Application of Fly Ash in ASHphalt Concrete : from Challenges to Opportunities
Fly ash has been effectively used for many years in producing high performance concrete, with limited use in asphalt pavements. This is possibly because the performance benefits that fly ash provides to asphalt mixtures are under-investigated. The reported research investigated the interaction of fly ash with different types of asphalt binders and documented important improvements found in the critical properties of asphalt. Microstructural investigation demonstrated in previous work, that crack-arresting behavior was successfully induced by evenly distributed fly ash particles within the bitumen matrix. Investigation of the rheological performance of blends of asphalt binders with different types of ash using dynamic shear rheometer confirmed the feasibility of using fly ash to improve the performance of asphalt
Review of sustainability, pretreatment, and engineering considerations of asphalt modifiers from the industrial solid wastes
Abstract The escalating mass of solid waste at an overwhelming sum requires a global attention to strive for efficient waste management and to outsource the ecological treatments. The asphalt pavement industry that consumes a vast scale of natural resources while contributing to thermal and greenhouse emissions is viewed as a high potential alternative for the application of solid waste as asphalt modifier and substantial waste reduction. In efforts to urge for cleaner and greener asphalt production, a growing trend towards usage of solid waste as a renewable material is paving a sustainable future for the asphalt pavement industry. The economic options of incorporating solid waste into the asphaltic mixture coupled with proven effective performances are a green and cost-effective alternative to mitigate various pavement distresses. Various options either as coarse or fine aggregates and as fillers in powder, ash, or fibre form are to stimulate further research interest to incorporate a diversified range of solid waste into the asphalt binder and asphalt mixture. Prior to incorporating solid waste into the asphaltic mixture through the selected options, prerequisite tests in addressing engineering limitations due to the unknown properties of solid waste are reviewed. The concerns on environmental impact are given heavy metals leaching possibilities into water sources are addressed by Toxicity Characterization Leaching Procedure test, to leverage further the systematic reuse of solid waste in steering towards the cleaner production of the asphalt mixture. The microcosmic traits of solid waste namely surface morphology, mineralogical composition and chemical composition are summarized based on the usage of Scanning Electron Microscope, X-Ray Diffraction, and X-Ray Fluorescence, respectively. This systematic review is an enactment and stimulus for researchers to have a general overview before incorporating solid waste into asphalt mixture.
L1 Adaptive Controller for Attitude Control of Multirotors
In this work we show an application of L1 Adaptive control theory for attitude control of UAVs. We implement the flight control system on a multirotor to show robustness and precise attitude tracking in the presence of modeling uncertainties and environmental disturbances. We choose backstepping control architecture, since the kinematics and dynamics of multirotors in most cases can be written in strict feedback form. We further exploit the fact that the kinematics of the plant, while free of uncertainties, is nonlinear, which makes it highly suitable for dynamic inversion control at each level of backstepping. On the other hand, plant dynamics is uncertain and is affected by environmental disturbances such as wind gusts, unmodeled dynamics etc. Therefore, we consider 3 variants of the control architecture. The first method uses backstepping to determine the moment demand and augments it with the L1 adaptive controller to account for uncertainties and provide robustness with guaranteed transient performance. The second architecture apply the concept of L1 adaptive backstepping to the same problem; and the third architecture uses L1 backstepping for quaternion representation of the system dynamics, which helps to avoid the singularities associated with Euler angles.