Tg) of structural epoxy adhesive) on the behavior of near-surface mounted (NSM) carbon fiber-reinforced polymer (CFRP)-strengthened reinforced concrete (RC) beams. The study includes experimental work as well as analytical and numerical analysis. To this end, fourteen beams have been tested up to failure in two different series. In series 1, specimens with three different CFRP areas have been tested at two different temperatures . In series 2, and with the aim of evaluating the effect of higher temperatures, only one CFRP area was tested under four different temperatures . Experimental results are evaluated in terms of load–deflections, failure modes, and bond performance. Furthermore, the experimental load–deflection curves are satisfactorily compared to both analytical predictions and finite element (FE) numerical simulations. In both cases, shrinkage and temperature effects on the short-term response of flexural elements have been accounted for. No significant reduction in stiffness and ultimate load was observed for specimens being tested up to 60 °C (in the range of epoxy Tg), showing FRP rupture failure in all of them. For specimens under 70 and 85 °C, the failure mode changed from FRP rupture to FRP end debonding and concrete crushing, respectively.This paper presents a study of the effect of high service temperature (near or beyond glass transition temperature ( In the past decades, fiber-reinforced polymer (FRP) materials have been produced in different configurations and have been widely used for different purposes, such as the strengthening of reinforced concrete (RC) structures. Currently, externally bonded reinforcement (EBR) and near-surface mounted (NSM) are the two most used strengthening techniques in civil structures. In the EBR technique, the FRP is bonded to the previously prepared concrete surface, usually with an epoxy resin, while in the NSM technique, a groove is cut in the concrete cover and the FRP bar or strip is inserted and bonded using groove filler, which is typically an epoxy adhesive or a cement grout. The improvement of the bond performance, along with higher protection against potential aggressive environmental exposure and vandalism actions, are some of the advantages of the NSM technique ,2,3.Tg), their mechanical properties may change [Tg. In this same line, Michels et al. [Tg, whilst Klamer et al. [Tg. Furthermore, Ferrier et al. [Tg for avoiding temperature effects in the creep of epoxies with lower range of Tg (Tg < 55 °C). Moreover, other studies [gT to avoid premature debonding of FRP sheets from concrete surface. These limitations are related to the EBR technique, while for the NSM technique, less information is available, and no specific limitation has been stated.The performance of the NSM strengthening system relies on the bond capacity of the joint between concrete and FRP material, which in turn depends on the properties of the adhesive , among other parameters. Typically, epoxy adhesives can be affected by temperature, as near or beyond the glass transition temperature , was studied and analyzed in . ResultsIn addition to experimental work, finite element methods have been also widely used to simulate the FRP-strengthened beams and columns under different loading and environmental conditions ,41,42,43Tg) on the flexural performance of NSM carbon FRP (CFRP)-strengthened RC beams when different strengthening areas of CFRP are used. For this purpose, an experimental program has been carried out, and results are analyzed in terms of flexural behavior, failure modes, and bond performance along the FRP laminate. Additionally, experimental results are also compared to analytical predictions and numerical simulations with the finite element method. The influence of shrinkage and temperature on the short-term response of the specimens was included in both analytical calculations and numerical predictions.According to the literature, it is seen that there are a limited number of studies related to the flexural performance of NSM FRP-strengthened RC beams under high service temperature, which justifies the need for further research in this field. The present work aims at studying the effect of relatively high service temperature , Y indicates the series of specimens, and Z is the temperature applied to the beam . For example, SB1S-1-R refers to the strengthened beam with one strip in series 1 of specimens at 20 °C. Details of the specimens are shown in Beams to be tested at high temperature were submitted to a heating process before instantaneous testing. The heating was applied on the tension face of the beam by using silicone rubber fiberglass-reinforced heating blankets. An insulating support was used to hold the heating blankets in contact with the tension face of the beam. A proportional integral derivative (PID) controller was utilized for the heating process, and Type-T thermocouples, located between the heating blankets and the concrete surface, were used as temperature controlling sensors. The evolution of temperature with time at different locations is shown in In all the cases, a hydraulic jack applied the load onto the specimens through a spreader beam. The load was applied under displacement control mode at a rate of 0.6 mm/min.Five linear vertical displacement transducers (LVDTs) were used to record the vertical displacements, and two other LVDTs were utilized to measure the settlement of the supports. Due to the use of heating blankets in the soffit of the beam, two LVDTs were installed to the side faces of the beam under each loading point. Furthermore, end slips of the NSM CFRP strip were measured with two horizontal LVDTs see a. The meA strain gauge was installed at the midspan section of specimens on FRP surface (SGf) to assess strain variation with load. Furthermore, to evaluate the bond behavior between the CFRP strip and concrete, 14 additional strain gauges (SGf1 to SGf14) were installed along the strengthening strip for SB1S-1-R and SB1S-1-40 specimens see b. To avoMoreover, to record the temperature variation, temperature gauges (thermocouples) were installed in specimens under temperature at the surface of the concrete at the top and soffit of the beam and inside the groove. The temperature variations were recorded during the heating process as well as during the flexural tests. The position of the thermocouples is shown in 3, the maximum aggregate size was 12 mm, and the water/cement relationship was 0.46. For concrete of series 2, the cement type was I-42.5R, with a content of 333 kg/m3, the maximum aggregate size was 10 mm, and the water/cement relationship was 0.48. In both series, a viscosity modifier and underwater admixture were used to improve workability. The experimental compressive strength, tensile strength, and modulus of elasticity of concrete were determined from three cylinder tests (300 mm high and 150 mm diameter) according to UNE-EN 12390-3:2003 [The specimens were cast in lab conditions with conventionally vibrating procedure. Two different concrete batches were used. For concrete of series 1, the cement type was I-42.5R, with a content of 390 kg/m0-3:2003 , UNE-EN 0-3:2003 , and ASTThe mechanical properties of steel bars were obtained from tension tests based on UNE-EN ISO 15630-1 . The yieThe CFRP laminates used in the experimental work consisted of unidirectional carbon fibers (with a volume content fiber higher than 68%) held together by an epoxy vinyl ester resin matrix . The mecA two-component epoxy adhesive was used to bond the CFRP strip to a concrete groove. According to the manufacturer’s product guide specification , the comMechanical properties of the epoxy adhesive were assessed according to ISO-527-1 . A modulTg) of the epoxy adhesive is of interest. According to the literature, there are two different well-known methods to obtain gT of the adhesive: differential scanning calorimetry (DSC) [Tg, three temperatures were measured: the extrapolated onset temperature (Tf), the mid-point temperature (Tm), and the extrapolated end temperature (Te). The DMA test is an alternative method to determining the Tg and viscoelastic properties of polymeric materials. In this study, a METTLER TOLEDO DMA/SDTA861e analyzer with a 3-point bending test configuration and 45 mm between supports was utilized. The specimens were subjected to a heating rate of 2 °C/min within a temperature range of 30 to 100 °C. A 5 µm, constant displacement amplitude was applied at a frequency of 1 Hz. Tg was obtained by analyzing the storage modulus (E′), the loss modulus (E″), and the loss factor (tanδ) as functions of temperature. In the present work, both methods (DSC and DMA) were utilized to determine the Tg after 12 days of curing time at room temperature. According to the test results, presented in Tg cannot be considered as a unique temperature, but rather, it should be considered as a range of temperatures, as stated elsewhere [Tg was in the range of 53.9–65.3 °C.As mentioned previously, the aim of this study is to evaluate the effect of high service temperature on the flexural behavior of NSM CFRP-strengthened beams. Therefore, characterization of the glass transition temperature (ry (DSC)  and dynary (DSC) . The DSClsewhere . The resIn this section, experimental results are presented and discussed in terms of load–deflection curve, failure mode, and strain distribution along the CFRP strips. Analytical predictions for the load–deflection relationship are also presented.In the analytical work, equilibrium of forces and moments is applied, where the following assumptions have been considered: (i) strain compatibility; (ii) Bernoulli’s hypothesis; (iii) perfect bond, and (iv) the parabola–rectangle stress–strain curve defined in Eurocode 2 . Based oConcrete shrinkage is a reduction in its volume due to moisture loss. This reduction starts after casting the concrete and depends on the water/cement ratio, ambient humidity, shape of aggregates, mixture properties, curing method and temperature, and geometry of specimens, among other parameters. In plain concrete without reinforcement, this shortening would happen without any restrictions. However, in the case of reinforced concrete, the presence of the embedded reinforcement acts as an impediment to free shrinkage. As a result of the restrain provided by the reinforcement, compressive and tensile loads appear in the reinforcement and the concrete, respectively, therefore causing unsightly cracks in concrete. Additionally to these premature cracks, in those cases where non-uniform distribution of reinforcement in section depth exists, an additional curvature can be observed .Shrinkage is an important parameter in predicting the long-term deflection of RC flexural members, although depending on the amount of shrinkage and reinforcement ratio, it may have a significant influence even in the short-term behavior of RC elements ,56,57,58In this work, shrinkage before flexural loading was assessed since shrinkage strain recorded from the day of casting was significantly higher for specimens in series 2 (344 µε) when compared to that of series 1 (88 µε).cE is the modulus of elasticity of concrete, ucrA is the area of uncracked transformed section, and ucrB and ucrI are the first and second moments of inertia of the area of the uncracked transformed section, respectively. Moreover, crA, crB, and crI are the corresponding values for the cracked transformed section. Furthermore, ∆M and ∆N are the restraining moment and axial force against shrinkage.shε is the shrinkage in concrete and cA and cB are the area of concrete and the first moment of inertia of the area of concrete (ignoring steel as shrinkage takes place only in concrete).The original uncracked and cracked responses (moment–curvature relationships) of a flexural specimen without considering the shrinkage are shown in ucrφ) and cracked (crφ) additional curvatures are applied, so that the black dash lines in shM), the intersection point between red dash lines is obtained (point B). This means that if shrinkage of the flexural element is accounted for, point B should be the origin of the moment–curvature response. Hence, a reduction in the cracking moment equal to ∆shM should be applied  of the present work, with and without considering the effect of shrinkage are presented in yP) and ultimate (uP) loads of the strengthened specimens were accordingly increased, irrespective of the applied temperature  generated a small reduction in the stiffness of the specimens. Moreover, the ultimate capacity of the beams in this series decreased by 3.48%, 3.95%, and 10.45% for CB-2-70, SB2S-2-70, and SB2S-2-85, respectively. No change was observed in SB2S-2-60 specimen. In unstrengthened beams, the increase in the temperature derived in a reduction of the cracking load and stiffness of system (see Tg) was followed by bond decrease and, subsequently, the efficiency of strengthening system was slightly reduced, thus making beams more susceptible to premature debonding.According to stem see . This recrP), yielding load (yP), ultimate load (uP), ultimate CFRP strain , and failure modes are presented and compared to analytical predictions in cm(T)f, ct,sp(Tf), and c(T)E are the compressive strength, the splitting tensile strength, and the modulus of elasticity of concrete at temperature T (in °C), respectively. Moreover, cmf, ct,spf, and cE are the compressive strength, the splitting tensile strength, and the modulus of elasticity of concrete at T = 20 °C, respectively.Experimental results in terms of cracking load . It should be noted that no premature failure  occurred when temperature in the range of Tg was applied (T = 60 °C), thus showing a good performance related to end debonding for the NSM strengthening system. Nevertheless, it must be noted that additional experimental work is needed to confirm the findings of the experimental program presented in this communication.As previously mentioned, fib Bulletin 90  recommenThe distribution of strains along the CFRP strips can give useful information about the bond behavior  and its influence on cracking phenomena. Instrumentation with strain gauges presented in Nonlinear finite element (FE) analysis of control and CFRP-strengthened beams subjected to four-pointed loads was carried out to compare with the results obtained from the experimental work. A three dimensional FE model was created using the well-known commercial FE program ABAQUS .FE models include concrete, steel reinforcements , CFRP strips, and epoxy. Concrete and epoxy are modeled by an eight-node linear hexahedral solid element with reduced integration (C3D8R), steel reinforcements are modeled by a two-node linear 3D truss element (T3D2), and FRP strips are modeled by a two-node linear beam (B31). A mesh convergence analysis was performed to select the optimum mesh sizes for different parts involved in the FE model. In this study, it was observed that the meshing refinement was not sensitive after having the maximum mesh size of 25 mm for all elements except epoxy that had 10 mm mesh size. By taking advantage of symmetry in two perpendicular planes, only a quarter of the beam was modeled. Boundary conditions of the experimental test set-up were considered. Finite element mesh along with the boundary conditions is shown in Considering perfect bond, steel reinforcements and CFRP strips are embedded inside the concrete and epoxy, respectively. In order to address this condition, the embedded region function of ABAQUS is used. Moreover, the tie constraint function is assumed to simulate the interaction in the interface between epoxy and concrete. The selection of these interfacial behaviors is based on the fact that the bond was good enough and bond failure took place only in one of the beams of the present experimental program . As a result of this, specimen SB2S-2-70 is not included in the numerical simulations.Similar to the case of analytical predictions presented in ψ), flow potential eccentricity (є), the ratio of the biaxial compressive stress to the uniaxial compressive stress (bσ0c/σ0), the ratio of the second stress invariant on the tensile meridian to that on the compressive meridian (cK), and viscosity (µ). In this numerical study, these parameters are considered as ψ = 36°, є = 0.1, bσ0c/σ0 = 1.16, cK = 0.67, and µ = 0.0005.Steel reinforcement is modeled as an isotropic bilinear elasto-plastic material, while epoxy is modeled as isotropic linear elastic material and CFRP is modeled as brittle material . Moreover, to simulate the inelastic behavior of concrete, concrete damage plasticity (CDP) is used. This continuum, plasticity-based, damage model for concrete is applicable to different loading conditions and can be utilized for concrete with embedded reinforcement . This moα1 and α2 are two dimensionless coefficients that define the tensile post-cracking stress–strain relationship of concrete . This behavior can be attributed to 40 °C being far below the Tg, the stiffness and the ultimate load of strengthened and unstrengthened specimens decreased. The interface bond capacity between epoxy and concrete could have been affected, and the efficiency of the strengthening system showed some reduction, thus making the beam to be more prone to experience end deboning failure.In series 2, as a result of the increase in temperature near or beyond the In both series of specimens, the failure mode of the control unstrengthened beams was concrete crushing after steel yielding. For the strengthened beams under 20, 40, and 60 °C, the failure mode was FRP rupture. With the increase of temperature up to 70 °C, the beam failed by end debonding. Finally, specimens under 85 °C experienced concrete crushing and, as a result, the load suddenly dropped without giving place to end debonding. This failure mode can be attributed to the reduction in mechanical properties of concrete and epoxy when submitted to higher temperature.No end debonding or significant reduction in ultimate load occurred for specimens being tested up to 60 °C, thus showing a good performance of the NSM strengthening system.Tg generated a small reduction in the stiffness of the specimen and a decrease by 3.48%, 3.95%, and 10.45% in the ultimate capacity of beams CB-2-70, SB2S-2-70, and SB2S-2-85, respectively.The application of temperature exceeding the epoxy The effect of temperature on the experimental bond behavior of specimen at 40 °C was studied in one of the strengthened beams . With the increase in the temperature, strains (and stresses) in the CFRP strip increased.A systematic procedure was applied to consider the effect of shrinkage in short-term response of the specimens. It was observed that the increase in the concrete shrinkage resulted in a reduction of the elements’ stiffness and cracking load. Good agreement was observed between analytical predictions and experimental results.A simple but trustable FE model accounting for initial shrinkage and effects of temperature was created to be compared with experimental work. In all cases, numerical models correctly predict the experimental load–deflection responses and failure modes.In the present work, an experimental program to study the influence of high service temperature on the flexural performance of NSM CFRP-strengthened RC beams is presented. The experimental results are compared to analytical and numerical predictions. Based on the data presented, the following conclusions can be drawn:


When operating within the environments rich with sodium chloride, steel bars of reinforced concrete structures are often subject to corrosion caused by surrounding erosive materials, and the associated rust expansion force due to corrosion takes a critical role in determining the durability of relevant reinforced concrete structures. By investigating the corrosion course of steel reinforcement with theory of elasticity, a numerical rust expansion model is established for the moment of concrete surface rupture based on non-uniform sin function. Cuboid reinforced concrete specimen with squared cross sections is tested to analyze the rust expansion when concrete cracks due to corrosive forces. The utility of the established expansion model is validated by numerical simulation with Abaqus through the comparison between the associated outcomes. The impacts of steel bar diameter and concrete cover thickness on the magnitude of rust expansion force are discussed. While corrosion courses and behaviors attributed to chloride corrosives can dramatically vary due to diverse service environments and different rebar sections, in general, when rebar corrosion occurs, the bond strength between concrete and steel bars often decreases significantly when a certain level of rust accumulation reaches. Meanwhile, volume expansion as a consequence of rust accumulation, can result in serious rupture failure of concrete elements2. After concrete cracks, rebar corrosion will be exacerbated due to the increased exposure of more reinforcements to surrounding humid conditions. Eventually, the durability of the associate components and even the entire structures can be severely damaged4.The presence of chlorides in marine environments, e.g. coastal regions, remains one of the leading drivers of corrosion of steel bars embedded in reinforced concrete structures5 for simulation purpose. Experiments results were used for model verification. Mir et al.6 proposed an enhanced numerical forecast model for predicting service life of reinforced concrete structure by considering chloride and oxygen concentrations. Amey et al.7 introduced an environmental approach for estimating the possible service life of concrete structures in different operation circumstances. Several potential influencers covering surface conditions, chloride movements, medium temperature, seasonal impacts, and construction differences, were considered during the prediction process. Multiple concrete mixtures at diverse quality levels were assed in their illustrations.In order to understand the nonlinear behavior of reinforced concrete beam under corrosion during fatigue loading process, a piecewise linear model was proposed by Zhang et al.8 explored the patterning of bar corrosion and the cracking mechanism of concrete cover for corner reinforcement. Gaussian models were adopted for characterizing dynamic propagation patterns of rust relative to corroded bar positions. German and Pamin9 employed the damage-plasticity model of Abaqus on the basis of finite element method to study reinforcement corrosion. In case of multiple steel bars, if concrete cover is limited, fractures often occur between reinforcements and concrete cover. Consequently, moisture and chloride can easily reach reinforcements and exacerbate corrosion. When concrete cover is relatively thick, fractures often only appear between reinforcements.Using digital microscopy technique, Ye et al.10 showed that reinforcement corrosion often presents more seriously on one specific face and then gradually reduces on other faces. To research the crack development due to corrosion in concrete, Chen11 invented finite element model and boundary element model. Non-uniform distribution of rust around bar cross sections was taken into account which presented a more realistic reflection on the practical situation of chlorides penetrating through member covers to surfaces. Yang et al.12 demonstrated a dynamic corrosion process model considering non-uniform expansion of reinforcement. Complex functions were applied to calculate stresses in concrete. The starting time of concrete fracturing was decided by relating material, geometry and corrosion properties.Yuan and JiConcrete cracking due to reinforcement corrosion stands one of the major drivers of concrete structure failure. Reinforcement corrosion course is often non-uniform along bar circumference. To characterize the stress distribution in concrete and determine initiation of concrete cracking, more realistic models for describing non-uniform corrosion courses are substantially demanded. This paper proposes a reinforcement corrosion model with sine theory to simulate the corrosion scenario where all the rebar sections are under corrosion and the face exposed to concrete cover has more serious corrosion. The rebar rust expansion force at the moment of cracking is derived. It analyzes such common parameters as rebar diameter, expansivity of corrosion products and thickness of concrete cover, and the impacts of individual parameters on rust expansion force by comparison.q means rust force and q1 represents error reinforcement rust force.For model construction, it assumes that when steel bars corrode, with the Cartesian coordinate system, the thickness of rust products displays in sine function pattern. Rust products are presumed to expand over the steel bars and exert forces outwards to surrounding concrete components. Rust products are subject to constraint pressure from concrete and steel bars and the distribution pattern of the corresponding rust force follows sine function curve, as shown in Figs. 12 is followed for the analysis with the sketch of computation shown in Fig. d, and the radius of reinforcement is r. Taking the concrete part as the research object, the coordinate system is established with the center of the steel bar as the origin of the coordinate axis, as shown in Fig. When creating non-uniform sine function rust expansion force model, to simplify the computation course, fundamental elasticity theoryq means rust force and q1 represents error reinforcement rust force.Reinforced concrete specimen is divided into reinforcement and concrete sections for calculation by the theory of mechanics of elastic contacts. In Cartesian coordinate system, the outline of rust expansion force due to reinforcement corrosion follows sine function which can be used to characterize the approximation of the corresponding distribution pattern as in Eq. .1\documeConcrete section is taken as research object and with the center of circular hole as its origin, the polar coordinate system is set up. Stress function Φ is assumed as Eq.  and A. BϬρ and Ϭφ means radial stress and circumferential stess, τρφ is tangential stress.Stress components are obtained through Eq. :\documenBoundary conditions are shown as the following:Stress components are eventually derived:uρ is displacement at the point ρ in the direction of radius.Due to rust expansion forces, the interface concrete undergoes outward radial displacement on all the cross sections. The thickness of rust products on the interface between concrete and reinforcement equals the summation of the radial displacement of concrete and the depth of reinforcement corrosion. That is, on the interface between concrete and reinforcement, the deformation compatibility should be satisfied with radial displacements.Radial displacement of concrete can be obtained:ρ) between bars and concrete is considered. In one unit length of reinforced concrete, the displacement due to rust products is equal to the radial displacement of concrete due to rust expansion force q. Then the below can be established.n is volume expansion rate of corrosion products and is generally 2–4; η is corrosion rate of reinforcement.Compatibility of deformations on the interfaces (at r = Combining Eqs. –7), rus, rus7), 4 N/mm2 and 0.2. For theoretical validation, using the values r = 8 mm, d = 23 mm from previous literature13, by the above Eq. , the elasticity modulus of concrete Ec and Poisson’s ratio are respectively set to 2.8 × 1015 is adopted with attribute and parameter values shown in Table 2 to simulate reinforcement expansion process. Normal displacements associated with the side faces of the established model are relatively small. For modeling convenience, the boundary conditions are defined to constraint the normal displacements of four side faces16.Abaqus6.14 software is used for the numerical simulation based on finite element method. A simulation object is set up in the dimensions of 46 mm × 46 mm × 300 mm, with a circular hollow having the section radius of 8 mm. Classical fracture and damage modelThe Mess stress obtained by numerical simulation under non-uniform corrosion is found in Fig. 2. A V-shape expansion pattern is discerned for stress distribution. In Region A, more than half of the tensile stresses are higher than the ultimate tensile strength. Therefore, it can be judged that concrete cracks first appear in Region A, before the expansion force reaches 1.74 N/mm2. Since the boundary conditions are set to have zero normal displacements on the four side faces, more expansion forces are required to enable the stress to reach ultimate tensile strength. For this perspective, it should be reasonable to receive a value greater than the experimental result which is 1.2 N/mm2 in existing literature14.Figure The stress around circular hollow increases with the rise in expansion force, demonstrating a clear layering style. Meanwhile, the outline initiates as being drop-shaped. As the expansion forces increase, the upper tensile stress grows rapidly, while the lower tensile stress develops slowly or even suspends, as shown in Fig. As the rust expansion force grows, the tensile stress first presents in the inner part and gradually expands to the surface regions with a tendency of continual expansion, as in Fig. 14. It used deformed steel bar in HRB335 with carbon ≤ 0.25%. Theoretical yield strength and tensile strength are greater than 335 N/cm2 and 490 N/cm2, respectively.The corrosion of steel bars implanted in concrete negatively impacts the relevant structures by reducing the corresponding durability. Nevertheless, rebar components can positively enhance the corresponding structures in the capacity of resisting bending and tensile loads. Overall, net benefits are generated as the consequence of embedding steel bars in concrete for reinforcement. Currently, in China, multiple types of rebars exist with different diameter sizes of 8 mm,16 mm, 32 mm and 40 mm. Steel bars in distinct diameter sizes possibly exhibit varying corrosion rates along with unsimilar magnitudes of rust expansion force, when concrete cracks. By controlling all the other parameters constant and altering diameter size of steel bars, the corresponding rust expansion forces at the moment of concrete cracking are calculated. The selected bar diameters are 8 mm,16 mm, 20 mm with the respective corrosion rates corresponding to concrete failure being listed in Table 2When concrete cracks, the relationship profiles between rust expansion force and bar diameter size are plotted in Fig. When corrosion occurs to steel bars, for specific reinforced concrete structures, the thicker the concrete cover is, the more rust expansion force it requires to crack the concrete cover. Apparently, from this perspective, the durability and safety of reinforced concrete structures can be enhanced by thickening the associate concrete layer for protection. On the other hand, the protection covers in super depth can lead to over extensive fracture gaps when the relevant structure cracks due to rust expansion. Over extensive cracks on concrete protection layer could cause unnecessary panics among the connected users of concrete structures.The relationship between rust expansion force and concrete protection layer under diverse rust expansion rates is presented in Fig. For theoretical computation, rust expansion is modelled based on the assumption of perfect elasticity. In addition, the compression course of rust products is neglected in order to simplify the computation process. Then, the expansion rate is actually calculated relative to the volume after compression. From the above formula , rust pr17. According to the impacts of rust volume expansion rate on rust expansion force, it appears feasible to lower down the corrosion-induced rust expansion force in reinforced concrete structures by either adjusting constituents in steel bars or modifying associate processing technologies to reduce rust expansion rate. Unfortunately, few studies related to rust products have been conducted, and the majority of the relevant researchers intensively used the parameter values regarding elasticity modulus, Poisson’s ratio and volume expansion rate of steel rust products from literature16. If more realistic information on elasticity modulus and Poisson’s ratio was added during the theoretical modeling process, more accurate results on rust expansion force would have been obtained.It can be visually observed from Fig. From the cross-verification process between theoretical modeling and numerical simulation, comparable results are obtained from the established non-uniform rust expansion model against numerical simulation. While numerical simulation considers plastic deformation phase, it defines boundary conditions to prescribe the lower part of model object to be tensile in normal direction, which makes the simulated rust expansion force larger than that received from analytical modeling process.Through the analyses of the impacts of rebar diameters and concrete cover depth on rust expansion force, when concrete cracks, under the same rebar size and concrete cover depth, numerical simulation produces greater rust expansion force than theoretical modeling process.This paper establishes a sine-function-based model to investigate rust expansion process of reinforced concrete cuboid specimen with squared cross sections, along with its verification through numerical simulation by Abaqus using finite element analysis. The conclusions are as follows:


An innovative beam concept made from hollow FRP tube with external flanges and filled with crumbed rubber concrete was investigated with respect to bending and shear. The performance of the rubberised-concrete-filled specimens was then compared with hollow and normal-concrete-filled tubes. A comparison between flanged and non-flanged hollow and concrete-filled tubes was also implemented. Moreover, finite element simulation was conducted to predict the fundamental behaviour of the beams. The results showed that concrete filling slightly improves bending performance but significantly enhances the shear properties of the beam. Adding 25% of crumb rubber in concrete marginally affects the bending and shear performance of the beam when compared with normal-concrete-filled tubes. Moreover, the stiffness-to-FRP weight ratio of a hollow externally flanged round tube is equivalent to that of a concrete-filled non-flanged round tube. The consideration of the pair-based contact surface between an FRP tube and infill concrete in linear finite element modelling predicted the failure loads within a 15% margin of difference. Recently, an externally flanged FRP tube has been developed as a reinforcing component to structural members. These lightweight, high strength and corrosion free FRP tubes offer dimensional stability for structures and rapid installation in construction sites. This technology has been developed primarily to reduce the volume and overall mass of concrete structures, and can minimise costs, improve durability and reduce the carbon footprint of the built asset ,2. The aRecently, externally flanged FRP tubes have been used in composite piles for retaining wall applications where the tubes were filled with concrete to resist bending loads from adjacent soil pressure ,4. This Several researchers have investigated hollow and concrete-filled FRP tubes with a variety of sections, including circular ,10,11, sMany studies have been conducted to promote the use of crumb rubber/waste in concrete ,23. SukoThe main objective of this study is therefore exploring the opportunities for utilising crumbed rubber concrete as an infill material for externally flanged FRP tubes with the aim of manufacturing composite railway sleepers. The bending and shear behaviour of rubberised-concrete-filled FRP tubes was investigated and compared with hollow and normal-concrete-filled FRP tubes. Finite element analysis was conducted to predict the overall behaviour of the beams. The results obtained from this study will provide guidelines for designing structural components fabricated with externally flanged FRP tubes.2 and 888,000 mm4, respectively. The mechanical properties of externally flanged FRP tubes were obtained from the technical data sheet [The externally flanged FRP tubes were composed of glass fibre reinforced polymer and vinylester resin and were manufactured using pultrusion process. Most of the fibres were oriented in a longitudinal direction while a small quantity of transverse fibres provided lateral stability. The cross-sectional area and moment of inertia with respect to the x-axis are approximately 1585 mmta sheet  providedA medium-strength premix cement concrete called ‘normal’ concrete and a concrete mix with 25% (by weight) of crumb rubber named ‘rubberised’ concrete were used to fill the hollow tubes to increase sustainability and promote a circular economy. The crumb rubber was added to increase the total volume of concrete without changing the initial premix cement:concrete ratio of the normal concrete ingredients. This implies the addition of crumb rubber did not replace either coarse or fine aggregates in the concrete but was added as an additional material. The nominal maximum size of coarse aggregates in the premix concrete was 5 mm. The clean- and angular-shaped crumb rubber was supplied by Chip Tyre, Australia, having been recycled from automotive and truck scrap tyres. The nominal maximum size and fineness modulus of the crumb rubber used in the concrete were approximately 5 mm and 5.03, respectively . The measured mechanical properties for both normal concrete and rubberised concrete at 28 days are also reported in The bottoms of the tubes were sealed with plastics and placed vertically using clamps before pouring concrete from the top. Concrete cylinders were prepared from the same mix to determine the necessary properties in accordance with AS 1012.9  and AS 1This study mainly investigated two parameters: (a) hollow and filled sections, and (b) normal concrete (NC) and rubberised concrete (RC). These two parameters were considered in order to investigate three different properties: (a) bending; (b) horizontal plane shear and (c) vertical plane shear. Moreover, the performances of externally flanged FRP tubes were compared with non-flanged round tubes to identify the structural benefits of the flanges. Accordingly, The schematic diagram of the test setup is provided in Different failure behaviours were observed depending on the test setup and filling types. These failures were classified into five major categories: transverse bending of the flanges, tube ovalisation, cracks at tube–flange junction, cracks at mid-depth and flange buckling. Each of them is described next.Transverse bending of the flanges: The flanges were bent in a transverse direction at the point of load application , horizontal plane shear capacity by 160% (from 6.05 kN to 15.75 kN) and vertical plane shear capacity by 240% (from 9.10 kN to 30.85 kN). The specimens with infill concrete failed in flange buckling (large span test) and longitudinal shear cracks (short span test). These failures were observed at higher loads in comparison to the load that caused tube ovalisation and increased the moment and shear capacity. It can be seen that concrete filling is more effective in improving shear capacity (up to 240% improvement) than bending strength (32% improvement). In a concrete-filled FRP tube, the flexural load is mainly carried by the outside FRP shell while the infill concrete improves shear capacity. This is similar to sandwich panels, where the top and bottom skins are designed to provide strength and stiffness to the panel while the core provides shear stiffness . This ex2 to 35.75 kN m2). This observation is different from the non-flanged hollow and concrete-filled tubes, where concrete filling can improve bending stiffness up to 100% [Similar results were observed for bending stiffness properties, where concrete filling only improved bending stiffness by 2.6%  as shown in The alternative approach to increase bending stiffness without increasing significant structural weight is an increase in FRP tube thickness. Idris and Ozbakkaloglu  mentione2 to 35.35 kN m2) while the horizontal plane shear and vertical plane shear capacity reduced by 9% (from 15.75 kN to 14.30 kN) and 10% (from 30.85 kN to 27.70 kN), respectively. The small degradation of the properties can be attributed to the lower strength and elastic modulus of the rubberised concrete compared to normal concrete, as indicated in The effect of rubberised concrete as a filling material can be seen from the results of normal-concrete-filled and rubberised-concrete-filled FRP tubes. For a particular test setup, there was no major differences in failure modes except an additional longitudinal crack observed at the mid-depth for short span (SBS and ABS) specimens filled with rubberised concrete . This adThe effect of external flanges is examined by comparing the results between flanged and non-flanged round tubes. The results of hollow and concrete-filled flanged round tubes are taken from this study while the results for non-flanged round tubes are extracted from a similar study conducted by Fam et al. . Fam’s s2/(kg/m) to 10.47 kN-m2/(kg/m)) for the hollow section and 7% (from 10.58 kN-m2/(kg/m) to 11.30 kN-m2/(kg/m)) for the concrete-filled section. This increased capacity can be attributed to the fact that the external flanges stabilised the round tube and provided resistance against premature failure. It is interesting to see that the stiffness/FRP weight of the hollow externally flanged round tube (10.47 kN-m2/(kg/m)) was similar to the concrete-filled non-flanged round tube (10.58 kN-m2/(kg/m)). This indicates that both the structural weight and the use of concrete can be minimised by using externally flanged FRP tubes, without sacrificing stiffness, which is the primary design criterion for FRP structures.Filling the hollow tube with concrete stabilised the beam section from ovalisation by increasing internal resistance, which improved shear capacity by 240% and bending strength by 32%. This indicates that the concrete filling is more effective if the externally flanged FRP tube is used in shear-dominated structures.Concrete filling increases the bending stiffness by only 2.6% while an increase of FRP tube thickness from 3 mm to 10 mm can double the bending stiffness. Therefore, increasing tube thickness is more effective than filling the tube with concrete when there is a need to improve bending stiffness.Adding 25% crumb rubber in OPC concrete reduces the moment capacity by 17%, bending stiffness by 1%, horizontal plane shear by 9% and vertical plane shear by 10% due to the lower strength (9 MPa) and elastic modulus (17 GPa) of rubberised concrete compared with OPC concrete (30 MPa strength and 25 GPa modulus) as an infill material. However, the rubberised-concrete-filled specimen is 9% lighter and more sustainable than a normal-concrete-filled specimen.External flanges that stabilise the round tube increase its strength-to-FRP weight ratio and stiffness-to-FRP weight ratio up to 87% and 22%, respectively, compared with equivalent non-flanged FRP tubes. Moreover, the stiffness-to-FRP weight ratio of hollow externally flanged round tube is similar to concrete-filled non-flanged round tube, indicating that the external flanges can minimise both the structural weight and the usage of concrete.The fundamental load-displacement behaviour of the externally flanged FRP tubes can be predicted within 15% using finite element analysis. To achieve accuracy up to that level, the contact surface between an FRP tube and infill concrete needs to be modelled with pair-based flexible–flexible contact for a frictional coefficient of 0.25.This study investigated the flexural and shear behaviour of externally flanged FRP tubes filled with rubberised concrete. Their behaviour was examined experimentally under four-point bending, short beam shear and asymmetrical beam shear, and analysed numerically to predict their load-displacement response. The results are compared with hollow, normal-concrete-filled and equivalent non-flanged profiles from which the following conclusions are drawn:The application of externally flanged FRP tubes is increasing for manufacturing walls and floors, insulated panels, void formers, shear connectors, hollow-core concrete panels and other civil engineering structures. As the main purpose of this study was to understand the behaviour of externally flanged tube for manufacturing composite railway sleepers, full-scale railway sleepers in which externally flanged FRP tubes are used as reinforcement are recommended for further investigation. The flexural and shear behaviour investigated in this study will provide guidance to design engineers for the effective utilisation of externally flanged FRP tubes in civil constructions.


Biomolecular systems show how host–guest binding can induce changes in molecular behavior, which in turn impact the functions of the system. Here we report an artificial host–guest system where dynamic adaptation during guest binding alters both host conformation and guest dynamics. The self-assembled cage host employed here possesses concave walls and a chirotopic cavity. Complementarity between the curved surfaces of fullerenes and the inner surface of the host cavity leads the host to reconfigure stereochemically in order to bind these guests optimally. The curved molecule corannulene undergoes rapid bowl-to-bowl inversion at room temperature. Its inversion barrier is increased upon binding, however, and increased further upon formation of a ternary complex, where corannulene and a cycloalkane are both bound together. The chiral nature of the host also leads to clear differences in the NMR spectra of ternary complexes involving corannulene and one or the other enantiomer of a chiral guest, which enables the determination of enantiomeric excess by NMR. The preparation of artificial host–guest systems that display dynamic adaptation during guest binding is challenging. Here the authors report a chiral self-assembled tetrahedral cage featuring curved walls that reconfigures stereochemically to fit fullerene guests, regulates corannulene inversion, and enables the determination of co-guest enantiomeric excess by NMR spectroscopy. Artificial molecular systems that mimic the sophisticated processes of induced fit and property regulation via ternary complex formation are challenging to design, but important in producing complex and functional systems of molecules5, and in understanding the molecular basis of binding in relevant biological processes.Recognition and binding processes involving biomolecules, such as enzyme–substrate, antibody–antigen, and protein–protein, are integral to living systems. In many cases, the conformations and shapes of biomacromolecules can change to fit the target substrate, in a process known as induced fit6, which have promising applications as light-harvesting materials7, and corannulene, a bowl-shaped hydrocarbon that can be considered a sub-unit of a fullerene. Corannulene undergoes rapid bowl inversion at room temperature, with an energy barrier calculated to be 11.5 kcal mol−1 9. Stabilization of the planar transition state to corannulene inversion has been achieved by threading this molecule through a cationic macrocycle10, and through compression within an anthracene-walled host11. Manipulation of corannulene to slow its inversion rate, in contrast, is a harder goal, having only been achieved through chemical modifications12.Curved aromatic molecules are well-suited to investigations into complex host–guest phenomena, as their interactions principally involve dispersion forces. These include fullerenes13. These cavities can be used for the stabilization of labile species15, separations18, and catalysis24. Principles have been developed to enable the selective binding of specific guests, or classes of guests, from among many chemically similar prospective guests in solution30. These principles guide the design of artificial hosts to maximize host–guest interactions, with greater shape complementarity often leading to additional selectivity and affinity32.Metal-organic cages provide confined inner phases that are usefully distinct from the outside environmentIn this work, we employ these ideas to prepare a host with curved walls, designed to interact with the curved π-conjugated surfaces of fullerenes and corannulene. Fullerenes induce a configurational change in the host, highlighting the impact of the guest on the host. The dynamic inversion of corannulene is restricted inside the host, demonstrating host impact on the guest. Further, co-guests form ternary complexes, resulting in further modulation of the behavior of both guests inside the cage. The corannulene guest also reports on the stereochemistry of a chiral co-guest.A was designed around a phosphangulene core  bis(trifluoromethylsulfonyl)imide (Zn(NTf2)2) in acetonitrile.Subcomponent ore Fig. , which w1 from racemic A gives rise to a large set of stereochemical possibilities, as each metal center may adopt Δ or Λ handedness, each ligand may possess M or P helicity. The observation of only one set of ligand proton signals in the 1H NMR spectrum of 1 allows us to infer that self-assembly occurred stereoselectively in two ways. First, the two ligand enantiomers narcissistically self-sorted  and T2 36, only one was observed. The X-ray crystal structure of 1 showed that 1 adopted exclusively the T1 configuration 1 and (M4−Δ4)1. The transformation of 1 from its T1 configuration to T2 following guest uptake was confirmed by CD studies of enantiopure 1 and its corresponding fullerene host–guest complexes  × 103 M−1 2⊂1 were observed by 1H NMR. Competitive binding experiments indicated a higher affinity of 1 for corannulene over pyrene, which may result from the better fit of the bowl-shaped corannulene to the concave ligands  was determined to be 17.9 ± 0.3 kcal mol−1, which is notably higher than the experimentally-determined value for a monosubstituted corannulene 8 and the extrapolated value for free corannulene 9.The chirotopic cavity of Hq′ Fig.  are diasres Fig. . The exc4+ was found to accelerate the bowl-to-bowl inversion of corannulene bound within it, by stabilizing the planar transition state10. We infer that cage 1, in contrast, acted to stabilize the ground state of curved corannulene through binding to the curved inner surface of the cage. Thus, encapsulation inside 1 raises the barrier to corannulene inversion, provided the transition state is not also stabilized.Macrocyclic ExBox1, we infer that space remains to accommodate a second guest. Cycloalkanes (CnH2n) with five to eight carbons were found to be suitable second guests, forming ternary complexes. The encapsulation of a second guest was signaled by shifts in the 1H NMR spectra  and Ka2  are shown in Supplementary Table Ternary complexes were observed to form for guests that did not bind in the absence of corannulene, such as cyclohexane. Upon addition of excess cyclohexane to a solution of est Fig. . The encsts Fig. . A 1H NO6H12•corannulene⊂1  to corannulene inversion at least 3.7 kcal mol−1 greater for C8H16•corannulene⊂1 than for corannulene⊂1 at 348 K, cumulative with the 6 kcal mol−1 barrier increase due to encapsulation within 1  also bound within 1 together with corannulene, requiring this co-guest to bind (Supplementary Section R-MB•corannulene⊂(M4−Δ4)1 and R-MB•corannulene⊂(P4−Λ4)1 1 and corannulene⊂(P4−Λ4)1 do not discriminate when binding the enantiomers of MB.Enantiopure P4−Λ4)1 together with corannulene and racemic MB produced similar 1H NMR spectra, corroborating non-enantioselective guest binding  of chiral MB.Enantiopure cage P−Λ41 togeMB mixtures with different degrees of ee were combined with (P4−Λ4)1 and corannulene (Supplementary Section MB reflected well the ratios between the R and S enantiomers of the guest (Supplementary Table R/S ratios were also reflected in the integrals of the signals of the encapsulated corannulene (Fig. To support this hypothesis, ed with P−Λ41 and 1 enabled it to bind fullerenes well, reconfiguring stereochemically in order to optimize host–guest contact. The chirotopic space within 1 enabled the exploration of its stabilization of the bowl-shaped ground state of corannulene, which in turn served to “pad” the cavity in order to optimize the binding of cycloalkanes in ternary complexes. Ternary complexes involving chiral guests can report upon the guest’s stereochemistry. The ability of the guests to influence each other’s dynamics suggests novel applications where guest motions might be geared together—for example, the ring-flipping of corannulene might compress a second guest, thus accelerating a reaction with an unfavorable volume of activation, such as an intramolecular cycloaddition.The concave panels of host Supplementary Information


While respondents scored highly (>87%) on knowledge on effective use, unnecessary use, and associated side effects of antibiotics, lower scores were recorded for knowledge on the spread of antibiotic resistance (52.9%). Pharmacists support easy access to guidelines on managing infections in 56% of cases, and easy access to materials advising prudent antibiotic use and resistance in 39.8% of cases. One-third of respondents (37.0%) reported no knowledge of any initiatives on antibiotic awareness and resistance. Pharmacists were aware (13.3%), unaware (36.2%), or unsure (50.5%) of the existence of a national antibiotic resistance action plan. Pharmacists indicated an interest in receiving more information on resistance to antibiotics (55.2%), medical conditions for which antibiotics are used (53.1%), how to use antibiotics (45.1%), prescribing of antibiotics (34.4%), and links between the health of humans, animals, and the environment (28.6%). Findings can inform antimicrobial stewardship with required interventions to improve antibiotic use.Antimicrobial resistance (AMR) is a serious healthcare problem that affects public health globally. Appropriate understanding and knowledge of prudent antimicrobial use and resistance, along with providing evidence-based information sources, are needed for informed antibiotic prescribing practices. This study aimed to assess the knowledge, opportunity, motivation, behavior of pharmacists and their information sources regarding antibiotic use and resistance in Jordan. An online cross-sectional questionnaire was developed and administered to pharmacists during the period of July–September 2021. The survey is an adapted version of the validated European Centre for Disease Prevention and Control (ECDC) survey for antibiotic use and resistance. Pharmacists from all sectors ( Antimicrobial resistance (AMR) is a serious healthcare problem that affects public health globally, posing a significant challenge, and requires collaborative efforts to combat it ,2. AMR cAntimicrobial stewardship should include a team of multidisciplinary healthcare professionals and is implemented to varying degrees in different countries ,13. AntiThe present study aimed to evaluate pharmacists’ knowledge, attitudes, and behaviors about antibiotics, antibiotic use, and antibiotic resistance in Jordan. A secondary aim was to explore pharmacists’ preferred sources of information and evaluate their awareness of available information and initiatives on prudent antibiotic prescribing in Jordan. A total of 384 respondent pharmacists constituted the study sample. There were more females (70.1%) than males, and most were within the age group of 22–35 years (78.6%). The predominant role was most frequently identified as generalist , and the most predominant practice places  were the community pharmacy , hospital , and industry . Seventy percent of the respondents had been practicing in their role within the pharmacy profession for 5 years or less. The demographic and background variables are summarized in Respondents achieved high scores in assessment of actual knowledge related to items about antibiotic use . ConsideHigh levels of perceived knowledge were expressed by the study sample, e.g., 88.0% of the respondents strongly agreed or agreed with the statement concerning knowledge of antibiotic resistance . On the p = 0.070). On the other hand, when the association between the age of the community pharmacist respondents and those who answered all the knowledge questions correctly was conducted, the results revealed that pharmacists who were younger than 35 years old were more likely to answer all the questions correctly (p = 0.050).Regarding the behavior of pharmacists in promoting prudent antibiotic use, 48.2% of the respondents dispensed an antibiotic once a day or more than once a day in the previous week, 13.3% of the respondents gave out resources on prudent antibiotic use or management of infection once a day or more than once a day in the previous week, and 36.2% of respondents gave out advice related to prudent antibiotic use or management of infections once a day or more than once a day in the previous week. Details regarding these items are summarized in Regarding information resources on antibiotic use and resistance, the most frequently (80.5%) used social media sites for professional activities were Facebook, followed by Instagram (20.1%), Google (18.5%), LinkedIn (11.7%) and YouTube (11.2%) .The survey assessed reasons why respondents were not able to give out advice or resources as they dispense antibiotics, and it was found that the most frequently cited reason (45.3%) was that the patient was not interested in information. Other common reasons were that there were no resources available (37.0%) and insufficient time (27.1%). Only 25.8% of respondents were able to give out advice or resources as needed. The most frequent information resource to which respondent pharmacists regularly referred in the management of infection was continuing education training courses (60.9%). Other frequent resources reported were clinical practice guidelines (35.9%), previous clinical experience (29.2%) and professional resources/publications (28.4%). In relation to having received any information about avoiding unnecessary dispensing of antibiotics in the last 12 months, 57.0% of the respondents answered yes, 35.4% answered no and 7.6% were unsure .A sub-analysis of those who answered yes to whether they received any information about avoiding unnecessary dispensing of antibiotics in the last 12 months was performed. Results revealed that the common resources used were published guidelines (47.5%), their workplace (26.0%) and colleague or peer (25.6%). The overwhelming majority (95.0%) of respondents believed that the information received contributed to changing their views about avoiding unnecessary dispensing of antibiotics. The most common influential resources on changing views were published guidelines (42.0%), scientific organizations (19.2%) and the pharmacist workplace (17.4%). Again, the majority (92.7%) of respondents believed that the information received had an impact on changing their practice in dispensing antibiotics. Few (3.2%) respondents believed that the information received did not have an impact in changing their practice in dispensing antibiotics; the reasons given were that they did not think that the message was important, they forgot, and they did not have the opportunity. Regarding topics about which they would like to receive more information, 55.2% of respondents selected resistance to antibiotics, 53.1% selected medical conditions for which antibiotics are used, 45.1% chose how to use antibiotics, 34.4% chose prescription of antibiotics and 28.6% selected links between the health of humans, animals and the environment. Regarding initiatives in Jordan that focus on antibiotic awareness and resistance, the most common initiatives reported were awareness arising from professional organizations (24.0%), conferences/events focused on tackling antibiotic resistance (21.9%), TV or radio advertising for the public (18.2%) and toolkits and resources for healthcare workers (18.2%). Full details regarding awareness of these initiatives by the respondents is presented in p = 0.050). The study group consisted primarily of respondents who have been practicing in their current profession for 5 years or less (70%).Antimicrobials have been the frontline in the human battle against microorganisms; however, excessive use is seriously threatening their efficacy . Health Overall, the responding pharmacists’ performance was good on knowledge of issues related to antibiotic use and resistance. This was apparent in the items related to, among others, antibiotic use (not effective) against viruses or cold and flu. On the contrary, performance on actual knowledge scales was considerably lower relating to the spread of resistance and the increased risk of resistance in every person treated with an antibiotic. The results are consistent with a study performed in 30 EU/EEA countries, which showed that 97% of the pharmacists surveyed agreed or strongly agreed to the statement “I know what antibiotic resistance is” . EvidencKnowledge is not the sole factor that influences healthcare providers’ and pharmacists’ behavior toward more prudent antibiotic use ,38,39. HIn this study, almost half of the respondents dispensed antibiotics. However, fewer pharmacists provided advice or resource to patients once a day or more to support prudent antimicrobial use. It is well known that indiscriminate antibiotic use is associated with problems in the healthcare systems ,7. PharmBearing in mind that antimicrobial stewardship is not applied routinely in the community setting, efforts from community pharmacists should focus on audit, monitoring and education . In the The present study has the strength of using well developed and validated methods ,21. NeveIn conclusion, the present study assessed the knowledge, opportunity, motivation, behavior and information sources of pharmacists in Jordan regarding the antibiotic use and resistance. The results of this study highlight the need for public health interventions . Efforts are needed to improve the awareness of pharmacists about appropriate antibiotic use and resistance. The findings can inform antimicrobial stewardship with required interventions to improve antibiotic use. Policymakers, clinicians, and professional bodies can be informed about the status quo of the pharmacists in their progress toward better behavior to support prudent antimicrobial use via the model capabilities, opportunities and motivators in the present study.A 10 min online structured cross-sectional survey was developed and distributed to pharmacists in Jordan . The surAn invitation to participate in the study reached the target population online, using the social media platforms of pharmacists’ professional groups, e.g., Facebook. The invitation included a brief description of the study and a link to the survey. Participants were informed that the survey was anonymous, i.e., no personal identifiers of respondents or geolocations were collected, and that the responses were confidential. The completion of the questionnaire was voluntary, and participants could withdraw from the study at any time. The survey was administered to pharmacists during the period of July–September 2021.The present study was based on an adapted version of the carefully developed and thoroughly validated survey by the European Centre for Disease Prevention and Control (ECDC) ,21. AdapBased on the COM-B model, the survey was composed of the following parts. Demographic and background items (5 items) included sex, age, experience, governate and predominant role. Items on capability, included items related to quantification of the degree of knowledge and level of understanding of the issue of AMR. They included assessment of both actual knowledge and perceived knowledge. In the assessment of the actual knowledge of antimicrobial resistance (8 items), the respondents choose whether the key knowledge statement is true or false. Assessment of perceived knowledge (5 items) was performed using a Likert scale. Three items on opportunity used a Likert scale that assessed access to guidelines and educational material. Two items on motivation included a Likert scale that assessed how much the respondents agree with the implication of the dispensing of antibiotics and the emergence of resistance and the important role of the pharmacist in controlling antibiotic resistance. Three items on behavior included how often the pharmacist dispenses antimicrobials and provides advice for the individual patients. Other items related to information sources for the pharmacist regarding the antimicrobial use and resistance as well as initiatives at the country level that focus on antibiotic use and resistance.http://www.raosoft.com/samplesize.html; last accessed: 1 June 2021), based on a margin of error of 5%, confidence level of 95%, population size of 25,700 registered pharmacists with the Jordan Pharmaceutical Association [The sample size was determined, using the Raosoft sample size calculator  was used to run the analyses.Descriptive statistics, such as means, frequencies and standard deviations, were used to summarize the data. Means were compared using independent samples t-test and one-way ANOVA test. The chi square test was used to assess the association between categorical variables. A


Recycled aggregate is a good option to be used in concrete production as a coarse aggregate that results in environmental benefits as well as sustainable development. However, recycled aggregate causes a reduction in the mechanical and durability performance of concrete. On the other hand, the removal of industrial waste would be considerably decreased if it could be incorporated into concrete production. One of these possibilities is the substitution of the cement by slag, which enhances the concrete poor properties of recycled aggregate concrete as well as provides a decrease in cement consumption, reducing carbon dioxide production, while resolving a waste management challenge. Furthermore, steel fiber was also added to enhance the tensile capacity of recycled aggregate concrete. The main goal of this study was to investigate the characteristics of concrete using ground granulated blast-furnace slag (GGBS) as a binding material on recycled aggregate fibers reinforced concrete (RAFRC). Mechanical performance was assessed through compressive strength and split tensile strength, while durability aspects were studied through water absorption, acid resistance, and dry shrinkage. The results detected from the different experiments depict that, at an optimum dose , compressive and split tensile strength were 39% and 120% more than the reference concrete, respectively. Furthermore, acid resistance at the optimum dose was 36% more than the reference concrete. Furthermore, decreased water absorption and dry shrinkage cracks were observed with the substitution of GGBS into RAFRC. Recycled concrete aggregate (RCA) is made by crushing, sieving, and cleaning this waste material from demolished concrete. Using recycled aggregates (RA) likewise decreases the raw material demand by extracting them from the ground, which also reduces the negative environmental effects. By volume, RA comprises 60–70% of natural aggregates and 30–40% mortar from old cement. Compressive strength and other characteristics of RCA are affected by parent concrete properties, workability, mix proportion, etc. . The mecDifferent cementitious materials such as fly ash , silica A general observation is that tiny fibers are additionally imposing in decreasing the width of plastic shrinkage cracks than thick fibers, according to past literature such as in ACI 544.5R-10 . The posA primary objective of this research was to focus on utilizing recycled coarse aggregate (RCA) in concrete production. A brief literature review shows that RCA decreases the performance of concrete due to its porous nature, which absorbs more water, resulting in the pore in hardened concrete. The second objective of this study was to add GGBS into recycling coarse aggregate concrete to offset its porous nature by filling voids and by the pozzolanic reaction, which enhances the mechanical performance of recycled coarse aggregate concrete. Zaid et al. showed that although pozzolanic materials improved the compressive strength of concrete, however, the concrete still had less tensile capacity, resulting in brittle failure that is unacceptable . FurtherOrdinary Portland cement (OPC) type-1 as per ASTM C150  was usedLocally accessible river sand in the SSD (saturated surface dry) condition was used as a fine aggregate for all mixes. Normal weight crush stone in the SSD condition was used as the coarse aggregate for all mixes in this study, which was obtained from Margallah Wah Cantt Punjab Pakistan. Recycled aggregate was collected by crushing waste construction. Furthermore, the physical properties of the aggregates are shown in 3. The physical and chemical properties of GGBS used in this study are given in Ground granulated blast-furnace slag (GGBS) is cheaply accessible in significant amounts and appropriate for the production of larger amounts of cement concrete production. The granulated slag is dry and ground to a fine powder, which is called ground granulated blast-furnace slag (GGBS). GGBS is usually off-white and has a bulk density of approximately 1200 kg/mThe workability of fresh concrete was measured through the slump cone test in accordance with the ASTM standard . CompresBefore the start of the mixing process, the necessary amount of each concrete ingredient was weighed. The speed of the mixer was kept constant at 35 rev/min for the mixing of concrete ingredients. Coarse aggregate was put into the mixture first and then fine aggregate, both materials were dry mixed, then the required amount of cement, steel fibers, GGBS were added, and superplasticizers were mixed in water, which were added over time, and mixing was conducted for about 10 min for all mixes. According to the standard ASTM , the casWorkability of fresh concrete is a mixed property that includes the different requirements of stability, mobility, compatibility, finish ability, and place ability . Figure The workability of concrete decreased as the proportion of RCA enhanced compared to the blank mix. The maximum slump was achieved at 0% substitution of RCA while the minimum slump was obtained at 60% substitution of RCA, as shown in 2 in GGBS with calcium hydrates (CH) of cement creating secondary cementitious compounds that resulted in the greater density of concrete [concrete . Additioconcrete . Therefoconcrete .The compressive strength of concrete is one of the most important properties of concrete, which can be defined as the ability of the cylindrical sample to resist stresses when it is subjected to compressive force in a compressive testing machine. A standard-sized cylinder of 300 mm in length and 150 mm in diameter was cast and tested to find the compressive strength of concrete under the ASTM standard , as show2 in GGBS with CH of cement, producing additional cementitious compounds [ompounds ,19. The ompounds . Additioompounds .The compressive strength of concrete improved with the addition of fibers because of the prevention of micro-cracks. When the initial cracks arrived at the fiber reinforced concrete, the path of the cracks was diverted by the matrix interface. Therefore, the concrete with fibers can endure more loads, which results in greater compressive strength. It should also be noted that the fibers have the capability of crack bridging, which acts as a crack arrestor and decreases the crack propagation in concrete. The fibers can withstand load until or unless the binder matrix pulls out . This leA similar experiment was also carried out in which 28 days of the control mix was considered the reference mix, to which the other mix was compared, as shown in The ability of a cylindrical sample to resist the stresses when it is subject to tensile (stretching or pulling) force is called the tensile strength of that material. The direct tensile strength of concrete is not possible because of the eccentricity and grip of the sample. Therefore, indirect split tensile strength can be determined by placing the cylindrical sample in the compressive machine to split in the vertical diameter, as shown in 2) in GGBS with calcium hydrate (CH) of cement, giving a supplementary cementitious gel ) [2) is freely available at a higher dose of GGBS, which causes the alkali-silica reaction [(C–S–H)) . Accordi(C–S–H)) . Howeverreaction . Additioreaction . Lateralreaction .3 box was used to obtain strain readings. Strain readings were recorded at regular intervals. Strain gauges were attached in the direction of the compressive load. The compressive load was applied by using the compressive testing machine. PStress–strain curves of both steel fiber reinforced concrete and without steel fiber concrete contained ascending and descending portions similar to the conventional concrete. From the test outcome, it can be observed that the stress required to initiate the initial strain of the steel fiber reinforced and without steel fibers reinforced concrete was approximately similar. The ultimate stress in the steel fiber reinforced concrete was greater than the concrete made with GGBS. This is due to the prevention of micro cracks. When the initial cracks arrived at the fiber reinforced concrete, the path of the cracks was diverted by the matrix interface, which resulted in more load. However, the ultimate strain of GGBS concrete was much lower than that of steel fibers reinforced concrete, which resulted in brittle failure. This is due to fact that fibers act as crack stoppers, which delay the generation of micro-cracks. It has also been reported that an increase in fiber percentages results in more ductility, toughness, and strength . Adding Water absorption is one of the simple tests to detect the durability of concrete. Higher water absorption results in lower durability of concrete. More water absorption also leads to freezing and thawing action, which results in the degradation of concrete. According to past literature, higher water absorption of concrete causes freezing and thawing action, particularly when concrete is placed in abruptly changing temperatures .3 (nitric acids), and H2SO4 (sulfuric acids), etc. In this study, H2SO4 (sulfuric acid) was considered as an acid attack on the concrete specimens with different proportions of RCA, GGBS, and SF.Different aggressive acids are available such as HCL (hydrochloric acids), NHOConcrete durability can also be detected through dry shrinkage tests. Water and chemicals can easily enter into the concrete body through small shrinkage cracks on the surface of the concrete, which causes the deterioration of concrete, resulting in less durable concrete.Drying shrinkage with respect to time for varying dosages of RCA, GGBS, and SF is given in SEM was used to evaluate the microstructure analysis of steel fibers, GGBS, and recycled aggregate in concrete as per the ASTM C1293 267 test . ScanninIt is well-known that RCA decreases the mechanical and durability performance of concrete due to its porous nature, which absorbs more water from the concrete and hence no water is available for hydration and workability . Therefo2) with lime (CH). The quantity of calcium hydrate (CH) is more than SiO2, which converts all SiO2 into the C–S–H gel and hence no further silica (SiO2) is available for the reaction with CH, which forms the C–S–H gel. All silica (SiO2) converts into C–S–H gel. CH remains unreactive, forming weak pockets resulting in lower strength of concrete. It has been also reported that CH reacts with another chemical ingredient present in concrete, resulting in less durable concrete [concrete . Additioconcrete . BGGS, wThe effect of GGBS and steel fibers on machine performance, durability aspects, and microstructure analysis of recycled aggregate concrete were studied in this research. Based on experimental results, the following conclusions can be drawn.The workability of fresh concrete decreased as the percentage of RCA increased due to the porous nature of RCA, which absorbs more water. GGBS improves the workability of RAC by filling the voids of the recycled aggregate and hence more free water is available for workability. Additionally, the larger surface area of SF requires more water–cement pastes to coat them, which results in less workable concrete.At optimum dose , compressive strength was 39% higher than the reference concrete at 28 days of curing while the split tensile strength was 120% more compared to the reference concrete at 28 days.Microstructure analyses such as XRD and SEM showed that GGBS has the creditability to be used as a pozzolanic material.Decreased in water absorption and shrinkage cracks were observed with the substitution of GGBS due to the combined pozzolanic and micro fillers, which gives a denser concrete. It also indicates that the acid resistance of concrete improved with the addition of GGBS.The utilization of recycled concrete aggregate as a coarse aggregate in concrete protects granite stone, which is one of the quickly diminishing raw materials. When GGBS is added to concrete, the reduction in limestone, which is a raw ingredient essential for cement production, is reduced, and hence the sustainability quality in the production of concrete is enhanced. This will considerably lower the emissions of carbon dioxide, nitrogen dioxide, and other dangerous gases to the environment and assist in limestone conservation. It can be noted that the addition of steel fibers improves the concrete mechanical and durability performance with the composite addition of GGBS and recycled aggregate. Therefore, concrete production can be made sustainable by implementing the procedure used in the current study by the incorporation of recycled aggregate, GGBS, and steel fibers.


ESBL-producing coliforms were found to be more prevalent in urban samples than in rural samples. Shotgun sequencing showed that sediment samples were dominated by the phylum Proteobacteria , while in the water samples, Cyanobacteria were the predominant phylum . Antibiotic resistance genes were detected in all samples, but their abundance varied 1,525-fold between sites, with the highest levels of antibiotic resistance genes being present in urban surface water samples. The abundance of antibiotic resistance genes was significantly correlated  with the abundance of bacteria originating from the human gut, which suggests that the release of untreated sewage is a driver for the spread of environmental antibiotic resistance genes in Bangladesh, particularly in highly urbanized settings.In many low- and middle-income countries, antibiotic-resistant bacteria spread in the environment due to inadequate treatment of wastewater and the poorly regulated use of antibiotics in agri- and aquaculture. Here, we characterized the abundance and diversity of antibiotic-resistant bacteria and antibiotic resistance genes in surface waters and sediments in Bangladesh through quantitative culture of extended-spectrum beta-lactamase (ESBL)-producing coliforms and shotgun metagenomics. Samples were collected from highly urbanized settings (IMPORTANCE Low- and middle-income countries (LMICs) have higher burdens of multidrug-resistant infections than high-income countries, and there is thus an urgent need to elucidate the drivers of the spread of antibiotic-resistant bacteria in LMICs. Here, we study the diversity and abundance of antibiotic resistance genes in surface water and sediments from rural and urban settings in Bangladesh. We found that urban surface waters are particularly rich in antibiotic resistance genes, with a higher number of them associated with plasmids, indicating that they are more likely to spread horizontally. The abundance of antibiotic resistance genes was strongly correlated with the abundance of bacteria that originate from the human gut, suggesting that uncontrolled release of human waste is a major driver for the spread of antibiotic resistance in the urban environment. Improvements in sanitation in LMICs may thus be a key intervention to reduce the dissemination of antibiotic-resistant bacteria. The prevalence of antibiotic-resistant bacteria causing infections is increasing globally, but the clinical issues, including significant morbidity and mortality, posed by these bacteria are particularly alarming in low- and middle-income countries (LMICs) –4. Propo–One of the challenges of studying antimicrobial resistance (AMR) is to disentangle the spread of resistant bacteria and antibiotic resistance genes between humans, animals, and the wider environment . For thiEscherichia coli among healthy humans is relatively high in Bangladesh, as it is in other LMICs  and ponds with no history of antibiotic use (n = 6) were sampled. Further information on sampling locations and protocols is provided in Materials and Methods and Freshwater surface water and sediment samples were collected from 24 sites across 3 districts in Bangladesh . However, there was no statistically significant difference in the viable counts of ESBL-producing coliforms in urban and rural samples (We quantitatively determined the burden of extended-spectrum beta-lactamase (ESBL)-producing coliforms in the water and sediment samples from the different sampling locations and found that ESBL-producing coliforms were detected in significantly more urban samples (12/14) than rural samples (15/34)  clustering of sediment and water samples , while in the water samples, Cyanobacteria  was the dominant phylum  of bacteriophage DNA. The sediment samples were dominated by typical soil bacteria such as Pseudomonas, Azoarcus, and Anaeromyxobacter, while the water samples were dominated by cyanobacteria such as Cyanobium, Microcystis, and other typical aquatic bacterial species from the phyla Proteobacteria and Actinobacteria  were also identified at different sampling sites. It was apparent that three of the Dhaka water samples contained bacteria which are typically found within the gastrointestinal tract, including Escherichia coli, Streptococcus infantarius, Bifidobacterium adolescentis, and Prevotella copri. Through microbial source-tracking analysis of our shotgun sequencing data using the FEAST algorithm (P < 0.01) than the rural samples without previous antibiotic use  and sediment (n = 24) samples. Species-level abundance was determined by the analysis of shotgun metagenomic sequencing data by the MetaPhlAn2 package. Colors reflect the relative abundance of each individual taxon. The samples and species are clustered by Bray-Curtis dissimilarity. Download FIG S1, PDF file, 0.9 MB.Heatmap of species-level abundances for surface water . There was no significant difference in diversity between either of the rural sediment sample types (P < 0.005), but there was no significant difference between the urban water samples and either of the rural sample types.Based on species-level data , the urble types . On the n = 99) followed by the rural samples with previous antibiotic use (n = 49), while the rural samples with no previous antibiotic use had the fewest resistance genes (n = 36) (n = 24). There were 17 ARGs shared between all three sample types, including five different beta-lactamase genes belonging to the blaOXA and blaRSA families.A total of 114 different antibiotic resistance genes (ARGs) that confer resistance to 16 antibiotic classes were identified in the 48 samples from sediment and surface water. The urban samples had the greatest number of ARGs ((n = 36) . There wP < 0.0001). The urban sediment samples collected from around the city of Dhaka were found to have a significantly greater  total ARG abundance  than the rural samples with prior antibiotic use  (P > 0.99) between ARG abundance in rural sediment with prior antibiotic use versus sediment from rural sites in which antibiotics had not been used. ARG levels in the water samples reflected that of the sediment samples, with the total ARG abundance in urban samples  being significantly higher  than the rural samples with previous antibiotic use  but not significantly different from the rural samples with no previous antibiotic use . As with the sediment samples, there was no significant difference found between either of the rural sample types .The abundance of antibiotic resistance genes varied 1,525-fold between sites, with sample SAM6  having the lowest abundance (0.078 reads per kilobase of reference sequence per million sample reads [RPKM]) and sample WD7 (surface water sample collected in Dhaka) having the highest ARG abundance (120.45 RPKM). Of the paired sediment and water samples, the ARG abundance was, on average, 3 times greater in the water samples than the sediment samples  . HoweverThe individual antibiotic resistance genes were collated into 16 classes that cover resistance to specific antibiotics and a separate class for genes conferring antibiotic efflux mechanisms . Efflux R2 = 0.73; P = 8.9 × 10−15) between the aggregated abundance of ARGs and the levels of human gut bacteria, as identified by FEAST, across our study   .rep) genes. Eleven contigs in our data set contained rep genes , whereas the urban water samples had significantly more ARG-bearing plasmid contigs than the rural samples with no previous antibiotic use   . There w < 0.05) . All of 10.1128/mSystems.00137-21.5TABLE S3Table S3, PDF file, 0.1 MB.Contigs with one or more antibiotic resistance genes identified by PlasFlow as plasmids. Download Copyright © 2021 McInnes et al.2021McInnes et al.https://creativecommons.org/licenses/by/4.0/Creative Commons Attribution 4.0 International license.This content is distributed under the terms of the In this study, we used quantitative culture and metagenomic techniques to understand the community composition and the level of antibiotic resistance genes in rural and urban surface water sites across Bangladesh. Selective plating showed that ESBL-producing coliforms were more prevalent in urban surface water than rural settings, consistent with reports of antibiotic-resistant fecal coliforms in rivers across Asia , 32. HowPseudomonas, Azoarcus, and Hydrogenophilacea, which is in line with other studies which have shown that sediment is dominated by the phylum Proteobacteria  rather than the location they were collected from. Sediment samples were dominated by bacteria belonging to the genera bacteria . Water sre ponds . Microcyo humans . The twoce water .parC and gyrA genes, so the absence of dedicated resistance genes in these ecosystems may be unsurprising . Using PlasFlow on the metagenomic assemblies, we were able to assign antibiotic resistance genes to 93 plasmid contigs, revealing that urban samples had a higher number of plasmids carrying antibiotic resistance genes. This suggests that, particularly in urban water bodies, there exists an increased potential of horizontal gene transfer of mobile genetic elements carrying antibiotic resistance genes.By creating a metagenomic assembly of our short-read sequencing data, we were able to identify contigs which contained plasmid replication initiation genes and found that IncP, IncQ, and various small plasmid types were most common. Only the IncQ1 plasmid pWD1 contained an antibiotic resistance gene  or sediment (S) followed by aquaculture (A) or control . Sample sites were designated using Mymensingh (M), Shariatpur (S), or Dhaka (D), and a number was included to differentiate samples. Further metadata on the samples, including temperature, pH, and dissolved oxygen levels, are provided in Water and sediment samples were screened for the presence of ESBL-producing coliforms by quantitative plating on Brilliance ESBL agar (Oxoid). For sediment, 0.1 g of the sample was mixed with 0.9 ml of sterile saline solution, and 50 μl was spread onto the agar plates. For water samples, 50 μl of the undiluted sample was spread onto the media. Plates were incubated for 48 h at 37°C. In accordance with the manufacturer’s instructions, blue, pink, and green colonies were designated coliforms and counted.DNA was extracted from the Sterivex filters and sediment samples using the DNeasy PowerWater kit (Qiagen) and the DNeasy PowerSoil kit (Qiagen), respectively, in accordance with the manufacturer’s instructions. DNA concentrations were quantified using the Qubit dsDNA HS assay kit (Thermo Fisher), with all samples yielding more than 0.2 ng/μl. Negative-control runs were performed for both kits by isolating DNA from sterile, distilled water: these yielded no detectable DNA. Metagenomic DNA libraries were prepared using the Nextera XT library prep kit (Illumina). The libraries were pooled and sequenced on the HiSeq 2500 sequencing platform (Illumina) using a 150-bp paired-end protocol. Paired reads were adapter trimmed, and both duplicates and reads less than 50 bp were removed using Trimmomatic 0.30 with Q15 as the sliding window quality cutoff .To perform taxonomic profiling, the paired-end sequencing reads were mapped against clade-specific markers using the MetaPhlAn2 package v.2.7.7 . The MetPRJNA254927, PRJEB7626, and PRJEB6092, which had previously been used as sources for source-sink analysis  in R (Antibiotic resistance genes were identified using the ShortBRED package v.0.9.5 . The CARdf) in R .https://github.com/tseemann/abricate) to identify the presence of antibiotic resistance genes. Resistance genes were identified which had at least 95% identity and 50% coverage compared to the CARD database. Plasmid contigs were similarly queried against the PlasmidFinder database (Metagenomic sequencing reads were assembled using the MEGAHIT v.1.1.3 assembler using default parameters . Contigsdatabase  to identdatabase . When enThe Shannon diversity index of the samples was calculated in R v.3.4.3 using the diversity function of the vegan package v.2.5-7 . NonmetrPRJEB39306.The short-read raw sequencing data have been submitted to the European Nucleotide Archive with accession number