Freeze-thaw damage is one of the main threats to the long time performance of the concrete pavement in the cold regions. This project aims to evaluate the influence of the freeze-thaw damages on pavement distresses un...Freeze-thaw damage is one of the main threats to the long time performance of the concrete pavement in the cold regions. This project aims to evaluate the influence of the freeze-thaw damages on pavement distresses under different climate conditions. Based on the Long-Term Pavement Performance （LTPP） data base, the freeze-thaw damage generated by four different kinds of climate conditions are considered in this project： wet-freeze, wet-non freeze, dry- freeze and dry-non freeze. The amount of the transverse crack and the joint spalling, along with the International Roughness Index （IR/） are compared among the test sections located in these four different climate conditions. The back calculation with the Falling Weight Deflectometer （FWD） test results based on the ERES and the Estimation of Concrete Pavement Parameters （ECOPP） methods are conducted to obtain concrete slab elastic modulus and the subgrade k-value. These two parameters both decrease with service time under freeze condition. Finally, MEPDG simulation is conducted to simulate the IR/development with service year. These results showed the reasonable freeze-thaw damage development with pavement service life and under different climate conditions.展开更多
This study investigates the influence of using ground palm oil fuel ash(G-POFA) from 10%-30% as cement replacement(by weight) on the cement mortar's pH under various curing conditions. These findings were suppleme...This study investigates the influence of using ground palm oil fuel ash(G-POFA) from 10%-30% as cement replacement(by weight) on the cement mortar's pH under various curing conditions. These findings were supplemented by thermal gravimetric analysis(TGA). Moreover, the resistance of G-POFA blended cement mortars to water absorption and sorptivity was determined. Further, the k-value test was carried out to explain the pozzolanic and filler behavior of G-POFA and to support the results obtained from TGA. It was found that there was no significant impact of several curing conditions on the pH of mortars. The mortar with 10% G-POFA in replacement of cement(G-POFA-10) exhibited the best resistance against water absorption and sorptivity.展开更多
Soil erodibility(K-factor)is an essential factor in soil erosion prediction and conservation practises.The major obstacles to any accurate,large-scale soil erodibility estimation are the lack of necessary data on soil...Soil erodibility(K-factor)is an essential factor in soil erosion prediction and conservation practises.The major obstacles to any accurate,large-scale soil erodibility estimation are the lack of necessary data on soil characteristics and the misuse of variable K factor calculators.In this study,we assessed the per-formance of available erodibility estimators Universal Soil Loss Equation(USLE),Revised Universal Soil Loss Equation(RUSLE),Erosion Productivity Impact Calculator(EPIC)and the Geometric Mean Diameter based(Dg)model for different geographic regions based on the Chinese soil erodibility database(CSED).Results showed that previous estimators overestimated almost all K-values.Furthermore,only the USLE and Dg approaches could be directly and reliably applicable to black and loess soil regions.Based on the nonlinear best ftting techniques,we improved soil erodibility prediction by combining Dg and soil or ganic matter(SOM).The NSE,R^(2)and RE values were 0.94,0.67 and 9.5%after calibrating the results independently:similar model performance was showed for the validation process.The results obtained via the proposed approach were more accurate that the former K-value predictions.Moreover,those improvements allowed us to effectively establish a regional soil erodibility map(1:250,000 scale)of water erosion areas in China.The mean K-value of Chinese water erosion regions was 0.0321(t ha h).(ha MJ mm)^(-1)with a standard deviation of 0.0107(t ha h).(ha MJ mm)^(-1);K-values present a decreasing trend from North to South in water erosion areas in China.The yield soil erodibility dataset also sa-tisfactorily corresponded to former K-values from diferent scales(local,regional,and national).展开更多
文摘Freeze-thaw damage is one of the main threats to the long time performance of the concrete pavement in the cold regions. This project aims to evaluate the influence of the freeze-thaw damages on pavement distresses under different climate conditions. Based on the Long-Term Pavement Performance （LTPP） data base, the freeze-thaw damage generated by four different kinds of climate conditions are considered in this project： wet-freeze, wet-non freeze, dry- freeze and dry-non freeze. The amount of the transverse crack and the joint spalling, along with the International Roughness Index （IR/） are compared among the test sections located in these four different climate conditions. The back calculation with the Falling Weight Deflectometer （FWD） test results based on the ERES and the Estimation of Concrete Pavement Parameters （ECOPP） methods are conducted to obtain concrete slab elastic modulus and the subgrade k-value. These two parameters both decrease with service time under freeze condition. Finally, MEPDG simulation is conducted to simulate the IR/development with service year. These results showed the reasonable freeze-thaw damage development with pavement service life and under different climate conditions.
文摘This study investigates the influence of using ground palm oil fuel ash(G-POFA) from 10%-30% as cement replacement(by weight) on the cement mortar's pH under various curing conditions. These findings were supplemented by thermal gravimetric analysis(TGA). Moreover, the resistance of G-POFA blended cement mortars to water absorption and sorptivity was determined. Further, the k-value test was carried out to explain the pozzolanic and filler behavior of G-POFA and to support the results obtained from TGA. It was found that there was no significant impact of several curing conditions on the pH of mortars. The mortar with 10% G-POFA in replacement of cement(G-POFA-10) exhibited the best resistance against water absorption and sorptivity.
基金This study was supported by the National Natural Science Foundation of China(Grant no.41401299)the National Basic Research Program of China(Grant no.2007CB407201)the USDA-ARS Grazinglands Research Laboratory.The authors would like to thank Dr.Römkens M.J.M.,Dr.Xiangming Xiao,the editors and anonymous reviewers for their helpful comments and suggestions.
文摘Soil erodibility(K-factor)is an essential factor in soil erosion prediction and conservation practises.The major obstacles to any accurate,large-scale soil erodibility estimation are the lack of necessary data on soil characteristics and the misuse of variable K factor calculators.In this study,we assessed the per-formance of available erodibility estimators Universal Soil Loss Equation(USLE),Revised Universal Soil Loss Equation(RUSLE),Erosion Productivity Impact Calculator(EPIC)and the Geometric Mean Diameter based(Dg)model for different geographic regions based on the Chinese soil erodibility database(CSED).Results showed that previous estimators overestimated almost all K-values.Furthermore,only the USLE and Dg approaches could be directly and reliably applicable to black and loess soil regions.Based on the nonlinear best ftting techniques,we improved soil erodibility prediction by combining Dg and soil or ganic matter(SOM).The NSE,R^(2)and RE values were 0.94,0.67 and 9.5%after calibrating the results independently:similar model performance was showed for the validation process.The results obtained via the proposed approach were more accurate that the former K-value predictions.Moreover,those improvements allowed us to effectively establish a regional soil erodibility map(1:250,000 scale)of water erosion areas in China.The mean K-value of Chinese water erosion regions was 0.0321(t ha h).(ha MJ mm)^(-1)with a standard deviation of 0.0107(t ha h).(ha MJ mm)^(-1);K-values present a decreasing trend from North to South in water erosion areas in China.The yield soil erodibility dataset also sa-tisfactorily corresponded to former K-values from diferent scales(local,regional,and national).
