Short fibers have been widely used to prepare the fiber reinforced asphalt concrete (FRAC). However, internal interactions between fiber and other phases of asphalt concrete are unclear although experimental methods have been used to design the FRAC successfully. In this paper, numerical method was used to investigate the reinforced mechanism of FRAC from microperspective. 2D micromechanical model of FRAC was established based on Monte Carlo theory. Effects of fiber length and content on stress state of asphalt mortar, effective modulus, and viscoelastic deformation of asphalt concrete were investigated. Indirect tensile stiffness modulus (ITSM) test and uniaxial creep test were carried out to verify the numerical results. Results show that maximum stress of asphalt mortar is lower compared to the control concrete when the fiber length is longer than 12 mm. Fiber reduces the stress level of asphalt mortar significantly. Fiber length has no significant influence on the effective modulus of asphalt concrete. Fiber length and content both have notable impacts on the viscoelastic performance of FRAC. Fiber length should be given more attention in the future design of FRAC except the content.
The calcareous coal gangue, fly ash, lime powder and a small amount of cement mixture, which are selected from the Hanxing area, are mixed into a calcareous coal gangue mixture. An experimental study was done on the cleavage strength of this mixture. According to the method of uniform design, 8 groups of test matching scheme of calcareous coal gangue mixture were designed. The experiments were conducted on calcareous coal gangue mixtures in various matching proportions. The experimental results are analyzed by regression analysis model. The regression equation between the calcareous coal gangue mixture indirect tensile strength (cleavage strength) and the admixture dosage is established. By using the regression analysis model, the influence of the dosage of fly ash, calces, and cement on the calcareous coal gangue mixture's indirect tensile strength is analyzed.
In this paper, an interfacial penny-shaped crack between magnetoelectroelastic thin film and elastic substrate subjected to mechanical and electric loads is investigated. Four kinds of crack-face magnetoelectrically boundary conditions are adopted. Using Hankel transform technique, the mixed boundary value problem is reduced to a system of singular integral equations. The integral equations are further reduced to a system of algebraic equations with the aid of Jacobi polynomials. The stress intensity factor and energy release rate are determined. Numerical results reveal the effects of electric and magnetic loadings, magnetoelectroelastic boundary conditions and material parameters of composite on crack propagation and growth. The results seem useful for design of the magnetoelectroelastic composite structures and devices of high performance.
Considering the freeze-thaw damages of coal gangue-fly ash-lime (CG-FA-L) mixture road base, this paper applies the computed tomography (CT) scan to investigate the freeze-thaw damage features of the mixture. Several freeze-thaw tests were carried out to disclose the attenuation law of the frost-resistance coefficient of the mixture. The micro-defect propagation of the CG-FA-L was analyzed by comparing the gray level histograms of the CT images on each specimen before and after freeze-thaw cycles. The loss of cross-sectional area in each specimen was calculated quantitatively by image segmentation. The results show that the frost-resistance index attenuated linearly with the increase in the number of cycles; the defects induced by freeze-thaw cycles were mostly less than 15mm deep, and grew at an increasingly fast speed as the number of cycles surpassed 5; the micro-defect caused by freeze-thaw action mainly affected the depth between 15 and 35mm; under the freeze-thaw cycles, the micro-defects inside the mixture mostly appeared in the cementitious materials of the fly ash and lime; the CT technology was applied satisfactorily in the analysis on the freeze-thaw features of the CG-FA-L mixture.
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