This paper develops the mechanical and durable samples of C50 high-performance concrete, studies the mechanical properties, crack resistance, sulfate attack resistance, frost resistance, and impermeability of concrete with different mineral admixtures of mineral powder and fly ash, and obtains the best mineral admixture of mineral powder and fly ash to improve the performance of high-performance concrete. The results show that the doping effect is the best when the ratio of prepared mineral powder to fly ash is 3:2. With the increase in the mineral powder–fly ash admixture, the slump and expansion of high-performance concrete decrease rapidly at first and then slowly. In total, 60% doping is the turning point; the compressive and flexural strengths of concrete decreased slowly at first and then rapidly. Taking 30% of the admixture as the turning point, 35% of the mineral powder fly ash is generally selected. By mixing and adding a certain proportion of fly ash and mineral powder admixtures, the crack resistance of concrete is enhanced, and the shrinkage and cracking are reduced. The corrosion resistance coefficient will exceed 88%, the relative dynamic elastic modulus will exceed 95%, and the impermeability grade will reach P17. The durability of concrete can be improved by adding mineral admixtures. In civil engineering, the proper selection of construction materials is crucial to the development of the project. With the development of science and technology, housing construction will use a variety of materials to improve performance . In the The aim of this study is to analyze the characteristics of high-performance concrete and find the optimal mineral powder–fly ash composite admixture to provide data support for the selection of concrete for civil construction, provide a reference for practitioners and decision-makers, and also provide insights for future research directions. By analyzing high-performance concrete, the incorporation of mineral admixtures is of significant technological innovation. Although there have been studies on the performance of high-performance concrete in civil construction, there are some shortcomings. Previous studies may have been limited in analyzing high-performance concrete in depth without comprehensively examining its actual performance under different environmental conditions. Practical applications are constrained by cost and preparation processes, and the variations in performance in different environments needs to be studied in depth. Finally, more research is needed on economic evaluation to ensure the long-term viability of high-performance concrete. Although progress has been made, further research is needed to gain a more comprehensive understanding of the application of high-performance concrete in civil construction.In the study conducted by Guo et al., the thermal treatment and utilization of flue gas desulphurization gypsum as an admixture in cement and concrete were investigated . The potHigh-performance concrete has many performance advantages, and its application in civil engineering will greatly improve the quality of civil engineering and promote the sustainable development of civil engineering. The most important advantage of high-performance concrete is its excellent compactness and impermeability, and its fluidity and segregation resistance are better . When prThe main factors that affect the performance of concrete are water–binder ratio and cementitious materials. By adding various mineral admixtures to concrete, the water–binder ratio and the dosage of cementitious materials can be adjusted to realize the influence on workability and mechanical properties in civil engineering . High-peIn this paper, different water–binder ratios, the dosage of cementitious materials, the dosage of additives, and mineral admixtures of C50 high-performance concrete will be used to analyze the changes in the mechanics and durability of high-performance concrete. The properties of high-performance concrete include mechanical properties, crack resistance, frost resistance, impermeability, and so on.The mechanical property test of high-performance concrete will be carried out according to the cement concrete test regulations. The specimen used in the unconfined compressive strength test was a 15 cm × 15 cm × 15 cm cube, the curing period was set to the specified age test, and the load was increased at a speed of 0.5~0.8 MPa/s. A cuboid with a size of 15 cm × 15 cm × 550 cm was used for the flexural strength test, and its curing period was set to a specified time.The early crack resistance experiment was evaluated by the early cracking of concrete. In the test, the specimens were set to different curing periods of temperature, humidity, and time, and the test environment was set to temperature, humidity, windless, and windy conditions. A specimen of 60 cm × 6 cm × 5.3 cm was used in the test, and steel bars were used in the mold to restrain the contraction of the flat plate. In total, 2 h after the specimen was formed, the concrete surface was blow dried at a wind speed of 0.8 m/s, and the cracking time and the number of cracks of the specimen were recorded until the time reached at least 24 h.2SO4 solution with a temperature of 25–30 °C into and submerge the surface of the specimen for at least 20 mm. After soaking, empty the solution and air dry it within half an hour. After air drying, raise the temperature in the specimen box to 90 °C and bake it for 6 h. After drying, cool to room temperature, repeat drying and wetting cycles several times, and then test the compressive strength of the sample.Sulfate corrosion resistance test was mainly based on the standard of long-term performance and the durability test method of ordinary concrete. Samples were made of 10 cm × 10 cm × 10 cm concrete samples, which were divided into 5 groups. In the test, two days before the curing of the samples, dry the samples to be cured and put them in a 90 °C oven, bake them for 24 h until they are dried, then naturally cool them to room temperature in a dry environment, and put them in a box of samples. Pour the 5% NaThe frost resistance test was mainly based on the test regulations of cement and cement concrete for highway engineering. The specimen is 10 cm × 10 cm × 40 cm, and the freeze–thaw cycle tests of 50, 100, 150, 200, 250, and 300 times were carried out to measure its relative dynamic elastic modulus.For the impermeability test, according to the long-term performance and durability test method of ordinary concrete, six cone-shaped specimens with upper diameters of 175 mm, lower diameters of 180 mm, and heights of 150 mm were prepared. The initial pressure was set to 0.1 MPa in the test, and 0.1 MPa water pressure was added every 8 h. When 3 of the 6 cone-shaped specimens had water under pressure overflowing, the test was stopped.The experimental sequence of this paper was to make experimental concrete samples with different doping ratios according to the experimental needs. Firstly, its mechanical properties , crack resistance, frost resistance, and impermeability were tested, in turn, to optimize the optimal doping ratio.The vibrating table shall conform to the relevant provisions of the current industry standard “Vibrating table for concrete test” IG/T245, the vibration frequency shall be 50 Hz and 2 Hz, and the vertical amplitude of the center point of the vibrating table shall be 5 mm and 100 mm under no load. The tamper should comply with the relevant provisions of the current industry standard “Concrete slump meter” JG/T 248, with a diameter of 16 mm and a length of 600 mm.At 5 mm, the end should be hemispherical. The hammerhead quality of the rubber hammer or mallet should be 0.25 kg~0.50 kg. Before the specimen is formed, the size of the test mold shall be checked and shall comply with the relevant provisions of this standard; wipe the test mold clean, and evenly coat a thin layer of mineral oil or another isolation agent that does not react with concrete on the inner wall of the test mold. The isolation agent on the inner wall of the test mold should be evenly distributed without evident deposition. Before the concrete mixture enters the mold, it should ensure its homogeneity. According to the consistency of the concrete mixture or the purpose of the test, the appropriate molding method should be determined, and the concrete should be fully dense to avoid delamination and segregation.In the mechanical experiments of high-performance concrete materials, the proportion of mineral admixtures determines the performance of concrete. In this paper, 60% mineral powder and 40% fly ash are selected, according to the compressive strength, flexural strength, and detailed inspection of the percentages of different components . The minDuring the test, the mixing amounts of composite mineral admixtures were set as 0%, 15%, 30%, 45%, and 60%, respectively. The mixing amount mainly referred to the proportion of total cement and mineral admixtures. In this experiment, the mechanical properties of concrete with different mineral admixtures of mineral powder and fly ash were tested. For the experimental method, refer to GB/T 50082-2009’s Test Method for Durability and Long-term Mechanical Properties of Concrete. From the figures and tables, it can be seen that the mineral powder–fly ash composite admixture with different dosages has an evident influence on the mechanical properties of concrete. When the dosage of composite mineral admixture increases gradually, the slump and expansion of high-performance concrete will increase rapidly. When the dosage reaches more than 50%, the concrete will show greater fluidity, and the slump and expansion of the concrete will increase slowly when the dosage exceeds 70%. With the increase in the amount of composite mineral admixture, the slump loss of concrete decreases rapidly at first and then slowly, and the amount of 60% is the turning point.The compressive strength and flexural strength of composite mineral admixtures with different amounts were obtained through experiments. It can be seen from the figures and tables that the compressive and flexural strength of concrete decreases slowly at first and then quickly with the continuous increase in the amount of composite mineral admixture. When the amount is 0~30%, the strength of concrete has no evident change. When the amount of admixture exceeds 30%, the compressive strength and flexural strength of concrete will decline rapidly. This is mainly because the hydration of cement increases the activity of mineral powder and fly ash in the composite mineral admixture gradually, which promotes the secondary hydration reaction of free calcium oxide and highly alkaline C-S-H and improves the strength of concrete. Therefore, the composite mineral admixture of C50 high-performance concrete should be 30–45%. Considering the stability of concrete performance and economic cost, the amount of mineral powder–fly ash composite mineral admixture is generally 35%.It can be seen from The crack resistance, sulfate attack resistance, frost resistance, and impermeability of C50 high-performance concrete are studied through experiments. The shrinkage-cracking model is used to quantitatively analyze the early cracking model of concrete, and the shrinkage crackings of different types of concrete are predicted by the model. The main factors leading to concrete shrinkage cracking are temperature deformation, shrinkage deformation, drying shrinkage deformation, elastic modulus, tensile strength, etc. . These fIn this paper, the change in compressive strength of samples after the wet–dry cycle is used to characterize the damage to concrete. For concrete, its frost resistance has a great influence on its durable service life. When civil engineering projects are located in harsh areas, its frost resistance requirements are very strict. In this paper, the relative dynamic modulus of 28 d concrete under different freeze–thaw cycles is tested by experiment. The impermeability of concrete is the main cause of chloride ion corrosion on concrete. In this paper, the influence of mineral admixture on the impermeability of concrete is analyzed by testing the impermeability grade of concrete with only one mineral admixture and composite mineral admixture at the age of 28 days. The impermeability of concrete is given in This thesis aims to investigate the key performance characteristics of high-performance concrete materials in civil construction, including the analysis of compressive strength, durability, crack control, and sustainability, to guide material selection and engineering application based on scientific data for the construction field. Through the comprehensive study of different ratios, admixtures, and construction processes, it aims to deepen the understanding of high-performance concrete and provide feasible suggestions for practical engineering applications.(1)In this paper, the ratio of mineral powder to fly ash is 3:2, and different amounts are mixed in the concrete. With the increase in the admixture, the slump and expansion of concrete decreased rapidly and then slowly, and the admixture of 60% was the turning point. With the increase in the mineral powder–fly ash composite mineral admixture, the compressive strength and flexural strength of concrete first decreased and then decreased rapidly. When the admixture is 0–30%, the change in concrete strength is not evident. When the admixture exceeds 30%, the compressive strength and flexural strength of concrete decrease rapidly. After mixing mineral powder, the shrinkage of concrete changes greatly in one day, and the larger the dosage the smaller the shrinkage of concrete. Generally, 35% of mineral powder–fly ash composite mineral admixture is used;(2)A certain proportion of fly ash and mineral powder admixture can directly improve the early crack resistance of high-performance concrete; fly ash can enhance the crack resistance of concrete and reduce shrinkage and cracking, but the role of mineral powder is not evident. When the composite mineral admixture is incorporated into concrete, the corrosion resistance of concrete will be more than 88%, whereas the corrosion resistance of concrete with fly ash alone is less than 81%. After more than 300 freezing and thawing cycles, the relative dynamic modulus of C50 high-performance concrete will be more than 95%, and the relative dynamic modulus of concrete with a single admixture of fly ash is higher than that of concrete with a single admixture of mineral powder. Composite mineral admixture helps to improve the impermeability of concrete, which will reach the grade of P17. Admixture of only one mineral admixture is also effective in improving the impermeability of concrete, which reaches the grades of P11 and P13 for (KF)-only and (FMH)-only concretes. An admixture of mineral admixtures helps to improve the durability of concrete.Compared to the study of single admixtures, the use of composite admixtures can cover more material combinations, thus providing a more comprehensive understanding of the multidimensional effects of different admixtures on concrete performance and providing a more scientific basis for the application of concrete.Concrete with a composite admixture of fly ash and mineral powder has multiple advantages. Introducing these auxiliary materials, fly ash and mineral dust, into the concrete preparation process not only significantly improves the strength and durability of concrete but also helps to improve the flow and workability, making construction easier. The silicate and aluminate components of these materials participate in the hydration reaction of cement, enhancing the matrix structure of concrete and effectively inhibiting temperature rises and crack formations. Meanwhile, being environmentally friendly, the reuse of waste helps to reduce resource consumption and achieve sustainable construction. In addition, the addition of fly ash and mineral powder can also slow down drying and shrinkage, reducing the risk of cracking. However, the proportioning should be rationalized according to the specific situation, and the effects of different sources and properties on the performance of concrete should be fully considered to ensure that the concrete meets the design requirements.However, the source and quality of admixtures will have an impact on the experimental results, and there is a need to ensure the consistency and reproducibility of the experiments. Although the results under laboratory conditions provide insights into the effects of composite admixtures, in actual engineering applications, there are factors such as environment, construction, and durability, which require more practical validation and in-depth research.In this paper, C50 high-performance concrete material is taken as the research object; the mechanical properties, crack resistance, sulfate resistance, frost resistance, and impermeability of concrete with different amounts of mineral powder–fly ash composite admixture are studied by analyzing the performance characteristics of the high-performance concrete; and the optimal mineral powder-fly ash composite admixture is obtained, which provides theoretical data support for improving the performance of high-performance concrete. The main research results are as follows.Experiments have proved that the selection of 35% ground mineral powder–fly ash as composite mineral admixture is most effective in ensuring the compressive strength and carrying strength of concrete.The mixed admixture of fly ash and mineral powder can significantly enhance the crack resistance, corrosion resistance, and durability of high-performance concrete, as well as improve the impermeability.The performance analysis of this thesis provides a useful discussion of high-performance concrete materials in civil construction; however, the depth and practicality of the research can be further enhanced by incorporating more performance indicators, abundant experimental data, in-depth mechanistic analysis, and case studies of practical applications. In addition, taking sustainability and future trends into account will also provide a more comprehensive perspective on the development of the high-performance concrete field.


This article considers the prospects of the application of building structures made of polymer concrete composites on the basis of strength analysis. The issues of application and structure of polymer-concrete mixtures are considered. Features of the stress-strain state of normal sections of polymer concrete beams are revealed. The dependence between the stresses and relative deformations of rubber polymer concretes and beams containing reinforcement frame and fiber reinforcement has been determined. The main direction of the study was the choice of ways to increase the strength characteristics of concrete with the addition of a polymer base and to increase the reliability of structures in general. The paper presents the results of experimental and mathematical studies of the stress-strain state and strength, as well as deflections of reinforced rubber-polymer beams. The peculiarities of fracture of reinforced rubber-polymer beams along their sections have been revealed according to the results of the experiment. The peculiarities of fracture formation of reinforced rubber-polymer beams have also been revealed. The conducted work has shown that the share of longitudinal reinforcement and the height of the fibrous reinforcement zone are the main factors. These reasons determine the characteristics of the strength of the beams and their resistance to destructive influences. The importance and scientific novelty of the work are the identified features of the stress-strain state of normal sections of rubber-concrete beams, namely, it has been established that the ultimate strength in axial compression and tension, deformations corresponding to the ultimate strength for rubber concrete exceed similar parameters for cement concrete 2.5–6.5 times. In the case of the addition of fiber reinforcement, this increase becomes, respectively, 3.0–7.5 times. Sustainable economic development of the countries in the world has become one of the main global environmental problems in many countries, and in the last decade, it has been paid much attention. There is an urgent need to develop appropriate strategies for the disposal of various types of waste such as plastic, tires, rubber, and glass. It is estimated that around 1.5 billion rubber tires are disposed of worldwide every year. The materials used in the production of tires are made up of complex mixtures. As a result, the share of discarded recycled tires is relatively low, with over 50% remaining unused.Rubber industry waste and used tire rubber (UTR) is a non-degradable material that is not properly recycled. UTR also takes a significant amount of time to naturally degrade due to the cross-linked structure of the polymer material and additives such as stabilizers. Burning UTR releases toxic gases. Landfills and waste disposal cause serious environmental pollution of soil, water, and air. It pollutes the soil by killing beneficial bacteria and releasing toxic gases. Waste can be considered a potential resource and valuable material. A logical way to reduce the negative impact of rubber waste and its cost is to use it in construction and industry. Natural aggregates are more valuable than waste. When looking for economically viable deposits to extract non-metallic materials, factors such as transportation costs, the quality of the aggregate suitable for mining, government regulation, and the cost of operating and maintaining vehicles are taken into account. At the same time, transport costs for aggregates are very high. In addition, the energy required to crush the rock into aggregates is proportional to the area of the new surface, and therefore it constitutes a significant part of the energy consumed in the production of aggregates . UTR easPolymer concretes are widely used in the construction industry and other industries. To date, a large amount of experimental data on the study of their structure and properties has been accumulated . At the Polymer concretes are a type of polymer composite material. The main area of application of such composites is construction. In modern representation, polymer composites are a rather complex hierarchical system formed as a result of physical and chemical interactions between its structural components . The maiIn this paper, the most promising polystructural theory of construction composites is taken as the basis. It is based on the concept that consists of the representation of construction composites as polystructured. They are composed of many structures, passing one into another according to the “structure-in-structure” principle, in which there are fractions of additional composite materials of several sizes (powder and granules) . There iTo ensure a reliable efficient operation of elements made of new types of concrete, it is necessary to study the stress-strain state arising under the action of forces of various kinds, in particular, a bending moment. In this connection, the study of resistance to the bending moment action of normal sections of beams made of reinforced polymer concrete (ACRP) (beams containing a reinforcement frame and fiber reinforcement located at different heights of the section relative to the bottom edge) is of scientific interest and a practical important research task.The conducted research analysis of force resistance of polymer concrete and reinforced concrete bendable elements has shown that the application of polymer concretes and structures on their basis is actually because of their inherent high operational characteristics. It is important to study the degree of influence of dispersed reinforcement on the performance characteristics of polymer concrete structures. The main methods existing today for polymer concrete structures’ calculation are quite limited in terms of the used materials. Their main scope is structures made of furfural acetone concrete, polyester, and epoxy concrete. This is due to the existing wide experimental base containing these materials and a large number of obtained empirical dependences .to carry out an analysis of force-resistance studies of polymer concrete and reinforced concrete beams;to evaluate the physical conditions of polymer concrete structures based on rubber additives;to conduct experimental studies of the stress-strain state and strength and deflections of ACRP beams;to reveal the peculiarities of failure of ACRP beams by their cross-sections;to reveal the peculiarities of the formation of the failure of ACRP beams;to reveal the peculiarities of the development of deflections of ACRP beams.In this regard, to improve the strength of polymer concretes and the reliability of structures, as well as to predict the properties of the material and products made of it, the following tasks were set in this article:There is a sufficiently large production and waste volume of synthetic rubber and rubber products in modern industry ,3. TheirBased on previous studies, the optimum ratios of hardening group components containing a binder, aggregate, and filler were determined . It was Based on the analysis of literary sources and in the course of experimental studies, the authors obtained a comparative table  of polymIn practice, the property that determines the scope of polymer concrete is heat resistance at 80–150 °C. At the same time, when the operating temperature of polymer concrete increases, its strength, and modulus of elasticity decrease. Having low heat resistance, polymer concretes nevertheless belong to the class of non-combustible materials, since the content of organic matter in them is low as compared to the proportion of inorganic components.Since a promising direction in the study of polymer concretes is to reinforce them with dispersed reinforcement, additional reinforcement was used in the fabrication of specimens . As a renormal stresses, corresponding in shape to the diagram of mechanical tests for axial compression and tension of polymer concrete;the hypothesis of planar sections .Three equations were made by the authors to obtain calculation formulas:moments of forces equilibrium;projections of forces on the neutral plane equilibrium;equations of a ratio of boundary deformations or heights of compressed and stretched zones of the element cross-section. The scheme of forces and the stress diagram in the cross-section normal to the longitudinal axis of the bendable polymer concrete element, when calculating its strength, is shown in The basis of the methodology for calculating polymer concrete structures is set out in . The strFirst of all, let us write an equation for the moments of forces equilibrium.When reinforcing the tensile and compressed zones of the bendable polymer concrete element , the cala is a tension region height;M is a bending of the beam during tests;sR is a design resistance of the longitudinal bar;sA is an area of reinforcement in the tension region;sA’ is an area of reinforcement in the compression region;µ is a reinforcement ratio in the tension region; formula :(2)ξ=xh0µ’ is a reinforcement ratio in the compression region;comprR is a design resistance in the compression region.The calculation procedure  for the x based on Formula (3) and use it in Formula (2). Let us also express Let us express According to , the strStresses in the longitudinal reinforcement The reinforcement deformations are equal to:In the first case, the height of the compressed zone is expressed through the deformation of the reinforcement:On the other hand, it is possible to make through the deformation of the outermost stretched fiber, that is, through the ultimate tensile strength:By projecting the forces onto the neutral plane, we obtain:The reinforcement factor is determined by the formula:The compressive edge stresses σb<0.75R . Let us BHP has a high tensile strength , as wellthe percentage of the longitudinal gain that has the greatest effect on the resistance of the normal part bending element;the height of the dispersion reinforcement zone (measured from the bottom edge) with the same percentage of fiber reinforcement over the volume of the reinforced part .The testing of beams made of rubber concrete involved test specimens-beams of all series made having a section size of 6 × 12 cm and a total length of 140 cm. The beams were manufactured according to the Central Asian standards, GOST 948-2016 (ICS 91.080.40), the Interstate Standard of Reinforced-Concrete, and Polymer-Concrete Lintels. The determining parameters of the beams are the following: the length (L) is from 1030 (mm) to 5950 (mm); the width (B) is from 120 (mm) to 250 (mm); the height (H) is from 60 (mm) to 585 (mm). The beams are tested by means of two symmetrically applied forces in the thirds of the span (pure bending test procedure). In this way, the samples of the beam were made of reinforced rubber fiber concrete. The dispersion reinforcing fiber was made of waste metal cord from the tire industry. Various parameters are assigned in the experiment:The response function is the strength; they combine the crack resistance of an element of the normal cross-section, as well as their good deformability. The boundary conditions of the area of variation of the experimental parameters are established on the basis of the analysis of the literature . The proThe test procedure complies with GOST 10180-2012 and ICS 91.100.30, Methods for Strength Determination Using Reference Specifications. In the laboratory, before testing the samples, the temperature is maintained at 20 ± 5 °C and the relative humidity of the air is at least 55%. Under these conditions, the samples were in the dismantle form before the test for at least 24 h. The control samples were tested on the day of testing the beam. The beams were loaded with two equal concentrated loads, applied vertically in the thirds of the span. In the case of this type of load application, the value of the bending moment, arising in the beam, increases from zero on the support to the maximum value under the point of load application. Between the points of load application, the transverse force is zero, and the value of the bending moment is constant and equal to the maximum value (the pure bending zone). A general view of testing the samples of rubber concrete beams is shown in The beam samples were tested using a laboratory press “INSTRON 600KN” (60 tons), certified and meeting the requirements of GOST 10180-2012 and ICS 91.100.30 “Methods for Strength Determination Using Reference Specifications”. The load on the sample was fed at a constant rate until destruction.3 and a dynamic viscosity of up to 12 Pa × s;Cis-polybutadiene low molecular weight CBLMW-R rubber (ISO 6743/4). CBLMW-R rubber has a density of 910 kg/m2/g, having the following composition by mass in %: Al O23—16.5–22.5; CaO was 5.5–5.5; Fe O23 was 13.5–15.5; SiO2 was 47–55; MgO was 2–3; K2 O was 1–2; Na2 O was 1; S O23 was 0.4–0.3; others were 6–15;fine-dispersed filler being ash of a specific surface of 2500...2700 cm3;vulcanization activator was zinc oxide ZnO (ISO 10262-2016) white powder having a density of 5600–5700 kg/m3;vulcanization gas pedal was tetramethyl thiuram disulfide (Tiuram-D) (ISO 4097 2013) being powder of gray-white color and density of 1300–1400 kg/m3;calcium oxide CaO was a white powder having a density of 2500–2900 kg/m3 after 28 days of preparation. The mixture can be without additives or with various substances introduced into the composition in a certain proportion. The compressive load is 2500 kg/cm. Frost resistance is more than 100 cycles. The bulk density is 1100–1600 kg/m. True density kg/m3 3100. The setting speed is from 45 min to 10 h. The average weight of Portland cement is 3 tons/m3;Portland cement. It consists of the following ingredients: clinker ; gypsum; plasticizing, hydrophobic, acid-resistant additives; domain fee. The chemical composition of cement: 21.55% silicon oxide and 65.91% calcium oxide. Portland cement is the most durable and high quality, therefore it is widely distributed on the market. It is a cement that is capable of showing an average compressive strength of about 500 kg/m3, having a melting point of 114 °C;sulfur technical (ISO 3704-76) is a bright yellow powder with a concentration of 2070 kg/mmetal fibers made from scraps of metal cord by sawing. The fibers obtained in this way are wave-shaped fibers at a ratio of a length to a wire diameter of 1/100;sand and crushed granite  are selereinforcing steel bars having a diameter of 8, 10, 12, 14, 16, and 18 mm and a steel wire of a diameter of 5 mm.The following materials were used in the work:Determination of the actual physical and mechanical characteristics of steel reinforcement was carried out using the Instron 1500HDX testing system. Measuring the longitudinal parameter with 270 uses a base of a 20-mm strain gauge for deformation. A set of equipment was used to control the stress-strain state (VAR) stage, namely, deformation 2 MG plus design and CATMAN-AP software . The conThe component composition of rubber concrete (as a percentage of the element weight) supplemented with dispersed reinforcement, which provides the best strength characteristics and chemical resistance, is shown in 3 in tons) [To manufacture concrete specimens without the filler, the concrete of a composition having a similar modulus of elasticity to that of rubber concretes was chosen. The composition of the cement concrete used for making experimental specimens without the filler (mass per 1 min tons)  was as fThe production of the elements made of fiber-reinforced polymer concrete (FRPP) with the arrangement of fibers along the entire section height  was carried out in one stage.washing the fine and coarse aggregate;preparation of curing group components and fibers;dosage of ingredients;drying of the components;mixing of the components.Based on , the preDosing of sand and gravel was carried out on the scales VPS-40 M having an accuracy of 5 g. The dosing of other components was carried out on the electronic scales CAS ER JR-15CB having an accuracy of 1 g due to their smaller weight .The components were mixed in a high-speed propeller-type mixer. The polymeric binder was prepared by combining CBLMW-R rubber with hardening group components and the fine filler with fly ash. The mixing time of the binder was 80 s at 1000 rpm. Then fine aggregate and fibers mixed with the coarse aggregate were introduced into the prepared mixture. The resulting polymer concrete mixture was prepared in the same mixer at a speed of 180 rpm for 200 s.Before laying the FCPB mixture in the form, the surface is smeared with waste oil to facilitate removal later from the formwork. The prepared mixture was placed in the molds and compacted on the vibrating table with a vibration duration of 100 ± 30 s. An indication of sufficient compaction of the polymer concrete mixture is the release of the binder on the surface and the cessation of the intensive formation of air bubbles .After performing the above operations, the mold with the mixture was placed in a dry heating chamber (dryer), where FKPB was cured at 115 ± 5 °C for 12 h (taking into account the heating time of 17 h). Unpacking was performed after the complete polymerization and cooling of the samples.Fabrication of FKPB elements with the fiber arrangement in the tensile zone  was carried out in two similar stages according to the works .The fabrication of FCPB elements took place in one step using metal cord fibers.The reinforcement of all series of experimental beams was a welded frame, shown in The test procedure corresponds to the methods outlined in the regulatory literature .The test of the manufactured beams was carried out using concentrated loads. The load was applied vertically and distributed in the third part of the beams’ span. In the case of a loading scheme for beams, the bending moment arising in the beams is 0 on the support. Already under the point of application of the load, the moment increases to a maximum value. Between the points to which the load is applied, the value of the transverse force is zero. The bending moment at the same point has a constant value equal to the maximum value. A diagram of the load distribution on the test specimens is shown in The beam samples were tested on the laboratory presses of INSTRON800KN (80 tons), certified, and they met the requirements . The loaThe maximum value of the pressing force was the value of the breaking load during beam testing. It was determined by a force sensor. At this value, the yield strength of the reinforcement was reached. Glued strain gauges made it possible to measure longitudinal deformations. Deformation measurements were carried out in a normal section. The strain gauge base was 2 cm. A linear displacement transducer, a plunger, with an accuracy class of 0.2%, was used to measure the vertical displacements of the beams.During the given tests, the crack opening width and height were measured. The crack opening width was measured with a micrometer; a duplicate measurement was made with a caliper.Before testing, the specimens were inspected and measured. Roughness and burrs on the surface of the beam material were removed with an angle grinder. The side surfaces of the beams were ground to facilitate visual observation of the appearance and distribution of cracks due to the dark surface of the material. Before attaching the load cells, the surface of the beam was ground with an angle grinder and degreased with acetone. After that, the load cells were pressed to the surface of the structure with glue.With each polymer-concrete beam, control samples-prisms (4 cm × 4 cm × 16 cm) and specimens-eights with the size of a working area of 3 cm × 4 cm and a total length of 40 cm were made. To control the deformation-strength characteristics, control samples-cubes (10 cm × 10 cm × 10 cm) and prisms (4 cm × 4 cm × 16 cm) were made with each concrete beam. Three control samples were produced. Studies of prisms and cubes were carried out under central compression and octagonal samples were tested under central tension.Compression tests of beams, concrete prisms, and concrete cubes were performed according to the requirements  on an INTensile tests of fiber-reinforced polymer concrete (FRPB) specimens were carried out taking into account the requirements of ISO 1920-1:2004 and recommendations on testing methods for polymer concretes  on a tenIn order to determine the relationship between stress and relative deformation occurring in FCPB, required for a comprehensive study of the cross-section of the deflection of a curved element, a control sample being a prism and a sample, eight were made from each experimental beam. Test methods of specimens, their geometrical parameters, and schemes of measuring instruments arrangement are given in Based on the diagram shown in The relationship between compressive stresses and relative strains is shown below.Based on the analysis of The dependencies in the analytical form between compressive stresses and relative deformations of FKPB products are presented in Experimental studies have shown that the percentage of longitudinal reinforcement and the height of the diffuse reinforcement zone are the main factors affecting the normal cross-sectional strength of the ACPB bending element. The parameters and test procedures of the test sample in the study of strength in normal cross-section are given in As a result of the experimental studies, the values of the breaking bending moments depending on the percentage of longitudinal reinforcement and the height of the fiber reinforcement zone were obtained. These are presented in The study of the composition in The study of the composition of In the range of longitudinal reinforcement percentage values of 0.6–6.5%, the dependence in The linear dependence between the parameters of the percentage of longitudinal reinforcement and the bending moment is maintained over a sufficiently large segment. This is a segment of the values of the percentage of longitudinal reinforcement equal to 0.8–6.3%. A further increase in the percentage of longitudinal reinforcement leads to a change in the nature of the destruction. The destruction of ACPBF beams occurs already in the compressed zone. The strength of the sections almost does not change in the presence of such destruction. It is important to note that the failure of ACPBF beams having a percentage of longitudinal reinforcement equal to 0.8–6.3% began in the stretched zone, i.e., when the reinforcement reached its yield strength. In the over-reinforced beams (µ = 8.4%) the failure is brittle, i.e., it occurs in the compressed zone .The failure of ACPBF beams having a percentage of longitudinal reinforcement equal to 0.78–6.3% began in the tensile zone, i.e., when the reinforcement reached its yield strength. In addition, in the over-reinforced beams (µ = 8.4%) the failure is brittle, i.e., it occurred in the compressed zone. That is, the failure of ACPBF beams is similar to that of ACPBF beams with the addition of fibers. In the tested beams , relative strains in the outermost compressed fibers of the rubber and reinforcement reach the limit values almost simultaneously .The failure of ACPBF beams having the zone reinforcement, i.e., possessing 3/4 of the cross-sectional height and longitudinal reinforcement in the range of 0.8–4.95% occurred when the reinforcement reached its yield strength, i.e., in the tensile zone. In the over-reinforced beams (µ = 6.4%) the failure is brittle in nature, i.e., it occurred in the compressed zone. Consequently, to increase the bearing capacity of ACPBF beams having 3/4 of the cross-sectional height with a percentage of longitudinal reinforcement greater than 4.95%, it is necessary to reinforce the compressed zone. The earlier destruction of the ACPBF elements with zone reinforcement in the compressed zone is conditioned by the fact that the strength of the stretched zone corresponds to the solid ACPBF elements. At the same time, the strength of the compressed zone is lower than that of ACPBF elements, because the ultimate strength of non-dispersion reinforced ACPBF in compression is lower than that of ACPBF with the fiber. This leads to the fact that due to the higher tensile strength of ACPBF, the crack height develops and, consequently, the position of the neutral axis shifts towards the outermost compressed fiber, and the compressed zone is fractured .u-µ”. It is worth noting that the increase in the difference of bending moment values for CPB and ACPB beams with fiberglass, with µ = 6.3% is due to the fact that in CPB beams the beginning of reinforcement flow almost coincided with the material reaching its yield strength in the compressed zone, but occurred slightly earlier [The magnitude of the destructive bending moment during destruction along the compressed zone changes insignificantly. Due to the fact that the deformation of the reinforcing bar does not reach the yield strength compared to the previous series of beams, it, as a result, leads to the curvature of the graph “M earlier .To compare the load-carrying capacity of ACPB bending elements with longitudinal reinforcement having the load-carrying capacity of reinforced concrete elements, beams containing the B25 class concrete with different reinforcement contents were tested .The results of the pure bending test of reinforced concrete beams are summarized in It is worth noting that ACPB beams  failed in the tensile zone. Reinforced concrete beams with the same content as the longitudinal reinforcement failed in the compressed zone .As a result of the experiments, we can say the following:1. The normal sections of ACPBF bending elements strength exceeds the strength of reinforced concrete elements having µ = 0.8% by 70.56%, µ = 1.25% by 44.8%, µ = 1.8% by 36.8% and by 98.9% (for beams with µ = 3.55%).2. The normal sections of the durability of the ACPB bending elements is higher than the durability of reinforced concrete elements having µ = 0.8% by 33.7%, µ = 1.25% by 21.5%, µ = 1.8% by 17.2% and by 91.2% (for beams having µ = 3.55%). The strength of normal sections of FRCP bending elements having a zone reinforcement is higher than the strength of reinforced concrete elements having µ = 0.8% by 64.6%, µ = 1.8% by 27.3%, and by 93.4% (for beams possessing µ = 3.55%).The bearing capacity of the bending elements with fiber reinforcement in the tensile zone and with fiber reinforcement throughout the cross-section height is higher than that of similar ACPB (without dispersion reinforcement) bending elements . This isThe bearing capacity of polymer concrete bendable elements is higher than that of similar concrete elements with longitudinal reinforcement. It is related to a number of factors: a part of polymer concrete of the stretched zone above the formed crack participates in the work of normal sections; high adhesion of reinforcement and structural material  prevents sudden development of plastic deformations in reinforcement; higher strength of the compressed zone material. We cannot exclude the fact that the material of the structure in the gap between the cracks takes part in the work of the element as a whole.It should be noted that CPB is a more plastic material, which is confirmed by the deformation diagrams in In order to verify the theoretical conclusions and evaluate the results of the experiment of polymer concrete beams, finite element modeling was implemented in the Ansys software package (PC), taking into account the nonlinear properties of materials. Articulated boundary conditions are set on the right support of the beam, prohibiting only vertical movements, but allowing all rotations. Hinged-fixed boundary conditions are set on the left support. The span between the centers of the supports is 1.2 m. The length of the support zone was 60 mm, and the length of the beam overhangs was 70 mm. Two concentrated forces act on the beam, mirrored in the same way as the test scheme .In the Ansys environment, as an element simulating the concrete body of the sample, an eight-node finite element Solid 65 was chosen, which has the ability to simulate plastic deformations, cracks, and destruction. This finite element implements the Willam-Warnke concrete deformation model. This dependence is an ellipse equation describing the deviatoric section.When specified in a PC, the model includes the following parameters: stress-strain diagram for compression, modulus of elasticity, ultimate compressive and tensile strength, Poisson’s ratio, and shear force transfer coefficient for closed and open cracks.For modeling longitudinal and transverse reinforcement, the Beam 188 finite element was used, which is a rod, spatial finite element.Based on the results of the calculation, the values of the destructive bending moments were obtained. The results of numerical studies of armocouton beams in the Ansys environment are graphically presented in Simulation of the state of the beam before its destruction shows the general logic of the destruction of bending elements. This logic is consistent with the standard model, which observes the cracks’ appearance and their subsequent development.The study results of concrete strength control (CSC) of bendable elements are summarized in The dependence of the ultimate bending moment on the percentage of longitudinal reinforcement for CPB-reinforced beams is shown in The Willam Warnke strength theory developed for composite materials (implemented in this work with the help of Ansys) allows the calculation of ACPB beams. The performed calculations and their comparison with experimental data showed that the maximum discrepancy for the strength values obtained by empirical and calculated methods was 14% (in the series of BPC beams). In addition, a similar deviation of 7.4% for BPC-8 beams was already obtained. The greatest discrepancy between the results was achieved for ACPB BPC beams and amounted to 18.0%.That in turn will allow the conducted experimental studies to replace the numerical ones, but in conditions of non-compliance with the design requirements or deviation from the norms in the tests, these features should be additionally taken into account in the modeling.1. The features of the stress-strain state of normal sections of ACPB beams are revealed. It has been established that the tensile strength in axial compression and tension, deformations corresponding to the tensile strength for CPB, exceed the similar parameters for the used cement concrete 2.5–6.5 times. According to the results of the work, it was found that the addition of fiber reinforcement increased the tensile strength of the BPS 3.0–7.5 times.2. The percentage of longitudinal reinforcement and the height of the fiber reinforcement zone are the main factors influencing the strength and crack resistance of normal sections of the ACPB bending elements. The destruction of ACPB and ACPBF bending elements with a percentage of longitudinal reinforcement of less than 6.3% occurs in the tension zone, and with a percentage of longitudinal reinforcement of more than 6.3%, the destruction occurs in the compressed zone.3. Increasing the height of the fiber reinforcement zone of the CPB from 0 mm to 120 mm, the strength of normal sections of bending elements with a percentage of longitudinal reinforcement µ = 0.8% increases by 28%. The strength of normal sections of elements with µ = 6.3% increases by 14%, for elements having µ = 8.4% the strength of normal sections practically does not increase. It has been established that fiber reinforcement increases the moment of formation of cracks in structures up to 1.5 times, and the bearing capacity of structures as a whole increase up to 1.3 times.4. It has been experimentally determined that the addition of fiber over the entire height of the element section with the same percentage of longitudinal reinforcement increases the moment of cracking of the ACPBF of the bent elements compared to the elements from the CPB (without dispersed reinforcement) up to 1.5 times. It can be compared to the ACPBF elements with zone reinforcement (with fiber reinforcement at 3/4 of the section height) of up to 1.08 times.5. Ultimate deflections of ACPB bending elements are less than deflections of ACPBF bending elements with zone reinforcement of up to 18.5%. Deflections of ACPB beams with a percentage of longitudinal reinforcement µ ≤ 1.8% are similar to reinforced concrete bending elements made of heavy cement concrete.


Immunoglobulin G4‐related disease (IgG4‐RD) is a recently described rare systemic fibroinflammatory disease with an estimated incidence of less than 1 in 100,000 persons per year. The disease can affect virtually any organ and is characterized by unifying histopathological findings. Recently, four subgroups of patients have been characterized: hepatobiliary, head and neck, Mikulicz syndrome and retroperitoneal fibrosis, who illustrate the mainly abdominal and ENT tropism of the disease. Yet, thoracic involvement is not uncommon. It can be detected in up to 30% of patients with systemic IgG4‐RD and is the exclusive manifestation of the disease in about 10% of cases. Clinical symptoms are nonspecific and may include dyspnoea, cough or chest pain. Chest CT findings are heterogeneous and primarily include peribronchovascular thickening, nodules, ground‐glass opacities and lymphadenopathy. There is no specific diagnostic test for IgG4‐RD thoracic involvement, which may mimic malignancy or vasculitis. Therefore, a cautious approach is needed to make an accurate diagnosis: a search for extra‐thoracic manifestations, elevated serum IgG4 levels, circulating levels of plasmablasts and pathologic evidence of disease is warranted. Although very suggestive, neither the presence of a polyclonal IgG4 lymphoplasmacytic infiltrate, storiform fibrosis or obliterative phlebitis are sufficient to confirm the histological diagnosis. Steroids are recommended as first‐line therapy. Rituximab or disease‐modifying antirheumatic drugs may be used in relapsed or rare cases of steroid‐refractory disease. In this review, we summarize current knowledge regarding the pathophysiology, epidemiology, diagnostic modalities  and treatment of IgG4‐RD thoracic involvement. Immunoglobulin G4‐related disease (IgG4‐RD) is a recently described systemic fibroinflammatory disease characterized by unifying histopathological findings.IgG4‐related disease.The description of the first cases of IgG4‐RD dates from 1961: Sarles et al. reported chronic autoimmune pancreatitis in patients with a distinctive histological feature of fibrosis and lymphoplasmacytic infiltration.Today, the use of the term IgG4‐RD has reached a consensus and is based on precise classification criteria published in 2019.As a matter, the thoracic involvement of IgG4‐RD has been only recently described.The presence of elevated serum IgG4 levels, the heavy infiltration of lesions by IgG4 plasma cells,IgG4 is the smallest subclass of immunoglobulin and represents about 5% of total IgG. It is a particular immunoglobulin that is usually considered non‐inflammatory because of its inability to activate the complement pathwayAmong the B cells involved in IgG4‐RD, plasmablasts (defined as CD19low CD38+CD20−CD27+ cells) have been the most studied.FH17 (CCR6+CXCR3−).Oligoclonal expansion of IgG4+ plasmablasts that occurs in IgG4‐RD patients is characterized by somatic hypermutations of the rearranged immunoglobulin heavy chains, suggesting T‐cell dependent stimulation. Among T cells, circulating follicular helper cells (Tfh) could play a major role in IgG4‐RD. Circulating Tfh cells produce IL‐4, which is involved in class‐switching of B cells to both IgG4 and IgE. Numbers of circulating Tfh cells correlate with number of circulating plasmablasts and serum IgG4 concentrations.The existence of a type 2 helper (Th2) immune response in IgG4‐RD patients is supported by the increased expression of IL‐4, IL‐5 and IL‐13.Innate immunity is involved in the pathogenesis of IgG4‐RD. Anti‐inflammatory polarized M2 macrophages are implicated in tissue fibrosis in IgG4‐RD. These cells are observed in fibrotic areas and their number is correlated with the degree of tissue fibrosis.Except for one case report of identical twins with IgG4‐RD,To date, the incidence of the disease has been estimated in Japan to be approximately 1 per 100,000Like IgG4‐RD, thoracic involvement is typically seen in middle‐aged to elderly adults, more commonly in men than women.Isolated thoracic involvement was estimated to occur in 13% of patients.IgG4‐RD usually manifests subacutely. More than half of the patients are asymptomatic according to several studies.Chest CT‐scan is the most widely performed imaging method to evaluate IgG4‐RD thoracic involvement. Chest CT‐scan presentation of IgG4‐RD is polymorphic and non‐specific.n = 31).Through literature, seven main patterns of thoracic IgG4‐RD involvement are describedn = 90). The GGO pattern was the most common according to Inoue et al.n = 13), and Seraya et al.n = 16), whereas it was the nodular pattern in the study by Kang et al. .The relative frequency of these different patterns fluctuates between studies. In a cohort of 48 patients with thoracic involvement, we found that peribronchovascular involvement was the most frequent, affecting 60% of those patients. Fujinaga et al.Even in the setting of well‐known IgG4‐RD, any chest imaging abnormalities are not necessarily secondary to IgG4‐RD. Thus, classification criteria for thoracic involvement have been developed by Corcoran et al. to assess the responsibility of the disease in observed thoracic lesions.Some thoracic imaging patterns might be associated with specific IgG4‐RD extra‐thoracic involvements. For example, our previous study of 48 patients with IgG4‐RD thoracic involvement suggested that round‐shaped GGO may be associated with a more frequent IgG4‐related pancreatitis, that lymph node enlargement might be associated with a greater frequency of sialadenitis, and that interstitial disease could be associated with a more frequent hypereosinophilia.18F‐FDG PET/CT can also be used for a comprehensive assessment of organ involvement. It could have greater sensitivity for detecting disease in arteries (aortitis and periaortitis), salivary glands and lymph nodes.18F‐FDG PET/CT can be useful detecting clinically asymptomatic IgG4‐RD organ involvement in the thorax, then selecting the most diagnostically informative biopsy site, assessing response to therapy and monitoring for disease relapse.Biologically, two key markers for diagnosis and follow‐up of the disease have been identified to date: serum IgG4 level and detection of circulating plasmablasts.Elevated serum IgG4 concentration (>135 mg/dl) represents an important diagnostic consideration. This threshold is part of all classification and diagnosis criteria, including the last ACR‐EULAR criteria published in 2019, but exhibits inconstant sensibility and specificity and so a low positive predictive value (34%) for the diagnosis of IgG4‐RD.Flow cytometric detection of circulating plasmablasts is also a useful biomarker for diagnosing IgG4‐RD. A 900/ml cut‐off could be associated with reported sensitivity more than 90% and specificity of 80%.Moreover, a nonspecific biological inflammatory syndrome is often noted. Elevated C‐reactive protein levels are found in a quarter of patients, but this increase is usually modest.Many other markers, that we not detailed in this review, are currently under investigation in IgG4‐RD.IgG4‐RD demonstrates common histologic features in most of organs that may be affected. The three main histopathological characteristics of IgG4‐RD are the presence of a polyclonal lymphoplasmacytic infiltrate, a storiform fibrosis and obliterating phlebitis.The dense lymphoplasmacytic infiltrate is composed of T cells, B cells, occasional germinal centres and plasma cells. It can cause obliteration of the venous channels, leading to obliterative phlebitis. An essential feature of this infiltrate is the abundant presence of IgG4 plasma cells, which should be assessed semi‐quantitatively by immunostaining of the total number of IgG4 cells per high‐power field  and measurement of the IgG4/IgG plasma cell ratio .At the thoracic level, different organs can be investigated, with few histological specificities. Regarding lymphadenopathies, five morphological subtypes have been described,Regarding the lungs, histopathology of lesions shows diffuse lymphoplasmacytic infiltration, obliterative vascular changes and fibrosis with occasional eosinophilic infiltration.Regarding the pleura, histological patterns correspond to those commonly observed in most of the other affected organs, with a threshold of >50 IgG4/plasma cells (/hpf).Several procedures are available to collect a sample of involved tissue, depending on the organ concerned, the location of the lesion, the patient's medical history and the experience of the centre. Mediastinal lymph nodes can be reached by endobronchial ultrasound (EBUS‐TBNA), surgical sampling or mediastinoscopy, while pleural involvement can be reached by percutaneous core cutting needle or surgical sampling.The diagnosis of thoracic involvement of IgG4RD is a challenging process based on the agreement of clinical, biological, imaging and histological findings. Virtually, all intrathoracic organs can be affected Table  but no fClinically, the presence of extra‐thoracic organ involvement, especially in organs frequently affected by IgG4‐RD , supports the diagnosis. However, thoracic involvement may be isolated.The diagnostic approach Figure  thereforClassification and diagnosis criteria for IgG4‐RD have been published periodically since the recognition of the disease.The most recent classifications are the ACR/EULAR criteria, published in 2019.In 2017, comprehensive diagnostic criteria were published by Umehara et al., revised in 2021.In order to standardize the criteria for evaluating response to treatment, which may vary from one specialty to another, an IgG4‐RD Responder Index was developed in 2012.Treatment of all symptomatic patients is recommended. Conversely, asymptomatic patients, such as those with isolated chest adenopathy, may remain untreated. Treatment of localized forms of the disease, such as a pulmonary nodule or inflammatory pseudotumour, may be limited to surgical removal. In other cases, the treatment of IgG4‐RD thoracic disease is based on immunosuppressive drugs.International consensus statement on the treatment of IgG4‐RD has been published in 2015,Rituximab is an anti‐CD20 monoclonal antibody that has been shown to be effective in reducing steroid dosage in IgG4‐RD patients with steroid dependence. The treatment is usually prescribed at the dose of 1 g on Day 1 and then on Day 15. Its effectiveness is generally maintained for several months. In the study by Carruther et al.,Disease‐modifying anti‐rheumatic drugs  are not very effective for induction of remission but may be used for steroids sparing.Several emerging therapies offer promise. A phase 2 clinical trial of anti‐CD19 antibody inebilizumab showed an interesting outcome in 12 patients (decrease in IgG‐RD Responder Index score by ≥2 points).IgG4‐RD is a fibroinflammatory disease that can affect virtually all organs, mainly occurring in middle‐aged to elderly male patients. In the thorax, the disease can occur in all compartments , most often in association with extra‐thoracic manifestations. Clinical manifestations are nonspecific and usually lacking. CT‐scan findings can be divided into seven distinctive patterns, whose prognostic characteristics have yet to be determined. Diagnosis is based on a combination of clinical, biological and histological findings, as no marker is specific for the disease. Diagnostic approach must always consider screening for differential diagnoses especially when the disease affects a single organ, is identified incidentally on radiological studies, or is diagnosed unexpectedly in pathological specimens. Thoracic IgG4‐RD is generally highly responsive to immunosuppressive therapy with steroids and/or rituximab, but relapse is common. Further studies are needed to better characterize thoracic involvement of the disease, its triggers, pathophysiology and prognostic factors to elucidate more effective and specific therapies.Romain Muller, Mikael Ebbo and Nicolas Schleinitz conceived and designed the work. Romain Muller and Mikael Ebbo drafted the article. Paul Habert, Laurent Daniel, Antoine Briantais, Pascal Chanez, Jean Yves Gaubert and Nicolas Schleinitz critically reviewed the manuscript.None declared.


Infection rounds in Intensive Care Units (ICU) can impact antimicrobial stewardship (AMS). The aim of this survey was to assess the availability of microbiology, infection, AMS services, and antimicrobial prescribing practices in the UK ICUs. An online questionnaire was sent to clinical leads for ICUs in each region listed in the Critical Care Network for the UK. Out of 217 ICUs, 87 deduplicated responses from England and Wales were analyzed. Three-quarters of those who responded had a dedicated microbiologist, and 50% had a dedicated infection control prevention nurse. Infection rounds varied in their frequency, with 10% providing phone advice only. Antibiotic guidance was available in 99% of the units; only 8% of those were ICU-specific. There were variations in the availability of biomarkers & the duration of antibiotics prescribed for pneumonia , urinary, intra-abdominal, and line infections/sepsis. Antibiotic consumption data were not routinely discussed in a multi-disciplinary meeting. The electronic prescription was available in ~60% and local antibiotic surveillance data in only 47% of ICUs. The survey highlights variations in practice and AMS services and may offer the opportunity to further collaborations and share learnings to support the safe use of antimicrobials in the ICU. Antimicrobial therapy is a cornerstone in treating critically ill patients presenting with suspected infection. The surviving sepsis guidelines highlight the importance of prompt, appropriate antibiotics in such patients . AntibioMicrobiology services and surveillance: access to and input by microbiology and infection prevention and control specialists.Antibiotic prescription practices.The availability and use of diagnostics and biomarkers to influence antibiotic de-escalation and duration of antibiotics for common infections leading to ICU admissions.Availability of data management systems related to antibiotic use.International healthcare organizations, including the World Health Organization (WHO) recommend that antimicrobial stewardship (AMS) activities are crucial to tackling AMR . MultidiThe survey questionnaire was developed by members of the intensive care and microbiology team using an online survey engine . This suThe survey was reviewed by several intensive care consultants to confirm that the questions were both clear and appropriate before being disseminated. The hospital ethics department was approached and deemed ethics approval not to be required.The UK Critical Care Networks for England, Wales, and Northern Ireland (Adults)  were appAt the end of the 6-month period, the survey responses were assessed. In centers where multiple responses were received, the first response was retained, and further responses were not included. Following this process, analysis of the responses was completed.The themes covered by the survey can be viewed in . Most quA total of 101 responses were received from the 217 individual ICUs across England and Wales. Of the 101 responses, there were 14 duplicate responses from a second or third clinician responding from the same ICU. This led to a total of 87 responses from the 217 ICUs listed in the 2021 Directory of Critical Care Networks for adults giving an overall response rate of 40%.Of the 21 areas across the critical care network, there was significant variation in the response rate. 93% of responses were from regions within England, and the remaining 7% were from Wales. There were no responses from Northern Ireland and Scotland. 91% of respondents were consultants, 8% were pharmacists, and the remaining 1% were non-consultant level doctors. 80% of responses were from clinicians working in general ICUs, with 20% from specialist ICUs . The participated ICUs varied in size, with a bed capacity of fewer than 15 beds (49%), 16–30 beds (30%), 31–45 beds (18%), and more than 45 beds (2%).The survey showed that 87.4% of ICUs used hospital or trust-wide antimicrobial guidance to aid the empirical choice of antibiotic. Only 8% had local ICU-specific antibiotic guidance A. AlmostMost units (76%) had a dedicated microbiologist or infectious diseases specialist available. This input was provided daily by 48.3%, three times weekly by 20.7%, and 10.3% had no dedicated specialist input but had specialist infection telephone advice when needed. Just over 46% of respondents had a dedicated infection prevention specialist nurse available in their unit C,D.The majority (59%) of respondents reported having electronic antibiotic prescribing, 37% were non-electronic prescribing, 1% were unsure, and 3% were in the process of acquiring electronic antibiotic prescribing platforms. Whilst 64% prescribe empirical antibiotics with a limit on duration, 20% reported that some, but not all, empirical antibiotics were duration limited, with 16% saying there was no duration restriction when prescribing empirical antibiotics. Free text comments included: antibiotic duration was usually discussed with the microbiologist, empirical antibiotic prescriptions usually had a review date but not a stop date, while others had formal stop dates for all antibiotics.We asked regarding the standard duration of antibiotics for common ICU infections, including septic shock, community-acquired pneumonia, ventilator-associated pneumonia, hospital-acquired pneumonia, proven line-related infection, primary intraabdominal sepsis, and community-acquired upper and lower urinary tract infections. For these eight infections surveyed, there was a range of antibiotic duration from 1–3 days to 11–14 days. The common duration of antibiotics was 7 days. Details of the standard duration of antibiotics prescribed are presented in We asked about the accessibility to local antibiotic consumption data and whether this data were routinely discussed in a multi-disciplinary meeting (MDT). Data were available and discussed in a multi-disciplinary meeting in 13% of ICUs surveyed, 23% had data available, but this was not discussed in an MDT setting; 24% of data were not available, and 33% were unsure if they had access to local antibiotic consumption data. 7% selected others, and comments included that only pharmacists and microbiology staff had access to this data.All respondents had routine access to biomarkers that may guide antibiotic prescription and duration of therapy We surveyed if data management systems were available to audit antibiotic use either from electronic or paper-based clinical notes. 36% reported that an electronic case-based data collection is available, 25% have manual case-based data collection, 21% have no data collection, and 22% were unsure. When asked about participation in clinical research, 79% said they participated in ICU clinical research, 14% were not participating in any research, and the remainder were unsure.Early and appropriate treatment of infections in critically unwell patients is crucial to reduce morbidity and mortality. However, overuse of antimicrobials can be associated with increasing resistance (AMR), a rapidly growing global problem. The World Health Organization has advised setting up antimicrobial stewardship programs to help combat AMR . It encoAmong those surveyed, the majority (87.4%) followed hospital or trust-wide antibiotic prescription guidance, and only 8% had local ICU-specific guidance. Despite being critically ill, a standard antimicrobial regimen similar to a ward-level hospitalized patient can be instituted unless there are specific risk factors or prior evidence of colonization of resistant organisms. Several observational studies have shown reduced mortality when following guidelines for community-acquired pneumonia ,10. For In order to make an informed decision regarding the choice of antibiotic, the availability of microbiology epidemiological and/or local resistant data is essential. In this survey, 36% reported no access to epidemiological data, and 17% were unsure. In contrast, international studies report much higher accessibility to local epidemiology data (>80%) ,14,15. AUnder half (46%) of units had access to a dedicated infection control nurse, a specialist nurse who could act as a link between ICU and the infection control team. Their role is to increase awareness of emerging infection control issues and motivate staff to improve practice ,18. TheyInput from a clinical microbiologist or an infectious diseases specialist can be useful in the decision-making process regarding antibiotic stewardship during the daily multidisciplinary (MDT) ward rounds. Not only facilitating stopping and de-escalation of antimicrobials but also selecting the most appropriate antimicrobial based on specific host factors. A study found input from an infection specialist was associated with significant antimicrobial modifications or discontinuation of antimicrobials. . In our In our survey, 59% of respondents reported having access to electronic antibiotic prescribing, lower than the data from a French ICU study, which reported ~94% availability of electronic prescribing but only 54% using them ,22. ElecSixty-four percent of respondents stated that all empirical antibiotic prescriptions are duration limited. A further 20% reported some but not all were duration limited, with 16% saying there was no duration limitation when prescribing empirical antibiotics. However, some centers commented that they had review dates but no automatic stop date. The duration varied  depending on the source of infection. A documented planned review of the duration is an important part of antibiotic stewardship in the ICU, particularly for those with a shorter ICU stay. This is to avoid unnecessarily prolonged duration and minimize the risk of resistance development and adverse effects such as Clostridium Difficile . Data frGuidance on the duration of antimicrobial therapy for sepsis is limited. The general recommendation  from the Surviving Sepsis Campaign suggests that 7–10 days of antibiotic coverage is likely sufficient for most serious infections associated with sepsis and septic shock. However, positive microbiology and/or lack of source control and neutropenia may need longer courses . Our surPseudomonas aeruginosa; this trial excluded immunocompromised individuals [P. aeruginosa with shorter courses [Moreover, around 90% of responders reported an antibiotic regimen duration between 4–7 days for the treatment of community-acquired pneumonia (CAP), hospital-acquired pneumonia (HAP), and ventilator-associated pneumonia (VAP). This is reassuring and in line with the findings from a multi-center randomized controlled trial of VAP where a 5-day course of antibiotics is non-inferior to a longer course regarding clinical cure, readmissions, and mortality at 30 days . Similarividuals . The inf courses .Source control and/or intravenous administration of antimicrobials are the mainstay for the treatment of line-associated infections. The American guidelines recommend differing durations depending on the organism cultured and clinical context . In our Surgical source control is an essential treatment for complicated primary intra-abdominal sepsis (peritonitis), both therapeutically and diagnostically. The optimal duration of definitive treatment has yet to be established. However, between 7 and 14 days have generally been an acceptable duration, and some experts recommend up to 3 weeks ,37. A prWith regards to the utilization of biomarkers and rapid access diagnostic platforms, all had access to C-reactive protein; 80% and 68% had access to procalcitonin (PCT) and Beta-D-glucan, respectively. There has been a marked increase in the use of PCT since the COVID-19 pandemic, from 47.6% to 84.4% ,42. A raThe survey also showed that antibiotic consumption data are not commonly discussed in a multidisciplinary setting. While these data are generally available to pharmacy departments, its accessibility to prescribers is crucial for benchmarking with comparator ICUs to improve prescribing practices, which are all part of antibiotic stewardship . For theOur study has several limitations. There is no detailed information about the capacity of ICUs enrolled in the study in terms of case mixes, severity, occupancy, and served populations, which can impact clinical practice. Not all centers responded to the survey request, which is a major limitation as the data we have is relatively limited. While we approached 217 centers from all current Critical Care Research Networks, only 87 (40%) provided a response. The electronic approach and approaching clinical leads for ICU rather than all intensive care doctors in each hospital may have introduced selection bias. Approaching ICU clinicians directly would probably have resulted in more responses and potentially more understanding and ownership of working within antimicrobial stewardship programs implementation initiatives. Moreover, we acknowledge that this is an in-house or self-developed survey without external testing, and most of the data was from England and may not be transferable to Northern Ireland or Scotland. Nevertheless, this is the first national intensive care survey on microbiology services availability and antibiotic stewardship.The survey demonstrates significant variations in practice and service availability. Our findings clearly demonstrate that not all ICUs have regular infection or microbiology specialist multi-disciplinary ward rounds. This can be addressed through directorships or commissioning teams with clear specifications for ICU services. Societies and colleges can also provide guidance on the minimum required input from infection specialists and other multidisciplinary teams like pharmacists with clear descriptions of roles and responsibilities. Furthermore, systems and access to data regarding antibiotic consumption and resistant data should be timely not only to infection specialists or pharmacists but also to intensivists, allowing MDT decision-making with regard to empirical antibiotic choices and further guidance. This can be achieved via prior agreed governance meetings, e.g., quarterly, to discuss antibiotic consumption and antibiotic-resistant data, depending on local needs. Finally, participation in innovation, audit, quality improvement projects, and research is crucial to improve the quality of care. The development of a collaborative network of intensive care, clinical microbiology, and infectious diseases (NICCMID) specialists may help to coordinate these nationally to align the national and international strategies to improve ICU patient care while minimizing antibiotic usage and future resistance.


Acute pancreatitis is a complex inflammatory disease with significant morbidity and mortality. Despite advances in its management, the role of antibiotics in the prophylaxis and treatment of acute pancreatitis remains controversial. The aim of this comprehensive review is to analyze current evidence on the use of antibiotics in acute pancreatitis, focusing on prophylactic and therapeutic strategies. Prophylactic use aims to prevent local and systemic infections. However, recent studies have questioned the routine use of antibiotics for prophylaxis and highlighted the potential risks of antibiotic resistance and adverse effects. In selected high-risk cases, such as infected necrotizing pancreatitis, prophylactic antibiotic therapy may still be beneficial. As for therapeutic use, antibiotics are usually used to treat infected pancreatic necrosis and extrapancreatic infections. When selecting an antibiotic, the microbiologic profile and local resistance patterns should be considered. Combination therapy with broad-spectrum antibiotics is often recommended to cover both Gram-positive and Gram-negative pathogens. Recent research has highlighted the importance of individualized approaches to antibiotic use in acute pancreatitis and underscored the need for a tailored approach based on patient-specific factors. This review also highlights the potential role of new antimicrobial agents and alternative strategies, such as probiotics, in the management of acute pancreatitis. Acute pancreatitis (AP) is a serious inflammatory process that can range from a mild, self-limiting condition to a life-threatening disease with significant morbidity and mortality. The exact mechanisms that trigger the onset of AP are not yet fully understood but are thought to involve a complex interaction of genetic, environmental, and lifestyle factors. The initial event in the development of AP is the inappropriate activation of pancreatic enzymes within the acinar cells; under pathological conditions, such as bile reflux, alcohol abuse, or gallstones, the activation of pancreatic enzymes occurs prematurely within the pancreas itself. Once activated, they can directly damage acinar cells, leading to their necrosis. The release of pro-inflammatory cytokines, such as interleukin-1β (IL-1β) and tumor necrosis factor-alpha (TNF-α), further amplifies the inflammatory response. These cytokines recruit and activate immune cells, including neutrophils and macrophages, which infiltrate the pancreas and release additional inflammatory mediators, exacerbating tissue damage and promoting the production of reactive oxygen species (ROS), resulting in oxidative stress .Another crucial pathophysiological mechanism underlying AP is bacterial translocation, which refers to the migration of bacteria and their products from the gastrointestinal tract to extraintestinal sites; possible disruption of the intestinal barrier allows gut bacteria to migrate into the systemic circulation and reach the pancreas, triggering local and systemic inflammatory responses .The Atlanta criteria, first established in 1992 and revised in 2012, are widely used to standardize the diagnosis and classification of AP . AccordiIn addition to the Revised Atlanta Classification, several scoring systems have been developed to assess the severity and prognosis of AP: the Ranson criteria, which evaluate clinical and laboratory parameters at admission and within 48 h to predict the severity of the disease ; the AcuAdvancements in imaging techniques have also contributed to classification. CT scans are routinely used to assess the extent of pancreatic inflammation and detect complications such as necrosis, abscess formation, and pseudocysts. The Balthazar scoring system, based on CT findings, categorizes acute pancreatitis into several grades ranging from A to E, depending on the severity and extent of pancreatic involvement .In this heterogeneous clinical setting, the indications and timing for antibiotic therapy have been the main controversial topics in recent decades. The results of the first meta-analyses indicated a beneficial effect of antibiotic prophylaxis , while the second group did not receive antibiotic therapy and was considered the control group (n = 371). The study did not identify significant differences in the incidence of infected pancreatic necrosis, surgical intervention, and mortality when comparing the two groups. Interestingly, antibiotic prophylaxis was associated with a statistically significant decrease in the incidence of nonpancreatic infections. A subsequent meta-analysis [Prophylaxis is the administration of antibiotics to patients who do not have a clinical infection with the goal of preventing pancreatic infection . Accordianalysis   ,32 and pDespite its possible clinical benefits, antibiotic prophylaxis is also correlated with risks, including increased prevalence of multi-drug-resistant bacteria and incidence of fungal infection, among other effects ,28. FungAlthough antibiotic prophylaxis is not recommended by international guidelines, the clinical use of prophylactic antibiotics in SAP has become widespread; a retrospective study conducted in the United Kingdom in 2018  showed hSeveral guidelines clearly recommend antibiotics for the treatment of infected severe acute pancreatitis ,25. An iHistorically, surgical intervention, such as open necrosectomy, was the primary treatment modality of IPN . HoweverThe American Gastroenterological Association Institute guidelines state that carbapenems, quinolones, and metronidazole, which are known to penetrate pancreatic necrosis, may be helpful in individuals with infected necrosis and may be useful to delay or sometimes avoid surgical intervention and reduce morbidity and mortality . The optNonpancreatic infections mainly include pneumonia, bacteremia, central venous catheter infections, urinary tract infections, and cholangitis . In the In SAP, pancreatic or peripancreatic necrosis is initially aseptic and may develop into infected necrosis if contaminated with intestinal bacteria. Translocation of intestinal bacteria is facilitated by intestinal barrier disruption, immunosuppression, and bacterial dysbiosis in combination ,57 Figu. Most ofA recent study  found thAs analyzed earlier, in SAP, pancreatic or peripancreatic necrosis is initially aseptic and may develop into infected necrosis if infected with intestinal bacteria. Several factors contribute to the development of bacterial translocation in AP. Firstly, the increased pancreatic duct pressure and obstruction, characteristic of this condition, may result in the retrograde flow of pancreatic secretions into the common bile duct and duodenum. This retrograde flow can facilitate the migration of bacteria from the gut into the pancreatic tissue. Additionally, the inflammatory response triggered by the release of pancreatic enzymes can cause local tissue damage and compromise the integrity of the intestinal barrier. This disruption allows gut bacteria, including both commensal and potentially pathogenic organisms, to translocate into the systemic circulation and reach distant organs. Moreover, the release of inflammatory mediators, such as interleukins and TNF-α, can impair intestinal barrier function by disrupting tight junctions and reducing the production of protective mucus. The translocated bacteria can elicit an immune response, leading to the release of pro-inflammatory cytokines, the activation of immune cells, and the amplification of the systemic inflammatory cascade ,57,58,59In this context, the gut microbiome is potentially a promising target for AP treatment because it undergoes disruption during the disease’s etiology. Several studies have identified a dysbiosis of the gut microbiota during AP ,61,62,63According to the latest guidelines, antimicrobials are indicated in AP only when infection is either confirmed or strongly suspected. In recent decades, several RCTs and meta-analyses have been performed to evaluate the efficacy of antibiotic prophylaxis in reducing mortality and incidence of pancreatic and other organ infections in patients with SAP. Unfortunately, the results are inconclusive, likely due to differences in the class of antibiotics administered, timing of therapy, treatment outcomes, and study design. For these reasons, no conclusive judgments can be made about the overall efficacy of prophylactic antibiotics in acute pancreatitis. Future RCTs are urgently required to determine which subgroups may benefit from prophylactic antibiotics. Several studies have shown that antibiotic prophylaxis should be administered early, within 72 h of symptom onset or 48 h of hospitalization, underscoring the importance of timing of antibiotic initiation. The monitoring of blood levels of PCT and CRP can be useful in predicting the likelihood of developing IPN and can help identify patients who will benefit from early antibiotic therapy. Antibiotic prophylaxis is also correlated with risks, including increased prevalence of multi-drug-resistant bacteria and incidence of fungal infection; antimicrobial stewardship is needed in order to optimize the application of antibiotics to obtain the best therapeutic outcomes while avoiding side effects and decreasing the selective pressure that cause resistance emergence. Antibiotics play a critical role in the treatment of IPN and its associated complications. Early initiation of antibiotic therapy has been shown to improve treatment outcomes by reducing infection-related morbidity and mortality. Typically, broad-spectrum antibiotics, which are known to penetrate pancreatic necrosis, are used to cover both Gram-positive and Gram-negative pathogens, with adjustments based on local resistance patterns and microbiologic data. Nevertheless, alternative strategies such as probiotics may offer potential benefits. The gut microbiome is likely a potential target for treatment of AP, as dysbiosis and bacterial translocation play a pivotal role in the pathogenesis of AP and in the development of pancreatic and peri-pancreatic infections. Several studies have identified a dysbiosis of the gut microbiota during AP, characterized by an increase in the abundance of harmful bacteria  and a decrease in the abundance of bacteria producing short-chain fatty acids (SCFAs), which are thought to have anti-inflammatory properties . Because the evidence on the modulation of the gut microbiota by probiotics remains controversial to date, the use of probiotics is not recommended in severe AP.


Background: Antimicrobial resistance (AMR) is a global public health concern that has the potential to reverse decades of progress aimed at decreasing morbidity and mortality attributed to infectious diseases. In 2019, ~5 million deaths were associated with AMR, of which 1.2 million were attributed to antibacterial-resistant infections. Healthcare facilities where antimicrobials are frequently used are high-risk settings for the selection and spread of resistant bacteria, and they further contribute to the increase in the burden of AMR. We have documented the prevalence and indication of antibiotic use in a tertiary-care referral hospital in Freetown, Sierra Leone. Methods: This point-prevalence survey was conducted at Connaught hospital, a tertiary-care hospital in Sierra Leone, in November 2021. The hospital offers a range of medical and surgical services through 25 units and has 16 wards with >300 beds. Data on patient-level antibiotic use, including indications for use, were extracted from medical records using WHO point-prevalence survey (PPS) forms that had been pretested and validated. Data collection was conducted in all the wards over a 10-day period by trained healthcare personnel. On the day of the survey, only the medical records of patients on admission before 8:00 a.m. on that day were included in the study. Data entry, cleaning, and analysis were conducted using the WHO PPS platform. Ethical approval was obtained. Results: In total, 87 patient records were included in the survey. Most (71%) were women, and the average age was 30.6 years. The prevalence of antibiotic use was 66%, and the average number of antibiotics prescribed to patients since admission was 2. The 5 most prescribed antibiotics were metronidazole, ceftriaxone, amoxicillin and clavulanic acid, ampicillin and cloxacillin, and azithromycin. The parenteral route of drug administration was the mainstay. The most frequent indications for antibiotic prescription were community-acquired infection and surgical prophylaxis. Blood-culture requests were not ordered before the initiation of antibiotic treatment. Conclusions: This study was the first study to be conducted in Connaught hospital using the WHO PPS methodology. The survey reports a high prevalence (60%) of antibiotic use, and most treatment was done empirically. This finding is contrary to the WHO recommendation of <30% antibiotic use. This high prevalence of antibiotic use has the potential to increase the burden of AMR in the country. Therefore, there is an urgent need to strengthen Connaught hospital’s antibiotic stewardship program.Disclosures: None


The authors investigated the expression of IgG4 and IgG in cutaneous Rosai-Dorfman Disease (CRDD) to further improve the understanding of this disease.The authors retrospectively reviewed the clinicopathological features of 23 CRDD patients. The authors diagnosed CRDD by the presence of emperipolesis and immunohistochemical (IHC) staining of histiocytes consisting of S-100(+)/CD68(+)/CD1a(-) cells. The expressions of IgG and IgG4 in cutaneous specimens were assessed by IHC (EnVision) and quantitatively calculated by a medical image analysis system.All 23 patients, including 14 males and 9 females, were confirmed to have CRDD. Their ages ranged from 17 to 68 years (mean 47.91 ± 14.16). The most frequently affected skin regions were the face, followed by the trunk, ears, neck, limbs, and genitals. In 16 of these cases, the disease presented as a single lesion. IHC staining of sections showed that IgG was positive (≥ 10 cells/High-Power Field [HPF]) in 22 cases, while IgG4 was positive (≥ 10 cells/HPF) in 18 cases. Moreover, the IgG4/IgG proportion ranged from 1.7% to 85.7%  in the 18 cases.In the majority of studies, as well as in the current study, the design. RDD is a rare disease, so the sample size is small. In the next studies to come, the authors will expand the sample for multi-center verification and in-depth study.The positive rates of IgG4 and IgG and the IgG4/IgG ratio assessed through IHC staining may be important in understanding the pathogenesis of CRDD. KRAS and MAP2K1 may be related to the pathogenesis of RDD.Rosai-Dorfman's disease (RDD) is a rare disease of non-malignant histiocytosis that used to be referred to as sinus histiocytosis with a large number of lymphadenopathy. It was named for Rosai and Dorfman, who established it as a new entity in two reports in 1969 and 1972.Twenty-three cases were collected from two different hospitals during the period from August 2009 to August 2018. All cases were diagnosed by 2 senior pathologists according to the latest WHO diagnostic criteria. This work was authorized by the ethics committee and conducted under the ethical principles of the Human Rights Declaration adopted in Helsinki and was in accordance with the Rules for Good Practice in the Clinical Study. The authors informed all patients of informed consent.Skin biopsies were fixed in a buffered 10% formalin solution, processed, and embedded in paraffin. Paraffin blocks were cut into 4–5 μm sections using a microtome and placed on glass slides.Hematoxylin-eosin (HE) was used for classical histopathology and IHC was performed on the same biological material embedded in paraffin. Each immunostaining reaction included a negative control (without incubation with the primary antibody). The IgG4 and IgG antibodies (ready to use) were bought from Zhongshan Golden Bridge Biological Technology Company.2.IgG4(+) and IgG(+) cells were counted separately using an Olympus BX40 microscope and Image J 1.52a computer software. Three high-power fields (HPF) with the maximum number of positive cells were counted and an average number per HPF was counted. One HPF represents an area of 0.24 mmThe ages of the 23 patients with CRDD, including 14 males and 9 females, ranged from 17 to 68 years (mean 47.91 ± 14.16). Among them, 16 patients had single lesions, while the other 7 had multiple lesions. Ten patients presented with plaques, 12 patients presented with patches, and 1 patient presented with a sub-axilla mass. In most of the 23 cases of CRDD, the lesions were distributed on the face and chest. In 9 cases, the lesion was in another location such as a limb, back, or thigh. The clinical characteristics of all patients were described in The authors observed diffused infiltration of large histiocytes, plasma cells with scattered neutrophils, and lymphocytes in all sections A. In mosImmunohistochemical features were shown in Compared with classic systemic RDD, CRDD seems to occur more frequently in Asians and has a female predominance.In contrast to classic RDD with obvious systemic symptoms, CRDD is generally limited to the skin. Skin lesions of cutaneous RDD vary in morphology, size, color, and location. The clinical manifestations include papules, plaques, nodules, and pustules.+ plasma cell numbers has been found in 70 nodal and extranodal cases of RDD.Emperipolesis is a phenomenon of the lymphocytes in which they maintain their structure and function while entrapped in the cytoplasm of histiocytes. It is not a unique feature of CRDD and can also appear in Hodgkin lymphoma, malignant melanoma, and some other malignant tumors.The most recognized diagnostic standards for IgG4-RD based on its histology and IHC are as follows: (1) Diffuse or characteristic enlargement, tumors, nodules, or hypertrophy of one or more organs; (2) Serum IgG4 levels increased ≥1350 mg/L; and (3) Histopathology showing obvious lymphocyte and plasma cell infiltration and fibrosis, or the infiltration of IgG4-positive plasma cells with the ratio of IgG4/IgG-positive plasma cells being more than 40% and the quantity of IgG4-positive cells being more than 200/HPF in the skin.Generally, CRDD is a self-limiting and self-curing disease. However, in a minority of cases, the skin lesions present invasive growth that must be treated with excision, cryotherapy, methotrexate, retinoids, steroids, and/or thalidomide.Cutaneous RDD is a rare, nonmalignant disease characterized by certain clinical and pathological features. The presence of emperipolesis and IHC staining of histiocytes constituting S-100(+)/CD68(+)/CD1a(−) cells remains the main diagnostic criteria. Positive staining of IgG4 and IgG and the proportion of IgG4/IgG may be important for distinguishing RDD from IgG4-RD.Informed consent was obtained from all individual participants included in the study.This study was supported by the National Natural Science Foundation of China .Puyu Zou: Contributed to the critical literature review and study concept and design; wrote the manuscript, and did the statistical analysis.Yu Liu: Contributed to the critical literature review and study concept and design.Yi Zhan: Conducted data collection, analysis and interpretation.Xueru Zeng: Effectively participated in the research orientation, and the propaedeutic and therapeutic conduct of the studied cases.Guiying Zhang: Made a manuscript critical review of the literature and finally approved the final version of the manuscript.None declared.