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Significant amounts of finely ground waste powder are produced during the heating process of silica-rich limestone aggregates in asphalt concrete plants. This resulting by-product poses challenges and opportunities in the scope of environmental sustainability, waste management, and resource utilization. Some attempts were made to utilize limestone powder in concrete production; however, its use was limited to a small quantity. Thus, this paper explores the feasibility of utilizing a high proportion of silica-rich waste limestone powder (LSP) in combination with ground granulated blast furnace slag (GGBS) and fly ash (FA) as precursor materials in producing alkali-activated mixtures. A series of experiments were conducted to evaluate the mechanical properties, durability characteristics, and microstructural analysis of the developed water-cured alkali-activated mortars and concrete. The results showed that the mixtures having a high volume of LSP (40%–50%) and GGBS/FA as precursor materials demonstrated adequate flowability (186–240 mm), satisfactory compressive strength (33–45 MPa), and good durability (water absorption was in the range of 2.6%–3.8%). In addition, the microstructural analysis in terms of scanning electron microscope (SEM), energy dispersive spectroscope (EDS), and Fourier transform infrared (FTIR) spectrometer revealed a dense microstructure with gel formation, which was correlated to mechanical strength. Finally, the environmental impact based on the life cycle assessment was evaluated, and the developed mixtures exhibited an average emission reduction of 63% compared with traditional concrete. The findings of this study suggest that waste LSP, typically disposed in landfills, can be effectively utilized up to 50% in the production of environmentally sustainable concrete. [ABSTRACT FROM AUTHOR]

This work deals with the damping and vibration characteristics evaluation of sandwich beams based on higher-order shear deformation theories (HSDT's). The studied sandwich beams are composed of composite materials at faces and homogeneous, isotropic viscoelastic material in the core layer. This latter (viscoelastic material) is described by complex Young's modulus in the frequency domain. Indeed, the real part represents the stiffness, and the imaginary one describes the damping property. Nonlinear damping parameters and frequency curves are obtained using the nonlinear equation of frequency amplitude governed by multiple complex coefficients. In conjunction with a one-mode Galerkin's procedure, the harmonic balance method is employed to obtain the nonlinear loss factor and the response frequency curves. The nonlinear frequency value and, in turn, the system loss factor ratio are obtained for various amplitudes to examine the impacts of the ply angle of fiber-reinforced composite faces, the viscoelastic shear modulus, the shear deformation model, for considering different geometric and material parameters. In the framework of this study, one attempt is to describe a better way to achieve satisfactory passive vibration control of the laminated beams. [ABSTRACT FROM AUTHOR]

This paper seeks to study and investigate the wave dispersion behavior in porous functionally graded (FG) carbon nanotube-reinforced composite (CNTRC) beams. The beams comprise four patterns of single-walled carbon nanotubes (SWCNTs) distributed in the polymer matrix. The mixture rule is used to estimate the CNTR beams’ material properties. Innovative to this study are three porosity models describing the porosity distributions within the matrix and a three-unknown integral higher-order shear deformation theory (HSDT) modeling analytically the CNTRC beams with a novel shape function expressing the distributions of shear stresses and strains. The equations of motion for CNTRC beams are derived based on Hamilton’s principle. The stiffness and mass matrices are formulated by a generalized solution of harmonic wave propagation to express the wave dispersion relations. Numerical comparisons with previously published works verify the applicability of this mathematical model. The paper studies the effects of CNTs patterns through the polymer matrix, porosity models, and volume fractions of the porosity and CNTs. Based on the analytical results, augmenting the porosity and CNTs volume fractions leads to faster phase and group velocities. Furthermore, the impact of CNTs volume fractions, porosity models, and porosity volume fractions becomes more pronounced as the wavenumber increases. [ABSTRACT FROM AUTHOR]