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Tao Tao - One of the best experts on this subject based on the ideXlab platform.

  • laboratory analysis on the surface runoff pollution reduction performance of permeable Pavements
    Science of The Total Environment, 2019
    Co-Authors: Jia Liu, Hexiang Yan, Ziyuan Liao, Kui Zhang, Arthur R Schmidt, Tao Tao
    Abstract:

    Permeable Pavements are used to address the water quality impacts of urbanization. However, few quantitative relations are available on their pollutant removal performance with respect to varying conditions, especially for different components of a permeable Pavement. Individually, the water quality performance of the surface Pavement Layer and gravel Layer of a permeable Pavement under various conditions was determined in laboratory-scale Pavement cells. Our aim was to reveal the manner in which different factors influence the ability of these two Layers to remove total suspended solids (TSS), nutrients, including nitrate (NOx-N), ammonia (NH4-N) and phosphorous (TP), chemical oxygen demand (COD), and heavy metals (copper (Cu), lead (Pb), cadmium (Cd), and zinc (Zn)), and to provide quantitative understanding of these influences. The removal efficiencies of most stormwater runoff pollutants showed a significant variation with changing rainfall intensity. NH4-N, NOx-N, TP, and TSS removal exhibited statistically negative linear relationship with rainfall intensity. TSS removal was negatively correlated with TSS concentration for the gravel Layer, whereas no obvious trend was observed for the surface Pavement Layer. The statistical results obtained demonstrate that TSS, NH4-N, NOx-N, TP, and COD were removed mainly by the surface Pavement Layer. A smaller gravel gradation was more effective for removing most pollutants, except for NOx-N and COD. Positive linear relationships were observed between the gravel Layer thickness and pollutant (TSS, TP, NH4-N, Cu, and Cd) removal. More importantly, a simple mathematical model was developed to predict the overall performance of the permeable Pavement system. By comparing with the overall measured performance, a good performance was achieved, illustrating its promising application in the design of permeable Pavements.

Chris Abadie - One of the best experts on this subject based on the ideXlab platform.

  • design and construction of foamed recycled asphalt Pavement base materials
    2005 International Symposium on Pavement RecyclingUniversidade Presbiteriana Mackenzie, 2005
    Co-Authors: Louay N Mohammad, Murad Y Abufarsakh, Zhong Wu, Chris Abadie
    Abstract:

    Utilization of existing recyclable materials has always been a key to more efficient and economical highway construction. The use of foamed asphalt technique to stabilized recycled asphalt Pavement (RAP) is one strategy for an efficient use of salvage construction materials. The main objective of this study is to investigate the potential use of foamed asphalt treated RAP as a base course material in lieu of a crushed lime stone base underneath a concrete Pavement Layer. Test sections were constructed at US Highway 190 near Baton Rouge, Louisiana and used for field evaluation of the foamed asphalt RAP base. This paper presents the laboratory mixture design of the foamed asphalt RAP, the construction of experimental base section, and the field evaluation of the stiffness of the foamed asphalt RAP base Layers using different in-situ testing devices. Preliminary results of both laboratory and field tests showed that the use of foamed asphalt treated RAP mixtures is very promising and can be used as an alternative to traditional used lime-stone base underneath of a concrete Pavement Layer.

  • louisiana experience with foamed recycled asphalt Pavement base materials
    Transportation Research Record, 2003
    Co-Authors: Louay N Mohammad, Murad Y Abufarsakh, Zhong Wu, Chris Abadie
    Abstract:

    Utilization of existing recyclable materials has always been key to more efficient and economical highway construction. Use of the foamed-asphalt (FA) technique to stabilize recycled asphalt Pavement (RAP) is one strategy for an efficient use of salvaged construction materials. The main objective of this study is to investigate the potential use of FA-treated RAP as a base course material in lieu of a crushed-limestone base beneath a concrete Pavement Layer. Test sections were constructed at US-190 near Baton Rouge, Louisiana, and used for field evaluation of the FA RAP base. The laboratory mixture design of the FA RAP, the construction of the experimental base section, and the field evaluation of the stiffness of the FA RAP base Layers using different in situ testing devices are presented. Preliminary results of both laboratory and field tests showed that the FA-treated RAP mixtures are very promising and can be used as an alternative to the traditional limestone base beneath a concrete Pavement Layer.

Robert L. Lytton - One of the best experts on this subject based on the ideXlab platform.

  • SYSTEM IDENTIFICATION METHOD FOR BACKCALCULATING Pavement Layer PROPERTIES
    Transportation Research Record, 1993
    Co-Authors: Fuming Wang, Robert L. Lytton
    Abstract:

    In recent years Pavement structural evaluation has relied increasingly on determining material properties by nondestructive deflection testing and backcalculation procedures. The technique used to achieve a convergence of the measured and predicted deflection basins plays an important role in all backcalculation approaches. An iterative method based on the system identification (SID) scheme is developed, and the SID program is used in conjunction with a multiLayer elastic model (BISAR program) to backcalculate Pavement Layer properties. Numerical examples indicate that (a) the moduli backcalculated by the suggested SID method compare well with the results from MODULUS, which is a data base backcalculation program, and other developed iterative backcalculation programs; (b) the SID is a quickly converging procedure, and the influence of seed values, for a relatively wide range, on the derived results is negligible; and (c) it is able to backcalculate Pavement Layer thicknesses in addition to Layer moduli.

  • Backcalculation of Pavement Layer Properties
    Nondestructive Testing of Pavements and Backcalculation of Moduli, 1
    Co-Authors: Robert L. Lytton
    Abstract:

    This paper was prepared for the symposium as a state-of-the-art paper. The paper summarizes the history and present use of nondestructive testing (NDT) and speculates on future developments and uses of NDT in backcalculating Pavement Layer properties. The paper concentrates on the backcalculation of the elastic stiffness of Pavement Layers. Measurement methods include a variety of methods of applying loads to the Pavement and a number of sensors of the Pavement response. Loading methods include static or slowly moving loads, vibration, near field impulse, and wave propagation which applies to far field measurements. A fundamental distinction is drawn between near field impulse loads which closely simulate traffic loads and far field impulse loads, the results of which must be corrected substantially to provide realistic Pavement Layer moduli.

Netra Gurung - One of the best experts on this subject based on the ideXlab platform.

  • a laboratory study on the tensile response of unbound granular base road Pavement model using geosynthetics
    Geotextiles and Geomembranes, 2003
    Co-Authors: Netra Gurung
    Abstract:

    Abstract Traditional flexible Pavement design emphasizes Pavement Layer fatigue under repeated traffic loading, but the majority of Australian rural roads consist of bituminous surfaced unbound granular base. The performance of such Pavements depends upon complex environmental factors including shrinkage and swelling of the subgrade. This paper briefly explains the structural response of a Pavement base Layer under applied tensile forces in a laboratory set-up. The research involves a 100 mm thick fine crushed rock Pavement Layer, which has been stretched horizontally by the opening of a crack in the underlying subgrade and the tensile force–displacement responses were observed in the laboratory. Experimental results show higher tensile resistance of geosynthetics (geotextile, geogrid) inclusion in the Pavement base and such high tensile responses will significantly influence the behavior of the Pavement surfaces.

Michael Darter - One of the best experts on this subject based on the ideXlab platform.

  • Comparison of As-Constructed and As-Designed Flexible Pavement Layer Thicknesses
    Transportation Research Record: Journal of the Transportation Research Board, 2003
    Co-Authors: Goran Mladenovic, Y. Jane Jiang, Olga Selezneva, Susanne Aref, Michael Darter
    Abstract:

    Sound Pavement design is important for improving Pavement performance, but construction is equally critical. Because of variations in Pavement construction, the as-constructed Pavement Layer thickness varies spatially within a Pavement section, and the mean constructed Pavement Layer thickness often deviates from the designed values. The as-constructed Pavement Layer thicknesses are compared to their design values by using data from the newly constructed flexible Pavement sections in the Long-Term Pavement Performance program. First, the distribution type of the mean Layer thickness deviation was investigated, and a combined statistical test for skewness and kurtosis showed that the mean thickness deviations may be assumed to be normally distributed for a given Layer type and target thickness. Typical thickness deviation summary statistics values were derived to estimate the extent of deviations from the design thicknesses. Second, the analysis showed that elevation thickness data differ from the core examination data. Furthermore, as-constructed Layer thickness values were compared to their design values by looking into the percentage of the individual measurements falling into specified ranges from the design values and by using two-sided and one-sided t-tests to compare the mean constructed thicknesses and the design values. The analyses showed that the mean constructed Layer thicknesses tend to be above the design value for the thinner Layers and below the design value for the thicker Layers for the same Layer and material type. Results from the study will be useful as inputs for reliability-based design procedures.

  • Estimation of Pavement Layer Thickness Variability for Reliability-Based Design
    Transportation Research Record, 2003
    Co-Authors: Y. Jane Jiang, Goran Mladenovic, Olga Selezneva, Susanne Aref, Michael Darter
    Abstract:

    Estimating the variability of key Pavement design inputs is essential to reliability-based Pavement design. The thickness of most Pavement Layers has a great impact on the outcome of practically all analyses of Pavement performance. The within-section Layer thickness variability is investigated here, as is the extent of the mean Layer thickness deviation from its design thickness. Pavement Layer thickness data (elevation and core measurements) from a large number of newly constructed flexible and rigid Pavement sections in the Long-Term Pavement Performance (LTPP) program were examined. To determine the distribution type of the thickness data, a combined statistical test for skewness and kurtosis showed that (a) thickness variations within a Layer indicate a normal distribution for 86% of 1,034 Layers and (b) the mean thickness deviations from the design values may be assumed to be normally distributed for a Layer having a given type and design thickness. The estimated thickness-within-Layer variability values and the estimated typical thickness deviations derived from LTPP data may serve as benchmarks for use in Pavement design reliability, construction quality assurance specifications, and other research studies. In addition, statistical comparisons of Layer thickness variability indicators were made between the elevation and core Layer thickness data to determine whether there are systematic differences between these two measuring methods. These results will be very useful to both researchers and practitioners who develop or use reliability-based Pavement design procedures.