世界経済・社会統計 = World development indicators

http://www.diva-portal.org/smash/get/diva2:711917/FULLTEXT01

Polymer modification of bitumen : Advances and challenges

http://www.saetaequina.com/files/1-s2_0-S0950061811006763-main.pdf

A simple review of soil reinforcement by using natural and synthetic fibers

The population bomb.

http://research.me.mtu.edu/abstracts/Odegard%20-%20Nanoclay-%20modified%20asphalt%20materials.pdf

Nanoclay-modified asphalt materials: Preparation and characterization

This paper presents the development of micro-mechanical discrete element model for hot mix asphalt (HMA) mixtures modified with carbon nanofibers using the advanced imaging techniques. Shape-structural model of two-phased HMA consisting of aggregate and matrix was generated using cluster of small discrete disk-shaped particles for each phase. Three contact models, shear and normal stiffness, static and sliding friction, and inter-particle contact bonds were employed to model the constitutive behavior of the HMA mixture. To validate the developed DEM model an experimental study was executed. It was observed that the uniaxial compressive test simulation reasonably predicted the stress–strain behavior of the HMA mixture. The dynamic modulus and strength obtained from indirect tensile test were similar to the predicted moduli and strength using the DEM under the quasi-elastic state for all the HMA mixtures studied.

Imaged-based discrete element modeling of hot mix asphalt mixtures

This paper focuses on the microstructure and fracture surface morphology of neat and carbon nanofibers (CNF) modified asphalts and hot mix asphalt (HMA) mixtures using scanning electron microscopy (SEM). Asphalt binder was modified with 1.5 % of CNF by weight of binder. The modified asphalt was used to construct HMA mixtures at various CNF dosages, mixed with aggregate, using the Superpave Gyratory compactor. Small rectangular specimens extracted from the center of large HMA samples were tested under direct tension and the fracture surface was examined under SEM. The SEM analysis developed a fundamental understanding of the role that the CNF modification plays in the performance enhancement of asphalt and HMA mixtures. It was found that CNF not only possess good adhesion characteristics but also exhibits high connectivity and were evenly distribution throughout the binder. The fracture surface morphology also revealed that CNF exhibited crack bridging at micro/nano scale which may enhance the resistance to cracking due to repeated traffic loads.

Microstructure and fracture morphology of carbon nano-fiber modified asphalt and hot mix asphalt mixtures

Development of Geopolymer-based Cement Slurries with Enhanced Thickening Time, Compressive and Shear Bond Strength and Durability

Cement based brittle matrix composites that show deflection hardening called high performance fiber reinforced cementitious composites (HPFRCC) have the potential of offering high resiliency and environmentally sustainable benefits in numerous applications. HPFRCCs have been used in numerous applications; however, more information is needed to fully understand, predict the behavior, and add functionality to HPFRCCs. This experimental research program aims to develop and characterize a new type of HPFRCC, composed of polyvinyl alcohol microfibers, carbon nanofibers (CNF), and a high volume of fly ash to form a self-sensing HPFRCC. Processing of the CNF and the HPFRCC composite matrix are studied to ensure adequate fresh mix properties and fiber dispersion. The multi-functionality of the CNFs allow for increased mechanical properties and enhanced strain and damage sensing capabilities. Digital image correlation was used extensively to capture the tensile strain and provide a visualization of the behavior of the composite under increasing displacements. CNF contents of 0.167, 0.333, 0.5, and 1.0 % were studied. Through laser diffraction analysis, sonication of CNF in a CNF/water/superplasticizer solution was found to improve particle dispersion. Mechanical testing showed that dosages of CNFs less than or equal to 0.333 % increased compressive strength, tensile strength, and stiffness. CNF had little effect on tensile ductility and toughness. Piezoresistive self-sensing strain measurement was achieved in all specimens. The addition of CNF improved the strain-sensing and allowed for stronger correlations between measured strains and correlated gauge factors. Ultimately, a CNF content of 0.333 % showed optimal results in terms of enhanced mechanical properties and self-sensing behavior for strain.

Development and characterization of self-sensing CNF HPFRCC

This paper characterizes the viscoelastic response of asphalt matrix (AM) and hot-mix asphalt (HMA) mixtures under dry and moisturedamaged conditions. The AM and HMA mixtures were made with two types of aggregates and one asphalt grade. The hydrated lime was used as a binder additive to reduce the moisture sensitivity of the mixtures. A dynamic shear rheometer was used to conduct frequency sweep and creep tests at various temperatures with AM specimens. The indirect tensile load test was conducted to characterize the creep response, tensile strength, elastic and plastic, and fatigue properties of the HMA mixtures. The results indicated that the generalized creep compliance mechanical model can effectively characterize the viscoelastic response of the AM and HMA mixtures under both wet and dry conditions. The AM testing demonstrated that the lime modification significantly improves the viscoelastic properties of the moisture-damaged AM. The fatigue life of the HMA mixtures improved because of the decrease ...

Mohammad Jamal Khattak

Papers

Imaged-based discrete element modeling of hot mix asphalt mixtures

Microstructure and fracture morphology of carbon nano-fiber modified asphalt and hot mix asphalt mixtures

Development of Geopolymer-based Cement Slurries with Enhanced Thickening Time, Compressive and Shear Bond Strength and Durability

Development and characterization of self-sensing CNF HPFRCC

Viscoelastic Behavior of Hydrated Lime-Modified Asphalt Matrix and Hot-Mix Asphalt Under Moisture Damage Conditions