The Experts below are selected from a list of 183 Experts worldwide ranked by ideXlab platform
J Formosa - One of the best experts on this subject based on the ideXlab platform.
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use of weathered and fresh bottom ash mix layers as a Subbase in road constructions environmental behavior enhancement by means of a retaining barrier
Chemosphere, 2014Co-Authors: R Del Vallezermeno, J M Chimenos, J Giropaloma, J FormosaAbstract:The presence of neoformed cement-like phases during the weathering of non-stabilized freshly quenched bottom ash favors the development of a bound pavement Material with improved mechanical properties. Use of weathered and freshly quenched bottom ash mix layers placed one over the other allowed the retention of leached heavy metals and metalloids by means of a reactive percolation barrier. The addition of 50% of weathered bottom ash to the total Subbase content diminished the release of toxic species to below environmental regulatory limits. The mechanisms of retention and the different processes and factors responsible of leaching strongly depended on the contaminant under concern as well as on the chemical and physical factors. Thus, the immediate reuse of freshly quenched bottom ash as a Subbase Material in road constructions is possible, as both the mechanical properties and long-term leachability are enhanced.
Ahmed Ebrahim Abu Elmaaty Behiry - One of the best experts on this subject based on the ideXlab platform.
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evaluation of steel slag and crushed limestone mixtures as Subbase Material in flexible pavement
Ain Shams Engineering Journal, 2013Co-Authors: Ahmed Ebrahim Abu Elmaaty BehiryAbstract:Abstract Steel slag is produced as a by-product during the oxidation of steel pellets in an electric arc furnace. This by-product that mainly consists of calcium carbonate is broken down to smaller sizes to be used as aggregates in pavement layers. They are particularly useful in areas where a good-quality aggregate is scarce. This research study was conducted to evaluate the effect of quantity of steel slag on the mechanical properties of blended mixes with crushed limestone aggregates, which used as Subbase Material in Egypt. Moreover, a theoretical analysis was employed to estimate the resistance for failure factors such as vertical deformations, vertical and radial stresses and vertical strains of Subbase under overweight trucks loads. These loads cause severe deterioration to the pavement and thus reduce its life. The results indicated that the mechanical characteristics, and the resistance factors were improved by adding steel slag to the crushed limestone.
Yusuf Mehta - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of Compaction Characteristics of Unbound Material Using Superpave Gyratory Compactor During Construction and Trafficking
2020Co-Authors: Beena Sukumaran, Kevin Mcgarvey, Casey Hurt, Nicholas Lambert, Yusuf MehtaAbstract:The compaction characteristics of the unbound Material underlying the flexible pavement have been found to be critical to the performance of the pavement structure. This is especially so for airport pavements subjected to heavy aircraft loads. From previous tests at the National Airport Pavement Test Facility (NAPTF), it was found that the Subbase experienced excessive compaction during trafficking. This study focused on studying the compaction characteristics of the Subbase Material using the Superpave Gyratory Compactor (SGC) and correlating the measured performance with field performance data. Since the SGC has not been widely used for studying the performance of unbound Material, the compaction characteristics in the Superpave Gyratory Test were calibrated to field compaction of the Subbase Material during construction at similar moisture contents. The field data collected includes density measurements with each pass of the roller during compaction and the deflection of the pavement structure during aircraft trafficking. This is correlated with the data from the SGC including changes in density with additional energy input and it was found that the SGC can be used as a suitable predictor of compaction characteristics of unbound Material. This paper provides the airport pavement designers the efficacy of using the SGC as a means of evaluating the performance of unbound Material during construction and trafficking.
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Compaction of Granular Soils Using Superpave Gyratory Compactor at Higher Confining Pressures
2020Co-Authors: Michael Panko, Kevin Mcgarvey, Casey Hurt, Yusuf Mehta, Jeremy Stevenson, Sean Coffey, Beena SukumaranAbstract:Post construction densification of Subbase Material underneath flexible asphalt surfaces is believed to lead to the failure of pavements. The compaction characteristics for granular soils have been tested for decades using standard ASTM testing methods such as the Modified Proctor test. In an attempt to find an acceptable alternative testing method, base and Subbase Materials were tested using the Superpave Gyratory Compactor (SGC). The Modified Proctor test is the current standard method for determining the optimal moisture content (OMC) and maximum dry density of soils. However, only vertical work is done on the soil sample with this method. When the SGC is used to compact granular soils, vertical work is complemented by shear work applied to the soil sample due to the gyration angle. Effects of the combination of vertical and shear work on final density were examined analytically by observing compaction curves and final densities. The confining pressure and number of gyrations were the varied parameters. Densities achieved with the SGC were compared to the densities found using the Modified Proctor. With reliable field data, relatively high confining pressures and gyration counts could be used to simulate construction and trafficking of pavements experiencing higher loads. Increasing the number of gyrations appears to increase the densification of Subbase Materials. When increasing the confining pressure applied to samples, an increase in densification of the Materials is not immediately distinguishable indicating that most of the post construction densification of flexible pavements is due to shear work.
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Evaluation of the Compaction Characteristics of Unbound Material Using the Superpave Gyratory Compactor
Asphalt Material Characterization Accelerated Testing and Highway Management, 2009Co-Authors: Nicholas Lambert, Beena Sukumaran, Kyle Denny, Yusuf MehtaAbstract:During previous full scale tests at the National Airport Pavement Facility (NAPTF) at Atlantic City, significant consolidation of the Subbase layer occurred during aircraft trafficking accompanied by shear flow failure in the underlying low strength subgrade Material. In order to understand the compaction and shear flow characteristics of the Subbase layer during construction and trafficking, the Material was compacted in the Superpave Gyratory Compactor (SGC) at various stress levels and at different moisture contents. Since the SGC is primarily used for compaction of asphalt concrete, the compaction characteristics in the Superpave Gyratory Test were calibrated to field compaction of the Subbase Material during construction at similar moisture contents. The field data collected included the change in density of the Subbase layer during compaction with number of passes of the roller. The calibration was done by comparing the shape of the curve. The calibration provided the benchmark values for laboratory evaluation of unbound Material in SGC, such as stress level and the gyratory angle of testing. The shape of the compaction curve and the density at various gyrations levels provided an insight into the understanding of the compaction characteristics of the Subbase Material under roller compaction. This paper provides the airport pavement designers the efficacy of using the SGC as a means of evaluating the performance of unbound Material during compaction.
Beena Sukumaran - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of Compaction Characteristics of Unbound Material Using Superpave Gyratory Compactor During Construction and Trafficking
2020Co-Authors: Beena Sukumaran, Kevin Mcgarvey, Casey Hurt, Nicholas Lambert, Yusuf MehtaAbstract:The compaction characteristics of the unbound Material underlying the flexible pavement have been found to be critical to the performance of the pavement structure. This is especially so for airport pavements subjected to heavy aircraft loads. From previous tests at the National Airport Pavement Test Facility (NAPTF), it was found that the Subbase experienced excessive compaction during trafficking. This study focused on studying the compaction characteristics of the Subbase Material using the Superpave Gyratory Compactor (SGC) and correlating the measured performance with field performance data. Since the SGC has not been widely used for studying the performance of unbound Material, the compaction characteristics in the Superpave Gyratory Test were calibrated to field compaction of the Subbase Material during construction at similar moisture contents. The field data collected includes density measurements with each pass of the roller during compaction and the deflection of the pavement structure during aircraft trafficking. This is correlated with the data from the SGC including changes in density with additional energy input and it was found that the SGC can be used as a suitable predictor of compaction characteristics of unbound Material. This paper provides the airport pavement designers the efficacy of using the SGC as a means of evaluating the performance of unbound Material during construction and trafficking.
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Compaction of Granular Soils Using Superpave Gyratory Compactor at Higher Confining Pressures
2020Co-Authors: Michael Panko, Kevin Mcgarvey, Casey Hurt, Yusuf Mehta, Jeremy Stevenson, Sean Coffey, Beena SukumaranAbstract:Post construction densification of Subbase Material underneath flexible asphalt surfaces is believed to lead to the failure of pavements. The compaction characteristics for granular soils have been tested for decades using standard ASTM testing methods such as the Modified Proctor test. In an attempt to find an acceptable alternative testing method, base and Subbase Materials were tested using the Superpave Gyratory Compactor (SGC). The Modified Proctor test is the current standard method for determining the optimal moisture content (OMC) and maximum dry density of soils. However, only vertical work is done on the soil sample with this method. When the SGC is used to compact granular soils, vertical work is complemented by shear work applied to the soil sample due to the gyration angle. Effects of the combination of vertical and shear work on final density were examined analytically by observing compaction curves and final densities. The confining pressure and number of gyrations were the varied parameters. Densities achieved with the SGC were compared to the densities found using the Modified Proctor. With reliable field data, relatively high confining pressures and gyration counts could be used to simulate construction and trafficking of pavements experiencing higher loads. Increasing the number of gyrations appears to increase the densification of Subbase Materials. When increasing the confining pressure applied to samples, an increase in densification of the Materials is not immediately distinguishable indicating that most of the post construction densification of flexible pavements is due to shear work.
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assessment of field compaction of Subbase Material during construction and trafficking of heavy aircraft using the superpave gyratory compactor
2014 FAA Worldwide Airport Technology Transfer ConferenceFederal Aviation AdministrationStockton CollegeSRA International IncorporatedApplied Research, 2014Co-Authors: Carlos E Cary, Beena Sukumaran, C Kumpel, A Bagriacik, R Cohen, J Clark, M Lecorvaisier, A DaouadjiAbstract:Past full-scale pavement testing at the National Airport Pavement Test Facility (NAPTF) of the Federal Aviation Administration (FAA) has shown excessive compaction of the Subbase layer during trafficking. Modern construction compaction equipment is capable of achieving densities higher than maximum Proctor values at moisture contents drier than optimum conditions. Laboratory testing has been conducted at different moisture contents and confining pressures using the Superpave Gyratory Compactor (SGC). SGC results were found to be similar to that achieved by modern construction compaction equipment in the field. Different from the Proctor method, the shear work component added by the SGC closely replicates the aggregate crushing mechanisms observed in the field during construction and trafficking. Results suggest that the excessive compaction reported for the Subbase after trafficking is, in part, due to abrasion and attrition of the aggregate which reduces particle interlock and promotes additional compaction. Based on the test results, it is recommended to implement SGC based construction specifications in order to prevent excessive compaction from construction and trafficking. After achieving field construction density, the additional compaction observed in SGC test samples was found to be significantly smaller than the actual compaction observed in the pavement during trafficking. The suitability of the SGC to reproduce trafficking compaction in the field due to heavy aircraft loading is still under evaluation. Research efforts are currently directed to find a rational method for determining field compaction energy, which will lead to the development of a correlation between SGC test results and Material field performance during compaction and trafficking. Using compaction energy principles this correlation would allow determination of the number of roller passes required during construction in order to achieve any desired density-moisture condition. Preliminary results on the development of this approach are presented in this study.
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Evaluation of the Compaction Characteristics of Unbound Material Using the Superpave Gyratory Compactor
Asphalt Material Characterization Accelerated Testing and Highway Management, 2009Co-Authors: Nicholas Lambert, Beena Sukumaran, Kyle Denny, Yusuf MehtaAbstract:During previous full scale tests at the National Airport Pavement Facility (NAPTF) at Atlantic City, significant consolidation of the Subbase layer occurred during aircraft trafficking accompanied by shear flow failure in the underlying low strength subgrade Material. In order to understand the compaction and shear flow characteristics of the Subbase layer during construction and trafficking, the Material was compacted in the Superpave Gyratory Compactor (SGC) at various stress levels and at different moisture contents. Since the SGC is primarily used for compaction of asphalt concrete, the compaction characteristics in the Superpave Gyratory Test were calibrated to field compaction of the Subbase Material during construction at similar moisture contents. The field data collected included the change in density of the Subbase layer during compaction with number of passes of the roller. The calibration was done by comparing the shape of the curve. The calibration provided the benchmark values for laboratory evaluation of unbound Material in SGC, such as stress level and the gyratory angle of testing. The shape of the compaction curve and the density at various gyrations levels provided an insight into the understanding of the compaction characteristics of the Subbase Material under roller compaction. This paper provides the airport pavement designers the efficacy of using the SGC as a means of evaluating the performance of unbound Material during compaction.
Abdelhalim Azam - One of the best experts on this subject based on the ideXlab platform.
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evaluation of reclaimed asphalt pavement as base Subbase Material in egypt
Transportation geotechnics, 2020Co-Authors: Eman Mousa, Sherif M Elbadawy, Abdelhalim AzamAbstract:Abstract The application of reclaimed asphalt pavement (RAP) has become a common practice in road construction as a substitute to natural aggregate. The significance of RAP amount on the resilient modulus behavior, shear strength and hydraulic conductivity characteristics of unbound granular base Materials were investigated in this research. RAP was blended with crushed aggregate by different percentages ranging from 0% to 100% by the blend weight. The laboratory testing program includes modified compaction, California Bearing Ratio (CBR), permeability, and repeated and static triaxial tests. A descriptive statistical analysis was conducted on all testing results. Furthermore, the X-ray computed tomography (CT) scanning technique was applied to investigate the internal (micro) structure of specimens. It was noted that with the addition of more RAP to the blend the resilient modulus increased and the coefficient of permeability decreased. The apparent cohesion of the RAP blends increased almost linearly and the friction angle decreased as the RAP replacement level increased. The CT scanning results indicated that the virgin crushed aggregate has a higher void ratio than the RAP blends, which interpreted the lower permeability and higher resilient modulus of RAP blends. In conclusion, blending RAP with virgin aggregate produces superior quality Material for road bases.
