Consumption of water during hydration reactions and surface water evaporation result in the development of negative pressure in capillary pores of concrete at early ages. Capillary pore water potential (PWP) creates early-age shrinkage strain and increases the chance of early-age cracking. The aim of this study was to investigate the effects of internal curing (IC) and water-to-cementitious materials ratio (W/CMs) on the hydration reactions and PWP development in cement-based materials. For this purpose, 11 mortar mixtures with different W/CMs (0.3, 0.375, 0.45 and 0.525) and lightweight fine aggregate (LWFA) substitutions (10, 20, 30 and 50%), as well as, 9 concrete mixtures with different W/CMs (0.35, 0.42 and 0.5) and LWFA substitutions (10, 20, 30 and 40%) were made and evaluated through isothermal calorimetry and pore water potential tests. The results demonstrate that IC is efficient in both promoting hydration kinetics and suppressing capillary PWP development, especially for the mixtures with low W/CMs.
{"title":"PORE WATER POTENTIAL DEVELOPMENT IN CEMENT-BASED MATERIALS","authors":"Payam Vosoughi, P. Taylor, R. Horton","doi":"10.33593/7m31dw5c","DOIUrl":"https://doi.org/10.33593/7m31dw5c","url":null,"abstract":"Consumption of water during hydration reactions and surface water evaporation result in the development of negative pressure in capillary pores of concrete at early ages. Capillary pore water potential (PWP) creates early-age shrinkage strain and increases the chance of early-age cracking. The aim of this study was to investigate the effects of internal curing (IC) and water-to-cementitious materials ratio (W/CMs) on the hydration reactions and PWP development in cement-based materials. For this purpose, 11 mortar mixtures with different W/CMs (0.3, 0.375, 0.45 and 0.525) and lightweight fine aggregate (LWFA) substitutions (10, 20, 30 and 50%), as well as, 9 concrete mixtures with different W/CMs (0.35, 0.42 and 0.5) and LWFA substitutions (10, 20, 30 and 40%) were made and evaluated through isothermal calorimetry and pore water potential tests. The results demonstrate that IC is efficient in both promoting hydration kinetics and suppressing capillary PWP development, especially for the mixtures with low W/CMs.","PeriodicalId":265129,"journal":{"name":"Proceedings of the 12th International Conference on Concrete Pavements","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122327950","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Julia Neumann, Kristina Farwig, R. Breitenbücher, M. Curbach
In many countries like Germany, concrete pavements are normally built as Jointed Plain Concrete Pavements (JPCP). Due to a lack of alternatives, maintenance of concrete pavements usually requires a replacement of the whole pavement structure, which is labour- and resource-intensive. Therefore, new techniques like the application of thin concrete overlays as a partial repair of deteriorated concrete pavements have been developed. As a major disadvantage of such overlays, the existing joints in the retained concrete bottom-layer have to be transferred in the overlay in order to avoid reflection cracking. When using non-corrosive carbon-textile reinforcement in such concrete overlays, cracks might be distributed more finely, enabling jointless repairs while keeping a thin repair layer. In addition, the bond behaviour between the retained concrete and the applied concrete overlay as well as between the concrete overlay and the textile reinforcement is crucial for a successful repair. In this paper, the basic principles and feasibility of such a repair method are examined. On the one hand, the decisive influencing variables and parameters such as bond behaviour between the concrete layers and the cracking behaviour of the overlay are pointed out and discussed. On the other hand, the evaluated laboratory tests carried out are presented. These include large-scale beams built with an overlay on top of a retained concrete layer, which were subjected to cyclic flexural stress and to a subsequent detailed investigation of the bond behaviour and durability. Furthermore, the crack formation in the overlay was determined by means of tensile and flexural tensile strength tests.
{"title":"Thin Concrete Overlays with Carbon Reinforcement","authors":"Julia Neumann, Kristina Farwig, R. Breitenbücher, M. Curbach","doi":"10.33593/wpqei36n","DOIUrl":"https://doi.org/10.33593/wpqei36n","url":null,"abstract":"In many countries like Germany, concrete pavements are normally built as Jointed Plain Concrete Pavements (JPCP). Due to a lack of alternatives, maintenance of concrete pavements usually requires a replacement of the whole pavement structure, which is labour- and resource-intensive. Therefore, new techniques like the application of thin concrete overlays as a partial repair of deteriorated concrete pavements have been developed. As a major disadvantage of such overlays, the existing joints in the retained concrete bottom-layer have to be transferred in the overlay in order to avoid reflection cracking. When using non-corrosive carbon-textile reinforcement in such concrete overlays, cracks might be distributed more finely, enabling jointless repairs while keeping a thin repair layer. In addition, the bond behaviour between the retained concrete and the applied concrete overlay as well as between the concrete overlay and the textile reinforcement is crucial for a successful repair. In this paper, the basic principles and feasibility of such a repair method are examined. On the one hand, the decisive influencing variables and parameters such as bond behaviour between the concrete layers and the cracking behaviour of the overlay are pointed out and discussed. On the other hand, the evaluated laboratory tests carried out are presented. These include large-scale beams built with an overlay on top of a retained concrete layer, which were subjected to cyclic flexural stress and to a subsequent detailed investigation of the bond behaviour and durability. Furthermore, the crack formation in the overlay was determined by means of tensile and flexural tensile strength tests.","PeriodicalId":265129,"journal":{"name":"Proceedings of the 12th International Conference on Concrete Pavements","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129851316","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study is set out to examine the bending, toughness and fracture energy of RCC pavements produced by double drum vibratory hand roller (DDVHR) to simulate the real performance of RCC in the laboratory environment. To this end, four different binder dosages (200, 300,400, and 600 kg/m3) and two different aggregate gradations (Dmax 12 and 19 mm) were selected to investigate the effect of mixture design on bending, toughness and fracture energy of RCC mixtures. The different mixtures were poured into a large pavement mold (LPM), which was fabricated in laboratory, and compacted by DDVHR. After that, in order to determine the bending, toughness and fracture energy of RCC mixtures, LPM were cut to beam specimens with sizes according to Japan Concrete Institute (JCI). In addition, cores were taken from LPM to compare 28 days' compressive strengths and compaction ratios of the mixtures. At the end of the study, contrary to expectations, the fracture energies for all RCC mixtures except one combination were very close to each other. The increase in cement dosage or the maximum aggregate size did not lead to a significant change in the fracture energy. The mixture that was developed to obtain a high performance RCC appeared to have the lowest fracture energy. Above all, the compaction ratio of the mixtures was effective in the all results.
{"title":"Fracture Energy of Roller Compacted Concrete Pavements","authors":"E. Şengün, Burhan Alam, R. Shabani, I. Yaman","doi":"10.33593/zmke32q2","DOIUrl":"https://doi.org/10.33593/zmke32q2","url":null,"abstract":"This study is set out to examine the bending, toughness and fracture energy of RCC pavements produced by double drum vibratory hand roller (DDVHR) to simulate the real performance of RCC in the laboratory environment. To this end, four different binder dosages (200, 300,400, and 600 kg/m3) and two different aggregate gradations (Dmax 12 and 19 mm) were selected to investigate the effect of mixture design on bending, toughness and fracture energy of RCC mixtures. The different mixtures were poured into a large pavement mold (LPM), which was fabricated in laboratory, and compacted by DDVHR. After that, in order to determine the bending, toughness and fracture energy of RCC mixtures, LPM were cut to beam specimens with sizes according to Japan Concrete Institute (JCI). In addition, cores were taken from LPM to compare 28 days' compressive strengths and compaction ratios of the mixtures. At the end of the study, contrary to expectations, the fracture energies for all RCC mixtures except one combination were very close to each other. The increase in cement dosage or the maximum aggregate size did not lead to a significant change in the fracture energy. The mixture that was developed to obtain a high performance RCC appeared to have the lowest fracture energy. Above all, the compaction ratio of the mixtures was effective in the all results.","PeriodicalId":265129,"journal":{"name":"Proceedings of the 12th International Conference on Concrete Pavements","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128719079","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pavement design and evaluation analysis use mechanistic models to estimate pavement responses to applied loads. Finite element modeling is a common technique used to quickly and efficiently model rigid pavements that incorporate more complex phenomena that constructed, in-service slabs experience. While adding complexity increases the accuracy of the modeling when estimating pavement responses, significantly more computing effort is required. When combined with a cumulative-damage-based structural analysis, multiple model runs are needed to estimate damage over the number of incremental steps used. To bypass direct finite element modeling for multiple pavement systems, design methodologies such as the Mechanistic-Empirical Pavement Design Guide use artificial neural networks to store specific pavement response information for rapid recall as a type of non-linear regression made from pre-analyzed cases of a known set of input variables. These methodologies use the Principles of Similarity to reduce the complexity of modeling the pavement layering and environmental loads by considering a single reference pavement structure. Complexity can be reduced from 21 variables to nine key variables for modeling airfield pavements without introducing error and minimizing the total runs used. This paper provides a review of the Principles of Similarity and discusses how they are used to generate an efficient dataset for artificial neural network development. Examples showing how a single representative pavement system can yield proportional and scalable responses to numerous equivalent pavement systems are provided to illustrate the power of the Principles of Similarity in reducing modeling complexity and computational demands for higher-level pavement analysis efforts.
{"title":"Reducing Airfield Rigid Pavement Modeling Complexity: An Exercise Using the Principles of Similarity","authors":"Peter G Bly, L. Khazanovich","doi":"10.33593/tgharomm","DOIUrl":"https://doi.org/10.33593/tgharomm","url":null,"abstract":"Pavement design and evaluation analysis use mechanistic models to estimate pavement responses to applied loads. Finite element modeling is a common technique used to quickly and efficiently model rigid pavements that incorporate more complex phenomena that constructed, in-service slabs experience. While adding complexity increases the accuracy of the modeling when estimating pavement responses, significantly more computing effort is required. When combined with a cumulative-damage-based structural analysis, multiple model runs are needed to estimate damage over the number of incremental steps used. To bypass direct finite element modeling for multiple pavement systems, design methodologies such as the Mechanistic-Empirical Pavement Design Guide use artificial neural networks to store specific pavement response information for rapid recall as a type of non-linear regression made from pre-analyzed cases of a known set of input variables. These methodologies use the Principles of Similarity to reduce the complexity of modeling the pavement layering and environmental loads by considering a single reference pavement structure. Complexity can be reduced from 21 variables to nine key variables for modeling airfield pavements without introducing error and minimizing the total runs used. This paper provides a review of the Principles of Similarity and discusses how they are used to generate an efficient dataset for artificial neural network development. Examples showing how a single representative pavement system can yield proportional and scalable responses to numerous equivalent pavement systems are provided to illustrate the power of the Principles of Similarity in reducing modeling complexity and computational demands for higher-level pavement analysis efforts.","PeriodicalId":265129,"journal":{"name":"Proceedings of the 12th International Conference on Concrete Pavements","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130487509","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This research was based on the findings from a field study of slab placements representing different combinations of curing conditions and placement times. One of the key objectives was to collect data with respect to slab setting characteristics as a function of the quality of curing provided for each slab. The set is referred to herein terms of a gradient that forms due to environmental effects on temperature and moisture profile variations during the initial days after placement. These profile variations effect the degree of slab support. In other words, early-age concrete temperature and moisture history is a key factor affecting the set gradient, as well as a factor in slab curling and warping behavior (corner displacement). There is also a strain profile associated with the set gradient creating a level of stress that can be related to the development of early-age cracking similar to slab curling and warping. This early-aged behavior is mostly drying shrinkage driven, and is often manifested by the separation of the slab from the substrate along the edges and the corners of the slab. This paper mainly focuses on a framework to relate early-age slab damage to the probability of slab cracking later in the performance cycle. This relationship is elaborated with respect to curing quality and its effect on the development of the set gradient as well as its role in PavementME calibration results. The PavementME developers were aware that construction weather conditions affect concrete pavement performance via the inclusion of a set gradient in the computations.
{"title":"A Framework to Assess Early Concrete Slab Cracking","authors":"A. Joshaghani, D. Zollinger","doi":"10.33593/s9rfx1st","DOIUrl":"https://doi.org/10.33593/s9rfx1st","url":null,"abstract":"This research was based on the findings from a field study of slab placements representing different combinations of curing conditions and placement times. One of the key objectives was to collect data with respect to slab setting characteristics as a function of the quality of curing provided for each slab. The set is referred to herein terms of a gradient that forms due to environmental effects on temperature and moisture profile variations during the initial days after placement. These profile variations effect the degree of slab support. In other words, early-age concrete temperature and moisture history is a key factor affecting the set gradient, as well as a factor in slab curling and warping behavior (corner displacement). There is also a strain profile associated with the set gradient creating a level of stress that can be related to the development of early-age cracking similar to slab curling and warping. This early-aged behavior is mostly drying shrinkage driven, and is often manifested by the separation of the slab from the substrate along the edges and the corners of the slab. This paper mainly focuses on a framework to relate early-age slab damage to the probability of slab cracking later in the performance cycle. This relationship is elaborated with respect to curing quality and its effect on the development of the set gradient as well as its role in PavementME calibration results. The PavementME developers were aware that construction weather conditions affect concrete pavement performance via the inclusion of a set gradient in the computations.","PeriodicalId":265129,"journal":{"name":"Proceedings of the 12th International Conference on Concrete Pavements","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123652299","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Alkali-Silica Reaction (ASR) in concrete pavements has become a real problem in Germany in the end of the 1990s / beginning of the 2000s. In an extensive research project, the background for such ASR-damaging has been examined intensively at the Ruhr University Bochum. ASR in concrete pavements is not only influenced by the reactivity of the aggregate, but rather by a superposition of different influencing factors. For concrete pavements for example, there are specific conditions that increase an ASR significantly. On the one hand, concrete pavements are microstructurally damaged by the superposition of cyclic stresses induced by traffic and climate changes, and on the other hand they are exposed to alkaline de-icing agents during the wintertime. Thereby, an ASR-promoting external alkali supply is given. Three absolute preconditions are necessary for an ASR to occur: potentially reactive aggregates, sufficient supply of alkalis and an adequate degree of moisture. In Germany, there have been numerous measures taken in the last 10 to 15 years in order to prevent ASR-damages in concrete pavements. Already in 2005 the alkali-content (Na₂O-Equivalent) allowed in cements for concrete pavements has been limited to 0.8% by mass. Additionally, in each case the aggregates intended to be used must be assessed beforehand in a special procedure. Since these requirements were established by the highway-authorities in 2005 (with modifications in 2013) there have been no new damages related to ASR observed on concrete pavements, which have been constructed in compliance with these guidelines.
{"title":"Successful ASR Prevention in Germany: Influencing Factors and Adequate Measures","authors":"Robin Przondziono, R. Breitenbücher","doi":"10.33593/qwrsfal6","DOIUrl":"https://doi.org/10.33593/qwrsfal6","url":null,"abstract":"Alkali-Silica Reaction (ASR) in concrete pavements has become a real problem in Germany in the end of the 1990s / beginning of the 2000s. In an extensive research project, the background for such ASR-damaging has been examined intensively at the Ruhr University Bochum. ASR in concrete pavements is not only influenced by the reactivity of the aggregate, but rather by a superposition of different influencing factors. For concrete pavements for example, there are specific conditions that increase an ASR significantly. On the one hand, concrete pavements are microstructurally damaged by the superposition of cyclic stresses induced by traffic and climate changes, and on the other hand they are exposed to alkaline de-icing agents during the wintertime. Thereby, an ASR-promoting external alkali supply is given. Three absolute preconditions are necessary for an ASR to occur: potentially reactive aggregates, sufficient supply of alkalis and an adequate degree of moisture. In Germany, there have been numerous measures taken in the last 10 to 15 years in order to prevent ASR-damages in concrete pavements. Already in 2005 the alkali-content (Na₂O-Equivalent) allowed in cements for concrete pavements has been limited to 0.8% by mass. Additionally, in each case the aggregates intended to be used must be assessed beforehand in a special procedure. Since these requirements were established by the highway-authorities in 2005 (with modifications in 2013) there have been no new damages related to ASR observed on concrete pavements, which have been constructed in compliance with these guidelines.","PeriodicalId":265129,"journal":{"name":"Proceedings of the 12th International Conference on Concrete Pavements","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132871894","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Concrete overlays on asphalt pavement, also known as whitetopping, are growing in popularity as an option for the rehabilitation of distressed asphalt pavements. The performance of whitetoppings over the past several decades has shown that under heavy and frequent traffic loads, they can be susceptible to panel migration and faulting due to the lack of tie bars and dowel bars within the thin cross sections. One mitigation method to reduce panel migration and faulting is the inclusion of structural fibers into the concrete mix. While structural fibers have anecdotally been shown to contribute toward better performance in whitetoppings, few studies have quantified the benefits provided by the typical dosage of fibers used in recent specifications. Two sets of similarly designed experimental test sections constructed at the MnROAD test facility in 2004 and 2013, have provided the opportunity to evaluate and quantify the impact of structural fibers on whitetopping performance. This comparison of the performance between plain concrete and fiber-reinforced concrete overlay test sections includes analysis of material properties of the mixes, the difference in response to environmental and traffic loads, typical distresses, and ride quality. Based on the results of the analysis, recommendations were made with regards to whether the types and dosages of structural fibers used in the test sections made a sufficient impact on performance.
{"title":"Quantifying the Impact of Structural Fibers on the Performance of Concrete Overlays on Asphalt","authors":"T. Burnham, Michael Wallace, M. Barman","doi":"10.33593/0v4uc9j0","DOIUrl":"https://doi.org/10.33593/0v4uc9j0","url":null,"abstract":"Concrete overlays on asphalt pavement, also known as whitetopping, are growing in popularity as an option for the rehabilitation of distressed asphalt pavements. The performance of whitetoppings over the past several decades has shown that under heavy and frequent traffic loads, they can be susceptible to panel migration and faulting due to the lack of tie bars and dowel bars within the thin cross sections. One mitigation method to reduce panel migration and faulting is the inclusion of structural fibers into the concrete mix. While structural fibers have anecdotally been shown to contribute toward better performance in whitetoppings, few studies have quantified the benefits provided by the typical dosage of fibers used in recent specifications. Two sets of similarly designed experimental test sections constructed at the MnROAD test facility in 2004 and 2013, have provided the opportunity to evaluate and quantify the impact of structural fibers on whitetopping performance. This comparison of the performance between plain concrete and fiber-reinforced concrete overlay test sections includes analysis of material properties of the mixes, the difference in response to environmental and traffic loads, typical distresses, and ride quality. Based on the results of the analysis, recommendations were made with regards to whether the types and dosages of structural fibers used in the test sections made a sufficient impact on performance.","PeriodicalId":265129,"journal":{"name":"Proceedings of the 12th International Conference on Concrete Pavements","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123908695","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Around the world, urban development and densification leads to the Urban Heat Islands (UHI) effect, in which cities are warmer than adjoining rural areas. Cool pavements have been recommended as a mitigating strategy for the UHI effect. However, the spatial extent over which cool pavements need to be applied to achieve widespread mitigation has received little attention. A previously developed urban microclimatic model for the Power Ranch community in suburban Phoenix, Arizona, was used to investigate this question. The microclimatic model is used to investigate the effects of urban densification for the meteorological conditions at 5:00 PM on August 13, 2015. In the modeled scenario, the heights of the buildings were increased from 5 m to 10 m, a large, central park was redeveloped as a parking lot, and a reflective pavement was implemented in the parking lot. Both localized and downwind air temperature effects at 2m of this further densification were quantified in the modelling effort. For the lower building height, using typical concrete to redevelop the park as a parking lot increased the 2 m air temperature directly over and downstream by about 0.20℃. When a reflective concrete parking lot was used instead, the 2m air temperature decreased by 0.20℃ over and downstream. At 10 m building heights, the reflective parking lot decreased the 2 m air temperature by 0.20℃, however, its effect was more localized with less benefit for downstream areas. Thus, urban form with taller buildings affects the airflow, which requires a more distributed application of reflective surfaces to mitigate UHI.
{"title":"Cool Pavements for Sustainable Urban Development","authors":"Sushobhan Sen, J. Roesler, B. Ruddell, A. Middel","doi":"10.33593/xx1hzrq3","DOIUrl":"https://doi.org/10.33593/xx1hzrq3","url":null,"abstract":"Around the world, urban development and densification leads to the Urban Heat Islands (UHI) effect, in which cities are warmer than adjoining rural areas. Cool pavements have been recommended as a mitigating strategy for the UHI effect. However, the spatial extent over which cool pavements need to be applied to achieve widespread mitigation has received little attention. A previously developed urban microclimatic model for the Power Ranch community in suburban Phoenix, Arizona, was used to investigate this question. The microclimatic model is used to investigate the effects of urban densification for the meteorological conditions at 5:00 PM on August 13, 2015. In the modeled scenario, the heights of the buildings were increased from 5 m to 10 m, a large, central park was redeveloped as a parking lot, and a reflective pavement was implemented in the parking lot. Both localized and downwind air temperature effects at 2m of this further densification were quantified in the modelling effort. For the lower building height, using typical concrete to redevelop the park as a parking lot increased the 2 m air temperature directly over and downstream by about 0.20℃. When a reflective concrete parking lot was used instead, the 2m air temperature decreased by 0.20℃ over and downstream. At 10 m building heights, the reflective parking lot decreased the 2 m air temperature by 0.20℃, however, its effect was more localized with less benefit for downstream areas. Thus, urban form with taller buildings affects the airflow, which requires a more distributed application of reflective surfaces to mitigate UHI.","PeriodicalId":265129,"journal":{"name":"Proceedings of the 12th International Conference on Concrete Pavements","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129761392","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Ioannides, J. A. Harrison, Carlos R. Gonzalez, Peter G Bly
The so-called 72-in. rule, employed in U.S. Department of Defense rigid pavement design for establishing the number of strain cycles arising under a pass of any aircraft on a particular pavement system, is re-examined using mechanistic tools, particularly layer elastic theory and dimensional analysis. Field data collected at Denver International Airport are reproduced using analytical simulations, which permit the generation of analogous synthetic results pertaining to different pavement systems and aircraft gear configurations. The analysis affirms the expectation that the criterion for establishing the number of strain cycles cannot be simply a fixed value, defined exclusively by the tandem wheel spacing. Rather, the dual wheel spacing and the radius of each tire-print must also be taken into consideration. In addition, the radius of relative stiffness of the pavement system needs to be accounted for. In this study, these variables are accommodated in the form of three dimensionless independent input parameters. The single dependent variable is the ratio (trough strain / maximum strain), denoted herein as υ. A process is formulated to ascertain whether υ is positive or negative: if υ>0, then one strain cycle may be expected; if υ<0, then two strain cycles may be expected. Comparisons of the process outcomes to those from the 72-in. rule show excellent agreement for the Denver conditions, testifying to the admirable simplicity and laudable wisdom of the latter. The process may be further refined for application to more complex gear configurations, e.g., tridems.
{"title":"Accounting of Strain Cycles Sustained by Airfield Rigid Pavements","authors":"A. Ioannides, J. A. Harrison, Carlos R. Gonzalez, Peter G Bly","doi":"10.33593/crd3iwco","DOIUrl":"https://doi.org/10.33593/crd3iwco","url":null,"abstract":"The so-called 72-in. rule, employed in U.S. Department of Defense rigid pavement design for establishing the number of strain cycles arising under a pass of any aircraft on a particular pavement system, is re-examined using mechanistic tools, particularly layer elastic theory and dimensional analysis. Field data collected at Denver International Airport are reproduced using analytical simulations, which permit the generation of analogous synthetic results pertaining to different pavement systems and aircraft gear configurations. The analysis affirms the expectation that the criterion for establishing the number of strain cycles cannot be simply a fixed value, defined exclusively by the tandem wheel spacing. Rather, the dual wheel spacing and the radius of each tire-print must also be taken into consideration. In addition, the radius of relative stiffness of the pavement system needs to be accounted for. In this study, these variables are accommodated in the form of three dimensionless independent input parameters. The single dependent variable is the ratio (trough strain / maximum strain), denoted herein as υ. A process is formulated to ascertain whether υ is positive or negative: if υ>0, then one strain cycle may be expected; if υ<0, then two strain cycles may be expected. Comparisons of the process outcomes to those from the 72-in. rule show excellent agreement for the Denver conditions, testifying to the admirable simplicity and laudable wisdom of the latter. The process may be further refined for application to more complex gear configurations, e.g., tridems.","PeriodicalId":265129,"journal":{"name":"Proceedings of the 12th International Conference on Concrete Pavements","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127515850","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Superloads are typically defined as vehicles weighing greater than 890 kilonewtons (200,000 pounds), although the geometrics of the vehicle are also a consideration. The damage of these superloads on jointed plain concrete pavements (JPCP) as compared to a standard 80-kN (18-kip) single axle design load are not well defined. The purpose of this study is to identify the effects of these superloads on the performance of JPCP joints in comparison to that of standard traffic loads. One mechanism of failure at the transverse joints in JPCP is the degradation of dowel performance. This can decrease the effectiveness of the joint load transfer efficiency; thereby resulting in large differential deflections and the development of faulting. Therefore, to quantify the damage caused by superloads, typical load configurations were identified using superload permit data obtained from the Pennsylvania Department of Transportation. Using the typical superload profiles established from permit data, the effect on dowel performance is evaluated.
{"title":"Establishing Effects of Superloads on Doweled Jointed Plain Concrete Pavements","authors":"Charles Donnelly, J. Vandenbossche","doi":"10.33593/kpufzjey","DOIUrl":"https://doi.org/10.33593/kpufzjey","url":null,"abstract":"Superloads are typically defined as vehicles weighing greater than 890 kilonewtons (200,000 pounds), although the geometrics of the vehicle are also a consideration. The damage of these superloads on jointed plain concrete pavements (JPCP) as compared to a standard 80-kN (18-kip) single axle design load are not well defined. The purpose of this study is to identify the effects of these superloads on the performance of JPCP joints in comparison to that of standard traffic loads. One mechanism of failure at the transverse joints in JPCP is the degradation of dowel performance. This can decrease the effectiveness of the joint load transfer efficiency; thereby resulting in large differential deflections and the development of faulting. Therefore, to quantify the damage caused by superloads, typical load configurations were identified using superload permit data obtained from the Pennsylvania Department of Transportation. Using the typical superload profiles established from permit data, the effect on dowel performance is evaluated.","PeriodicalId":265129,"journal":{"name":"Proceedings of the 12th International Conference on Concrete Pavements","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123760250","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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