This paper presents an investigation of the tensile properties of two composites made from recycled polyethylene tetraphthalate, cement–concrete mix and standard polymer-based adhesive mixes, used in the construction industry. To describe tensile behavior, experimental measurements of each component of the resulting composite materials were processed in detail. It presents the possibilities of modifying materials suitable for building structures and at the same time provides an opportunity to get rid of polyethylene tetraphthalate (PET), which has already been recycled several times. Because the resulting composite contains a majority of the composite composition on a fragile basis, its use in practice depends on its simple thrust properties. In this paper, a study of the most important mechanical properties of a previously unused composite is presented. These properties were obtained experimentally using an innovative tensile test method. It is common knowledge that concrete belongs to the most widely used building materials. It can be defined as a composite material formed by hardening a mixture of its basic components . Currently, other types of binders are also used, such as asphalt  , polymerIn this experimental work, plain concrete without steel-reinforcing bars and wires with static functions are used. This type of concrete is characterized by high compressive strength but low tensile strength. Concrete reinforcement is necessary to precisely improve the concrete’s tensile strength. The most common methods of reinforcement are steel-reinforcing bars or wire. These favorably affect the bearing capacity in the tensile and shear zones of the element. Fiber reinforcement is a modern technique to strengthen concrete. This type of reinforcement is especially advantageous when reinforcing more complicated and thin elements where it is impossible to safely and correctly store ordinary arming reinforcement ,5,6. FibThis experiment focuses on the effective use of recycled polyethylene terephthalate (PET) in concrete because of the worldwide issue regarding its processing. Waste PET material is one of the most important and widespread in the world. PET is mainly used to produce beverage packaging. Current global PET production exceeds 6.7 million tons per year . PlasticHybrid composites are defined as systems in which one type of reinforcing material or filler is included in mixtures of different matrices . In thisThe significance of this research is in the previously unexplored composition of the materials. Their interconnection combines the ecological importance and economic utility of polymers in view of the enormous worldwide production of PET materials. It is one of the most efficient ways of using thermoplastics that are no longer recyclable. Furthermore, the properties of two differently hardening bonding materials are investigated: this hardening takes place on different chemical bases.Compared to research around the world, this type of material is being studied for a different application. The research presented here addresses the field of application in road construction. The research presented is on tensile stress, which is the basis of application for this purpose. A lot of research is devoted to standard cement–concrete and difficult-to-manufacture reinforcing fibers. The hybrid composite presented in the paper also has the advantage of ease of production of both binders and PET particles.In the conclusion of the article, there are also references to studies that present research on similar topics.As mentioned already, cement–concrete is the most used building material, having high compressive strength but low tensile strength. The compressive strength of concrete ranges from 5 to 50 MPa, but in tensile strength, it reaches only about a tenth of the value of its compressive strength. The filler fraction is very important, as it affects the strength of concrete. The overall properties of cement–concrete depend primarily on the composition and processing of the mixture. It is resistant to chemicals, high temperatures, durable and has volumetric stability. Its durability is great both in air and in water.This is a two-component chemical anchoring system based on vinylester resins with a short curing time. It works on the principle of the high reactivity of unsaturated vinylester resins in methacrylate monomers. Such a resin forms a strong and, at the same time, chemically resistant joint. The advantage is also the reduced hardening time and easy application, which is the main criterion in the design of the hybrid composite dealt with in this research work. The tensile strength of the vinylester anchor is approximately 13–14 MPa ,10,11.Based on the chemical nature of the polymer main chain, polyester resins can be classified into saturated and unsaturated forms. The main difference between saturated and unsaturated polyester resins is the existence of double bonds in the main chain. Unsaturated polyester resin has them in its main chain, whereas saturated polyester resin does not . PolyestPET is currently the most used polymer material (thermoplastic) for the packaging of various products . In geneOne of the process characteristics is the melt flow rate. The MFR (melt flow rate) is a parameter used to characterize the viscosity and flowability of plastic materials, including recycled PET. It is expressed in units of grams per 10 min (g/10 min). It measures the rate at which a polymer is able to pass through a calibrated orifice under standardized conditions.nM = 27 kg/mol, wM = 65 kg/mol, density 1168 g/cm3).Most of the non-alcoholic PET bottles used in Slovakia are made of PET material type KOSA PET 1101 (The melt flow rate (MFR) was measured according to ISO 1133. At a load of 2.16 kg and 280 °C, the MFR is 33.8/10 min.3 and the elasticity module is 1700 MPa. Tensile strength ranges from 25 to 34 MPa [Fibers obtained from PET bottles can be used in the concrete mixture at a high rate (up to 3% by weight of cement). Their density is 1.41 g/cmo 34 MPa ,14,15.It is important to note that reinforcing fibers do not improve tensile strength but regulate cracks. This increases the ability to withstand the reinforced elements. Some types of fibers used in the manufacture of concrete have very good resistance to impact, abrasion and total destruction. A longer steel or synthetic fiber can replace concrete reinforcement in certain situations .The polymer fibers were found to increase the splitting tensile strength of all types of FRC. The greatest increase in splitting tensile strength (up to 25%) was achieved when using PET fiber (length 80 mm) .The amount of PET waste continues to grow as PET production and consumption increase. PET waste has become a major problem of environmental pollution. The produced waste is discarded by burial or incineration. However, fiber concrete can use it. PET fibers can be obtained from PET waste by a simple cutting method without any chemical treatment.Tensile testing is used to measure the force required to break a composite specimen and to determine the extent to which the specimen will elongate to the point of breakage. These tests are important to generate a stress–strain diagram. The latter is used to determine the modulus of tensile strength.The mechanical behavior of materials is described by their deformation and refraction characteristics . Mechanical behavior depends on several variables, including material composition, testing methods and the nature of the stresses generated . Since tF, and it is tested for elongation until it breaks σ=FAx-axis direction ε used in the stress–strain diagram is calculated as the ratio of the change in the length of the specimen ΔL and its original length L0.The deformation in the tf is the maximum load maxF divided by the cross-sectional area A of the specimen (3).Determining the tensile strength is relatively simple. The test is repeatable. This material property is applicable for product quality control. Empirical relationships based on the correlation between tensile strength and properties such as hardness and fatigue resistance are often used in practice. For fragile materials, tensile strength is a valid design criterion. Tensile strength The advantage of this type of solution is the independence of the stress–strain curve from the dimensions of the specimen.A tearing machine or tensile testing machine is used to do this type of test. Together with other additional and auxiliary equipment, it is one of the basic equipment of every testing laboratory.y and the set of independent variables x is the objective of this analysis (16). This application is found in various areas.Regression analysis is primarily used to analyze interrelationships between variables. Its task is to find the mathematical regression function that best describes the course of dependence between variables. Analyzing the relationship between the dependent variable According to the number of unknowns variables, we divide the regression analysis intoHyperbolic regression analysis;Cubic regression analysis.a, b are determined by the least-squares method (17). The use of this method leads to the following mathematical equations:The parameters of hyperbolic regression a, b, c and d based on the following mathematical relationships:Cubic regression analysis can be used to calculate the coefficients a, b, c, d:A system of equations to find The display of the individual regression curves is shown in The biggest problem in testing is gripping the specimen. It is necessary to ensure that the specimen does not move in the gripping area under maximum load. A typical specimen for a uniaxial tensile test is shown in The measuring part is one of the most important components of the test specimen. The specimen is centered in the reduced section. The cross-sectional area of the measured part is reduced compared to the cross-sectional area of the remainder. It is important that the distance between the ends of the measuring part and the arms is large enough that the larger ends do not limit deformation.The length of the transition area (shoulder) should be at least as large as the thinnest part. The total length of the reduced part should be at least four times longer than the maximal cross-section dimension. The length of the measuring part should be proportionally longer to its section. Otherwise, the state of tension will be more complex than simple tension ,21.For standard tests, the prescribed number of samples must be observed. The standard currently specifies testing at least five test specimens. In the case of experimental work, this quantity is not defined. Dog-bone-shaped samples were cast from each mixture. One week after casting they were removed from the mold. The test specimens in which hydration took place hardened and solidified for 28 days. The preparation of the small-scale sample consisted of making a template and then preparing the forms .The template was created based on a predetermined design. The geometric design considers all the principles that need to be respected. The basis of the mold consisted of a wooden base, plastic mass and a stainless-steel element for the specimen-gripping hole .A transparent overlay film was stretched over the wooden substrate; this is for better post-hardening manipulation of the specimen. The plastic mass was adhered to the wooden base around the perimeter of the template. It was aligned at a height of 12 mm. The stainless-steel element was inserted inside after the template was removed and secured against displacement. Improper gripping of the specimen causes inaccurate test results, and therefore, the position of this element is very important.As already mentioned, the biggest problem is gripping the test object. The direction of the load applied to the specimen must be identical to the longitudinal axis of the specimen. The grip must be firm enough to prevent slippage between the bolts and the stainless-steel element embedded in the specimen a. IncorrThe standard gripping method was chosen for the waste PET specimens. Flat jaws were used for tensile tests up to 5 kN b. The ja3 of fresh concrete depends on different requirements. It is important to achieve complete hydration of the cement, to hydrate the surface of the aggregate, and to achieve the desired consistency of the fresh concrete. A total of 0.1 L of mixing water was used for every kilogram of dry mixture in our case. The strength of the concrete corresponds to class C20/25. The volume weight of the hardened concrete is 2100 kg/m3. The individual components were dosed by weight with an accuracy of ±0.5%. In a prepared plastic container, the dry mix and the required amount of mixing water were mixed using an agitator. A homogeneous mixture was formed to be ready for use in the specimens. Mixing of the mixture from the time of the first addition of water should take at least 5 min. The sufficiently mixed mixture was gradually added in layers to the prepared form.A dry mix method was used to make the specimens. This consisted of two components: naturally quarried aggregates and cement. The volume of mixing water needed to produce 1 mEach layer of concrete was gradually compacted. The mixture, thus prepared and sufficiently compacted, was left to work harden. After 7 days, the test specimens were removed .The chemical anchor PE 300 SF was required to make the polyester specimens. Due to its good mechanical properties, the tested specimen was reduced several times. Its shape was cut into cardboard paper. It was important to ensure even mixing of the two basic components of the sample. The sufficiently mixed mixture was poured into the form and aligned along the entire edge. The samples thus prepared were placed in a favorable location. The preparation of vinylester samples differs in the composition of the material used. A vinylester-resin-based chemical anchor was used instead of a polyester-resin-based chemical anchor. This material has better mechanical properties compared to the polyester based chemical anchor.Polyester 109 is a solution of unsaturated polyester resin in styrene. It consists of two components: a polyester resin and an initiator. Due to the high strength of this material, the shape of the specimens was identical to that of the polyester and vinylester test specimens. The form was made up of cardboard and a transparent cover sheet. The foil was also applied on top to avoid the mixture flowing into the mold perimeter walls. This prevented significant deformation of the shape of the samples. Once the mold was prepared and the surface was controlled, the polyester was dosed with the initiator. The ratio of the individual components is given by the manufacturer. To the required amount of polyester, 2% of initiator was added with stirring (polyester/initiator ratio 100/2). This material is characterized by a fast hardening time (up to 15 min at 20 °C). Consequently, it was necessary to work with a quantity of mixture that could be incorporated over time. The mixture thus prepared was spread evenly into the mold. The curing time is a maximum of 24 h.Specimens from waste PET bottles were used to test recycled polyethylene terephthalate . The samComposite materials are made up of two or more chemically different components. According to the type of material used (thermoset), the composite in this experiment can be divided into two groups: composite using vinylester and composite using polyester resin. In total, several test specimens were created. The individual specimens differed from each other in formulation. PET fibers are an important component of the composite. In this experiment, waste PET bottles were used. The plastic bottles were cut into thin fibers to obtain continuous fibers a,b.Straight plastic fibers usually have a low bond strength with concrete. The dispersion of the fibers in the specimen is critical to the tensile response of any type of fiber concrete. Therefore, it is necessary to ensure a constant casting process to achieve good mechanical properties and to ensure minimum dispersion of results. The specimens’ shape requires an optimal arrangement of fibers both on the shank and in the end zones.In the experiment, test specimens were fabricated using PET fibers with a dimension of 5 mm × 15 mm. A fiber volume greater than 5% in concrete causes serious homogeneity and workability problems. Therefore, the result for this variant of test specimens was unsatisfactory. Thus, the use of smaller chips of 2 × 5 mm was resorted to c. Not onAt the beginning of each experiment, it is necessary to weigh all the components that were used in the composite mixture. The proportions of the mixture by weight are given in Reactoplast was first mixed into the prepared container . The reason for this is to ensure even mixing of the PET fibers with the reactoplast. Polymerization starts as soon as the two components of the material are combined. Polymerization is a poly-reaction in which macromolecules are formed by the fusion of molecules of a base substance (monomer) without the formation of by-products. It takes place in three successive stages. The first phase is initiation. This triggers a reaction linking the monomer units. In this phase of polymerization, recycled PET fibers were added to the mixture and the mixture was allowed to mix for 2 min .It is necessary to work quickly due to the ongoing chemical reaction and rapid hardening. The processed mixture was poured in small volumes into a container containing the already prepared fresh concrete mixture. Mixing of all components was ensured by an agitator. This was used to achieve adequate workability and to maintain the required water/cement ratio. When all the ingredients were sufficiently mixed together, the composite began to be filled in small layers into the prepared mold. After each layer was placed, the concrete was compacted. The whole process took approximately 8 min. After 7 days of curing, the samples were removed from the mold. Due to the short time during the preparation of the test specimens, some of the mixture also got into the locations of the steel fixtures a,b. ThesThe solution of each experimental task can be divided into three phases: preparation, measurement and evaluation. The dimensions of the test sample as well as the test procedure are defined by the standard. Test specimens have been designed to be gripped well in the test fixture and to generate no stresses at the gripping points. These could negatively affect the result of the experimental measurements.The test was carried out on a SAUTER TVM-N test machine , which iL is also recorded. The standard test loading rate for is 1 mm/min. A single point on the specimen was fixed at the base, which will be supported by the type of the Sylvac deflection gauge. The ultimate strength of the material is derived from the maximum stress achieved in the tensile test.The screw passes through a stainless-steel hole in the sample. Double-sided grip is achieved in the test device by using an omnidirectional joint. This minimizes bending of the sample. The test device allows the sample to be loaded by a simple tension. The load is applied at a constant speed. The value of the force is recorded in the measuring notebook. Synchronously with the increase in force, the increase in the absolute elongation ΔL of the shank of the measured specimen at length xε and xσ must be interpreted graphically (stress–strain diagram). For this reason, all geometrical data  were statistically processed for each specimen. The cross-sectional area A was calculated from the average dimensions of b and h. The normal stress xσ was then found using relation (1). The relative strain xε is expressed by the accurately measured distance L. This parameter represents the distance between the fastening center point of the Sylvac gauge and the sensing tip of the indicator. This tip of the indicator leans on the fixed point on specimen. From the transformed values of xε and xσ, a stress–strain diagram is displayed. The results of the experiments are presented in the following chapter.The result of the test is a digital record of the force and the absolute deformation change. The data are recorded at a density of approximately 0.1 s. To evaluate the material properties, the relationship between the relative strain For a better overview of the scientific work, a flow chart has been prepared for this experiment . The floThis section presents the results obtained from tensile strength tests of cement–concrete, polyester, vinylester, polyethylene terephthalate, resin and composite specimens. Measurements on the specimens were taken up to the moment of rupture. For each specimen tested, deformation occurred in the narrower measuring section.The tensile force and elongation were recorded for each of the specimens under the same conditions. From these data, the normal stress, strain and tangential elastic moduli were expressed. The calculations were based on Equations (1) and (2). The important geometrical parameters of the test specimens were measured with a caliper. Each test specimen was given a stress–strain diagram based on the processed data. A total of 16 valid measurements were taken.For the evaluation of the measurement results on the cement–concrete specimens, the tangent to the curve of the stress–strain diagram was the most important. The curve starts at the point where the test line ended. It was caused by the reduced specimen size that was designed due to the small scale of the original test setup. For each of the samples, a deformation occurred in the shank of the test specimen .From the data obtained, the stress–strain diagrams were processed, which are shown in graphs 1, 2, 3, and 4—.In some cases, the measurements revealed that the specimen setting of the system at some point after the measuring device was started . SettlinThe actual analysis of the specimens focused on the tangential elastic modulus at the beginning of the branch (initiation elastic modulus), just before the failure limit, and the base elastic modulus. The measured and calculated elastic moduli are shown in The concrete used has a strength class C20/25 and a tensile strength of 1.5 MPa. For a better overview and comparison of the individual measurement results, a common stress–strain diagram was created for all the specimens . From thThe next in the series of materials tested were reactoplasts. In order to describe the interaction between the PET fibers and the reactoplast with the cement–concrete component of the composite, the tensile properties of the polymers were investigated. The small-sized specimens tested were dog-bone shaped. During the tensile test, failure of the specimens occurred in the measuring part of the specimen . Table 3A nonlinear regression model of the polymers was developed for further analytical and numerical calculations , Figure.The test specimens from the waste PET were measured without specimens which had been notched during molding. These specimens had different locations of damage than their measuring part, which would have negatively affected the statistical analysis. The processed PET material results are presented in the graphs. In evaluating the tensile test of the PET material, we also considered the basic modulus of elasticity—Based on the data obtained, the measurements were compared with each other a. The teThe evaluated experimental measurements were compared with the literature. After the comparison, the material properties of the waste PET are consistent.The composite specimens differed from each other not only in the composition and ratio of the individual components of the mixture but also in the color of the specimens themselves. Differences in the workability of the mixture and the associated consistency were observed when the specimens were prepared, which may have been mainly influenced by the proportion of the components and the preparation technology itself. PET fibers have low water absorption, so they cannot affect the hydration of the concrete. The hydrophobic property of PET fibers leads to the formation of purely mechanical bonds between the fibers and the cement matrix. The use of a combination of PET fibers and a vinylester anchor should provide better adhesion to the concrete mix. The stress–strain diagram of the specimen subjected to uniaxial tension is shown in The evaluation of this composite can be divided into three phases, namely: the finishing of the system; the beginning of the interaction; and the conclusion, where the polymers act without cement–concrete. The first phase is probably influenced by the composition of the chemical anchor. The latter consists of a vinylester and an admixture. Therefore, this component of the composite has the characteristic of a reinforcing fiber. In the analysis of the material, where the creep of the system occurs, it is unnecessary to deal with the tangential modulus of elasticity, given that the material has reacted to a small extent. This section is primarily about searching for the equilibrium position of the specimen relative to the gripping mechanism. Once the specimen was set in the correct position, the interaction of the components of the composite occurred. The measured modulus of elasticity was 32.38 GPa. The linear regression was evaluated using mathematical software. When the cement–concrete could no longer withstand the maximum stresses, decomposition occurred and polymers themselves reacted. At that point, the tensile stress started to increase significantly and reached its maximum value (1.04 MPa). The inclination of the failure plane of the specimen was approximately orthogonal to the applied load. Measurements showed that the cement–concrete component did not interact with vinylester as predicted. This behavior of the individual components resulted in improved mechanical properties, especially in the modulus of elasticity. The modulus of elasticity before the failure limit was 78.82 GPa.The stress–strain diagram can again be divided into three parts . It is eIn contrast to composite 1, the composite using polyester resin had significantly better interaction of all elements. The modulus of elasticity in the part where all components interacted was 25.39 GPa. A higher tensile force caused the co-acting cement–concrete component and reactoplasticide to separate, leaving only the individual PET fibers to act. Finally, the loading stopped due to excessive deformation of the specimen, and the specimen failed .The tensile stress reached its maximum value (1.01 MPa). The interesting thing about this type of stress–strain diagram is just the lower tensile strength, which was probably due to imperfect compaction. By an appropriate combination of material, ratio of components and technological procedure, we have succeeded in creating a composite that acts as a single homogeneous material.Specimens of cement–concrete composite reinforced with PET fiber and reactoplasticide were subjected to tensile tests. Using a Keyence VHX 7000N digital microscope, microscopic images were taken at the failure point of the specimen. The microscopic images provide insight into the structure of the composite, information on the bond and adhesion between the matrix and the reinforcement material. The composite reinforced with vinylester resin and PET fibers can be seen in The aim of this research work was to analyze and evaluate the behavior of the hybrid composite. The main idea of the work is to find out the mechanical properties of the investigated composite and its subsequent possible use in construction practice.The measurements were carried out on the premises of the University of Zilina on the SAUTER TVM-500N testing equipment. In total, several tests were performed, but only 16 measurements were included in the statistical data set.The advantage of these results is the independence of the stress–strain diagram (dependence of stress and strain) with the dimensions of the sample. For this reason, the design of scaled, long-necked, dog-bone specimens proceeded. This was also reflected in the resulting values, which, in some cases, reached thousandths of a millimeter. The result of the test was influenced by the material, geometry and the grip of the specimen itself. All the components included in the composite were tested; then, the composite itself was tested.During the experimental phase, recycling PET fibers were mixed with one of several selected types of reactive plastics to create a hybrid composite. They were then added to concrete to improve the material and structural performance of road construction. Road structures are cyclically stressed and undergo stress alternation, which is associated with fatigue phenomena. This experiment is a basic input for further research. The ecological and efficient use of this waste material are other main motivations for this work.The evaluation of the cement–concrete samples concluded that the resulting variations between measurements could be due to insufficient compaction rates. This was subsequently reflected in the resulting tensile strength, which ranged from 1 to 1.15 MPa. The purpose of this experiment was not to investigate the concrete itself, but its interaction with the other components of the composite. In analyzing the results, an exceptional phenomenon was found to occur with the setting of the test line. As it turned out, the sample started to strain after the testing device was started and eventually settled. The settlement of the test rig was related to the position of the sample and occurred in the part of the stainless-steel jig location. This caused the force to drop and the specimen to flatten. As a result of this phenomenon, the system structurally relaxed and only then started to react. Specimens in which this phenomenon was observed were excluded from the evaluation.For another one of the materials tested, the research was concerned with investigating the behavior of selected polymers in simple tension. Three types of reactoplastics  and one thermoplastic (PET) were selected. Due to the good mechanical properties of these materials, the size of the test sample had to be reduced several times. The experiments resulted in material characteristics under tensile stress. The properties of the individual components of the composite were investigated to describe their interactions in the composite, i.e., the participation of the PET fibers and the reactoplast with the cement–concrete component of the composite. Both reactoplasts and thermoplastics exhibit strongly nonlinear material behavior. In this work, several stress–strain diagrams were presented as results of tensile testing on test specimens. For further analytical and numerical calculations, nonlinear regression models of the polymers were also developed based on the assumption of their shape taken from the literature. All material property results were compared with those published in the literature, and it can be concluded that the individual material properties are in good agreement.At the end of the experiment, the composite itself was tested. Two different variants of the composites were tested. The results obtained from this experiment indicate that the workability of the concrete mix is largely influenced by the size and shape of the PET fibers. Polymerization and hydration took place in the samples, which could have a great influence on their material properties. The evaluation of the measurements of the composite samples would not be objective because the results were largely influenced by the degree of compaction. Interestingly, with a lower quality of compaction, it is possible to achieve relatively high elastic moduli see . The meaIn conclusion, it can be stated that with the correct ratio of individual components, it is possible to produce a high-quality composite containing waste PET fiber. This can be used for structural pavement layers. However, further research is needed. The durability and rheology of the material should be addressed. For the continuation of this experiment, the design and construction of a larger geometric specimen must also be addressed. This involves the design of the gripping part, the shape of the fibers and the sample preparation technology itself. By changing the preparation technology, we can achieve better mechanical properties of the composite. The main idea of the new technology is to mix monomers, PET fibers and a cement–concrete mix. By mixing these components, hydration starts to take place, because an initiator is added to the whole mixture; this triggers another chemical reaction (polymerization). These changes can lead to better material properties of the composite. Further research will establish the suitability of this type of composite in road construction, which is the main purpose of its use ,25,26.Several modern case studies also investigate other types of composites in different materials composition and obtain relatively similar results. These authors take recycled polymers, cement–concrete and components used in civil engineering into account ,29,30,31The main scientific research question of the investigated hybrid composites is to determine their mechanical properties. There is a clear description of material behavior under tension in the results chapter. This type of material has significant tensile stress due to the main component, cementitious cement, which becomes brittle after curing. It is generally acknowledged that plastic increases mechanical resistance dactylically.The hybrid composite under investigation is currently being investigated for its compressive and flexural properties. Methods for processing PET particles and analyzing their shapes are also being optimized. Particle geometry will influence the mechanical properties of the composite. The number of composite variations is increasing due to the use of new freely available polymer bases. Further research is being carried out on the dynamic properties of the materials and, in particular, material attenuation.


FRP (fiber-reinforced polymer)–concrete–steel double-skin square tubular (FCSST) columns are composed of an outside FRP tube, an inside steel tube and the concrete filled between them. Under the continuous constraint of the outside and inside tube, the strain, strength and ductility of concrete are improved significantly compared with those of traditionally reinforced concrete without lateral restraint. Additionally, the outside and inside tube not only function as the permanent formwork in casting but improve the bending and shear resistance of composite columns. Meanwhile, the hollow core also reduces the weight of the structure. Through the compressive testing of 19 FCSST columns subjected to eccentric load, this study focuses on the influence of eccentricity and layers of axial FRP cloth (away from the loading point) on the evolution of axial strain along the cross-section, axial bearing capacity, axial load–lateral deflection curve and other eccentric properties. The results can provide basis and reference for the design and construction of FCSST columns and are of great theoretical significance and practical value for the application of composite columns in the engineering of structures in a corrosive environment and other harsh conditions. Hollow-core concrete columns are widely used in high bridge piers, especially in seismic zones. The application of a hollow core can reduce the weight of the column, which thereby decreases the proportion of the self-weight of structures in designed force. Compared with traditional concrete columns reinforced by steel bars or tubes, concrete-filled double-skin steel tube columns present superior performances. Numerous studies ,2,3 haveThe FRP (fiber-reinforced polymer)–concrete–steel tube column, as a new core column, combines the advantages of its three individual materials: FRP, concrete and a steel tube. In terms of columns subjected to compressive, bending and horizontal reciprocating loads, the FRP used for the columns of structures has better specific strength and superior corrosion resistance than a steel tube ,5,6,7,8.The structural behaviors of an FRP–concrete–steel double-skin tubular column subjected to axial compression ,10,11,12Among these columns, the circular cross-section is the most popular. For example, Abdelkarim et al.  exploredAs mentioned above, the composite of FRP, concrete and steel adopted in columns can take full advantage of those positive performances in columns. Accordingly, this composite of FRP–concrete–steel in columns has great mechanical behavior, especially for columns under eccentric compression. Therefore, this column still has huge potential for application, i.e., for piers in a corrosive environment, support in industrial and civil buildings, etc. ,21,24,25However, considering the reliable beam–column connection, square columns ,31 are bSince glass-fiber-reinforced polymer (GFRP) has the advantages of low cost, easy fabrication and high tensile performance, it was used for the FRP cloth in this study. The outer two-way FPR cloth  and inner circular steel tube  were used as the reinforcement materials of a square tubular concrete column named FCSST (FRP–concrete–steel double-skin square tubular) column. The thickness of the FPR cloth was 0.17 mm. The tensile strength and elastic modulus of FRP, tested in accordance with GB/T 1446-2005  and GB/TA total of 19 columns of 5 series with varying eccentricities and layers of FRP cloth on the tension side see  were desFor all columns, as schematically shown in Strain gauge  attachment to steel tube. Before pouring the concrete, strain gauges 10 mm in length were attached on the outer surface of steel tube, especially for those columns whose eccentricity was not 0 mm. The two opposite axial strain gauges were attached on the mid-span surface of the steel tube to make sure that one could measure the axial compressive strain, and the other one could measure the axial tensile strain see . Preparing the formwork and concrete filling. The formwork was made of two crossed U-shaped forms with a steel tube installed inside. Then, the fresh concrete was filled between the steel tube and the formwork.FRP attachment and wrapping . The specimen surface was polished after curing for 28 days. First, the FRP cloth was vertically attached on the tension side. Second, the whole specimen was wrapped in 2 layers of FRP while making sure that the overlap area of FRP was as far as possible from the compression side. In addition, the two ends of each column were also wrapped by a CFRP (carbon-fiber-reinforced polymer) tie 100 mm in width for the purpose of premature failure of ends. Strain gauges attachment of FRP cloth. Four strain gauges 20 mm in length were attached on the mid-span surface of four sides of FRP cloth and used to test the axial strain of the FRP, as shown in Before the eccentric compression test, a column specimen with a steel cushion was placed on a knife-edge hinge, which was glued on the central testing platform by epoxy resin, as shown in During the test, three displacement meters (Hebei Xingtai Qiaoxi Kehua Resistance Strain Gauge Factory) were placed on the tension side along the axial direction of the column to measure the lateral deformation at different heights. A preliminary load of 10% ultimate load was carried out  before the formal test for all specimens. The loading mode adopted was loading-until-damage in the formal test. The specimens were loaded at increasing load level with a 40 kN gap before cracking and with a 20 kN gap after cracking. The damage was defined as FRP rupture, concrete crush or a sharp decrease in load, whichever came first. The strains of the steel tube and FRP cloth, as well as the lateral deformation of the column, were recorded synchronously by the data acquisition system . In the process of the eccentric loading test, the FCSST columns were subjected to the combined action of axial force and axial moment. Accordingly, deformations, including axial compression and bending, were developed, as shown in Based on the test observations and relative studies , the faiWhen specimen A0E0 failed, one narrow strip (2 cm in width) of FRP cloth at around 1/5 of the height from the top loading end broke from the corner, while one wide strip (5 cm in width) of FRP cloth at around 1/4 of the height from the bottom loading end of the loading side also broke from the corner. According to the damage condition a, there The failure modes of specimens A0E5-a b, A0E5-bThe axial strains along the cross-section of the columns were measured through the strain gauges attached on the surface of the FRP cloth and steel tube see  at the iGenerally, the strains at different positions from the center line were almost linear at different loading levels, especially at the initial loading. With the growth of the loading, the neutral axis continuously moved towards the center of the cross-section, which led to the occurrence of tensile strain, that is, tensile cracks appeared on the side far from the loading line. Strain gauge F75-T of the FRP, which crossed the crack, recorded a great tensile strain. As shown by specimen A2E45-b in Through the comparison of F75-C and F75-T strains of the FRP on the compression side and tension side, it was found that, when the eccentricity was smaller than 15 mm, the increase in F75-C and F75-T strain values was close to linear at the initial loading see a–c. ThisThe evolution of the ultimate bearing capacity of FCSST columns with varying eccentricity is shown in Compared with the effect of various FRP cloth layers, eccentricity had a more remarkable impact on the compression bearing capacity of the FCSST columns. In the case of low eccentricity, the failure zone of specimens  with low bearing capacity deviated from a certain range around the intermedial height of the columns. The axial bearing capacity of specimen A0E0 was 991.9 kN, while it reached 1032.4 kN for specimen A1E5-a with a one-layer FRP cloth, although it was subjected to a loading with 5 mm eccentricity. Meanwhile, obvious local concrete crushing was observed. Under axial eccentric load and with an increase in lateral deflection, the actual eccentricity will vary along the height of specimens, which deviates from the initial value with the growth of the loading. In addition, the local deformation near the failure zone will enhance the growth of the eccentricity.e = 15 mm, the bearing capacity of A1E15-a and A2E15-a was obviously greater than that of A1E15-b and A2E15-b. The reason was that the damaged area of A1E15-b and A2E15-b was relatively far away from the intermedial height of the columns. Significant local deformation occurred, with the concrete being crushed and the FRP being pulled apart. Under the same load, the actual bending moment changes along the height of specimens, and the changing may be different even for the same specimen with the same eccentricity. In addition, under the same load, the specimen subjected to a greater actual eccentricity will have a relatively larger bending moment, which makes the bearing capacity decrease in different degrees correspondingly. That was also true for the six specimens  with e = 45 mm. The only difference for them was that the damaged area was further away from the cross-section at the intermedial height of columns but was closer to the reinforced zone at the end. Some specimens  even only had local damage in the reinforced area.In this study, it was the case that two specimens of the same group (which were supposed to be the same) had a significantly different bearing capacity. Comparing the four specimens with According to e = 5 mm, the column  wrapped by a one-layer FRP cloth on the tension side produced the curve that reached the peak phase after an approximate linear elastic stage and then went through a gentle decrease stage, which suggests that the column generally lost its bearing capacity. It can be seen from e increased up to 15 mm and above, the curves of those columns  wrapped by one or two layers of FRP cloth on the tension side showed a completely different trend. That is, the whole curve presented a parabola that first increased gradually and then decreased slowly. The curves of those with e = 15 mm and above showed a more moderate slope at the initial ascent stage. The slope declined gradually with the growth of e eccentricity compared with that of the column with 5 mm eccentricity and changed continually until it entered a flat strengthening stage. Except for the curve of the column with 5 mm eccentricity, all curves of the columns with different eccentricity were basically similar. The only difference was that, under the same load, the deflection with the growing e increased gradually, while the area under the curve decreased, suggesting a declining energy dissipation capacity of the columns [The axial load–lateral mid-span deflection curves of the FCSST columns are presented in  columns .With the different layers of FRP cloth and at the same eccentricity, it can be seen from It can be seen that the FCSST columns obtained a larger axial load than the traditional steel-bar-reinforced concrete (steel–RC) column specimens . In addiH is the height from the measuring point to the bottom of columns with the growth of e eccentricity, and n is the ratio of the applied load to peak load. When the eccentricity was 5 mm, it was found that, as in e = 15 mm, 30 mm and 45 mm, the evolution curves of lateral deflection along the height of columns were similar to those of previous eccentricity studies [In order to present the lateral deflection development more visually, the evolution curves of lateral deflection along the height of the columns under different eccentricity were drawn, as shown in  studies . That isMost of the lateral deflection curves in this study showed a difference from the results of previous eccentricity studies ,42,43. T(1)Under eccentric loading, the axial strain of the cross-section at the intermedial height of columns presents a nearly linear development along different distances from the center line, especially in the initial loading stage;(2)The axial compression bearing capacity of columns with large eccentricity is small. With the increase in axial FRP cloth on the tension side, the corresponding ultimate bearing capacity tends to increase gradually;(3)e = 5 mm), the axial load–lateral deflection curve of columns is similar to that of axial compression. When eccentricity is large , the development of the axial load–lateral deflection curve is similar. Additionally, their area under the curve decreases gradually, which indicates that the ability to absorb energy declines correspondingly. Therefore, the axial FRP cloth on the tension side can well prevent growing lateral deflection;When eccentricity is small ((4)Based on the test results and analysis, two suggestions for the structural design and testing method are provided as follows: (1) two-way FRP cloth can be used for the reinforcement of columns, especially for the reinforcement of the tension side of columns under eccentric loading; (2) in order to fully utilize the performance of FCSST columns and avoid local premature failure, the two ends (top and bottom) of the column should be reinforced by FRP cloth before testing.The experimental results and failure mode of 19 FRP–concrete–steel double-skin tubular (FCSST) square columns subjected to eccentric loading were investigated. The failure mechanism, the evolution of axial loading along the cross-section and the change in lateral deflection along the height of the columns were discussed. In addition, the influence of eccentricity and axial FRP cloth on the bearing capacity and axial load–lateral deflection curves of the columns was analyzed. The following conclusions were drawn:


Background: In 2016, the CDC released the Core Elements of Outpatient Antibiotic Stewardship, which extended the requirements previously released for hospital facilities and nursing homes to the outpatient setting. Several regulatory agencies focused on outpatient antimicrobial use. However, The Joint Commission and the Ambulatory Surgery Center (ASC) Leapfrog Group excluded ambulatory surgery centers from their medication management standards and questions. Due to the public health and patient safety benefits of implementing an antimicrobial stewardship program (ASP) and increasing regulatory interest in the matter, the Hospital Corporation of America (HCA) Ambulatory Surgery Division formally launched a nationwide ASP for its ambulatory surgery centers in March 2021. Methods: HCA is a large healthcare system with 146 ASCs in 16 states in 2021. The structure of the ASCs are local surgery centers with a medical director, a nurse responsible for infection prevention, and a pharmacist at a regional level. The types of surgeries vary based on location and ASC site. In 2019, a multidisciplinary team formed the corporate planning committee. The program was modeled after the CDC Core Elements and The Joint Commission’s requirements for an ASP. Each ASC was asked to build a local ASP team, led by a local physician and a regionally based pharmacist. In addition, a stewardship goal was established to update all preoperative antibiotic surgical-site infection prophylaxis order sets. The corporate committee provided educational resources, including evidence-based guidelines for appropriate antibiotic selection for surgical-site infections. They collected antibiotic cost per case as a baseline metric to track and analyze. Pediatric, ophthalmic, and gastrointestinal endoscopic procedures were excluded from the program. Results: From January 1, 2020, through December 31, 2021, including only centers that were operational during this period and excluding single specialty endoscopy centers, antibiotic cost per case decreased annually from $2.38 to $1.84 , and the postoperative infection rate also declined from 0.370 to 0.304 . Conclusions: Our findings suggest that implementing a health-system–wide outpatient antibiotic stewardship program in the ambulatory surgery center setting is feasible and may contribute to decreased antibiotic cost per case and improved postoperative surgical site infection rates.Disclosures: None


For 4 mm lengths of glued joints, the breaking force was higher than for 2 mm for both file types (K and H). In the case of K-type files, the breaking force was higher for cyanoacrylate and composite adhesives than glass ionomer cement. For H-type files, no significant difference in joint strength was found between binders at 4 mm, while at 2 mm, a much better connection was obtained for cyanoacrylate glue than prosthetic cements.One recommended technique for removing broken root canal instruments is to glue the fragment into a cannula adapted to it . The aim of the study was to determine the influence of the adhesive kind and length of the joint on the breaking force. During the investigation, 120 files (60 H-files and 60 K-files) and 120 injection needles were used. Fragments of broken files were glued into the cannula using one of three materials: cyanoacrylate adhesive, composite prosthetic cement, or glass ionomer cement. The lengths of the glued joints were 2 and 4 mm. After the polymerization of adhesives, a tensile test was carried out to find a breaking force. The results were statistically analyzed ( Fracture of root canal instruments is a possible complication during endodontic treatment ,2. In a Due to the imperfection of the instruments, the complex anatomy of the teeth , and possible human error, fatigue and torsion failure can occur almost simultaneously. In some cases, a broken file can be left in the tooth. In many situations, however, an attempt should be made to remove the broken fragment of the endodontic instrument ,6. CurreOne of the oldest and best-known systems is the Masseran kit, introduced about 50 years ago. It consists of a trepans with a diameter of 1.2 mm to 4.4 mm, an extractor, and forceps. Using the trepan, a tunnel is cut around the broken instrument for half its length. An extractor is placed over the protruding fragment of the instrument and carefully unscrewed counterclockwise. This method is relatively simple, but the whole kit is expensive. In addition, it is useless in narrow canals with a thin layer of dentin and in curved canals because its use may cause perforation of the root. Furthermore, the Masseran kit cannot always be used when broken files need to be removed from the posterior canals or when patients are unable to open their mouths wide. Due to the length of the individual instruments, it is not always possible to manipulate the fingers in more difficult situations . The MeiA system that uses the philosophy of the tube technique but with some modification is the Removal System (IRS) Superior EditionTM  . The setIt has a characteristic window, which plays a significant role in anchoring the broken fragment in the sleeve. The limitations of using the IRS system are similar to those of the Masseran kit . As instSome authors also recommend the use of cyanoacrylate glue . The latThe aim of the study is to compare the strength of the bond between the endodontic file and the cannula using three binders and two types of K and H stainless steel files.The quality of the connection between the broken file fragment and the injection needle is independent of the length of the file fragment glued inside the needle, the type of binder, and the type of endodontic file (K files vs. H files).The quality of the connection between the broken fragment of the file and the injection needle varies depending on the length of the fragment of the file glued inside the needle, the type of binder, and the type of endodontic file (K files vs. H files).One hundred and twenty files (60 H-type files and 60 K-type files) and 120 injection needles (size G21) were used for the study . All fil® = GCFP), and chemically cured composite cement . Some of the sets of glued joints of H and K files with cannulas were embedded in epoxy resin. Furthermore, the samples were grounded and polished to obtain longitudinal cross-sections of glued joints. With the use of a light microscope , the glued joints were assessed. The actual embedding length and true length of glued joints were measured. The embedding length was measured as the length of fragment files inserted into the canula. The true length of the glued joint was measured in such a way that the measurements of joint length start or end in the area of lack of adhesive on both sides of the endodontic file.File fragments were placed in the v-block of the device and moved to the stop. Following that, the file was pressed down with a clamp, the stop was moved away, and the cannula was filled with a suitable binder and put on the file to a length of 2 mm or 4 mm. One of the following materials was used as a binder: standard cyanoacrylate adhesive (CA) , glass ionomer cement , considering the following: r et al. , and assp < 0.05).After polymerization, the compound between the tubes and the endodontic instruments was used for pull-out tests (static tensile tests). The results were statistically analyzed , confirming that the matched method and file sticking device were effective and characterized by high accuracy (The larger the surface of the bonded joint (file-cannula), the greater the probability of clinical success. Of course, in a clinical situation, it is always necessary to carefully consider whether a larger fragment of the file can be exposed ,19. In taccuracy . However−5 to 50,000 Pa·s [This state of affairs is probably greatly influenced by the viscosity of the adhesive used. The rheological properties of the adhesive are of great importance when it flows into narrow gaps and surfaces with irregularities. In the cases considered, the low viscosity of the adhesive will be conducive to filling the gaps created as a result of fitting the file with the cannula. Cyanoacrylate adhesives, among others, have low viscosity. Cyanoacrylates are one-component, room-temperature curing adhesives that are available in a variety of viscosities, from water-thin liquids to thixotropic gels . The dyn000 Pa·s ,24. ImpoThe length of the bond was measured in such a way that the length of the bond was taken to end at the point of lack of glue on both sides. Such a measurement, although it does not fully reflect the area of the glued surface, increases the probability of a lack of adhesive mass around the entire perimeter of the glued parts. The results are shown in the chart below .The graph  clearly This article also compares the size of the connection force between the needle and the broken files, depending on the binder used. K-type files demonstrated better binding quality for CA and MCE compared to GCFP at both embedding depths. In the case of H-files inserted to a depth of 4 mm, no statistically significant difference was observed in the strength of the file-cannula connection, regardless of the type of binder used. For the H-files at an embedding depth of 2 mm, a clearly stronger bond was achieved with CA compared to the prosthetic cements. No statistically significant differences in the strength of the bond made with GCFP and MCE were observed for H files with an embedment depth of 2 mm .So, the conducted experiments show that the cyanoacrylate adhesive is a very good alternative to the prosthetic cements used in the case of removing both broken K and H files for both embedding depths. If it is necessary to remove K-files from the canal, the best option is to use cyanoacrylate glue or Maxcem Elite (MCE) prosthetic cement. Maxcem Elite is a composite cement. Thanks to the chemical binding process, no polymerization lamp is needed. In addition, it is a self-etching material and does not require the use of any binding systems or additional preparation of the glued surfaces. This applies to both prosthetic cases and the use of this cement to remove broken files using the tube technique. An additional advantage of the above-mentioned material is the fact that it is produced in packages with a self-mixing tip, thus reducing the risk of procedural errors during material processing.In the present study, the worst bond quality was observed after the use of GC Fujii glass ionomer cement (GCFP), especially with K-files. In the group of H-type files with an embedding depth of 4 mm, no significant differences in the strength of the glued joint were found. It is worth noting, however, that the absolute values (mean and median) were worse in the subgroup where the GCFP material was used. In the group where glass ionomer cement was used, no prior surface preparation was required. Files were also glued in without surface preparation using the two previously discussed binders. Although this contributed to the standardization of the tests , it could have contributed to worse results in the group where GCFP cement was used. The manufacturer of GCFP recommends additional preparation of the tooth surface with a conditioner in order to improve the bonding quality. No conditioner was used in our experiment, and it is not known whether its use would have any effect on the quality of the connection between the needle and the file. The reason for not using the conditioner in this experiment is the fact that the use of the conditioner in clinical conditions could cause complications during treatment, e.g., the cannula and the file sticking to the tooth tissue. Bürklein et al. compared the force needed to break the file-cannula connection with and without additional surface modification prior to the application of a light-cured composite. The study compared GC Metalprimer, Prime, and Bond active, NaOCl (3%), citric acid (15%), and phosphoric acid (37%). It was found that Prime and Bond active significantly increased the adhesion of the light-polymerized composite to the surface of files made of nitinol (NiTi). It should be noted that the authors used a slightly different material (binder) and nickel-titanium files instead of steel, so their test results cannot be compared with our present findings. Wfelemeier et al. found that composite cements provided a better bond between the broken file and cannula compared to cyanoacrylate adhesive. It is worth noting, however, that different types of composite cements were used: Rebilda  and SDR . Rebilda is a dual-curing composite cement, and SDR is a light-curing only cement. Polymerization of the SDR composite took place thanks to optical fibers inserted into the cannula instead of the glued connection. No irradiation was used for Rebilda. The authors found the light-curing composite offered a better connection than the dual-curing composite cement .p < 0.05)  . The nulOur paper also analyzes the effect of the type of file on the quality of the glued joint, assuming that the files are glued to the same length with the same glue. After applying the cyanacrylate adhesive, no statistically significant differences in the strength of the bond were noted, regardless of whether the H or K files were removed . The results for prosthetic cements are different. After using the GCFP material, a better connection was found (greater force needed to break the needle-tool system) for H files than K files . However, after using the MCE material, no such differences were found between K and H files at a length of 4 mm, while a significantly better connection was observed with K files at a length of 2 mm .Differences in the strength of the connection between K and H files are probably due to significant differences in their construction , which mOur findings may help dentists better understand the tube technique and the relationships leading to the implementation of more effective clinical practices.If it is necessary to remove an H-type file from the root canal and if ~4 mm of the broken instruments can be exposed, it does not matter what material will be used as a binder. If it is possible to embed the H-type file in the cannula to only ~2 mm, cyanoacrylate glue should be chosen instead of the prosthetic cements presented here. If the dentist does not have cyanoacrylate adhesive available, it is better to use Maxcem Elite cement to remove the K-files from the root canal. In the case of H-files, the connection made with Maxc em Elite cement proved to be as effective as with GC Fujii cement. However, both cement joints performed worse than the joint made with cyanoacrylate adhesive.p < 0.0001). More than four polymerization cycles had no further benefit (p < 05).To date, very few experimental studies have evaluated the cements and binders used in the tube technique. However, one noteworthy study examined a very specific problem related to the removal of broken nickel-titanium files using a modified tube technique with a light-curing composite , the aimMost articles are case reports concerning the removal of broken files with a needle/cannula ,30,31,32However, regardless of the type of binder, it should be remembered that it is difficult to remove broken instruments using an injection needle in clinical conditions. It requires experience, time, and specialized instruments. The previous studies indicate a fairly high percentage of successful broken root canal tool removal using the tube technique, either in the form of ready-made kits or the use of an injection or hypodermic needle ,32,33,34As mentioned earlier, for the removal of the broken fragment of the file to be possible at all, it must first be visualized in the canal and “uncovered”, typically with the use of ultrasonic tips; in addition, the entire procedure must be performed under the magnification of the operating microscope. Despite the relatively cheap materials, such as injection needles or used binders, in practice, the entire procedure generates higher costs related to the purchase and use of additional necessary instruments . It is aIn addition to perforation, the procedure may result in the root canal becoming “clogged” by an uncontrolled leakage of the binder outside the cannula. Even in the case of small leakages, all adhesive residues must be removed from the tooth ,26,29. HWhen working with ultrasound, care must be taken with the power setting, and copious rinsing must be used to cool the tooth structure and adjacent anatomical structures. Improper use of ultrasonic instruments may result in the breakage of the ultrasonic file itself in the canal as well as potential periodontitis and bone inflammation due to excessive temperature on the external surface of the root. According to the literature, the power of ultrasonic devices should not be higher than about 30%. To reduce the risk of excessive temperature increase on the outer surface of the root, it is recommended to rinse the root canal abundantly and frequently, e.g., with sodium hypochlorite solution ,39.Regardless of the number and frequency of rinses used, the color of the root dentin should be observed during the procedure; if a yellow-brown discoloration appears, the canal should be immediately rinsed with a cold agent, and the power of the device should be reduced ,39,40. SIn our work, because the experiment was carried out in typical laboratory conditions, in vitro, without tooth extraction, no surgical microscope was needed to glue the broken file fragment. Similar conditions were noted in earlier publications ,15. ThisHowever, it was not possible to study any unmeasured displacement of the binder outside the cannula, which would limit or completely block the patency of the canal. The aim of the work was to determine the strength of the connection between the cannula (needle) and the broken file depending on the type of binder and the length of the insertion. It does not address any possible reaction between the cement and tooth tissues. In addition, the work does not deal with nickel-titanium alloy files, which are intended to be the subject of further research.The findings can also be influenced by the strength of the connection between the file-binder and the needle, which may be determined by the chemical composition of the root canal instrument alloy as well as the large cross-sectional variation between machine files. As such, the results of the current study should be applied only to situations where steel hand files are removed using the tube technique.Providing the largest possible bonding surface between the broken instrument and the cannula will enable the transfer of greater force, increasing the probability of removing the broken instrument from the canal.Cyanoacrylate adhesive is a very good alternative to prosthetic cements. Our findings may help dentists better understand the tube technique and the relationships leading to the implementation of more effective clinical practices.


Introduction: Surgical site infections (SSI) can be as high in gynecology and obstetrics surgeries compared to other areas. Antimicrobial prophylaxis is an effective tool in the prevention of SSIs; however, it is often not adequately administered, so this study aimed to understand the compliance and factors associated with the use of the clinical practice guidelines for antibiotic prophylaxis in gynecological surgeries in two hospitals in the city of Huanuco, Peru. Methods: An analytical cross-sectional study of all gynecologic surgeries performed during 2019 was performed. Compliance was determined based on the antibiotic chosen, dose, administration time, redosing, and prophylaxis duration. Age, hospital of origin, presence of comorbidities, surgery performed, as well as its duration, types of surgery, and anesthesia were considered as related factors. Results: We collected 529 medical records of patients undergoing gynecological surgery with a median age of 33 years. The prophylactic antibiotic was correctly indicated in 55.5% of cases, and the dose was correct in 31.2%. Total compliance with the five variables evaluated was only 3.9%. Cefazolin was the most commonly used antibiotic. Conclusion: Low compliance with the institutional clinical practice guidelines for antibiotic prophylaxis was identified, showing that antimicrobial prophylaxis in the hospitals studied was inadequate. Surgical site infections (SSIs) are the most frequent nosocomial infections in developing countries ,2. SSIs SSIs are a major source of healthcare expenditure in the Region of the Americas, with estimates suggesting that they cost between USD 3.5 and 10 billion annually. In addition to the direct costs of treatment, SSIs also result in approximately 90,000 readmissions each year, incurring an additional cost of USD 700 million .It has been described that cesarean delivery is associated with a 20 times higher risk of infection compared to vaginal delivery, with a rate of infection reported to be 1–25% . These sAntibiotic prophylaxis is defined as a brief course of antibiotic use initiated close to the surgical procedure and aimed at reducing the likelihood of developing SSIs . AntibioCompliance with clinical practice guidelines is crucial for ensuring the appropriate and effective use of antibiotics. These guidelines offer recommendations for the selection, timing, and duration of antibiotic prophylaxis based on patient characteristics and the surgical procedure . HoweverMistakes in the administration of antibiotic prophylaxis are common, with errors such as delayed initiation of antibiotics after the incision or even after the entire surgical procedure, use of antibiotics not recommended for a specific surgery, and inadequate dosing being reported. Patients admitted to gynecology and obstetrics wards are at higher risk of not receiving appropriate antibiotic prophylaxis for more than 24 h .The inappropriate use of antibiotic prophylaxis and the overuse of antibiotics have resulted in numerous negative outcomes, including increased adverse reactions, hospital cost overruns, bacterial resistance, and superinfections . The WorEnhancing compliance with clinical practice guidelines for antibiotic prophylaxis is a crucial strategy for reducing the inappropriate use of antibiotics. To address incorrect use, it is essential to judiciously follow the clinical practice guidelines that have already been published by various societies and institutions. By promoting adherence to established guidelines, healthcare providers can ensure that antibiotics are used appropriately and in the best interests of patient health ,18.The purpose of this study was to assess compliance with the American Society for Hospital Pharmacists (ASHP) clinical practice guidelines for antibiotic prophylaxis published in 2010 in two hospitals located in Huanuco, Peru. Additionally, we aimed to identify factors associated with compliance in these settings.During the study period, 529 medical records were collected from patients who underwent gynecological surgery with a median age of 33 years, the cesarean section being the most frequently performed surgery in 57.1% of the cases. The prophylactic antibiotic was correctly indicated in 55.5% of cases, and the dose was correct in 31.2%. Complete compliance with the five variables evaluated was only 3.9% .With regards to the prophylaxis administered, our findings reveal that 94.5% of patients were prescribed antibiotics, with 38.2% receiving antibiotic prophylaxis. Cefazolin was the most frequently used antibiotic in both cases .Finally, when comparing patient characteristics with the type of compliance, we observed that the surgery performed, the type of procedure, and the type of anesthesia were related to total compliance, while the hospital, the surgery performed, and the type of procedure to acceptable compliance .The use of antimicrobial prophylaxis in obstetric and gynecologic surgeries varies considerably according to geographical areas and socioeconomic and cultural contexts. The present study found that, of the total number of surgeries, antibiotics were used in 94.5%; however, the indication for antibiotic prophylaxis only corresponded to 38.2%. This is different from what was found by Uppendahl and Gil, who, in their respective studies, found a frequency of use of prophylaxis above 95% ,20, evenIt has been shown that the publication and follow-up of clinical practice guidelines improve the proper prescription of antimicrobial prophylaxis in surgery in hospitals where they have been implemented ,23,24. AWhile in surgeries that used antibiotics in general, cefazolin corresponded to only 37.6% of all indications; in cases where antimicrobial prophylaxis was indicated, cefazolin was used in 57.4%. A study in Jordan found that cefazolin was 85.4%, but in its correct dose, it was only 62.3% , while iThe present study has shown that the use of multiple antibiotics was more frequent in cases of treatment compared to prophylaxis. Specifically, 17% of cases involved the use of more than two antibiotics in treatment, while only 2.5% did so in prophylaxis. This finding highlights the importance of rational and conscientious antibiotic prophylaxis. Physicians who correctly prescribe antibiotic prophylaxis tend to use only one antibiotic, which is a significant advantage. However, previous studies have shown that antibiotic combination is still prevalent in some cases of prophylaxis, with Alemkere reporting that 39% of prophylaxis cases used antibiotic combinations . In anotEven after discharge, a significant proportion of patients were found to continue using antibiotics. Alexiou’s research showed that 15% of gynecologists prescribed antibiotic prophylaxis for two days or more , while AThe study revealed that the highest frequency of compliance was observed in the choice of the right antibiotic, while the lowest frequencies of compliance were observed in relation to redosing and duration of prophylaxis. A study in Israel showed that 95.6% of patients received the correct antibiotic . In contThe study’s findings regarding compliance with prophylaxis protocols in surgical patients are concerning. Total compliance with all five correct parameters was found to be only 3.9%, despite the fact that only clean and clean–contaminated surgeries were included in the analysis—all of which should have received prophylaxis instead of antibiotic treatment. When considering the appropriate choice of antibiotic and dose, as well as an additional correct parameter, acceptable compliance rates only reached 9.8%. These results are consistent with those of previous studies. Abdel et al. reported overall adherence of only 2.7% in all surgeries . In a laThe study found that the type of surgery was a statistically significant factor associated with both total and acceptable compliance, with cesarean sections showing better adherence to prophylaxis protocols compared to other types of surgeries. These findings are consistent with those of previous studies. For example, Uppendahl reported that myomectomy, laparoscopy, and ectopic pregnancy procedures received agents that were contrary to recommendations in up to 96% of cases . In contThe results indicate that there is a higher level of adherence to prophylaxis guidelines in emergency surgeries compared to scheduled surgeries. This is supported by Abubakar’s study, which demonstrates that the correct administration of prophylaxis is more frequent in emergency surgeries . HoweverThere were statistical differences regarding the type of anesthesia, being better in general anesthetics. This differs from that shown by Polla, where local anesthesia was more likely to receive adequate antibiotic prophylaxis . These dThe hospital of origin was found to have statistical differences only for acceptable compliance but not for total compliance. Previous studies, such as Brubaker’s, have found geographic differences in the likelihood of receiving the correct antibiotics, while Hamdaoui found that the proportion of antibiotic prophylaxis increased with the number of procedures, particularly in the case of abortion prophylaxis ,32. ThesThe present study has certain limitations that must be pointed out. First, the statistical results may be affected due to the low proportion of cases with adequate compliance. However, this was partly mitigated by categorizing compliance as complete or acceptable, resulting in consistent results among factors associated with compliance. Second, limited data on certain groups of related factors may restrict the generalizability of these findings to the broader population. Moreover, the study did not consider variations in surgical techniques or practices among surgeons, which could also affect compliance rates, nor the presence of pre-eclampsia or HELLP syndrome, which, although they do not usually require antibiotics beyond prophylaxis, patients with these conditions tend to have longer hospital stays, increasing the risk of iatrogenic infections and the need for antibiotic treatment. Finally, the study was conducted in only two institutions, which could limit the applicability of the findings to other healthcare settings or regions.An analytical cross-sectional study with retrospective data was conducted in the gynecology and obstetrics services of all surgeries that received antimicrobial prophylaxis. Antimicrobial prophylaxis was defined as the use of antibiotics before surgery to prevent infections associated with the surgical site. Age, hospital of origin, presence of comorbidities, type of surgery performed, duration of surgery, types of surgery, and anesthesia were all considered as related factors for analysis. Elective and emergency procedures were included.Data collection was performed in the gynecology and obstetrics services of the two leading hospitals of the city of Huánuco “Hospital Regional Hermilio Valdizan” and “Hospital II EsSalud-Huanuco” from 1 January to 31 December 2019. The selected hospitals serve as a point of reference for the entire region of Huanuco, offering gynecology and obstetrics services to a population of 375,000 women with over 80 available beds.The data collection process was carried out over a period of four months, from January to April 2022, during which all medical records and operative reports from both hospitals were reviewed. However, to ensure the validity of the study, certain patients were excluded from the analysis. Specifically, those who had previously used antibiotics during hospitalization or undergone surgery within the preceding three months were excluded, as these factors may have influenced the use of antimicrobials not recommended for antibiotic prophylaxis. In addition, procedures performed on individuals with severe immunosuppression, those who had been hospitalized for more than 48 h at the time of the procedure, individuals with suspected or confirmed colonization by resistant microorganisms, and those surgical histories and reports that did not present complete data related to prophylaxis were also excluded from the analysis.The investigators followed the U.S. Center for Disease Control (CDC) wound classification to include only clean and clean–contaminated wounds: Class I/Clean wounds are those which are uninfected and do not encounter any inflammation. Additionally, these wounds do not enter the respiratory, alimentary, genital, or uninfected urinary tract. Clean wounds are typically closed and, if needed, drained with closed drainage. If operative incisional wounds are a result of non-penetration (blunt) trauma and meet the criteria, they should be included in this category. Class II/Clean–contaminated wounds refer to operative wounds where the respiratory, alimentary, genital, or urinary tracts are entered under controlled conditions, and there is no unusual contamination. This category includes operations that involve the biliary tract appendix, vagina, and oropharynx, provided there is no evidence of infection or a significant breach in technique.All parameters were evaluated individually, according to the Guide for Surgical Prophylaxis published by the Institute for the Evaluation of Health Technologies and Research (IETSI) of the Peruvian Social Security . The IETSI guidelines follow the antibiotic prophylaxis guidelines of the United Kingdom and the American Society for Hospital Pharmacists (ASHP).Antibiotic type: this was deemed correct if the antibiotics used were recommended by prophylaxis guidelines and incorrect if any other antibiotic was administered;Appropriate dose: the dose was classified as correct if it corresponded to the dosage recommended by the prophylaxis guidelines and incorrect if any other dosage was indicated;Time of administration: this parameter was considered correct if the antibiotic was administered within 60 min prior to the incision and incorrect if it was administered beyond 60 min or after the incision;Duration of prophylaxis: the prophylaxis duration was deemed correct if the antibiotic was stopped on the same day of the surgery and incorrect if the antibiotic continued to be administered in the following days;Need for redosing: considered as correct to the administration of an additional dose of antibiotic during a surgical procedure when the procedure is prolonged beyond the recommended duration for the chosen antibiotic and was considered incorrect if the antibiotic was not re-administered or was administered before the recommended time.The study established the following parameters:For the purposes of the study, acceptable compliance was defined as prescriptions that adhered to the correct choice of antibiotic, appropriate dosage and redosing, and adherence to the recommended time or duration of prophylaxis. Meanwhile, total compliance was achieved when all five requirements were met for every surgery.p < 0.05 was predetermined. Stata v16 (StataCorp) was used for data analysis. The descriptive statistics used were mean, median, standard deviation, and percentiles according to their distribution for continuous variables and percentages for categorical variables. Only histories with complete data were used. Bivariate analysis was performed to explore the possible variables associated with total and acceptable compliance. The chi-square test was used to compare categorical variables, and the Mann–Whitney U test was used for nonparametric quantitative variables. The statistical significance level of This research was conducted in accordance with the ethical principles emanating from the regulatory standards for human health research and the Declaration of Helsinki of the World Medical Association and all its amendments. The Universidad Cientifica del Sur, through Research Ethics Committee, granted approval for the project, identified as number 026-2019. As the study relied on medical records, obtaining informed consent was not deemed necessary. This article represents the thesis submitted for a master’s degree in clinical epidemiology and biostatistics at the Universidad Científica del Sur.We conclude that antibiotic prophylaxis in gynecological surgeries in two hospitals in Huánuco is inadequate, and procedures have low compliance with institutional clinical practice guidelines. Cesarean sections and emergency surgeries are statistically related to better antibiotic prophylaxis prescriptions.