Performance assessment of the bond between FRP as externally bonded reinforcement (EBR) and concrete requires establishing bond-slip characteristics using appropriate experiments, one of which is the ...double shear bond test. Different versions of the said test, ranging from its traditional form to improved versions, exist. Yet, the improved versions themselves are not without shortcomings. The aim of this paper is to present a simple and improved double shear test setup, customized to ease its application in FRP-concrete bond tests in addition to satisfying other important functional requirements. Designed and fabricated as a Y-hook-cylinder system to substitute half of the traditional double shear specimen size, the simple feature of traditional approach is retained in the other half. Performance of the developed setup is, first, verified against that of the traditional approach on a number of specimens. Subsequently, the proposed system is used to conduct an exploratory study on the influence of coarse aggregate type on FRP-concrete bond behavior. Two concrete types are produced; one containing fresh aggregate and the other consisting of steel slag aggregate substituting 30% of the maximum fresh aggregate size in the first concrete type. Typical bond-slip models of the two specimen types are developed and compared with several other literature sources. The results, both in terms of the debonding load and bond-slip characteristics, show improvement in bond performance when a substrate failure occur in the specimens containing steel slag aggregate.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•There are five major laboratory test methods for FRP-concrete interfacial bond.•Attributes, characteristics and variations of each test method are analysed.•Different approaches and means for data ...acquisition are discussed.•There exist avenues for further development of existing test methods.•An improved version of double shear test setup is proposed.
Due to aging of existing structures and/or change of expected load patterns and their magnitudes, their strengthening becomes a necessity. The application of externally bonded fibre-reinforced polymer (FRP) for this purpose has gained popularity, among other methods, due to its simplicity and convenience. However, the full capacity of FRP strengthening system is sometimes undermined by the premature failure of the bond between FRP and the substrate. Consequently, many works are available in the literature that focus on studying the FRP-concrete bond strength. This paper presents a review of the existing experimental tests on the bond between FRP and concrete. The major approaches and their variations as implemented by various researchers are presented and discussed, followed by a section on the data acquisition systems. The pros and cons of each of the test methods are presented followed by some perspectives and the need for future research. Finally, a new testing configuration is proposed for the double shear lap test and its associated advantages over the conventional approach are discussed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Binary NiO-Fe
2
O
3
, NiO-CdO nanocomposites, and ternary NiO-Fe
2
O
3
-CdO nanocomposite are synthesized using facile co-precipitation method, and their photocatalytic and antibacterial properties ...are studied. The as-obtained products are characterized using different analytical techniques. The microstructural parameters were calculated using X-ray diffraction data. UV–vis spectra technique was used to calculate the bandgap and listed 3.1, 2.7, and 2.5 eV for NiO-Fe
2
O
3
, NiO-CdO, and NiO-Fe
2
O
3
-CdO nanocomposite, respectively. The photocatalytic activity of as-obtained products was tested under visible light against methylene blue (MB) dye. The NiO-Fe
2
O
3
-CdO nanocomposite has shown higher degradation efficiency as compared to binary nanocomposites and revealed improve electron–hole separation efficiency. The photocatalytic performance of NiO-Fe
2
O
3
-CdO nanocomposite was also tested for other synthetic dyes such as rhodamine-B (RhB), methyl orange (MO), and cresol red (CR). The antibacterial performance of grown products was tested against
E. coli
bacteria. The ternary NiO-Fe
2
O
3
-CdO nanocomposite has shown higher antibacterial activity than binary NiO-Fe
2
O
3
and NiO-CdO nanocomposites.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Novel tri-phase CuO–MgO–ZnO nanocomposite was prepared using the co-precipitation technique and investigated its physical properties using characterization techniques including XRD, FTIR, Raman, IV, ...UV-vis, PL, and SEM. The application of grown CuO–MgO–ZnO nanocomposite for the degradation of various dyes under sunlight and antibacterial activity against different bacteria were studied. The XRD confirmed the existence of diffraction peaks related to CuO (monoclinic), MgO (cubic), and ZnO (hexagonal) with CuO phase 40%, MgO 24%, and ZnO 36%. The optical energy gap of nanocomposite was 2.9 eV, which made it an efficient catalyst under sunlight. Raman and FTIR spectra have further confirmed the formation of the nanocomposite. SEM images revealed agglomerated rod-shaped morphology. EDX results showed the atomic percentage of a constituent element in this order Cu>Zn>Mg. PL results demonstrate the presence of intrinsic defects. The photocatalytic activity against methylene blue (MB), methyl orange (MO), rhodamine-B (RhB), cresol red (CR), and P-nitroaniline (P-Nitro) dyes has shown the excellent degradation efficiencies 88.5%, 93.5%, 75.9%, 98.8%, and 98.6% at 5 ppm dye concentration and 82.6%, 83.6%, 64.3%, 93.1%, and 94.3% at 10 ppm dye concentration in 100 min, respectively, under sunlight illumination. The higher degradation is due to the generation of superoxide and hydroxyl radicals. The recyclability test showed the reusability of catalyst up to the 5th cycle. The antibacterial activity against
Escherichia coli
,
Klebsiella pneumoniae
,
Proteus Vulgaris
,
Staphylococcus aureus
, and
Pseudomonas aeruginosa
bacteria with the zone of inhibition 30, 31, 30, 30, and 30 mm, respectively, was achieved.
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CEKLJ, 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
The performance of fiber reinforced polymer externally bonded to concrete is greatly influenced by the environmental conditions to which it is exposed during service. Temperature and humidity are the ...two common environmental factors that alter the bond behavior of externally bonded fiber reinforced polymer. This paper reviews the experimental and computational approaches used to evaluate the hygrothermal effects—that is, the effect of temperature and humidity—on the durability of the fiber reinforced polymer–concrete bond, as well as on the bond’s performance under loading conditions. Some experimental testing conducted in the laboratory and in situ are critically reviewed and presented. Implemented approaches for improving bond performance under hygrothermal conditions and their modeling techniques are also presented. The paper concludes by discussing the review’s salient issues. The ongoing wide application of externally bonded fiber reinforced polymer creates opportunities for new research on improving and predicting the bond strength of fiber reinforced polymer concrete under hygrothermal conditions.
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NUK, OILJ, SAZU, UKNU, UL, UM, UPUK
Novel photocatalytic and antibacterial material Zn0.9Ce0.05M0.05O (M = Er, Y, V) nanocrystals were synthesized via a facile co-precipitation technique and characterized by different analytical ...techniques. XRD confirmed the incorporation of Ce, Er, Y, and V, that without modifying the basic ZnO hexagonal wurtzite structure affects strongly structural properties. The Scherrer, W–H, and SSP methods were used to calculate different microstructural parameters using XRD data. The optical energy bandgap was found to be decreased in all co-doped samples (3.14–2.82 eV) calculated from UV–vis spectra by employing different methods. The effect of dopants ions on the optical properties of ZnO was also studied in detail. The FTIR spectrum inveterate the existence of Zn–O, and Zn-M–O (M = Ce, Er, Y, V) vibrational mode that further confirmed the incorporation of dopants ions. The photocatalytic performance of the grown products was evaluated under sunlight illumination against methylene blue (MB) dye. The antibacterial activity was performed against gram-positive Staphylococcus aureus and gram-negative Pseudomonas aeruginosa bacteria. The co-doped nanocrystals have shown enhanced photocatalytic and antibacterial activity as compared to Ce-doped ZnO but the Ce–V co-doped ZnO shown the highest activity. The influence of different operational parameters such as the amount of catalyst, the concentration of dye, and pH of the solution on photocatalytic activity of Ce–V co-doped ZnO nanocrystal was also studied and discussed in detail. The radical trapping experiments were also performed to identify the active species involved in photodegradation reaction. The recyclability test exhibited that Ce–V co-doped ZnO catalyst has high stability and can be reused up to the 6th cycles. Furthermore, a possible photocatalytic mechanism was also proposed for the photodegradation of MB dye.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Lightweight concrete (LC) is a viable alternative for conventional normal weight concrete (NC). It has a reduced weight and similar properties. However, shear provisions design codes are way behind ...for the case of the LC compared to the NC. This study evaluates the shear design of NC and LC specimens. First, an extensive experimental database of these specimens under shear was compiled. Then, selected shear provisions of design codes were outlined and applied for strength calculations. The calculated strengths were evaluated considering the experimentally measured ones to assess these design codes' overall accuracy and consistency. In addition, the effect of selected parameters (depth, concrete strength, flexure reinforcement ratio, shear span to depth ratio, and nominal maximum aggregate size) on the safety of the design was assessed. The third draft of the Eurocode was the most accurate and consistent for the shear design of LC and NC specimens. Finally, the Eurocode shear provisions draft was adapted, refined, verified, and proposed for the shear design of LC beams and slabs.
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IZUM, KILJ, NUK, OILJ, PILJ, PNG, SAZU, UKNU, UL, UM, UPUK
A significant amount of pollutants containing organics, toxic elements, and heavy metals are discharged daily from the textile and pharmaceutical industries into clean water leading to various ...diseases worldwide. In the present work, sunlight-mediated yttrium (Y)-praseodymium (Pr) co-doped ZnO photocatalysts anchored on reduced graphene (rGO) and conducting polymer (PANI) were synthesized via co-precipitation and ultrasonication approach for the photodegradation of synthetic dyes. The as-synthesized catalysts were characterized through XRD, FTIR, Raman, FE-SEM, UV–Vis, and PL for structural, morphological, and optical studies. The XRD diffraction peaks have confirmed the successful doping of Y and Pr without altering the basic hexagonal structure of ZnO and anchoring of rGO and PANI. FTIR demonstrated the Zn–O bond vibration, and Raman exhibited the peaks related to optical phonon modes of ZnO in all grown samples with a small shift. Roughly spherical particles anchored on PANI and rGO were confirmed by FE-SEM images. The optical energy bandgap has shifted towards the visible region for grown samples, evident from UV–Visible spectra. PL spectra exhibited lower recombination of charge carriers in rGO and PANI-based catalysts. The photocatalytic degradation experiment against methylene blue (MB) and methyl orange (MO) dyes under solar light demonstrated that rGO anchored catalyst completely degraded both dyes under 40 min solar light irradiation with an observed rate constant 0.1403 min
−1
, and 0.1402 min
−1
, respectively, and has higher reusability up to 6
th
cycle towards MB dye. The enhanced photodegradation efficiency is because of lower recombination of charge carriers in rGO-based composites than others, electron acceptor nature, fast electron mobility, massive surface area, and higher generation of reactive species such as superoxide and hydroxyl radicals (confirmed by scavengers tests). Moreover, the results exhibit the importance of grown catalysts for potential application in wastewater treatment.
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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, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Carbon-based materials are mostly used in supercapacitor due to control porosity, higher surface area, and easy processing for electrode production. However, it is still challenging to fabricate ...carbon/metal oxide-based nanocomposite electrodes with various structures and configurations for supercapacitors, particularly for miniaturized electronics. Here, in the present study, CeO
2
–Nd
2
O
3
/rGO ternary nanocomposite was synthesized by facial co-precipitation route, which evident enhanced capacitive performance than CeO
2
–Nd
2
O
3
binary composite, bare CeO
2,
and Nd
2
O
3
. The rGO was homogeneously anchored on the surface of CeO
2
–Nd
2
O
3
nanoparticles, forming a semi-spherical morphology. The electrochemical performance of all electrodes was investigated by different measurements. The ternary composite have a higher specific capacitance of 1265 F g
−1
at 3 A g
−1
current density and maintained 99% retention after 2000th cycles, showing excellent cycling performance and rate capability compared to other grown products. The excellent electrochemical pseudocapacitive performance of the ternary composite-based electrode could be ascribed due to rGO and its interfacial contact with CeO
2
–Nd
2
O
3
. The improved electrode conductivity generates plentiful active sites for charging and discharging and provides an easy path for the fast transportation of ions. These results open an innovative pathway for fabricating rGO and metal oxide-based composite in developing electrochemical energy storage devices for commercial production.
Graphical abstract
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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
Using a robust three‐dimensional generalized/eXtended finite element method (G/XFEM) algorithm, this paper presents a comprehensive study on multiple hydraulic fracture propagation and their ...interactions under different treatment conditions. Aimed at capturing the complex multiphysics behavior, the resulting nonplanar fracture footprints under mixed‐mode conditions are simulated using a formulation, which couples the solid/rock domain equations and the fluid flow within the fractures/crevices. Due to the small length scale of the fracture process zone relative to the surrounding formation size, as typically encountered in tight shale reservoirs, linear elastic fracture mechanics based on a regularized Irwin criterion is adopted to describe the fractured solid/rock response while a power law is used for the fluid flow by assuming a Newtonian fluid behavior. Equipped with the capability for mesh adaptivity and automatic time step search algorithms, the G/XFEM utilized to discretize the resulting system of coupled nonlinear equations allows the adoption of independent meshes for the background solid domain and the fracture surfaces without any matching/compatibility requirement between the two. Fracture propagation directions are decided based on the modes I, II, and III stress intensity factors that are extracted using the displacement correlation method. The presented model is first applied to a pair of misaligned fractures and then to an array of en échelon fractures for qualitative verification against a literature prediction by the boundary element method (BEM) and an observed field behavior, respectively. Next, simulation of several sets and configurations of multiple hydraulic fractures, resulting in a total of 23 parametric studies, are carried out to investigate the influences of fracture spacing, injection fluid viscosity, number of fracture clusters, and the type of remote stress conditions.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
