Self-healing concrete has established its effectiveness in repairing cracks, ultimately leading to improved durability. Additionally, there is a need to ensure that other crucial mechanical ...properties, particularly the strength of the intact (uncracked) material, remain uncompromised. Despite CaCO3 precipitation being the primary component of the bacterial reaction product responsible for healing cracks and enhancing concrete strength, leveraging the effect of bacteria on concrete's mechanical properties could be subjective, given that several factors could influence the mechanical properties in either a positive or an adverse manner. Existing reviews on the topic predominantly focus on self-healing performance (post-damage recovery), with none of the published reviews dedicated, purely, to the mechanical properties of intact self-healing cementitious/concrete material. This paper reviews the impact of bacteria on mechanical properties, with a focus on the control (intact) strength of concrete and mortar under various conditions, with or without the incorporation of other materials such as fibers, bacteria carriers, aggregate replacement, and cementitious material replacement. Since concretes with strong self-healing attributes but poor mechanical properties would be unsuitable for structural applications, a detailed correlation between the effect of bacteria on mechanical properties before and after self-healing activation is discussed. Research gaps are identified, and an outlook for future research is presented, along with the perspective of self-healing concrete/cementitious material production for robust mechanical properties. The study also contributes to addressing one of the identified research gaps – the need for a generalized self-healing performance index that incorporates both mechanical and self-healing efficiency of the material. This paper proposes a typical model for such an index and illustrates its application using numerous existing experimental results of bacterial self-healing concrete performance. This sheds light on the overall performance – both mechanical and healing – of the material.
•Critical review of bacteria-based self-healing agents' effect on uncracked concrete mechanical properties.•Closing the gap in existing review articles that mainly focus on post-damage self-healing performance.•Analysis of post-damage healing efficiency and its correlation with uncracked mechanical strength.•A data hub of different results of self-healing bacterial effects on strength.•Development of a unified performance index as a combined decision parameter for healing efficiency and strength properties.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The family of halide perovskite materials is extremely large and has gained huge attention because of their low manufacturing cost and extraordinary structural, optical, electrical, and ...optoelectronic properties. These materials also deliver a pattern for designing new materials for energy conversion and energy storage applications. Here, we synthesized potassium cadmium chloride KCdCl
3
-based halide perovskite nanocomposites with rGO and fullerene-C60 by facile solvothermal method and studied their physical and electrochemical properties. The orthorhombic phase of KCdCl
3
was confirmed from XRD spectra, and the existence of constituent elements (K, Cd, Cl, and C) was confirmed from EDX analysis. SEM images evident the successful anchoring of KCdCl
3
particles over rGO and C60. BET results revealed the high surface area, pore radius, and pore volume of the KCdCl
3
/C60 electrodes. Furthermore, the electrochemical measurements demonstrated that KCdCl
3
/C60-based electrodes have a higher specific capacitance of 1135 F/g at 5 mV/s and cyclic stability (97.6% retention over 3000th cycles) than other grown electrodes. Also, GCD measurement results revealed that KCdCl
3
/C60 electrode has a high specific capacitance of 1420 F/g, an energy density of 2052 Wh/kg, and a power density of 4.19 W/kg at 1.0 A/g than other electrodes. Finally, intensive discussion proposed that halide perovskite nanocomposite electrodes can be used efficiently as supercapacitors electrode materials for future development in this field.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
In this work, we focus on the synthesis of Cu
0.95
Zn
0.05
O and Cu
0.9
Zn
0.05
M
0.05
O (M = Cr, Co, Cd) nanocrystals by employing low-cost sol–gel method. The effect of single doping and co-doping ...on physical, antibacterial, and photocatalytic properties of CuO has been successfully investigated using characterization tools comprising XRD, SEM, FTIR, UV–Vis, and
I
–
V
measurements. X-ray diffraction pattern exhibited that the grown product of CuO has no traces of impurities, indicated the successful incorporation of dopants without changing monoclinic structure. The X-ray peak profile analysis was adopted to calculate the average crystallite size (
D
) by considering the contributions of lattice strain on peak broadening. The calculated direct energy bandgap indicated redshift (1.26 eV to 1.81) eV by co-doping. The
I
–
V
study revealed the enhancement in electrical properties by co-doping. The effects of co-doping on photocatalytic properties of CuO were studied by degradation of methylene blue (MB) and methyl orange (MO) dyes under direct sunlight. The Zn/Cd-doped nanocrystal has a higher degradation efficiency 98.4% against MB and 96.1% against MO dye in 50 min. The enhanced photodegradation is due to the generation of reactive species confirmed by scavenger's experiments. The recyclability test showed the reusability of grown catalyst up to the 4th cycle. The antibacterial property was studied against
Staphylococcus aureus
and
Klebsiella pneumoniae
bacterial strains, which showed the highest zone of inhibition 31 mm, and 32 mm for co-doped samples. Furthermore, the present study paves the path to modify the properties of CuO for optoelectronic devices, environmental, and biomedical applications.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
This work proposes the use of a mesh-free technique, derived from the generalized Taylor polynomials, for the analysis of axisymmetric plates and shells. The primary solution variable(s) is/are ...assumed to take the form of a truncated Taylor series around a point c, and the unknown coefficients of the expansion are determined using the governing differential equation(s) and boundary conditions. The method is free of shape-parameter calibration needed in some other famous mesh-free techniques such as the RBF, and is quite easy to formulate and program. Successful application of the method to several benchmark problems of axisymmetric plate and shell structures proves its robustness. The results have been verified using the existing rigorous analytical solutions that are in most cases not suited to practical engineering calculations.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
In this paper, a Stable Generalized/eXtended Finite Element Method (SGFEM) is combined with mesh adaptivity for the robust and computationally efficient simulation of mixed-mode brittle fracture ...propagation. Both
h
-refinement around the fracture front and
p
-enrichment of the analysis domain are used to control discretization errors. A Linear Elastic Fracture Mechanics (LEFM) model based on Griffith’s criterion is adopted. LEFM scaling relations are used at each fracture propagation step to back calculate SIFs that meet Griffith’s criterion. As a result, no iterations are necessary to find loading scaling parameters or fracture size that meets Griffith’s criterion. The method is validated against several experimental data sets for mode I and mode I+II fracture propagation problems. Very good agreement between SGFEM and experimental results is observed. These include fracture path, Crack Opening Displacement (COD), and load and fracture length versus COD curves. The computational efficiency of the method is also assessed.
Abstract
The performance of concrete structures strengthened with carbon fiber–reinforced polymer (CFRP) systems can depend heavily on the bond strength of the interface between the concrete and the ...reinforced polymer. Even though experimental testing can be used to derive suitable constitutive models, their interpretation and analysis is often limited by the reliability of available numerical/analytical models. The debonding in shear tests can be controlled by the highly nonlinear interaction of the bonded interface with the microcracks developing in the substrate. This process cannot be efficiently predicted by simplifying assumptions, which is why robust models accounting for those features, while relying only on material parameters that can be easily measured and interpreted, need to be developed. This paper introduces a framework for developing such models based on the discrete representation of fracture that can be easily deployed into existing finite-element codes. The substrate bond failure, in addition to the interface bond failure and any combination thereof, are automatically accounted for, and the cracks are not prespecified to the underlying finite-element mesh, which means that the results are mesh-insensitive and discretization-independent. A validation of the proposed framework was performed using modified double-shear bond tests between CFRP and concrete. An in-depth analysis was carried out to assess the influence of bond length and CFRP reinforcement area on the debonding behavior and ductility of the connection.
Based on the two-variable refined plate theory, free vibration of orthotropic plates is analyzed using the differential transform method (DTM) and the Taylor collocation method (TCM). The refined ...plate theory outperforms the classical plate theory, and its formulation is simpler than those of other higher-order theories. Without the need for any shear correction factor, the theory performs reliably. The plates considered have two opposite edges simply supported (Levy plates). The first part of the analysis considers three combinations of clamped, simply supported and free edge conditions for the other two edges, keeping one of them simply supported. Detailed formulations of DTM and TCM for the free vibration analysis are given and, consequently, used to predict the frequency parameters and the effect of various factors ranging from geometric to material parameters. Next, the paper presents analysis of some cases, the multi-span plates and plates with stepped thickness and end rotational springs, whose analytical solutions are not readily available, particularly based on the two-variable refined plate theory. In order to verify the results, formulations of three more plate theories, namely the classical or Kirchhoff plate theory, the first-order shear deformation theory of Mindlin and the high-order shear deformation theory of Sayyad and Gugal, were implemented and solved using the proposed methods.
•Verification of two variants of FRP-concrete double shear bond test setups.•Despite the good performance of 2-D FE model, the 3-D model outperforms it.•Experimental study of bond length effect on ...the FRP-concrete connection.•Benchmarked literature database of bond-slip models used for validation.•Simulation verifies that improved shear test setup can replace the classical one.
This paper studies the bond performance between fiber-reinforced polymer (FRP) and concrete using two variations of the double shear lap test setups. Experimental tests were conducted followed by a series of finite element simulations using cohesive zone model. The experiment utilized an improved double-pull shear setup with the tests conducted on specimens of varying FRP-concrete bond lengths. The numerical simulations were carried out for the improved as well as the traditional setups using two converged meshes with both 2- and 3-D spatial idealizations to study their relative performance. The results are discussed in light of the damage mechanism, load–displacement, strain and stress distribution, bond-slip behavior, and fracture energy. The tested specimens show no effect of bond length variation on the FRP-concrete interfacial strength so long as the bond length exceeds the effective bond length – Only the case of bond length lower than the effective bond length shows otherwise. The study also succeeds in validating the 2- and 3-D numerical simulations using the experiments in both the two cases of spatial idealizations and the two types of test setups in terms of strain and stress distributions, bond-slip curve, and fracture energy. However, while the 3-D models succeed in capturing the failure load accurately, the 2-D models fail to do so. Evidence of similar performance between the improved double shear test and traditional double shear test setups reaffirms the fact that the former could be used to replace the latter.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Due to their robustness in handling the inherent singularity difficulties associated with crack analysis, mesh-reduction methods present an avalanche of formulations in the literature which, ...sometimes, entails modifications to their conventional/standard forms for better results. Although such formulations provide a pool of alternative choices to the analyst, increase in their number requires some relative assessment between them in order to guarantee optimum choice of analysis tool. The present study assesses the applicability and relative performance of three such mesh-reduction methods, namely the radial basis function (RBF) method, the boundary element method (BEM), and the method of fundamental solution (MFS) for mode III crack analysis. In order to have a common ground for performance comparison, these methods are, first, tested in their most basic forms and simplest conventional formulations possible. Failure of some of them to provide reliable results calls for some enrichments. Yet, unless where necessary, efforts are made to ensure that unnecessary computationally expensive formulations are avoided. Consequently, the BEM formulation is not altered in any way, and modifications to both the RBF and MFS are limited to enrichment by the addition of, at most, one singular term and/or the domain-decomposition technique. Verification is achieved using the literature results and/or those obtained by FEM in this study. Summary of the relative advantages and limitations of the methods for mode III crack analysis is given to serve as a yard-stick based on which the choice of one over the others may be influenced.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
This paper presents a comprehensive fracture analysis of seawater-mixed concrete containing seasand and recycled concrete coarse aggregate based on the eXtended finite element method. Capable of ...simulating fracture problems without the need for a conforming mesh, the model was validated using a set of literature experimental results for specimens containing different compositions of the sustainable materials (seawater, seasand, and recycled concrete aggregate) under three-point bending test configurations. A series of parametric studies was then conducted to invesitgate the effects of beam size and notch-to-depth ratio for seawater-mixed specimens containing natural aggregates, followed by another parametric study on the effects of modulus of rupture, total fracture energy, concrete elastic modulus, and Poisson’s ratio of the material. The exercise resulted in a total of 32 simulation runs based on which the model presents unique attributes on the fracture behavior of this nonconventional sustainable material whose response has not been simulated previously although its fracture behavior could differ from that of normal concrete.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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