Natural resources have been excessively consumed, and large amounts of construction wastes have been generated, owing to the fast development of civil industry, causing crucial environmental issues. Therefore, reusable construction waste fabricated into recycled concrete offers a good strategy to solve this issue. Thus, this article first develops thin-walled steel tubes stub columns filled with self-compacting concrete containing recycled coarse aggregate. Afterwards, the compressive behaviors of the columns when undergoing axial compression loading to failure are explored. Subsequently, the effect of types of self-compacting concrete and wall thickness on failure modes and the relationships between load and displacement/strain is discussed comprehensively. Moreover, models of load–displacement/strain behaviors are proposed. The results show that columns with identical wall thicknesses containing both natural and recycled coarse aggregate display similar failure modes, mainly presenting as local buckling and rupture. The shape of the load–displacement/strain curves for identical wall thicknesses are almost the same. Nevertheless, the maximum load and stiffness of columns containing recycled coarse aggregate are lower than those of columns containing natural coarse aggregate. Additionally, the maximum loads corresponding to wall thickness of 1.2 mm and 3.0 mm are decreased by 18.4% and 5.8%, respectively. Moreover, the proposed models can reasonably evaluate the relationships between load and displacement/strain. This paper demonstrates that thin-walled steel tubular columns containing recycled coarse aggregate present positive compressive behaviors and thus exhibit great potential for developing environmentally friendly and sustainable civil infrastructures. Natural resources have been excessively consumed and large amounts of construction wastes have been produced owing to the fast development of the civil industry, resulting in crucial issues regarding the environment ,2,3,4. TSelf-compacting concrete possesses good fluidity and filling capacity, and is also non-segregating. It can spread into complicated positions without vibration. In addition, the hardened properties of self-compacting concrete are similar to traditional vibrated concrete ,16. TherIn recent years, making use of recycled aggregate to prepare self-compacting concrete has been appreciated as a good strategy to minimize construction and demolition wastes and protect the environment ,25,26,27Concrete-filled steel tube columns present high strength, favorable ductility, and fire resistance as structural members. Moreover, steel tube columns can serve as formwork when concreting. This can save costs and construction time . Thin-waPrevious studies have concentrated on using recycled aggregate in producing self-compacting concrete ,51,52,53Firstly, six thin-walled steel tube stub columns filled with self-compacting concrete containing recycled and natural coarse aggregate are manufactured. In addition, four of the columns contain recycled coarse aggregate with a replacement rate of 100%. The other two columns are filled with self-compacting concrete containing natural coarse aggregate. Moreover, wall thicknesses of 1.2 mm and 3.0 mm are adopted. Subsequently, the compressive load behaviors of the columns are explored. The effect of the wall thickness on axial compressive behaviors and failure modes is analyzed in depth. This paper aims to create steel tubes filled with concrete as sustainable construction members and offer guidance for designing and facilitating the application of thin-walled steel tube stub columns containing recycled coarse aggregate in civil industry.The differences between this work and the other existing studies are as follows. (1) the thin-walled steel tubes filled with self-compacting concrete containing recycled coarse aggregate. In this paper, we adopt a 100% replacement rate for the self-compacting concrete; (2) wall thicknesses of 1.2 mm and 3.0 mm are considered as the key parameters; (3) failure modes and axial compressive mechanical behaviors of the thin-walled steel tube columns filled with self-compacting concrete containing recycled aggregate are described; (4) theoretical models of the load–displacement/strain relationships of the columns containing recycled aggregate are proposed.ck and Ec stand for strength and modulus of elasticity of concrete, respectively. They are measured according to the specification [y, μs, and Es represent the yield strength, Poisson’s ratio, and modulus of elasticity of steel tubes, respectively. They are tested according to specification [In this paper, four thin-walled steel tube stub columns filled with self-compacting concrete containing recycled coarse aggregate with a circular cross section are fabricated. Another two thin-walled steel tube columns containing natural coarse aggregate are fabricated as control specimens. Two key parameters, wall thicknesses of 1.2 mm and 3.0 mm and types of coarse aggregates, are considered. Herein, the three specimens with a wall thickness of 1.2 mm are designed as one group. Two of them contain recycled coarse aggregate, and another contains natural coarse aggregate. Similarly, the wall thickness of the specimens of another group is 3.0 mm. Two of them contain recycled coarse aggregate, and another contains natural coarse aggregate. The diameter and height of the columns are set as 140 mm and 420 mm, respectively. The numbers, dimension, and properties of materials are shown in fication . Fy, μs,fication . Self-coSome studies on steel tubes filled with concrete have been conducted, and the dimensions D and L and concrete strength have been referenced. A summary of the parameters of tubes filled with concrete in previous studies is shown in Cement with a grade of 42.5 is adopted and it was purchased from Henan Yongan Cement Co., Ltd. . Two square steel plates are welded on to the ends of the steel tubes. The side length and thickness of the square steel plates are 180 mm and 10 mm, respectively. The steel plate and steel tubes can work as a mold while casting concrete. The center of the steel plate and steel tubes are in a vertical line. The concrete is cast into the steel tubes slowly, and no external vibration is used. The columns are cured in an experiment room kept at 20 °C and 95% relative humidity for 28 d after concrete casting. However, about 2 mm of shrinkage of the infill concrete was generated after 28 d. For the sake of ensuring that the steel tubes and concrete are in the same plane, the uneven space between steel tubes and concrete is filled with cement paste. The top ends of the steel tubes are welded with another steel plate before testing. The typical manufacturing process of the columns can be seen in The mechanical performance of the steel tubes, which are tested in accordance with the specification , are shoThe concrete used to fill the steel tubes and prepare the concrete specimen for measuring the mechanical properties is mixed together. Each type of concrete specimen is used to test the mechanical properties, including three cubes and six cylinders. After concrete casting, the concrete specimens and the columns are covered with plastic film and cured in the same conditions. Testing on the columns and concrete occurs at the same curing ages. An axial compressive loading test of the columns is carried out after curing for 28 d using a universal testing machine. Preliminary loading with a load amplitude of 20 kN and loading rate of 0.5 kN/min is carried out before formal testing. For the sake of ensuring that the columns are in the geometric center of the loading platform during the loading process, the location of the columns is adjusted carefully when the difference of the axial strains is more than 2% to guarantee that the column is in the center of the loading platform. The loading rate is applied with 0.5 mm/min in the formal loading stage. One-tenth of the calculated maximum load is set as the loading interval. In order to ensure the stability of the load and so that the collected data can more truthfully reflect the states, 3 min are maintained after each load interval is finished during the loading process. Loading is stopped after the load falls to 60 percent of the maximum load, and each column is tested for 2 h. Data of loads, displacements, and strains are collected automatically using a computer acquisition system during the loading process.Undergoing the axial compressive load, the columns present positive behaviors. Deformation along the axial direction changes approximately linearly with load. the ductility of the infill concrete has been enhanced owing to the confinement of the steel tubes. The columns present typical failure modes including local buckling and rupture. This characteristic is similar to high-strength thin-walled steel tubes filled with concrete columns. However, a failure slant angle close to 45° is generated on the infill concrete of the columns . No obviThe buckling and rupture of the columns with identical wall thicknesses of steel tubes is similar to each other. The relationships between load and displacement of the columns subject to axial compression are displayed in As shown in 2 values of the two fitting curves are 0.9997 and 0.9993, respectively. The fitting curves coincide well with the experimental curves. This indicates that the suggested model offers a considerably accurate evaluation of the relationship between load and displacement. The theoretical model between load and displacement with different wall thicknesses of 1.2 mm and 3.0 mm is expressed as Equations (1) and (2), respectively.The theoretical model between load and displacement of the columns containing recycled coarse aggregate is established by fitting the load–displacement curve and shown in This demonstrates that the maximum load and ductility are improved with an increase in the wall thickness, while they are decreased with an increase in the D/t ratio. The maximum load and the displacement corresponding to the maximum load of the columns with wall thicknesses of 3.0 mm are 25.3% and 3.8% higher than those of the corresponding columns with wall thicknesses of 1.2 mm, respectively.2 values of the two fitting curves are 0.9997 and 0.9993, respectively. The fitting curves coincide well with test curves. This indicates that the suggested model offers a good evaluation of the relationship between load and axial strain. The theoretical model of the relationship between load and axial strain with wall thicknesses of 1.2 mm and 3.0 mm is expressed as Equations (3) and (4), respectively.Similar to the proposed model on load and displacement, a theoretical model of the relationship between the load and axial strain of the steel tube columns containing recycled coarse aggregate is also established by fitting the load–axial strain curve and is shown in As shown in The average axial/transverse strains corresponding to the maximum load with steel tube wall thicknesses of 1.2 mm and 3.0 mm are 5870 με/6513 με and 6060 με/6880 με, respectively. Compared with the average axial/transverse strains of columns with a steel tube wall thickness of 1.2 mm, the axial and transverse strains corresponding to the maximum load with a wall thickness of 3.0 mm are increased by 3.1% and 5.3%, respectively.Thin-walled steel tube stub columns filled with self-compacting concrete containing recycled coarse aggregate are developed. The mechanical behaviors and failure modes of the columns undergoing axial compressive load to failure are investigated. The effects of wall thickness and types of self-compacting concrete on axial compressive behaviors are discussed. Theoretical models of the load–displacement/strain relationships are also proposed. Conclusions based on the results are as follows.(1) The thin-walled steel tube columns with identical wall thickness filled with self-compacting concrete containing recycled and natural coarse aggregate display similar failure modes. In general, local buckling and rupture are the typical failure modes. However, the positions of the buckling and rupture are mainly distributed on the surface near the ends of the columns with a wall thickness of 1.2 mm, while they are distributed close to the middle height of the columns with a wall thickness of 3.0 mm. Moreover, the buckling and rupture are generated earlier and more extensively with the thinner wall thickness.(2) The development trends of the relationships between load and displacement with identical wall thicknesses are similar to each other. Nevertheless, the maximum load and stiffness of the columns containing recycled coarse aggregate are lower than that of the maximum load and stiffness of the columns containing natural coarse aggregate. The load–displacement curves with thicker wall thickness present a longer plastic plateau after the maximum load, and better ductility.(3) The maximum load of columns containing recycled coarse aggregate is correspondingly lower than the maximum load of the columns containing natural coarse aggregate. Compared with the maximum load of columns containing natural coarse aggregate, the maximum load of columns containing recycled coarse aggregate is decreased by 18.4% and 5.8%, corresponding to wall thicknesses of 1.2 mm and 3.0 mm, respectively. Similarly, the displacement corresponding to the maximum load of columns containing recycled coarse aggregate is increased by 19.8% and decreased by 9.6%, respectively.(4) The models of the relationship between load and displacement/strain of the thin-walled steel tube columns containing recycled coarse aggregate subject to axial compression are established, and they present a good evaluation of load and displacement/strain.(5) The columns with identical wall thickness filled with two different types of concrete display similar relationships between load and strain. However, the stiffness in the elastic stage of columns containing recycled coarse aggregate is lower than that of the stiffness in the elastic stage of columns containing natural coarse aggregate. Confinement by the steel tubes of the concrete is weaker before the maximum load, and it becomes more intensive after the maximum load.This paper demonstrates that thin-walled steel tube columns containing recycled coarse aggregate present positive axial compressive behaviors and have great potential for applications in civil infrastructure, and promote the development of a renewable, sustainable, and carbon-neutral society. However, the results show that the maximum load, stiffness, and ductility of this column is a little lower than that of the corresponding values of the columns containing natural coarse aggregate. Moreover, the stability of the mechanical behaviors of the columns should also be explored comprehensively.


Cotton textile waste (CW) and crushed bricks (CB) are wastes generated by the textile and construction industries that cause adverse effects on the environment. This paper explores the effect of adding 1, 2, 5, and 10 wt.% of CW and CB, instead of natural sand under 1 mm (50 to 100 vol.%), on the properties of concrete. The study included the analysis of workability, density, water absorption, thermal conductivity, mechanical strengths, and electron microscopy. The results show that the presence of CW and CB increased the water required to obtain the same slump value as reference, R. Concretes with CW provided better performance in terms of density, water absorption (for 1 wt.%), and splitting strength (for 1 to 2 wt.%). The 28 days of compressive strength decreased with increasing CW (33.3 MPa for R and 26.9 MPa for 2 wt.% of CW). The partial substitution of sand decreased the workability and density and increased the mechanical strength of concrete. The presence of both CW and CB decreased workability, density, and mechanical strengths. Regarding the ability of concrete to transfer heat, the addition of CW and CB decreased the thermal conductivity value  for 1 wt.% of CW compared to 0.37 W/(m·K) for reference). Globally, the depletion of natural resources continues to accelerate while huge quantities of waste are still piling up . Each yeDue to the rapidly evolving fashion industry, there is a steady increase in the production of textile fibers, textile consumption, and textile waste . Over 9.2 K/W, 0.61 m2 K/W, and 0.67 m2 K/W).A novel technique for creating sound insulation materials was investigated by Dissanayake et al.  using waConstruction made up 37.5% of the total waste generation in the EU in 2020 . As a coCachim  stated tBased on these results, the present work aims to assess the effect of CW and CB on the performance of concrete. Cotton textile waste was chosen for this study because cotton and cellulose derivates represent 30–50 wt.% of the textile waste . In thisThe experimental program is presented below .The cement used was a commercial cement, CEM II/A-LL 42.5 R, produced by Heidelberg Materials Romania, complying with SR EN 197-1 . A naturIn order to obtain CB, the bricks with/without mortar were aggregated and then manually broken into more pieces to allow a better grinding process. The pieces were crushed with a jaw crusher, Retsch BB 200. The outcome dimension of the particles was modified by the change in distance between the two metallic plates. Due to the fragile nature of the bricks, the process was fast and had good efficiency. After crushing, the material was sieved to separate the particles under 1 mm. This portion of the material was used to substitute natural siliceous sand in CB concrete (50 to 100 vol.% substitution percent).The grading curve of the natural sand and crushed bricks with a maximum size of 1 mm is presented in 3 and of 0/1 mm sand was 2640 kg/m3.Water absorption of CB, tested according to SR EN 1097-6  was 33.73. The tensile characteristics of fabric and yarns depend on both fiber arrangements  inside the yarn and fabric structure and also on the tensile properties of fibers. The tensile properties of cotton fibers are influenced by the internal structure of the fibers. Cotton fibers are not homogeneous in their physical properties and dimensions. Their maturity, diameter, and fineness is different from fiber. Sometimes, even alongside the length of a fiber, there is a variation in physical properties, such as cellulose density. According to Asim et al. [CW was obtained by cutting used clothes into small pieces (approximately 20 mm × 20 mm), as shown in m et al. , the tenm et al.  obtainedBy testing some samples from cotton fabrics used in the research, the tensile strength values between 13 and 43 MPa were obtained.3, pH = 4.5, chloride content < 0.1%, and alkali content in the form of Na2O < 0.5%.A polycarboxylate superplasticizer, Viscocrete 2320, produced by Sika Romania, was used in the proportion of 1.8% with weight of cement. The admixture has a density of 1.042 ± 0.02 g/cma, and the water/cement ratio increases with the value of wa/c. Natural sand under 1 mm was substituted with CB at 50% and 100% replacement levels by volume. The textile wastes were added in proportion to 1, 2, 5, and 10 wt.% of the weight of cement.The evaluation of the concrete qualities with bricks and textile waste content was the primary goal of the experimental activity. The reference concrete’s mix ratio was developed using SR EN 206 + A2  and NE 0The following subsection describes how the concrete was produced. The dry weight of the concrete components was first measured in accordance with the mix design. Then, for 60 s, the aggregate and textile wastes were mixed. The mixer was filled with 30% water, and it was blended for 60 s. The mixer was filled with cement, which was then stirred for 60 s. The remaining water and superplasticizer were added to the mixer gradually while being stirred for 180 s to ensure uniformity.The vibrating table compacted the concrete after it had been cast into the mold, and it was then left at room temperature for 24 h. The concrete was removed from the mold and put in a typical curing environment with saturated humidity until it reached the testing age.The workability of fresh concrete was tested using slump and Vebe tests in compliance with SR EN 12350-1 and SR EN 12350-3 . The freThe density of 28-day-old concrete was tested according to SR EN 12390-7 . The voldm. The specimens were then cooled in an exicator. The dimensions of the faces immersed in water were measured, and the gross area, sA, was calculated. The lateral surfaces were sealed in order to ensure one-directional water flow through the samples. The samples were weighted and immersed in water (the immersed depth was kept at 3–5 mm). At different time intervals, t, , the concrete specimens were taken out of the tray, the surface water was wiped off, and the mass change was recorded, sm. Then, the samples were re-immersed. The test was performed based on SR EN 772-11 [The test was performed on three prismatic specimens measuring 40 mm × 40 mm × 160 mm for each mix. After curing for 28 days, the specimens were dried in an oven at 105 ± 5 °C until a constant weight was recorded, N 772-11 . The watThe compressive strength was tested according to SR EN 12390  on 100 mSplitting strength was conducted at 28th day on three concrete cubes with dimensions of 100 mm × 100 mm × 100 mm, using a WPM testing machine with a maximum load capacity of 300 kN. The flexural strength (one-point loading) was tested on three prismatic samples (40 mm × 40 mm × 160 mm) after 28 days, using the same machine that was used in the splitting test.The thermal conductivity of concrete was tested according to EN 12664 . The matThe hot plate temperature is controlled using a PID controller to a set value. Since the cold plate temperature is directly dependent on the cold-water temperature from the distribution network and cannot be modified, the hot water temperature is manually set so that a temperature difference of 15–20 K is recorded between the two plates.The thermal conductivity depends on both plates’ average temperatures, heat flowmeter output, and six calibration constants that depend on the apparatus.To acquire a better understanding of the macroscopic properties of concrete, microscopy tests were also carried out. The morphology of reaction products was studied via SEM analysis recorded on a SEM/EDAX High Resolution Scanning Electron Microscope, Quanta Inspect F FEG (resolution 1.2 nm) with EDAX (133 eV resolution at MnKα)—FEI Company. Prior to imaging, a small layer of conductive gold was applied to the samples. The chosen concrete was 28 days old.The workability of concrete was measured with the slump test and the Vebe test. The average slump of concrete was 3 mm, as shown in The Vebe test measures the consistency of concrete through the time in which the concrete changes from the truncated shape to the cylindrical shape under the effect of vibration. The Vebe time was between 5 and 10 s. It is clear that utilizing CB as a substitute for natural sand reduces the workability of concrete and necessitates the use of more water, depending on the content of CB. The concrete B100 (0/1 mm sand substituted with CB) needs more water than the concrete B50 in order to obtain the same slump. This is a consequence of the angular and irregular shapes of CB compared to the rounded and smoother particles of natural aggregate, which raises the friction between particles and affects the concrete’s workability . As a coThe water quantity added to concrete with 1% and 2% textile waste is slightly higher than that of the reference and smaller than in the case of concrete with crushed brick content. The addition of textile waste by up to 10% led to a significant increase in the necessary water to achieve the same slump of concrete.The presence of both textile waste and CB led to a significant increase in water added for obtaining concrete in comparison to reference, as a consequence of the water absorption of waste.The results exhibit an obvious reduction in the density of fresh concrete when crushed bricks and textile wastes are used . The rep3). The presence of both kinds of wastes led to a decrease in density by 3.8–10.5% in comparison to reference; the density values were from 2070 to 2170 kg/m3.The density of fresh concrete with textile waste was lower than the reference. Increasing the textile waste content decreased the density of fresh concrete; the minimum value was for concrete with 10% cotton waste .The results of capillarity can be seen in For both B50 and B100 mixes, a higher quantity of additional water led to increased water absorption. Compared to R, the replacement of natural sand with CB increased water absorption by 61% and 81% for 100 min, as shown in Concretes with both CW and CB consistently absorbed more water than C1 and C2. Higher cement matrix porosity is most likely a result of the higher water content of concrete. The water absorption decreased in the C1B50 > B50 > R and C2B50 > B50 > R series. Higher water absorption for concrete with recycled brick aggregate was also obtained by  and attrThe thermal conductivity test is significant for assessing the ability of concrete to transfer heat. Thermal conductivity, λ, was measured for selected concretes on slabs. The concrete with 1% CW had a λ of 0.32 W/(m·K). The presence of both CW and CB improved the thermal insulation ability of concrete  for C1B50 compared to 0.37 W/(m·K) for R). The concrete B50 had a λ of 0.35 W/(m·K). The lower λ values of concrete with textile wastes, in comparison to R, were consequences of the fact that textile waste has a conductivity value that is more than 10 times lower than that of concrete. Cotton’s limited ability to effectively transport heat is due to its poorer thermal conductivity (0.026–0.065 W/(m·K)) than many synthetic and other natural fibers ,45. FurtThe mechanical strength of concrete is presented in 2.For 50% substitution of natural sand under 1 mm with CB, it was observed a reduction in strength for 2 days and an increase for 28 days, compared to the reference (33.7 MPa for B50 and 33.3 MPa for R). CB seems to contribute to the densification of the concrete structure due to a higher content of fine particles , and the rough texture and angular shape of CB led to a denser interfacial transition zone between the ceramic aggregate and matrix. When the substitution percent of natural sand under 1 mm increased to 100%, compressive strength decreased at 28 days; the reduction was 22% compared to the reference and 23% in comparison to B50. The mixes B50 and B100 stand out for a significant increase in compressive strength over time compared to other mixes. Similar results were obtained by [The concrete with both CW and CB had a lower compressive strength than the concrete with only textile waste and reference, the decrease being significant for 2% textile waste. The decrease in compressive strength was 18…33.5% in comparison to concrete with textile waste (no bricks) and 35.1…49.3% compared to B50.In the case of flexural strength, the reference concrete had a value of 7.09 MPa (28 days), which represents 21.3% of compressive strength. The addition of textile wastes increased the ratio between flexural strength and compressive strength and slightly decreased the flexural strength compared to the reference. The concrete with the highest flexural strength was B50 (22.3% bigger than R). A complete substitution of natural sand under 1 mm with CB reduced the flexural strength by 30% compared to B50.The splitting strength of concrete with 1% and 2% textile waste was higher than R. The explanation for the increase in splitting strength is that cotton textile waste acts as reinforcement.The substitution of natural sand with CB had a positive effect on the flexural and splitting strength, probably due to the particle size distribution of CB and the pozzolanic activity of CB.p = 0.001, and Fcrit = 4.225). On the other hand, the relationship between the compressive strength (MPa) and the CW content (%) is presented in Based on the values from 2= 0.79, i.e., 79% of the thermal conductivity variation is explained by the variation of the splitting strength; the p-value is below 0.05). Also, the regression line from a linear regression analysis turns out to be the following:Based on the data obtained experimentally, it is found that the thermal conductivity correlates with only the splitting strength 2 hexagonal crystals. The SEM images of concrete R, B50, and C1B50 are presented in Partial substitution of natural sand with CB led to an improvement in the microcrystalline aspect of concrete B50 compared to R. Images from The addition of cotton textile waste in concrete  has led to increased water quantities required for obtaining concrete with the same slump value as reference, due to the absorption capacity of waste. The same trend was observed for concrete with CB  and concrete with both wastes. The additional water-influenced properties were tested. The density of fresh and hardened concrete decreased compared to the reference;The water absorption via capillarity increased for mixes with wastes because of the increased water/cement ratio, which led to a more porous cement matrix;The 28-day compressive strength of concrete with 1 and 2 wt.% CW was between 26.7 and 26.9 MPa, representing a decrease of 19.2% and 19.8%, respectively, compared to the reference. The compressive strength of concrete with 10 wt.% significantly decreased to 8.8 MPa, compared to 33.3 MPa for reference. The same observation is also valid for flexural strength. Concretes with 1 and 2 wt.% CW had higher splitting strength than reference due to their reinforcement effect;The partial substitution of natural sand under 1 mm with crushed bricks (50 vol.%) led to the 28 days’ mechanical strengths comparable to reference (compressive strength of 33.7 MPa compared to 33.3 MPa). The increase in CB concrete compressive strength over time was significant over time compared to other mixes, which suggests a pozzolanic reaction. When CB content increased to 100 vol.%, the mechanical strengths decreased;The incorporation of both CW and CB in concrete resulted in a decreased compressive and flexural strength, except for the splitting strength;From a statistical point of view, the conclusion stated above regarding the diminishing of mechanical strength with the increase in the addition of textile waste is supported by correlation coefficients lower than zero;The SEM and EDX analyses showed an improved microcrystalline aspect of concrete with crushed brick and the presence of hydrates on the CW;The addition of cotton textile waste in concrete leads to a decrease in the thermal conductivity to 0.32 W/(m·K) compared to 0.37 W/(m·K) for reference, improving the insulation properties, which are directly related to the buildings’ energy efficiency.This paper presents an experimental study on the effect of cotton textile waste (CW) and crushed bricks (CB) on the properties of concrete. The experimental data led to the following conclusions:The use of CW in concrete seems to be a viable solution with a positive impact on the environment, reduced greenhouse gas emissions, and minimized the landfill disposal through the successful use of these waste materials in construction. Further studies are necessary, especially aimed at the influence of the size of cotton waste on the properties of fresh and hardened concrete.


Prosthetic Joint Infection (PJI) causes significant morbidity and mortality for patients globally. Delivery of antibiotics to the site of infection has potential to improve the treatment outcomes and enhance biofilm eradication. These antibiotics can be delivered using an intra-articular catheter or combined with a carrier substance to enhance pharmacokinetic properties. Carrier options include non-resorbable polymethylmethacrylate (PMMA) bone cement and resorbable calcium sulphate, hydroxyapatite, bioactive glass, and hydrogels. PMMA allows for creation of structural spacers used in multi-stage revision procedures, however it requires subsequent removal and antibiotic compatibility and the levels delivered are variable. Calcium sulphate is the most researched resorbable carrier in PJI, but is associated with wound leakage and hypercalcaemia, and clinical evidence for its effectiveness remains at the early stage. Hydrogels provide a versatile combability with antibiotics and adjustable elution profiles, but clinical usage is currently limited. Novel anti-biofilm therapies include bacteriophages which have been used successfully in small case series. Prosthetic joint infection (PJI) has been a battle for the medical profession since prosthetic joints began to be implanted, and rates vary between 0.85% and 2% worldwide ,2. In AuPJI carries a significant burden for patients and healthcare systems alike. For PJI patients, treatment is prolonged and arduous, with psychosocial stress comparable to oncology patients . Long-teConventional treatment requires surgery and includes Single Stage Exchange arthroplasty (SSE), Two Stage Exchange arthroplasty (TSE) or Debridement, Antibiotics, and Implant Retention procedures (DAIR). This usually occurs in conjunction with long-term targeted systemic antibiotic therapy. Local administration of antibiotics aims to improve treatment success, limit antibiotic-associated adverse outcomes, and avoid antimicrobial resistance through reduced systemic exposure to antimicrobials. The goal of this review is to discuss administration of local antimicrobial agents and their carriers, and review current evidence in relation to PJI.The development of biofilm is thought to be the principal microbial factor leading to the observed outcomes of PJI management, and orthopaedic device related infection (ODRI) generally. Bacteria in an established biofilm are up to 10,000 times more resistant to antibiotic therapy than their free-floating planktonic counterparts . IrreverThe multi-layered structure of the biofilm, as seen in Successful methods of biofilm eradication therapy may result in increased treatment success and reduced procedural morbidity and complexity. Delivering local antibiotic therapy directly to the site of infection carries significant potential to achieve this goal. With greater biofilm destruction, it may improve success rates of current treatment strategies, broaden indications for less invasive surgical management, or in some cases may avoid surgery altogether. This has the potential to enhance the patient treatment experience, improve functional outcomes, and reduce the financial cost of PJI treatment.Placing antibiotics directly into the site of infection carries several advantages over systemic administration. It can provide significantly higher concentrations to infected tissue with reduced systemic exposure. This may lower rates of antibiotic-associated adverse events and decrease antimicrobial resistance through preservation of the gastrointestinal microbiome.Local antibiotics can be administered ‘naked’, or with a carrier to improve antibiotic elution. Antibiotic carriers include polymethylmethacrylate bone cement, calcium sulphate, calcium hydroxyapatite, bioactive glass, and hydrogels. Non-antibiotic options, such as bacteriophages and ceragenins, aim to destroy biofilm more efficiently but are still in initial stages of clinical development.Choosing an antibiotic to be used locally requires consideration of several factors. An antibiotic can be selected either to target a known organism, or empirically to target a spectrum of common PJI pathogens. Antibiotics may be toxic to bone and soft tissues in very high concentrations, but fluoroquinolones, tetracyclines, and rifampicin have been shown to be particularly toxic to osteogenic cells even at low levels . As withIdeal local antibiotic administration provides predictable, high concentrations in surrounding tissue with minimal systemic exposure or adverse events. Importantly, although antibiotic efficacy determinants of microbial killing are defined in planktonic form, determinants of antibiotic efficacy in local administration have not yet been fully determined.Staphylococcus aureus may have an MBEC of over 1000 μg/mL compared to its planktonic MIC of 2 μg/mL. Systemic therapy is unable to reach these levels safely . In. In95]. Bioactive glass (BAG) carries inherent antibacterial activity following implantation and can also act as an antibiotic carrier. It is an attractive option in osteomyelitis and fracture-related infection due to stimulation of bone formation to heal defects, and has been shown to improve local vascularity with proangiogenic properties . Once imThere are no published studies of clinical use of BAG in prosthetic joint infection currently, but non-antibiotic-laden BAG has been used in osteomyelitis treatment following surgical debridement. Lindfors et al. reported an overall cure rate of 89.7% at 31 months in a multinational register of 116 patients, predominantly involving post-traumatic long bone osteomyelitis . In thisHydrogels carry significant promise as a fully resorbable carrier that can be tailored to a specific clinical indication. They can be manufactured from multiple biodegradable polymers, with variable antibiotic release kinetics and degradation time of the gel ,121. TheClinical studies are limited to the use of Defensive Antibacterial Coating , which is the most studied and is already commercially available . DAC® isNanocarriers are complex molecular moieties that respond to internal or external stimuli for activation. Self-targeting carriers can respond to local changes in infected tissue, such as pH, hypoxia, macrophage presence, increased reactive oxygen species, local ligands, bacterial enzymes, or increased local temperature . NanocarNovel therapies provide opportunities to disrupt biofilms and overcome increased antibiotic resistance with new mechanisms of action.Bacteriophages (or phages) are naturally occurring bacterial viruses that are remarkably diverse and have co-evolved with bacteria throughout the history of life. Lytic phages undergo a life cycle of self-replication inside a bacterial cell following infection, before being released by lysing the bacteria. They were first recognised as a therapeutic option in 1917 but were quickly overtaken in the West by antibiotics. Development and clinical use did continue in Georgia and Russia, where phage cocktails are still available and clinically used. With a rise in antibiotic resistance, they have again become an area of interest in the West ,139,140.Staphylococcus aureus hip PJI, that later grew multidrug resistant (MDR) P. aeruginosa. Intra-articular phage cocktails were administered against both organisms, with additional targeted antibiotic therapy following a DAIR procedure. While eradication of these microbes was achieved, the patient remained on suppressive therapy for other identified bacteria, but achieved satisfactory function [P. aeruginosa during repeat TSE in a co-morbid patient with metabolic syndrome and chronic kidney disease [Clinical use of phages is currently limited to salvage treatment for PJI . Ferry efunction . This grfunction . Tkhilai disease . Patey e disease . Cano et disease .Ceragenins or cationic steroid antibiotics (CSA) are a novel antimicrobial class which mimic the activity of endogenous cationic antimicrobial peptides. CSA disrupt bacterial cell membranes through interaction with negatively charged phosphatidylglycerol and lipid A lipopolysaccharides . ActivitAntimicrobial peptides are short chains of amino acids with a broad-spectrum, rapid bactericidal action through direct disruption of bacterial cell membranes. Their targeted cell wall disruption allows them to be very effective against biofilm-bacteria during in vitro studies. However, their delivery is a significant issue, with rapid proteolytic degradation and host toxicity currently limiting clinical use, as well as reports of bacterial resistance .Quorum-sensing inhibitors are molecules that disrupt bacterial signalling pathways used to form and maintain the biofilm state and its associated resistance mechanisms. They carry in vitro promise; however, they are currently limited by a narrow therapeutic spectrum as not all species use the same signalling molecules. There are also safety concerns as they may disrupt the signalling of beneficial human microflora, leading to unintended side-effects .Other novel biofilm-disrupting methods include laser phototherapy of implants, bioelectric therapy, and ultrasound microbubble disruption, all of which have shown promise during in vitro or animal studies, but require further development .Prosthetic joint infection remains a major problem for patients, clinicians, and health systems. These infections often require major revision procedures and prolonged antibiotic therapy, and come with significant psychosocial stress and long-term risk of recurrence. They are costly to treat, and healthcare systems only face greater demand in the future. Overcoming the biofilm remains at the core of PJI treatment; however, no ideal solution currently exists. Improving current biomaterials, developing novel carriers, and creating new antimicrobial therapies carry the greatest potential.The ideal antibiotic carrier for local therapy delivers antibiotics for prolonged duration at effective concentrations, has complete antibiotic release, versatile compatibility with desired antibiotics, and full carrier resorption with minimal risk of allergies or adverse effects systemically or locally. However, all current carrier options are associated with issues, including suboptimal antibiotic delivery or compatibility, carrier persistence, local or systemic complications, or a lack of clinical evidence for their use. Ongoing research into antibiotic carriers including calcium hydroxyapatite, calcium sulphate, bioactive glass and hydrogels, and the development of purpose-built composite biomaterials aim to overcome current problems and develop an ideal antibiotic carrier for use in PJI. However, these novel options require further development in animal models and extensive safety studies before their widespread clinical use.There are still theoretical shortcomings with local antibiotic therapy, despite its many advantages. Even with much lower systemic antibiotic levels seen in local delivery, there remains a risk of systemic complications such as nephrotoxicity . Local aThere are several other limitations in our current understanding of local antimicrobial therapy. The most significant are the determinants of local antibiotic effectiveness. This leads to significant heterogeneity in testing methodology across studies and a lack of standardisation of research goals. Reported elution characteristics for various methods are therefore diverse, and it is difficult to evaluate and then successfully translate this into clinical practice. When measuring antibiotic elution, studies report the concentration within local joint fluid, often collected from a post-operative drain. This may misrepresent and reduce effective levels in local tissue . A key aIn this narrative review we have provided a comprehensive review of local antimicrobial administration options, focused on current clinical outcomes for this difficult patient population to aid clinical practice. We have evaluated antibiotic carriers in bone and joint infection more widely when clinical data in PJI are not available, and we aim to acknowledge literature gaps to guide further clinical and pre-clinical work. In summary, local antibiotic therapy has been demonstrated to improve PJI outcomes through a variety of delivery systems. PMMA is the best studied antibiotic carrier in PJI, with the unique ability to form structural spacers that also elute antimicrobials. However, it has suboptimal elution kinetics and is not compatible with all antibiotics. It often requires a second procedure for removal and has been associated with development of antimicrobial resistance due to carrier persistence. Resorbable carriers such as calcium sulphate and hydrogels aim to overcome these issues. Hydrogels are versatile carriers which are compatible with a wide variety of antimicrobial substances, including bacteriophage. They provide reliable elution profiles which may be tailored to meet requirements. Newer solutions such as nanocarriers and anti-biofilm agents aim to deliver antibiotic therapy and eradicate biofilm more effectively; however, these remain at the pre-clinical development stage.


Acknowledging the growing impact of nanotechnologies across various fields, this engaging research paper focuses on harnessing the potential of nano-sized materials as enhancers for concretes. The paper emphasizes the strategic integration of these entities to comprehensively improve the strength and performance of concrete matrixes. To achieve this, an analytical study is conducted to investigate the static behavior of concrete beams infused with different types of clay nano-platelets (NC’s), employing quasi-3D beam theory. The study leverages the effective Eshelby’s homogenization model to determine the equivalent elastic characteristics of the nanocomposite. The intricate interactions of the soil medium are captured through the use of a Winkler–Pasternak elastic foundation. By employing virtual work principles, the study derives equations of motion and proposes analytical solutions based on Navier’s theory to unravel the equilibrium equations of simply supported concrete beams. The results shed light on influential factors, such as the clay nano-platelet type, volume percentage, geometric parameters, and soil medium, providing insights into the static behavior of the beams. Moreover, this research presents previously unreported referential results, highlighting the potential of clay nano-platelets as reinforcements for enhancing structural mechanical resistance. Concrete, a widely used building material known for its cost-effectiveness, high strength, and durability , is suscNanoparticles, characterized by their size ranging from 1 to 100 nanometers, possess more unique physical, chemical, and mechanical properties compared to those of their bulk counterparts . When thDirect mixing entails the addition of nanoparticles directly into the concrete mixture during the mixing process. This approach requires meticulous control of the mixing conditions to ensure the uniform distribution of nanoparticles throughout the concrete matrix, ultimately influencing the overall properties of the composite material . Alterna2) nanoparticles on the mechanical behavior of impregnated concrete. Extensive research has been conducted to unravel their potential, shedding light on various aspects of their influence. For instance, Shokravi  was chosen to serve as an internal standard. The samples for QXDA were prepared by mixing a dry weight of 3.0 g of cement paste or cement nanocomposite paste, with 0.33 g of Corundum [Al2O3] as the internal standard [The X-ray diffraction measurements were conducted with a D8 Advance Diffractometer (Bruker-AXS) using Cu Ka λ = 1.5406 Å) radiation. The scanning range for the diffractometer was from 7° to 70° (2θ) with a scanning rate of 0.5°/min. Quantitative X-ray Diffraction Analysis (QXDA) with Rietveld refinement was conducted with Bruker DIFFRAC06 Å radiAs evident from the data presented in The evaluation of the mechanical performance of clay–concrete composites involved various testing methods, including compressive strength testing and flexural strength testing. Several studies have reported that the incorporation of nano-clay (NC) in cementitious materials results in an improved compressive and tensile strength ,56. The Furthermore, The durability of clay–concrete composites was evaluated using a range of testing methods, including water absorption and chloride ion penetration tests. These tests aimed to assess the ability of the composites to resist the ingress of water and the penetration of chloride ions. Water absorption testing helps determine the porosity and permeability of the composites, which are important factors affecting their durability. On the other hand, chloride ion penetration testing is performed to measure the resistance of the composites to chloride ion ingress, as chloride ions can cause structural deterioration. By evaluating these durability parameters, the performance and long-term serviceability of clay–concrete composites can be assessed and optimized.When it comes to the sulfate ion attack on concrete and cementitious materials reinforced with clay nanoparticles, there is currently a limited amount of research specifically addressing this particular case. However, in recent years, a growing body of research has shown that the incorporation of alternative nanomaterials, such as silica nanoparticles, can greatly improve the sulfate resistance of cement-based materials. This improvement is attributed to the reduction of microstructural pores. These studies have shown that the inclusion of silica nanoparticles can lead to improved sulfate resistance, particularly during the early stages of concrete curing ,66.Our research article is driven by the compelling experimental data that highlight the remarkable properties of nano-clays and their ability to enhance the overall behavior of concretes. Building upon these findings, our study aims to comprehensively explore the potential of montmorillonite, kaolinite, illite, and hectorite nano-clays, unveiling novel referential findings that have not been reported before.The primary focus of our research is to analytically model the bending behavior of concrete beams that are reinforced with varying types and proportions of clay nanoparticles. To achieve this, we employ analytical homogenization techniques, which enable us to unravel the intricate interplay between the presence of NCs and the structural performance of the beams.The integration of nanoparticles with diverse properties into a concrete matrix introduces a fascinating dimension of microstructural heterogeneity. The resulting effective elastic properties of this concrete-reinforcement combination are of great interest, and in this pursuit, the renowned Eshelby’s homogenization model , which wrV. These carefully chosen nanoparticles are randomly dispersed throughout a continuous matrix. This matrix, in its entirety, occupies the complementary volume known as mV, which is assumed to possess infinite extent and homogeneity, representing the concrete medium  are meticulously analyzed, utilizing the elastic properties of both the matrix and the included nanoparticles, while considering the geometric attributes of the RVE itself, as Clyne notes .TC for the nanocomposite is then derived using the following Equation (1):I is the identity matrix, and mC and rC are the stiffness tensors for the concrete matrix and the nano-reinforcement, respectively. As mentioned earlier, the volume fraction of the matrix and reinforcement are denoted by mV and rV, respectively. Additionally, Eshelby’s tensor S is related to the Poisson ratios of the nanoparticles.In terms of predicting the properties of a matrix that is reinforced with nano-sized inclusions. Eshelby’s homogenization model has demonstrated accurate predictions for inclusions in the shape of oblate and prolate spheroids when their volume fractions are below 30%, as Hull notes . In our mC and rC are expressed in Equation (2) as:For both isotropic materials, the stiffness’s E is the young’s modulus of either the concrete matrix or the nanoparticles reinforcement, and υ denotes the Poisson’s ratio. Indexes 1, 2, and 3 conform to the x, y, and z directions of the composite Cartesian co-ordinate system, respectively.In which S is given in Equation (3) as: (Binns [S are described in Equations (4a) and (4b) as:For reinforcement with platelets, Eshelby’s tensor : (Binns )(3)S=S1For all the others components:rυ denotes the Poisson’s ratio of nano-platelets reinforcements.Here, L’, width ‘b’, and total thickness ‘h’, as illustrated in In the following Section, the analytical formulation of the nano-clay-reinforced concrete beam based on the kinematic and physical assumptions of the refined quasi-3D theory of Thuc Vo et al.  is presex, y, and z), on which z is placed, is in the median plane of the beam.The impregnated clay nano-platelets are assumed to be randomly arranged in the concrete matrix, as shown in 3u is assumed to be divided into 3 components: bending (bw), shear (sw), and the thickness stretching effect (zw)  in the beam are described in Equation (5) according to the refined quasi-3D theory as follows:In order to include the thickness stretching effect in the bending analysis of our nanoparticle-reinforced concrete beam, the total transverse displacement i et al. ). Thus, 0u and 0v signify the displacement functions of the mid-planes of the beam. f(z) expressed in Equation (6) is the odd shape function used to expresses the distribution of shear strains throughout the beam’s depth:At this point, The linear strains components associated with the quasi-3D displacement equations are given in Equation (7):For normal and shear stresses of the nanoparticle-reinforced concrete beam, the constitutive equations can be expressed as Equation (9):Herein, bδU and kδW are the virtual variation in the internal strain energy of the beam and the elastic foundation, respectively, while δΦ is the virtual work performed by external bending forces.In this analysis, the principle of the virtual work is applied in order to provide the equations of motion of the nano-reinforced beam:Firstly, the expression of the virtual strain energy performed by the beam can be depicted as follows in Equation (11):Submitting Equation (7) into Equation (11) gives Equation (12) for the internal strain energy:bN, M, sM, Q, and zR) represent the following quantities:N’ represents the normal force in a structural element;‘bM’ denotes the bending moment about the beam’s local y-axis;‘sM’ indicates the shear force acting along the beam’s local z-axis;‘Q’ represents the torsional moment applied to the beam;‘zR’ represents the rotational moment about the member’s local z-axis.‘ where:In Equation (12), the stress resultants (By substituting Equation (8) into Equation (9) and the results into Equation (13), one obtains the stress resultants in form of material stiffness and displacement components, and the expressions are given as Equation (14):A, B, D, As, Bs, Ds, and Hs) and  are the beam stiffness, which are defined in Equation (15):In which (wK and sK) of the Winkler/Pasternak foundation model:In addition, the load–displacement formula between the concrete beam and the supporting foundation is expressed in Equation (16) by introducing the parameters :As for the nano-reinforced concrete beam subjected to mechanical bending loads ‘‘0δu, bδw, sδw, and zδw, the following equations of motion associated with the quasi-3D beam theory are obtained (Equation (18)):By combining Equations (12), (16), and (17) into Equation (10), and then integrating the coefficients of x = 0 and x = L, the beam must adhere the following boundary conditions:For a simply supported type edge, at = mπ/L and (Navier’s admissible displacement functions in the form of trigonometric series are presented in Equation (21), which are appropriate for such simply supported beams and can be used to solve the governing equations of motion.q” exhibits various patterns, as illustrated in In our analysis, we assume that the transverse bending load “Where the amplitude of each load according to Sayyad et al.  is desigFinally, in order to obtain analytical solutions, the results of the substitution can be arranged into the following matrix form:This Section presents an intriguing exploration of the mechanical bending behavior exhibited by concrete beams infused with an assortment of clay nano-platelets. Through the utilization of the refined quasi-3D beam deformation theory, we embark on the meticulous calculation of transverse displacements  elastic foundations are utilized in Equation (27):pK), shear modulus (pG), and Poisson’s ratio (pυ), as meticulously compiled in pE), we employ a conversion formula designed for isotropic materials, as expressed in Equation (28):In this analysis, we explore diverse nano-sized clay platelets (which take the form of disk-shaped particles) with different chemical compositions and elastic characteristics to unlock their potential as reinforcements in a concrete matrix. Building upon the insightful work of Wang et al. , we are mE) of 20 GPa and a Poisson’s ratio (mυ) of 0.2. By introducing these nano-platelets into the mixture, we seek to enhance the overall mechanical and physical efficiency of the composite material. To evaluate and predict the elastic properties of the resulting nano-composite material, we employ Eshelby’s homogenization approach. This approach allows us to assess the performance of different types of nanometric reinforcement in concrete matrices, enabling the comparative analysis of their effectiveness.In our study, we aim to create a nano-composite matrix by incorporating nano-platelets into a concrete mixture. The concrete matrix itself possesses specific elastic properties, including an elastic modulus (p), are implemented and presented in First, it is highly relevant to consider the accuracy of the current mathematical model based on the refined quasi-3D beam theory assumptions. Since there is a lack of numerical results in the existing literature specifically focusing on the flexural analysis of beams reinforced with clay nano-platelets, we consider the material and geometric properties of Thuc Vo et al.  for the f(z). This consistency demonstrates the reliability and accuracy of the adopted model in our analysis. On the other hand, when we compared the results obtained from the trigonometric beam theory (TBT) and the first-order beam theory (FBT), it was observed that the vertical displacement (The comparison of the results presented in rV) of montmorillonite (SWy-1) and hectorite (SHca-1) nano-platelets. The percentage variations in the added nanometric materials range between 0% and 30% of the total weight of the matrix.First, the analytical estimation was conducted using Eshelby’s homogenization approach to determine the reduced elastic constants “rV). Notably, the reduced stiffness “11, which represents the elastic stiffness in the length-wise direction of the structure. This improvement can be attributed to the superior elastic properties of hectorite nanoparticles.The results shown in Vr) of different clay nano-platelets, namely montmorillonite (SWy-1), kaolinite (KGa-1b), illite (ILT-2), and hectorite (Sha-1), on the non-dimensional transverse displacement (rV = 0% (non-reinforced concrete beam) to 0.74 at rV = 30% . This establishes hectorite as the most effective reinforcement among the various clay nano-platelets considered.Additionally, n) used in Equations (22) and (23) on the accuracy of the calculated transverse displacement of the beam. It is known that for the single sign type of loading, a single term (n = 1) is sufficient to generate accurate results. However, for other loading types such as a uniformly distributed load, a linearly distributed load, and a concentrated force, a convergence study is necessary to determine the number of iterations required to achieve accurate results.A convergence study is presented in n = 11) using Equations (22) and (23). However, for the subsequent results, a higher number of iterations (n = 201) was utilized to obtain more precise and accurate results. This choice was made considering the computational power available, allowing for more thorough calculations and improving the accuracy.As presented in rV = 30%. The results obtained reveal that the incorporation of nanoparticles in the concrete matrix leads to a stiffening effect, irrespective of the applied external bending load. Among the various loads examined, the uniform load emerges as the most significant factor influencing the transverse displacement, causing a substantial reduction of  using the quasi-3D beam deformation theory, which accounts for the thickness stretching effect.Consistent with previous observations, It is worth mentioning that the maximum deflection of the beam occurs at the mid-length position, a characteristic that can be attributed to the homogeneity achieved using Eshelby’s homogenization law. This homogeneity plays a pivotal role in distributing the load and deformation evenly along the beam, resulting in a concentrated deflection at the midpoint.L/h), representing the length-to-thickness ratio, on the non-dimensional transverse displacement (rV) up to 30% leads to a reduction in deflection for the concrete beams. This highlights the importance of reinforcement concentrations in enhancing the structural rigidity and mitigating deflection.Furthermore, the comparison between z = 0) of the beams. This symmetry is attributed to the achieved homogeneity between the reinforcements and the matrix, accomplished through the utilization of Eshelby’s homogenization approach, as well as the assumptions made regarding the distribution of clay nano-platelets within the concrete matrix.A notable observation from rV = 0%). This signifies the relatively higher deformation experienced by the non-reinforced beam. Conversely, the minimum axial displacement value is observed when the concrete beam is reinforced with hectorite clay nano-platelets. This suggests that the presence of hectorite reinforcement leads to the significant reduction of axial displacement, indicating its effectiveness in enhancing the stiffness and structural integrity of the concrete beam.Furthermore, it is worth noting that the maximum axial displacement -reinforced concrete beam is supported by an elastic foundation. In the subsequent analysis, we investigate the impact of various parameters associated with the Winkler–Pasternak elastic foundation on the static response, including the transverse displacements, normal stresses, and shear stresses of concrete beams reinforced with different types of clay nano-platelets.Taking into account both the shear layer constant and the spring constant, we examine the impact of the Winkler–Pasternak foundation on the transverse displacement of a nano-clay-reinforced concrete beam in Lastly, Clay minerals are widely abundant in the Earth’s crust and offer versatile applications due to their prevalence and cost-effective extraction. In this study, we delved into the potential of utilizing nanoscale clay additives to improve the elastic and physical properties of concrete beams. To investigate this, we applied the quasi-3D beam theory, which is used to consider the effects of thickness stretching, to analyze the static behavior of concrete beams reinforced with nano-scale clay (NC) additives. By examining the performance of these nano-clay-reinforced beams, we aim to uncover the benefits and implications of incorporating clay additives to enhance the properties of concrete structures.The addition of nano-sized clay platelets to concrete mixtures results in improved elastic characteristics, with the extent of the improvement being dependent on the volume concentration of these additives.Concrete structures reinforced with nano-clays exhibit exceptional optimization under external mechanical loads, enhancing their overall performance.When they are subjected to various external bending loads, concrete beams reinforced with clay nano-platelets demonstrate a significantly reduced transverse displacement (deflection), highlighting the efficacy of nano-reinforcements in minimizing structural deformations.Among the various types of clay nano-platelets considered, hectorite (SHca-1) is particularly effective in reducing transverse displacements, showcasing a reduction of approximately 42%. This performance surpasses those of illite (ILT-2), with a reduction of 39%, kaolinite (KGa-1b), with a reduction of 32%, and montmorillonite (SWy-1), with a reduction of 24%, in transverse displacement. These findings highlight the superior performance of hectorite nano-platelets in enhancing the structural stability and minimizing deformations in concrete beams.Incorporating an elastic foundation further contributes to stress reduction and deflection mitigation in nano-reinforced concrete beams, enhancing their overall structural integrity.Our investigation has yielded valuable insights and led us to the following noteworthy conclusions:However, it is important to recognize the limitations of our research, which exclusively centered on nano-clay platelets. In order to expand our understanding and encompass a broader range of structural elements, future investigations should delve into the effects of other nano-reinforcements on the properties of concrete beams, plates, walls, and other structural components. These endeavors should encompass analytical analyses to thoroughly evaluate the influence of these alternative nano-reinforcements. In doing so, we can gain a more comprehensive understanding of their potential and pave the way for further advancements in the field of reinforced concrete structures.


Immunoglobulin G4-related disease (IgG4-RD) is a rare fibro-inflammatory condition characterized by IgG4-expressing plasma cell infiltration of the skin and other organs, leading to profound itchiness. Oral corticosteroids are the first-line therapy for IgG4-RD but relapses and potential side effects are common. In this case, we discuss a patient with a hyperpigmented, scaling dermatitis on his arms, back, and chest with lichen amyloidosis (LA) that incompletely responded to corticosteroids. He had reduced quality of life secondary to chronic pruritus. Dupilumab, an IL-4 and IL-13 inhibitor, was initiated. He experienced a transient worsening, followed by complete resolution of his itch with remission of his rash. While the pathogenesis of IgG4-RD is not entirely understood, a T-helper 2 (Th2) immune response has been implicated, with interleukins (IL) 4, 5, 10, and 13 playing a role in IgG4 class switch, resulting in eosinophilia and elevated IgE. The strong response of dupilumab in this case may provide evidence in favor of the involvement of IL-4 and IL-13 in the pathogenesis of cutaneous IgG4-RD. Future clinical studies involving larger patient populations may be warranted. Immunoglobulin G4-related disease (IgG4-RD) is a rare fibro-inflammatory condition characterized by IgG4-expressing plasma cell infiltration of the skin and other organs . IgG4-RDOur patient is a Middle Eastern male with a past medical history of asthma and allergic rhinitis. In 1989, he presented at 36 years of age to an outside institution with sclerosing cholangitis and pancreatitis. He was diagnosed with IgG4-RD after serologic evaluation and a strong response to steroids. Over the next several decades, he experienced intermittent disease flaring on low–moderate dose prednisone. Of note, in 2016, he was diagnosed with stage IV chronic kidney disease secondary to systemic IgG4-RD; however, his renal function remained unchanged over the course of this case report .He first presented to our institution in 2016 with fatigue and elevated blood urea nitrogen (BUN) (68 mg/dL) : 5–25 mg/dL) and serum creatinine (2.8) (NR: 0.6–1.3 mg/dL), as well as a low estimated glomerular filtration rate (eGFR) of 23. His liver function tests (LFTs) were within normal reference ranges. A renal biopsy demonstrating severe interstitial nephritis with fibrosis was suspected by nephrology to be IgG4-related tubulointerstitial nephritis. At that time, he was diagnosed with stage IV chronic kidney disease (CKD). He quickly responded to high-dose steroids and was discharged on 20 mg/day of prednisone.During a rheumatology appointment in late 2016, the patient reported fatigue and severe, progressive pruritus over the past several months, interfering greatly with his quality of life. A diffuse, erythematous, confluent papular rash was observed on his back and arms. Dry eyes and mouth were also present, and his serum IgG was 506 mg/dL : 1–123 mg/dL). During this visit, the patient reported that a rash and severe, diffuse pruritus had started on his back and arms several years ago and was refractory to hydroxyzine, famotidine, moisturizing creams, dapsone cream, and topical corticosteroids. A prior biopsy showed interface dermatitis and perivascular inflammation with eosinophils. Steroid-sparing therapy with rituximab was initiated at the end of 2016. His rash and pruritus quickly improved, and his symptoms remained well-controlled after a steroid taper until November of 2019. His IgG4 level at that time was within the normal range (10 mg/dL). His pruritus later returned, and a hyperpigmented, scaling rash on his arms, back, and chest was identified. Rheumatology then placed a dermatology referral. Rituximab was continued through the middle of 2020 until he was hospitalized for suspected rituximab-induced neutropenia. He was discharged on 10 mg/day of prednisone without rituximab. His pruritus worsened over the next several months despite the addition of topical corticosteroids, and he presented to our dermatology clinic toward the end of 2020. His exam was remarkable for ill-defined, erythematous plaques on his abdomen A and darLab work was significant for peripheral eosinophilia, and a workup resulted in the following: a positive antinuclear antibodies test (1:80 nucleolar pattern); elevated absolute eosinophil count (AEC) (2820 cells/mcL) (NR: 30–350 cells/mcL); elevated IgE (281 IU/mL) (NR:1.5–144 IU/mL); normal adrenocorticotropic hormone, cortisol, and tryptase levels; and negative strongyloides and toxocara antibodies. A tangential biopsy of his abdomen demonstrated spongiotic dermatitis with mixed superficial and perivascular infiltrates with eosinophils A. An incGiven the constellation of conditions contributing to his pruritus, such as IgG4-RD, LA, and atopy, a course of dupilumab therapy was initiated at 600 mg as a loading dose followed by 300 mg biweekly injections. Worsening pruritus and erythema were reported after one month, and his AEC increased to 3610 cells/mcL. During this time, no changes in liver or renal function were observed and no new medications were initiated. One month later, his pruritus had significantly improved spontaneously, and his AEC was 580 cells/mcL. Three months after starting dupilumab, he noted further improvement in his pruritus, and his prednisone was tapered to 5 mg/day. His AEC was 220 cells/mcL, and his IgG was 382 mg/dL.At his 4-month follow-up appointment in early 2021, he reported a remarkable improvement in his quality of life. His LA demonstrated significant improvement , and hisGiven our patient’s clinicopathologic features and lab results, including peripheral eosinophilia and elevated IgE, we concluded his cutaneous findings and pruritus were compatible with a cutaneous manifestation of IgG4-RD that we termed IgG4-ADP ,12. AtteWhile the pathogenesis of IgG4-RD is not entirely understood, a T-helper 2 (Th2) immune response has been implicated, with interleukins (IL) 4, 5, 10, and 13 playing a role in IgG4 class switch, resulting in eosinophilia and elevated IgE. Dupilumab is an IL-4 and IL-13 antagonist that potentially inhibits Th2 IL production. In addition, dupilumab may inhibit IL-31 production, a cytokine implicated in pruritus [We report a case where dermatitis, itch, and peripheral eosinophilia were resolved with dupilumab treatment, with a significant improvement in quality of life sustained two years post-treatment initiation. This report provides additional insight into the pathogenesis of these diseases and further supports the efficacy of dupilumab in itch-related processes. Our patient experienced dramatically improved quality of life with initiation of therapy. Awareness of cytokines activated by IgG4 and how they manifest clinically and in ancillary studies is important for targeted therapy. Future clinical study of dupilumab and its use in the treatment of both systemic and cutaneous IgG4-RD in larger patient populations should be considered.This case report was not without limitations. Although skin biopsies cannot directly prove lesions are connected, the constellation of findings such as elevated eosinophils leading to pruritus and spongiotic dermatitis, as well as response to treatment, demonstrate evidence of a connection to IgG4-RD.


Physiotherapy, restrictions of physical activity, and weightbearing are part of the treatment of children with Legg–Calvé–Perthes disease (LCPD). Prescription practices are widely discussed and vary between pediatric orthopedic surgeons (POSs) and physiotherapists (PTs). The purpose of this study was to identify recommendations for treatment methods in clinical practice to find some consensus and elaborate guidelines.A web-based questionnaire including 3 cases of LCPD  was answered by 25 POSs and 19 PTs. They were asked to describe their preferred recommendations for physiotherapy, including stretching, strengthening, weightbearing, and physical activities in relation to, e.g., range of motion (ROM) pain, sex, and disease stage.ROM was considered to be important when recommending physiotherapy; PTs also recognized pain and disease stage. Sex was reported as a factor with low importance. Stretching exercises were recommended for all disease stages. Recommendations for strengthening exercises varied for the initial and fragmentation stages. None of the participants recommended total non-weightbearing. Most restricted trampolining, running, ball sports, and gymnastics in the first 2 stages of the disease and allowed swimming, short walks, cycling, and horse riding without restrictions for all stages.We found high agreement on recommending stretching exercises for all disease stages, but controversies regarding recommendations for strengthening exercises in the initial and fragmentation stages. No non-weightbearing treatment for the affected hip was recommended by any participants at any stage of the disease. There was no clear consensus regarding the appropriate timeline for resuming full activities. Legg–Calvé–Perthes disease (LCPD) is a pediatric hip disorder caused by ischemic necrosis of the femoral head ,2. ThereEarly in the pathologic process, the femoral head is vulnerable to mechanical forces, which might be responsible for its deformation ,5 and wePhysiotherapy has been shown to improve articular range of motion (ROM)  and muscThe aim of this study was to identify the recommendations for physiotherapy, physical activity, and restricted weight-bearing when treating children at different stages of LCPD in Sweden.https://www.project-redcap.org/), a web-based application for online surveys, containing a general section followed by 3 patient cases (see Supplementary data). Both quantitative and qualitative questions were included in the survey to achieve a view of the participants’ recommendations regarding physiotherapy (stretching and strengthening exercises) and physical activity in children with LCPD.A cross-sectional survey was created in Research Electronic Data Capture , and location of current practice. Questions on knowledge of any guidelines for physiotherapy or physical activity for children with LCPD and which factors the participant considered important when recommending physiotherapy and physical activity were also included. Factors were rated from 0 (not important) to 5 (very important) and included age at onset, ROM, sex, pain, lateral pillar classification (only for pediatric orthopedic surgeons [POSs]), and LCPD stage (see Supplementary data).The second part of the survey consisted of 3 typical patient cases at different stages of the disease according to the Waldenström classification: initial stage, fragmentation stage, and re-ossification stage  Figure .The questions covered recommendations regarding stretching exercises, strengthening exercises, weight-bearing restrictions of the affected hip, and restrictions of physical activities for each stage of the disease. The physical activities included leisure and sports activities, such as short (< 1 km) and long walks (> 1 km), swimming, cycling, horse riding, cross-country skiing, ball sports, gymnastics, trampolining, and school sports. For each activity, participants were asked to choose between 4 options: do not allow, allow with restrictions, allow, and recommend. Each question was reviewed in detail to ensure that the questions were understandable. Furthermore, the survey underwent 2 pilot tests on different occasions to confirm high quality.The Checklist for Reporting Of Survey Studies (CROSS) was applied.Members (n = 104) of the Swedish Pediatric Orthopedic Society (SBOF) and the Swedish Association of Physiotherapists as well as PTs affiliated with pediatric orthopedic departments in Sweden were invited to participate in this web survey. They received information concerning data collection, storage, and the purpose of the study, and they were asked to give consent to the publication of the survey’s results.Statistical analyses were performed using SPSS version 1.0.0.1508  and GraphPad Prism 9 . Data was analyzed with descriptive statistical methods using means, medians, and ranges.10.2340/17453674.2023.18341This study was approved by the Regional Ethical Review Board . The data that supports the findings of this study is available from the corresponding author (YDH) upon reasonable request. No funding was received. The authors declare no potential conflicts of interest. Completed disclosure forms for this article following the ICMJE template are available on the article page, doi: Responses from 33 POSs and 37 PTs were registered. 3 POSs and 13 PTs did not answer the first 2 mandatory questions (survey terms and whether they see children with LCPD), and 5 POSs and 5 PTs reported that they do not see children with LCPD. Therefore, 25 responses from POSs and 19 responses from PTs were included in the analysis . 2 remin20 of 25 POSs and 16 of 19 PTs reported that they treat ≤ 10 children with LCPD each year, and 2 of 25 POSs treated more than 20 patients annually. The mean work experience reported was 21 years (range 5–40 years) for POSs and 18 years (range 3–29 years) for PTs. Most of the POSs (23 of 25) were practicing in Sweden, representing 18 of the 27 hospitals that treat patients with LCPD. 1 POS was practicing in Iceland and 1 in the United Arab Emirates (both SBOF members). Two-thirds of the participants in both groups were not aware of any guidelines recommending physical activity for patients with LCPD.ROM was scored as an important factor by most of the POSs (21 of 25), followed by the age at onset (12 of 25), and the patient’s pain (11 of 25). Sex was considered as not important by 16 of the 25 participants and opinions regarding the importance of the disease stage or the Lateral Pillar classification varied. When recommending leisure and physical activities, ROM (19 of 25), patient’s pain (12 of 25), and age at onset (10 of 25) were considered important, whereas the patient’s sex was considered not important (15 of 24). Similarly, opinions concerning the importance of the disease stage or the Lateral Pillar classification varied .High agreement in recommending stretching exercises among the POSs was observed for all 3 patient cases; the highest score was given for the re-ossification stage . Only 1 POS did not recommend stretching exercises at all. Most POSs agreed on offering both a home program and referral to a PT in all 3 patient cases . There was high agreement on not only using a home program.Strengthening exercises were prescribed with an increased trend for each disease stage . For the initial stage, 10 of 19 POSs did not recommend strengthening exercises. Similar to the stretching exercises, most participants used both home programs and referral to a PT . There was high agreement on not using only a home program. Muscle groups that were recommended to stretch and strengthen are presented in For case 1 and case 3, most POSs reported weightbearing as tolerated  and only 2 POSs reported restricted weightbearing in each case. For the fragmentation stage (case 2), only 14 of 18 POSs reported weightbearing as tolerated, and 4 reported restricted weightbearing on the affected hip. None of the POSs recommended non-weightbearing for any of the cases.Most of the POSs did not impose any restrictions on the duration of activity . Only 1 POS reported restrictions on the duration of activity in the initial stage, and 1 POS in the re-ossification stage.In the initial stage, most POSs discouraged high-impact sports either completely or allowed these with restrictions. However, opinions varied on other activities. A similar pattern was seen for the fragmentation stage. For the re-ossification stage, agreement on whether to allow or restrict these activities was lower compared with the earlier 2 stages .There was high agreement on recommending low-impact sports. Opinions varied on returning to other activities. Some POSs remained cautious but others either allowed or even recommended these activities. The number of years in practice of the POSs showed no impact on the recommendations or restrictions given.In contrast to the POSs, PTs rated the patient’s pain as the most important factor when prescribing physiotherapy, followed by LCPD stage and ROM. Opinions varied regarding age at onset and sex .In accordance with the POSs, there was high agreement in recommending stretching exercises for all 3 patient cases. Most of the PTs recommended stretching at least once a day, and in the reossification stage half of the PTs proposed at least once a day and a third at least 3 times a week. PTs recommended strengthening exercises to a greater extent than POSs, mainly in the initial stage. Most of the PTs proposed strengthening exercises at least 2 to 3 times a week.In contrast to the POSs, higher consensus was found among PTs in restricting activities in the initial and fragmentation stages. In the re-ossification stage, agreement among PTs was higher than among POSs in restricting activities such as running, ball sports, alpine skiing, gymnastics, and trampolining.Activities that were allowed or recommended for the initial and fragmentation stages included swimming, cycling, horse riding and short walks, in agreement with the POSs. In addition, cross-country skiing and skating were approved for the re-ossification stage by both groups.PTs were asked about a recommendation on assistive devices. Mostly crutches and wheelchairs were prescribed in all 3 cases. Other devices mentioned were walking aids, walking frames, bicycles, and strollers. For case 3, more than half would not prescribe any assistive device.The aim of this survey was to gain valuable insight into the current recommendations for physiotherapy, physical activity, and weightbearing among POS and PTs when treating children at different stages of LCPD in Sweden. The study showed that ROM was considered to be important when recommending physical activity. Our study showed some inconsistency within professions and between POSs and PTs. This may be explained by different experiences and beliefs that might be important for the patient.Sex was reported as unimportant when recommending physiotherapy or leisure and sports activities, suggesting that participants do not treat girls differently, even though female sex has been shown to be associated with a worse outcome . ROM in Stretching was recommended by the participants for all 3 disease stages, which is in line with the survey by the British Society for Children’s Orthopaedic Surgery . In SwedWhether the strengthening exercises should be included early is not established in the literature. However, we found high agreement in recommending strengthening exercises first in the re-ossification stage with a special focus on the abductor muscles.Interestingly, there was 100% agreement in not recommending strict non-weightbearing of the affected hip, indicating a united approach by the participants on a matter that remains controversial internationally . This isWe showed inconsistencies regarding precautions, which might be problematic for both patients and parents as shown by Leo et al. , i.e. thThe response rate was difficult to determine because the survey was sent to all members of the professional societies (Swedish Pediatric Orthopedic Society and the Swedish Association of Physiotherapists). However, not all members treat pediatric patients or patients with LCPD specifically. The answers received were geographically dispersed, which implies that the participants with a special interest in treating patients with LCPD were represented by those hospitals with the competence to treat LCPD. In addition, most participants had long work experience, with none less than 5 years, and only 6 POSs with less than 12 years of work experience. Another caveat is the choice of cases that differed in several characteristics such as age, sex, disease stage, and clinical presentation, including surgery. Even though we intended to present typical cases, it may still be difficult to draw final conclusions based on these examples.When recommending physical therapy, ROM is considered to be important; PTs also recognize patients’ pain and disease stage as important. We found high agreement in recommending stretching exercises for all disease stages, but there are controversies regarding recommendations for strengthening exercises for the initial and fragmentation stages. Further, non-weightbearing treatment for the affected hip was not recommended at any stage of the disease but high consensus was found in discouraging high-impact activities in the initial and fragmentation stage and allowing swimming, short walks, cycling, and horse riding without restrictions for all stages. There was no clear consensus regarding the appropriate timeline for resuming full activities.The study confirms the necessity to identify which exercises and activities are the most beneficial for each stage and to give clear and consistent recommendations to children and parents. National and international guidelines should be created to ensure equal healthcare for all children with LCPD.10.2340/17453674.2023.18341The questionnaire distributed to pediatric orthopedic surgeons and physiotherapists is available on the article homepage, doi: Click here for additional data file.


The patient was diagnosed with IgG4-related pericarditis. Glucocorticoids resolved serological and imaging abnormalities. Prompt treatment improves the disease status.IgG4-related pericarditis has rarely been reported. Here, we report a case of IgG4-related disease that presented with pericardial effusion. A 67-year-old female who presented with palpitations and chest pain was admitted because of a large amount of pericardial effusion that required drainage. The patient underwent pericardial drainage, and the symptoms were gradually alleviated. IgG4 levels were elevated in the serum and pericardial effusions. A biopsy specimen of  IgG4-realated disease (IgG4-RD) is a relatively rare autoimmune disorder associated with elevated serum IgG4 concentration, lymphoplasmacytic infiltration of IgG4-positive plasma cells, and storiform fibrosis in various organs. Here, we present a case of IgG4-RD presenting with pericardial effusion.A 67-year-old female presented to our hospital with palpitations and chest pain. The patient had a history of asthma and diabetes mellitus (DM). Computed tomography (CT) revealed a large amount of pericardial effusion, and the patient was admitted .μL, eosinophil of 790/μL, total protein concentration of 9.3 mg/dL, C-reactive protein (CRP) concentration of 1.53 mg/dL, and N-terminal probrain natriuretic peptide (NT-proBNP) of 223 pg/mL. IgG and IgG4 levels were markedly elevated in the serum  and pericardial fluid . The IgE levels were also elevated (271 IU/mL). Elevations in viral antibody and tumor marker levels and serum autoantibodies related to collagen diseases were not observed. Electrocardiogram revealed a sinus tachycardia. The patient underwent pericardial drainage, and her symptoms were gradually alleviated. Positron emission tomography (PET)/CT revealed 18F-fluorodeoxyglucose (18F-FDG) uptake in the pericardium and submandibular gland  and an IgG4-positive/IgG-positive cell ratio of 40%  one or more organs showing diffuse or localized swelling or a mass or nodule characteristic of IgG4-RD, (2) serum IgG4 levels greater than 135 mg/dL, and (3) positivity for two of the following three criteria: (1) dense lymphocyte and plasma cell infiltration with fibrosis, (2) ratio of IgG4-positive plasma cells/IgG-positive cells greater than 40% and the number of IgG4-positive plasma cells greater than 10 per high-power field, and (3) typical tissue fibrosis, particularly storiform fibrosis, or obliterative phlebitis . Horie eMost patients with IgG4-related pericarditis show a rapid clinical response to steroid therapy , 9 and wThe diagnosis of IgG4-related pericarditis is often difficult based on histological analysis. PET/CT helps identify IgG4-related organs and is useful for evaluating the efficacy of steroid therapy for IgG4-related diseases.