accurate modeling of the main features of continuously reinforced concrete pavements (CRCP) is of primary importance in a mechanistic-empirical pavement design procedure. The use of the finite element (FE) method as a comprehensive tools for modeling the responses of rigid pavements (in general) and CRCP (in particular) has been limited because of the complexity of proper implementation by pavement engineers. Significant amount of research has been conducted to improve the design of CRCPs under traffic, environmental, and thermal loads. To develop a reliable model that better represents the behavior of CRCP, a clear understanding of the interaction between the concrete and steel is essential. This study presents an attempt to model the interaction between the CRCP concrete and steel using a 3-D finite element model. Concrete stress distributions due to linear temperature gradient within a concrete slab and bond slip relation between the concrete slab and reinforcing steel using connector elements were examined in this paper. The results presented demonstrate the importance of accurately modeling the bond slip between concrete and steel since it has a significant impact on the concrete stress distributions along the slab.
Evaluation of Interfacial Bond Strength Between Portland Cement Concrete and Asphalt Concrete Layers Using Bimaterial Semicircular Bend Test Specimen
Mirmilad Mirsayar, Texas A&M UniversityShow Abstract
Xijun Shi, Texas A&M University
Dan Zollinger, Texas A&M University, College Station
Portland cement concrete (PCC) / asphalt concrete (AC) bonded components are seen in both conventional pavement structures as well as overlays. Due to the environmental and traffic loads, cracks occur at the interface of the PCC and AC layers and finally, may propagate through the interface or one of the layers. Therefore, the evaluation of bond strength between these layers is important. This paper investigates bond strength between asphalt concrete and Portland cement concrete using a new sandwich test specimen. The developed specimen, called Bi-material semi-circular bend (BSCB) is made of asphalt concrete and the Portland cement concrete, cracked at the interface of the materials. First, the suggested specimen is introduced and characterized using finite element simulation. Then, the specimen is employed to obtain bond strength between asphalt concrete and Portland cement concrete under mixed mode loading, and at two temperatures: -20C and 20C. The fracture toughness at different mixed mode conditions is obtained, and finally, fracture criterion for the tested bonded joints is presented.
Ductile Concrete Material with Self-healing Capacity for Jointless Concrete Pavement Use
Zhigang Zhang, Chongqing UniversityShow Abstract
The existence of joint in concrete pavement tends to cause many distresses and driving discomfort, thus resulting in high maintenance cost and shortened service life. In this paper, the jointless function in concrete pavement will be achieved by utilizing ECC’s high ductility and self-healing capacity. From the preliminary experimental results, it is found that the ECC shows high strain capacity of 4.4% and deflection capacity of 7.9 mm under tension and bending, which overcomes the brittleness of normal concrete. The flexural and compressive strength of ECC is 12.2 MPa and 45.8 MPa, respectively, which could meet the requirements of heavy duty concrete pavement in accordance with design guidance in China. Under restrained shrinkage, ECC also shows a very low tendency to form fracture failure. Besides that, the self-healing phenomenon is observed in ECC. Its stiffness, tensile strain capacity and tensile strength shows a very high recovery level after self-healing, nearly approaching that of the virgin ECC of the same age. The water permeable coefficient of pre-damaged ECC decreases gradually with self-healing age, eventually close to that of virgin one. Based on above experimental results, it is concluded that ECC material, as expected, has the potential to be used in jointless concrete pavement.
Portland Cement Concrete Pavement Thickness and Shear Wave Velocity Variation Versus Observed Pavement Distresses
Lucio De Salles, University of PittsburghShow Abstract
Ryan Conway, University of Minnesota, Twin Cities
Lev Khazanovich, University of Pittsburgh
Randal Barnes, University of Minnesota, Twin Cities
DEIVIDI PEREIRA, Federal University of Santa Maria
Kyle Hoegh, Minnesota Department of Transportation
Thomas Burnham, Minnesota Department of Transportation
Concrete slab thickness is the key characteristic of a concrete pavement. It is the most important design parameter and the major focus of control and inspection during construction. It is widely accepted that thickness deficiencies can reduce performance. In order to investigate possible correlations between Portland cement concrete (PCC) with observed surface distresses, a combination of non-destructive ultrasonic thickness tests and distress surveys was performed in three existing highways prior to their rehabilitation. In addition to concrete thickness, concrete shear wave velocity was also measured in ultrasonic tests. Construction records were also reviewed. An in-depth statistical analysis was performed in order to investigate possible thickness/distress or velocity/distress relations using various predictors. While the results discussed here are limited by the small number of analyzed sections, they illustrate the importance of material quality and uniformity control during construction, since alterations in material properties significantly influenced pavement performance.