The elevated temperatures adversely affect the durability and lifespan of pavement.Understanding the factors that influence asphalt pavement temperature offers valuable insights for creating climate-friendly cities wi...The elevated temperatures adversely affect the durability and lifespan of pavement.Understanding the factors that influence asphalt pavement temperature offers valuable insights for creating climate-friendly cities with cooler pavement surfaces.In this study,three aggregates of varying types and colors,two types of bitumen(one without pigment and one with the addition of red pigment,Fe2O3),and two levels of mean texture depth(MTD),high and low,were utilized to create asphalt samples using Marshall's method.A total of 38 thermocouple sensors were employed to simultaneously record temperatures in three areas within the samples,as well as the temperatures in shaded and sunlit conditions over a period of 17 days.Furthermore,a comprehensive evaluation was conducted to assess the impact of each factor on the solar reflectance index(SRI).Twelve general linear models(GLMs)were developed using a full factorial design of experiment,and five models with an R2 greater than 95%were evaluated and analyzed.The analysis,based on the coefficients derived from the GLMs,indicates that the mean MTD is the most significant parameter affecting surface temperature.Pigment color emerged as the second most influential factor affecting both surface and bottom temperatures.Additionally,the findings revealed that MTD has the greatest impact on the SRI,followed by pigment color and aggregate color.It was also determined that the interaction between density,pigment color,and aggregate color plays a crucial role in determining the temperatures of both the surface and bottom of the specimens.展开更多
Bulk density(BD) is an important soil physical property and has significant effect on soil water conservation function. Indirect methods, which are called pedotransfer functions(PTFs), have replaced direct measurement...Bulk density(BD) is an important soil physical property and has significant effect on soil water conservation function. Indirect methods, which are called pedotransfer functions(PTFs), have replaced direct measurement and can acquire the missing data of BD during routine soil surveys. In this study, multiple linear regression(MLR) and artificial neuron network(ANN) methods were used to develop PTFs for predicting BD from soil organic carbon(OC), texture and depth in the Three-River Headwater region of Qinghai Province, China. The performances of the developed PTFs were compared with 14 published PTFs using four indexes, the mean error(ME), standard deviation error(SDE), root mean squared error(RMSE) and coefficient of determination(R^2). Results showed that the performances of published PTFs developed using exponential regression were better than those developed using linear regression from OC. Alexander(1980)-B, Alexander(1980)-A and Manrique and Jones(1991)-B PTFs, which had good predictions, could be applied for the soils in the study area. The PTFs developed using MLR(MLR-PTFs) and ANN(ANN-PTFs) had better soil BD predictions than most of published PTFs. The ANN-PTFs had better performances than the MLR-PTFs and their performances could be improved when soil texture and depth were added as predictor variables. The idea of developing PTFs for predicting soil BD in the study area could provide reference for other areas and the results could lay foundation for the estimation of soil water retention and carbon pool.展开更多
Skid resistance is an important parameter for highway designs, construction, management, maintenance and safety. The purpose of this manuscript is to propose the correlation between skid resistance, which is measured ...Skid resistance is an important parameter for highway designs, construction, management, maintenance and safety. The purpose of this manuscript is to propose the correlation between skid resistance, which is measured as skid resistance trailer, and mean profile depth （MPD） or the macro surface texture, which is measured by vehicle mounted laser, so that highway agencies can predict the skid resistance of pavement without the use of expensive and time consuming skid resistance trailer, which also causes disruption of traffic in use. In this research skid numbers and MPD from 5 new asphalt pavements and 4 old asphalt pavements were collected using a locked wheel skid trailer and a vehicle mounted laser. Using the data collected, a correlation between the skid number （SN40R） collected by locked wheel skid tester and the texture data or MPD collected by a vehicle mounted laser operating at highway speeds was developed. The proposed correlation for new pavements was positive for MPD values less than 0.75 mm to reach a peak SN40R value, then there was a negative correlation as the MPD increases until the MPD value was equal to 1.1 mm and beyond the MPD value of 1.1 mm to the maximum value of 1.4 mm, SN40R value remained almost constant. There were significant data scatter for the MPD value of 0.8 mm. To explain these results, water film thickness during the friction test was calculated and the critical MPD was defined. The effect of sealed water pool on the SN40R was discussed. The test result showed a similar trend for older asphalt pavements, but with lower SN40R values due to the polishing of pavement micro-texture by traffic. Hence, a reduction factor was proposed for older pavements based on cumulative traffic volume for the above correlation to predict the skid resistance of older pavements.展开更多
Segregation in hot mix asphalt(HMA)mixtures is defined as the separation of the coarse aggregate particles in the mixtures from the rest of the mass.Segregation can be a result of aggregate stockpiling and handling,pr...Segregation in hot mix asphalt(HMA)mixtures is defined as the separation of the coarse aggregate particles in the mixtures from the rest of the mass.Segregation can be a result of aggregate stockpiling and handling,production,storage,truck loading practices,con-struction practices,and equipment adjustments.Segregation is usually evaluated visually,which is considered as a subjective method with no definite limits and depends on the evaluator’s opinion.This study uses two mechanistic surface texture indicators,i.e.,mean texture depth(MTD)that is measured using sand patch method and mean profile depth(MPD)using laser texture profilometer to evaluate if a road section is segregated or not.The sand patch method is standardized in ASTM E965-15(2019)"for Measuring Pavement Macrotexture Depth Using Volumetric Technique".MPD is covered by the inter-national standards ASTM E1845-15"Standard Practice for Calculating Pavement Macrotexture Mean Profile Depth".Using both measured MTD values at grid point crossings,and average MPD values at 25 m intervals in the wheel paths,in addition to the use of statistical analysis of the obtained data,assuming that the obtained data are normally distributed and finding the 95%probability limits of the MTD and MPD values,it is possible to prove the closeness of the obtained texture depth indicator data,homogeneity of the road section,and that the segregation is only present at very limited localized locations.展开更多
Pavement skid resistance is critical for contributing to traffic safety.In this study,two pavement specimens were fabricated using different aggregate gradations and binder contents.Compaction efforts were made to ens...Pavement skid resistance is critical for contributing to traffic safety.In this study,two pavement specimens were fabricated using different aggregate gradations and binder contents.Compaction efforts were made to ensure the same porosity of the two specimens.Some parameters related to the surface morphology were measured using the sand patching method and a 3D laser.The parameters include mean texture depth(MTD),interface roughness(R_(a)),skewness(R_(sk)),kurtosis(R_(ku)),fractal dimension(D)and parameters related to material ratio curve.Relationships between these parameters and skid resistance were quantitatively developed.Skid resistance increased along with the increase of MTD,R_(a) and D.From the surface A to surface B,MTD increased from 0.23 to 1.10 mm,R_(a) increased from 0.93 to 1.80 mm,D increased from 2.25 to 2.43 and the British Pendulum Number increased from 80 to 97 accordingly.The comprehensive analysis could assist scholars and practitioners to facilitate the understanding of tyre-pavement interaction and further assist pavement design.展开更多
文摘The elevated temperatures adversely affect the durability and lifespan of pavement.Understanding the factors that influence asphalt pavement temperature offers valuable insights for creating climate-friendly cities with cooler pavement surfaces.In this study,three aggregates of varying types and colors,two types of bitumen(one without pigment and one with the addition of red pigment,Fe2O3),and two levels of mean texture depth(MTD),high and low,were utilized to create asphalt samples using Marshall's method.A total of 38 thermocouple sensors were employed to simultaneously record temperatures in three areas within the samples,as well as the temperatures in shaded and sunlit conditions over a period of 17 days.Furthermore,a comprehensive evaluation was conducted to assess the impact of each factor on the solar reflectance index(SRI).Twelve general linear models(GLMs)were developed using a full factorial design of experiment,and five models with an R2 greater than 95%were evaluated and analyzed.The analysis,based on the coefficients derived from the GLMs,indicates that the mean MTD is the most significant parameter affecting surface temperature.Pigment color emerged as the second most influential factor affecting both surface and bottom temperatures.Additionally,the findings revealed that MTD has the greatest impact on the SRI,followed by pigment color and aggregate color.It was also determined that the interaction between density,pigment color,and aggregate color plays a crucial role in determining the temperatures of both the surface and bottom of the specimens.
基金supported by the National Key Technology R&D Program of China(No.2009BAC61B01)the National Basic Research Program(973Program) of China(No.2012CB95570002)the Innovative Team(Investigation and Management for Agricultural Land Resource) of Predominant Science and Technology in Chinese Academy of Agricultural Engineering
文摘Bulk density(BD) is an important soil physical property and has significant effect on soil water conservation function. Indirect methods, which are called pedotransfer functions(PTFs), have replaced direct measurement and can acquire the missing data of BD during routine soil surveys. In this study, multiple linear regression(MLR) and artificial neuron network(ANN) methods were used to develop PTFs for predicting BD from soil organic carbon(OC), texture and depth in the Three-River Headwater region of Qinghai Province, China. The performances of the developed PTFs were compared with 14 published PTFs using four indexes, the mean error(ME), standard deviation error(SDE), root mean squared error(RMSE) and coefficient of determination(R^2). Results showed that the performances of published PTFs developed using exponential regression were better than those developed using linear regression from OC. Alexander(1980)-B, Alexander(1980)-A and Manrique and Jones(1991)-B PTFs, which had good predictions, could be applied for the soils in the study area. The PTFs developed using MLR(MLR-PTFs) and ANN(ANN-PTFs) had better soil BD predictions than most of published PTFs. The ANN-PTFs had better performances than the MLR-PTFs and their performances could be improved when soil texture and depth were added as predictor variables. The idea of developing PTFs for predicting soil BD in the study area could provide reference for other areas and the results could lay foundation for the estimation of soil water retention and carbon pool.
基金sponsored by a research contract from the New Jersey Department of Transportation (FHWA-NJ-2009020)
文摘Skid resistance is an important parameter for highway designs, construction, management, maintenance and safety. The purpose of this manuscript is to propose the correlation between skid resistance, which is measured as skid resistance trailer, and mean profile depth （MPD） or the macro surface texture, which is measured by vehicle mounted laser, so that highway agencies can predict the skid resistance of pavement without the use of expensive and time consuming skid resistance trailer, which also causes disruption of traffic in use. In this research skid numbers and MPD from 5 new asphalt pavements and 4 old asphalt pavements were collected using a locked wheel skid trailer and a vehicle mounted laser. Using the data collected, a correlation between the skid number （SN40R） collected by locked wheel skid tester and the texture data or MPD collected by a vehicle mounted laser operating at highway speeds was developed. The proposed correlation for new pavements was positive for MPD values less than 0.75 mm to reach a peak SN40R value, then there was a negative correlation as the MPD increases until the MPD value was equal to 1.1 mm and beyond the MPD value of 1.1 mm to the maximum value of 1.4 mm, SN40R value remained almost constant. There were significant data scatter for the MPD value of 0.8 mm. To explain these results, water film thickness during the friction test was calculated and the critical MPD was defined. The effect of sealed water pool on the SN40R was discussed. The test result showed a similar trend for older asphalt pavements, but with lower SN40R values due to the polishing of pavement micro-texture by traffic. Hence, a reduction factor was proposed for older pavements based on cumulative traffic volume for the above correlation to predict the skid resistance of older pavements.
文摘Segregation in hot mix asphalt(HMA)mixtures is defined as the separation of the coarse aggregate particles in the mixtures from the rest of the mass.Segregation can be a result of aggregate stockpiling and handling,production,storage,truck loading practices,con-struction practices,and equipment adjustments.Segregation is usually evaluated visually,which is considered as a subjective method with no definite limits and depends on the evaluator’s opinion.This study uses two mechanistic surface texture indicators,i.e.,mean texture depth(MTD)that is measured using sand patch method and mean profile depth(MPD)using laser texture profilometer to evaluate if a road section is segregated or not.The sand patch method is standardized in ASTM E965-15(2019)"for Measuring Pavement Macrotexture Depth Using Volumetric Technique".MPD is covered by the inter-national standards ASTM E1845-15"Standard Practice for Calculating Pavement Macrotexture Mean Profile Depth".Using both measured MTD values at grid point crossings,and average MPD values at 25 m intervals in the wheel paths,in addition to the use of statistical analysis of the obtained data,assuming that the obtained data are normally distributed and finding the 95%probability limits of the MTD and MPD values,it is possible to prove the closeness of the obtained texture depth indicator data,homogeneity of the road section,and that the segregation is only present at very limited localized locations.
基金funded by the National Natural Science Foun-dation of China (Grant Nos.52008405 and 51778638),to which the authors are very grateful.
文摘Pavement skid resistance is critical for contributing to traffic safety.In this study,two pavement specimens were fabricated using different aggregate gradations and binder contents.Compaction efforts were made to ensure the same porosity of the two specimens.Some parameters related to the surface morphology were measured using the sand patching method and a 3D laser.The parameters include mean texture depth(MTD),interface roughness(R_(a)),skewness(R_(sk)),kurtosis(R_(ku)),fractal dimension(D)and parameters related to material ratio curve.Relationships between these parameters and skid resistance were quantitatively developed.Skid resistance increased along with the increase of MTD,R_(a) and D.From the surface A to surface B,MTD increased from 0.23 to 1.10 mm,R_(a) increased from 0.93 to 1.80 mm,D increased from 2.25 to 2.43 and the British Pendulum Number increased from 80 to 97 accordingly.The comprehensive analysis could assist scholars and practitioners to facilitate the understanding of tyre-pavement interaction and further assist pavement design.
