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Zhanping You - One of the best experts on this subject based on the ideXlab platform.
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investigating the sensitivity of aggregate size within sand mastic by modeling the microstructure of an asphalt Mixture
Journal of Materials in Civil Engineering, 2011Co-Authors: Zhanping You, Sanjeev AdhikariAbstract:The objective of this study is to investigate the sensitivity of aggregate size within sand mastic by modeling the microstructure of an asphalt Mixture. The sensitivity of the maximum aggregate size on the sand mastic phase is investigated through discrete-element simulations. A three-dimensional (3D) discrete-element model of asphalt Mixture was prepared from X-ray computed tomography (X-ray CT) images. In the discrete-element model, an asphalt Mixture is divided into aggregate, sand mastic, and air void phases. In this study, the sand mastic is defined as fines and fine aggregates mixed with asphalt binder. Three different nominal maximum aggregate sizes (NMASs) of sand mastic, namely, 1.18 mm, 0.6 mm, and 0.3 mm, were used in the 3D model to investigate the best gradation of sand mastic. The dynamic moduli of three different NMASs of sand mastic were measured for use in the 3D discrete-element modeling simulation. Laboratory-measured dynamic moduli of asphalt Mixtures were compared with prediction results. The sand mastics with NMASs of 1.18 mm and 0.6 mm could be used to predict the asphalt Mixture Modulus across a range of temperatures and loading frequencies with good accuracy. The sand mastic with a NMAS of 0.3 mm overpredicted at high and low temperatures. The overprediction resulted from the difficulty of proper visualization of the smaller aggregate size in the model.
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Microstructural and Micromechanical Properties of Field and Lab-compacted Asphalt Mixtures
2009Co-Authors: Zhanping You, Sanjeev Adhikari, Eyad A Masad, Qingli DaiAbstract:This paper has two main objectives. The first objective is to study the microstructural properties such as air void distribution under laboratory and field compaction patterns of asphalt Mixtures. The second objective is to investigate the air void effect of the mechanical properties of the asphalt Mixtures under the field and laboratory compaction using distinct element models (DEM). The laboratory and field compacted specimens were simulated using two dimensional (2D) and three-dimensional (3D) DEM. The laboratory specimens and field core asphalt Mixture samples were scanned with X-ray computed tomography techniques to obtain the images of the asphalt Mixture microstructure with the air void distributions. Then, these specimens and samples were used to investigate the air void effect of the mechanical properties. The samples were from both laboratory and field compaction. Laboratory compaction was conducted using a Superpave gyratory compactor. Field cores were obtained from the asphalt pavements. 2D and 3D distinct element models were prepared in order to evaluate the stiffness properties of the Mixtures. In the 2D models, both vertical and horizontal-cut images of the 3D specimens were used. In addition, the relationship between the Mixture Modulus and the air void levels was investigated.
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Prediction of Dynamic Modulus of Asphalt Concrete using Two-Dimensional and Three-Dimensional Discrete Element Modeling Approach
GeoCongress 2008, 2008Co-Authors: Sanjeev Adhikari, Zhanping You, M. Emin KutayAbstract:The objective of this study is to predict the asphalt Mixture dynamic Modulus using both two-dimensional (2D) and three-dimensional (3D) discrete element models (DEM) generated using the X-ray computed tomography images. An experimental program was developed with a uniaxial compression test to measure the dynamic Modulus of asphalt mastic and asphalt Mixtures at different temperatures and loading frequencies. In the DEM simulation, the mastic properties and aggregate elastic Modulus were used as input parameters. The strain response of the asphalt mastic and Mixture models under a compressive load was monitored, and the dynamic Modulus was computed. The Mixture properties were obtained using images of aggregate, mastic, and air voids from the X-ray CT. The experimental measurements of dynamic Modulus were employed to compare with the 2D and 3D predictions. It was found that the 3D discrete element models were able to predict the Mixture Modulus across a range of temperatures and loading frequencies. The 3D DEM models prediction is much better than that of the 2D DEM models.
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Aggregate Effect on Asphalt Mixture Properties by Modeling Particle-to-Particle Interaction
Analysis of Asphalt Pavement Materials and Systems, 2007Co-Authors: Zhanping You, William G. Buttlar, Qingli DaiAbstract:A number of researchers have studied aggregate characteristics including elongation, flatness, and other shapes that are believed to affect asphalt Mixture properties such as internal resistance, rutting resistance, tensile strength, and complex Modulus etc. However, the aggregate Modulus also affects the asphalt Mixture Modulus significantly, which has not been taken into consideration. In this paper, the effect of aggregate particle-to-particle interaction was studied through numerical modeling using the discrete element modeling (DEM) approach. The individual material phases (e.g., aggregates and mastic) were modeled with clusters of discrete elements based upon laboratory testing of the individual phases. For a given set of material parameters for each phase, the degree of particle-to-particle contact in an asphalt Mixture was found to have a profound influence on overall Mixture Modulus. A parametric investigation of aggregate Modulus revealed that the contribution of aggregate Modulus to overall Mixture Modulus was very significant. Pending further experimental verification on asphalt Mixtures, this finding may shed new light on the importance of aggregate stiffness on overall Mixture properties.
Theodore L. Laufenberg - One of the best experts on this subject based on the ideXlab platform.
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Fire and bending properties of blockboard with fire retardant treated veneers
Holz als Roh- und Werkstoff, 2006Co-Authors: Theodore L. Laufenberg, Nadir Ayrilmis, R. WhiteAbstract:Untersucht wurden die Abbrand- und Biegeeigenschaften von Tischlerplatten, deren Deckfurniere mit unterschiedlichen Feuerschutzmitteln behandelt worden waren. Die Mittelschicht der Tischlerplatten bestand aus unbehandelten Tannenholzleisten. Die Decklagen bestanden aus imprägnierten Ekaba Furnieren. Die Furniere waren entweder mit Borsäure (BA), Disodium-Oktoborat-Tetrahydrat (DOT), Aluminium-Trihydrat (ATH) oder einer Mischung aus BA und DOT imprägniert worden. Festigkeits- und Steifigkeitsversuche wurden gemäss der europäischen Norm EN 310 durchgeführt. Das Brandverhalten der Tischlerplatten wurde mittels eines Kegel-Kalorimeters abgeschätzt. Die Behandlung der Furniere hatte einen geringen Einfluss auf die Biegefestigkeit, wohingegen die Steifigkeit bei den stärksten Behandlungsstufen signifikant verringert war. Die Imprägnierungen reduzierten die erwartete Flammenausbreitungsgeschwindigkeit signifikant. This study evaluated fire and bending properties of blockboards with various fire retardant treated veneers. Blockboards were manufactured using untreated fir strips and sandwiched between treated ekaba veneers at final assembly. The veneers were treated with either boric acid (BA), disodium octoborate tetrahydrate (DOT), alumina trihydrate (ATH), or a BA/DOT Mixture. Modulus of rupture and Modulus of elasticity tests were performed according to European Standard EN 310. Blockboards were also tested for fire resistance as indicated by a cone calorimeter. Treatments had little negative effect on flexural strength; flexural stiffness was significantly lower for the highest treatment levels. Treatments resulted in a significant reduction in predicted flame spread rate.
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Fire and bending properties of blockboard with fire retardant treated veneers
Holz als Roh- und Werkstoff, 2005Co-Authors: Theodore L. Laufenberg, Nadir Ayrilmis, Robert H. WhiteAbstract:This study evaluated fire and bending properties of blockboards with various fire retardant treated veneers. Blockboards were manufactured using untreated fir strips and sandwiched between treated ekaba veneers at final assembly. The veneers were treated with either boric acid (BA), disodium octoborate tetrahydrate (DOT), alumina trihydrate (ATH), or a BA/DOT Mixture. Modulus of rupture and Modulus of elasticity tests were performed according to European Standard EN 310. Blockboards were also tested for fire resistance as indicated by a cone calorimeter. Treatments had little negative effect on flexural strength; flexural stiffness was significantly lower for the highest treatment levels. Treatments resulted in a significant reduction in predicted flame spread rate.
Robert H. White - One of the best experts on this subject based on the ideXlab platform.
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Fire and bending properties of blockboard with fire retardant treated veneers
Holz als Roh- und Werkstoff, 2005Co-Authors: Theodore L. Laufenberg, Nadir Ayrilmis, Robert H. WhiteAbstract:This study evaluated fire and bending properties of blockboards with various fire retardant treated veneers. Blockboards were manufactured using untreated fir strips and sandwiched between treated ekaba veneers at final assembly. The veneers were treated with either boric acid (BA), disodium octoborate tetrahydrate (DOT), alumina trihydrate (ATH), or a BA/DOT Mixture. Modulus of rupture and Modulus of elasticity tests were performed according to European Standard EN 310. Blockboards were also tested for fire resistance as indicated by a cone calorimeter. Treatments had little negative effect on flexural strength; flexural stiffness was significantly lower for the highest treatment levels. Treatments resulted in a significant reduction in predicted flame spread rate.
Sung-do Hwang - One of the best experts on this subject based on the ideXlab platform.
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A predictive equation for dynamic Modulus of asphalt Mixtures used in Korea
Construction and Building Materials, 2010Co-Authors: Yoon-ho Cho, Dae-wook Park, Sung-do HwangAbstract:Abstract The dynamic Modulus of an asphalt Mixture is widely used as an important material property in mechanistic–empirical (ME) pavement design and analysis because it accounts temperature and time-dependent asphalt Mixture Modulus. The aim of this study is to evaluate the dynamic Modulus of asphalt Mixtures used in Korea and develop a predictive equation for Korea ME pavement design guide based on the results of dynamic Modulus tests. Asphalt Mixtures contained a granite aggregate with PG 58-22 and PG 64-22 asphalt binders were tested at five different temperatures (−10, 5, 21, 40, and 55 °C) and six different loading frequencies (0.1, 0.5, 1, 5, 10, and 25 Hz). A predictive equation was constructed based on the test data, and compared and verified between the measured and the predicted dynamic Modulus. From the results, it was found that the predictive equation correlated well with the measured values.
Sanjeev Adhikari - One of the best experts on this subject based on the ideXlab platform.
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investigating the sensitivity of aggregate size within sand mastic by modeling the microstructure of an asphalt Mixture
Journal of Materials in Civil Engineering, 2011Co-Authors: Zhanping You, Sanjeev AdhikariAbstract:The objective of this study is to investigate the sensitivity of aggregate size within sand mastic by modeling the microstructure of an asphalt Mixture. The sensitivity of the maximum aggregate size on the sand mastic phase is investigated through discrete-element simulations. A three-dimensional (3D) discrete-element model of asphalt Mixture was prepared from X-ray computed tomography (X-ray CT) images. In the discrete-element model, an asphalt Mixture is divided into aggregate, sand mastic, and air void phases. In this study, the sand mastic is defined as fines and fine aggregates mixed with asphalt binder. Three different nominal maximum aggregate sizes (NMASs) of sand mastic, namely, 1.18 mm, 0.6 mm, and 0.3 mm, were used in the 3D model to investigate the best gradation of sand mastic. The dynamic moduli of three different NMASs of sand mastic were measured for use in the 3D discrete-element modeling simulation. Laboratory-measured dynamic moduli of asphalt Mixtures were compared with prediction results. The sand mastics with NMASs of 1.18 mm and 0.6 mm could be used to predict the asphalt Mixture Modulus across a range of temperatures and loading frequencies with good accuracy. The sand mastic with a NMAS of 0.3 mm overpredicted at high and low temperatures. The overprediction resulted from the difficulty of proper visualization of the smaller aggregate size in the model.
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Microstructural and Micromechanical Properties of Field and Lab-compacted Asphalt Mixtures
2009Co-Authors: Zhanping You, Sanjeev Adhikari, Eyad A Masad, Qingli DaiAbstract:This paper has two main objectives. The first objective is to study the microstructural properties such as air void distribution under laboratory and field compaction patterns of asphalt Mixtures. The second objective is to investigate the air void effect of the mechanical properties of the asphalt Mixtures under the field and laboratory compaction using distinct element models (DEM). The laboratory and field compacted specimens were simulated using two dimensional (2D) and three-dimensional (3D) DEM. The laboratory specimens and field core asphalt Mixture samples were scanned with X-ray computed tomography techniques to obtain the images of the asphalt Mixture microstructure with the air void distributions. Then, these specimens and samples were used to investigate the air void effect of the mechanical properties. The samples were from both laboratory and field compaction. Laboratory compaction was conducted using a Superpave gyratory compactor. Field cores were obtained from the asphalt pavements. 2D and 3D distinct element models were prepared in order to evaluate the stiffness properties of the Mixtures. In the 2D models, both vertical and horizontal-cut images of the 3D specimens were used. In addition, the relationship between the Mixture Modulus and the air void levels was investigated.
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Prediction of Dynamic Modulus of Asphalt Concrete using Two-Dimensional and Three-Dimensional Discrete Element Modeling Approach
GeoCongress 2008, 2008Co-Authors: Sanjeev Adhikari, Zhanping You, M. Emin KutayAbstract:The objective of this study is to predict the asphalt Mixture dynamic Modulus using both two-dimensional (2D) and three-dimensional (3D) discrete element models (DEM) generated using the X-ray computed tomography images. An experimental program was developed with a uniaxial compression test to measure the dynamic Modulus of asphalt mastic and asphalt Mixtures at different temperatures and loading frequencies. In the DEM simulation, the mastic properties and aggregate elastic Modulus were used as input parameters. The strain response of the asphalt mastic and Mixture models under a compressive load was monitored, and the dynamic Modulus was computed. The Mixture properties were obtained using images of aggregate, mastic, and air voids from the X-ray CT. The experimental measurements of dynamic Modulus were employed to compare with the 2D and 3D predictions. It was found that the 3D discrete element models were able to predict the Mixture Modulus across a range of temperatures and loading frequencies. The 3D DEM models prediction is much better than that of the 2D DEM models.