The flexural strength of Slender steel tube sections is known to achieve significant improvements upon being filled with concrete material; however, this section is more likely to fail due to buckling under compression stresses. This study investigates the flexural behavior of a Slender steel tube beam that was produced by connecting two pieces of C-sections and was filled with recycled-aggregate concrete materials (CFST beam). The C-section’s lips behaved as internal stiffeners for the CFST beam’s cross-section. A static flexural test was conducted on five large scale specimens, including one specimen that was tested without concrete material (hollow specimen). The ABAQUS software was also employed for the simulation and non-linear analysis of an additional 20 CFST models in order to further investigate the effects of varied parameters that were not tested experimentally. The numerical model was able to adequately verify the flexural behavior and failure mode of the corresponding tested specimen, with an overestimation of the flexural strength capacity of about 3.1%. Generally, the study confirmed the validity of using the tubular C-sections in the CFST beam concept, and their lips  led to significant improvements in the flexural strength, stiffness, and energy absorption index. Moreover, a new analytical method was developed to specifically predict the bending  strength capacity of the internally stiffened CFST beams with steel stiffeners, which was well-aligned with the results derived from the current investigation and with those obtained by others. The usefulness of various types of concrete-filled steel tube (CFST) has been proven in modern composite structural projects since they have achieved better performances  than the corresponding conventional concrete/steel members under axial and flexural loading ,2,3,4. IParticularly, the adequacy of using the Slender steel tube section  in the concept of CFST beams has been previously investigated ,12,13,14The research topic of CFST has received considerable attention over the past few years from a wide range of structural engineering scholars. A dependent stress–strain model was developed for the CFST column . The fleIn recent years, engineers have been increasingly utilizing the recycled aggregate generated from the demolition of existing materials and waste materials in the field of construction ,32,33,34uM) of the internally stiffened CFST beam’s cross-section with varied numbers/sizes of steel stiffeners; this constitutes one of the main novelties of the current research work. Therefore, five CFST specimens were prepared for this purpose and were experimentally tested under pure flexural loading, including one specimen without concrete filling material (hollow tube section). The finite element (FE) ABAQUS software was used to develop and analyse an additional 20 models that were designed to examine the effect of further parameters that were not explored experimentally.The main objectives of this research can be highlighted as follows: The first aim was to examine the suitability of using the new concept of cold-formed tubular cross-sections fabricated from two pieces of galvanized C-sections (face-to-face connection) in the Slender CFST beam’s system, in which the lips of these C-sections are expected to behave as internal steel stiffeners along the top and bottom flanges. Second, this research project aimed to explore the behaviour of the proposed Slender CFST beams, specifically when recycled-aggregate concrete mixture is used instead of the normal concrete mixture, in order to reduce the self-weight and cost of the beam’s section. Lastly, to date, all of the theoretical methods for predicting the flexural strength of CFST beams were developed according to different standards, and they were mostly intended to be applied for beams with conventional tube sections (unstiffened sections). As such, this study aimed to develop a new analytical method that can theoretically predict the flexural strength capacity , maximum elongation (%), ultimate tensile strength (uf), and elastic modulus (sE) were 489 N/mm2, 27.4%, 558 N/mm2, and 201 × 103 N/mm2, respectively, and these results were obtained from the direct tensile of coupons test.Steel tube: Three coupons were cut from the cold-formed C-sections and prepared in accordance with the ASTM-E8/E8M-2009 standard. The average results of the yield tensile strength (3), and RAC (4.75–16 mm) with a density of 1278 kg/m3; these densities were much lower than that of the raw coarse aggregate (1490 kg/m3). As explained earlier, the first concrete mixture was prepared without the use of any recycled aggregate . The second concrete mixture (RC30) was prepared by replacing 30% (by volume) of the raw coarse aggregate by EPS beads only. Meanwhile, the concrete mixtures RC50 and RC70 were also made by replacing 30% of the raw aggregate with EPS beads and adding another 20 and 40%  of RAC, respectively, bringing the total replacement to 50 and 70%, respectively. In addition, silica fume (SF) material was used to enhance the bonding performance between the cement and EPS beads, as previously advised in [Concrete mixtures: the recycled aggregates used in the suggested concrete mixtures were EPS beads (4–6.3 mm) with a density of 9.5  showed the inward tube’s buckling failure at the support points only, wherein the failure of tube’s webs was increased gradually by increasing the applied load, as shown in Furthermore, the 20 mm lips located at the top and bottom edges of the prefabricated cold-formed C-sections were well bonded with the concrete core, thus implying that these lips functioned sufficiently as internal stiffeners for the top and bottom flanges of the steel tubes of these filled specimens. Therefore, the outward buckling failure occurred only at the half-width of their top flanges see b. These uM), and the moment vs. strain relationships of the tested specimens. The relationships between the bending moment and the deflection at mid-span for the tested specimens are compared in uM values, after which these curves behaved as elasto-plastics up to the loading limits of about 70–80% of their uM values . Thus, due to further outward buckling failure, the same moment–deflection curves showed fully plastic behaviour with continual slow decreases. The uM value of the filled specimens was recorded at the deflection limit of eL/50 e− L/60 [uM) was achieved, at which the bottom flanges started to buckle inwardly at the supporting points; furthermore, as a result of extreme tube buckling failure, the loading curve began to descend.This section discusses the flexural behaviour, ultimate moment capacity ; these values were 53.7 kN·m, 52.6 kN·m and 51.5 kN·m, for specimens FB-RC30, FB-RC50 and FB-RC70, respectively. In addition, it was noticed that, regardless of the aggregate replacement percentages, the concrete filled tubular specimens achieved much higher flexural strength capacity values as compared to the capacity of the hollow specimen (HB), with a strength improvement of about 363 to 381%. It is worth mentioning that the self-weight of the tube beam was substantially increased due to the addition of the filled concrete; however, the flexural strength was remarkably enhanced, as stated above (363–409%). From the structural engineering point of view, this represents a very important finding regardless of the increment of the weight, and, in this case, the role of the structural engineer, who can prospectively determine scenarios in which this would be reliable for the targeted purpose of construction projects. On the other hand, the cost was also found to be a vital element in the construction design when we compared the concrete cost with the steel cost; this was the case because, in global terms, the cost of 1 ton of steel is about 15–20 times the cost of 1 ton of concrete material.The Furthermore, the moment vs. longitudinal tensile strain relationships obtained at the mid-span of the steel tube of the filled specimens are presented in iK) and serviceability stiffness (sK) levels of tested specimens are usually measured from the moment vs. mid-span curvature relationships [uM and 0.6uM, respectively. The iK and sK values of the tested specimens are presented in 2 and 1121 kN·m2 for iK and sK, respectively. These values increased to 2216 kN·m2 and 1924 kN·m2 for the FB-RC0 specimen due to the influence of the normal concrete infill material. In general, similar flexural stiffness improvement behaviours were recorded for all of the filled recycled concrete materials , but with slightly lower values than that of FB-RC0, since they had lower concrete modulus (cE) values. For example, compared to the FB-RC0 specimen (0% aggregate replacement), the FB-RC70 specimen, which was filled with recycled concrete (30% EPS plus 40% RAC) achieved lower iK and sK values . From the above discussion, it can be concluded that even when using the recycled aggregate in the concrete infill materials of the cold-formed CFST beams, the flexural stiffness can nevertheless be significantly improved, to a far greater degree than that of the corresponding hollow tube beam.The initial stiffness  analysis. In order to reduce the time conception of the analyses of the models, a typical 3D quarter model was built to simulate the actual tested CFST specimen, as shown in The main component materials of the currently developed FE CFST models are the concrete infill and the steel tube (double C-sections). For the concrete component, the C3D8R element type was used, which has eight nodes integrated with six degrees of freedom, while, for the steel tube components, the type S4R shell element was used. The penalty friction coefficient of 0.75 was adopted in the current FE analysis to realise the mechanical interaction between the surfaces of the steel and concrete parts. In general, several parameters that mainly affected the proper friction coefficient values, such as the loading type, the size/shape of the beam’s cross-section, and the properties of the materials were selected ,56,57,58Consequently, the material properties of the steel tube and concrete components of the FE model were the same as those of the corresponding tested specimen. Generally, the concrete material is considered to be a brittle material since it cracks under tension-related stress and is crushed under compression stress . Thus, tThe validity of the current FE models was confirmed via the corresponding experimental results; almost all of the filled specimens with varied concrete mixtures achieved similar behaviours and close flexural strength capacities. Thus, the FB-RC30 specimen (a steel tubular beam filled with a recycled concrete mixture of 30% EPS beads) was selected to verify the relevant FE model. The numerical analysis showed that the moment vs. mid-span deflection relationship of the FB-RC30 (FE) model sufficiently agreed with that of the corresponding tested specimen (FB-RC30), as shown in uM, iK and sK values derived from their FE analyses.After confirming the validity of the developed CFST model, additional models were built and analysed to investigate the influence of further parameters. In particular, the effects of varied tube thickness (1.0 mm to 3.0 mm), concrete infill strength (14.6 MPa to 55.0 MPa), steel yield strength (275 MPa to 550 MPa), and steel tube depth (150 mm to 250 mm) were studied, and these were categorized into groups A, B, C and D, respectively. In iK and sK values improved significantly with the increases in the steel tube’s thickness and/or the depth of the studied models (group A and D), while very limited improvements were recorded when only the concrete compressive strength was increased (models in Group C). For example, the FB2-A model achieved iK and sK values of 2375 kN·m2 and 2125 kN·m2, respectively. These values were improved by about 50–55% (3575 kN·m2 and 3285 kN·m2) when only the tube’s thickness increased from 1.5 mm to 3.0 mm (FB5-A). Moreover, the stiffness iK and sK values of the FB1-B model were improved by about 18–19% (2819 kN·m2 and 2529 kN·m2) when only the cuf value increased by about three times (from 14.6 MPa to 45 MPa).The stiffness values of the analysed FE models are given in uM) of the analysed FE models are given in uM values; these improvements were even more significant than the effects of tube’s depth (Group D). Meanwhile, increasing the strength of the concrete infill led to limited improvements in their uM values. This can be considered a reasonable outcome since the tube’s thickness directly increased the overall area of the steel cross-section, including the internal stiffeners (the lips of the C-sections) at the top and bottom beam’s flanges. Similar outcomes have been recorded in other studies for the conventional CFST beams that were investigated here [uM value of 55.4 kN·m; this value was increased to about 30.6% (72.4 kN·m) and 60.3% (88.8 kN·m) when only the tube’s thickness was increased to 2.0 mm and 2.5 mm, respectively. Meanwhile, the same uM value (55.4 kN·m) for the FB1-B model, in which concrete infill of 14.6 MPa strength was used, was increased by about 12.2% (62.2 kN·m) when a three-times-higher compressive strength was used .The ultimate bending strength capacities  obtained from existing experimental and numerical approaches. The theoretical expressions that are presented in the AIJ-1997 [sE and sI are the modulus of elasticity and moment of inertia, respectively, for the steel part. cE and cI are the modulus of elasticity and moment of inertia, respectively, for the concrete part. The C1 is a reduction factor for the concrete stiffness part, which is taken to be 0.6 in EC4-2004, and 0.2 in AIJ-1997. However, in the ANSI/AISC 360-10 standard, the C1 value is estimated to be 0.6 + 2s/(As + Ac)A, but should not exceed 0.9. The cE value in Equation (1) is 9500 ck +(f 8)1/3, 4700 c)0.5 for the EC4-2004, AISC-2010 and AIJ-1997 standards, respectively. Furthermore, the theoretical methods developed by Han et al. [iK and sK) were adopted.This section evaluates the currently known flexural stiffness values , and the experimentally and numerically obtained values (obtainedK), are compared in iK) are slightly overestimated by the theoretical prediction, which is acceptable since it is within ±20% [K-AIJ) as compared to the other standards and methods, since this standard uses the lowest concrete stiffness redaction factor (C1 = 0.2). Additionally, the EC4-2004 and ANSI/AISC 360-10 standards showed a more conservative prediction for the stiffness values (K-EC4 and K-AISC) at the serviceability level (see iK and sK).The predicted values of flexural stiffness  values obtained for the tested and analysed CFST models were evaluated, using the existing theoretical methods given by EC4-2004 [uM values of the currently investigated beams and models are compared, using the above theoretical methods , with those obtained from the current experimental and numerical investigations, including six models analysed by others [uM values of the investigated CFST beams and models, with reasonable coefficient of variation (COV) values, since these methods were mainly developed for conventional CFST beams . In u-EC4M achieved a mean value (MV) of 0.643. However, u-HanM and u-ZandM achieved higher MVs, which were 0.740 and 0.734, respectively, since these two methods took into account the effects of the total area of the steel (s)A of the CFST beam’s cross-section. The above comparison confirmed that the lips of the C-sections used in the Slender CFST beams investigated in this study behaved as internal steel stiffeners, which led to sufficient improvements in their flexural strength capacities [The ultimate flexural strength -to-thickness (t) ratio, usually known as the slenderness ratio (λ), is used as a limit for this classification in the majority of related standardised codes. In the current study, the slenderness limits that are specified in ANSI/AISC 360-10 [nM) and the slenderness ratio (λ) of the cross-section of CFST beam’s tube. First, the tube’s cross-section was classified as a “Compact section” if the λ value was within the limits of the compactness ratio (pλ), which was equal to 2.26 (sE/yF)0.5. Second, if the value of λ was larger than that of pλ, but within the limits of the noncompactness ratio (rλ), which was equal to 3.0 (sE/yF)0.5, then the tube’s cross-section was classified as a “Noncompact section”. Third, when λ exceeded the limit of rλ but was within the limits of the maximum ratio (limitλ), which was equal to 5.0 (sE/yF)0.5, then the cross-section of the CFST beam’s tube was classified as a “Slender section”. This was the case because the ANSI/AISC 360-10 code does not permit the use of Slender CFST beams if their λ values exceed the maximum limit (limitλ).Generally, the cross-sections of steel tubes are classified into Compact, Noncompact and Slender sections based on their ability to buckle under compression stress. The tube’s effective-width (C 360-10  (ChapternM) was developed based on the fundamental theory of stress block diagrams of CFST beams that are internally stiffened with steel stiffeners, as shown in i.This method was limited to rectangular CFST beams with internal stiffeners under pure static bending.ii.The shear span-to-depth ratio was assumed to have no significant effects on the CFST beam’s deflection behaviour ,61.iii.Full interaction between the concrete infill and the steel tubes/stiffeners was assumed ,51,61.iv.effw) was used instead of the overall effective tube width (effW) for estimation of the stiffened slenderness ratio (st = weff/tλ). In another words, (st = weff/tλ) was used instead of (eff/tλ = W) for the classification.In the classification of the stiffened steel tube of the CFST beam, the effective flat width between the web and stiffener  at both the tension and compression zones. The concrete compression stress was assumed to be within the limits of the ultimate strength (cuf) and distributed as a rectangular stress block to the N.A. position.Compact section see a: this six.yF [cuf and distributed as a triangular stress block to the N.A. position.Noncompact section see b: this sFy ,64. The x.yF at the maximum tension face and within the limits of the buckling stress (crF) at the maximum compression face [cuf.Slender section see c: this sion face ,64. For xi.nM for each section classification could be expressed as follows:Finally, when the forces over the stiffened CFST beam’s cross-section attained equilibrium see , the sumIn this study, a novel analytical method for the prediction of the nominal moment (stλ) and the λ values in uM values obtained from the current study and the additional models analysed in [nM), with MV and COV values of 0.831 and 0.049, respectively, as compared to the existing theoretical methods shown in Accordingly, the embedded steel stiffeners that were provided to stiffen the sections of the CFST beams/columns significantly reduced the flat distance of their tube’s flanges/walls, which led to a delay in the tube’s buckling failure, as discussed earlier in this paper and previously confirmed in the literature ,22,47. Olysed in , the new➢The experimental investigation confirmed that the bending capacity of the suggested prefabricated Slender CFST beams made from two pieces of C-sections was enhanced by about 3.7 times even when filled with 70% replacement recycled concrete material.➢Under the static bending load, the prefabricated tubular steel beams (double C-sections) filled with recycled concrete  behaved very similarly to the conventional CFST beams. Additionally, the lips of these C-sections were adequately bonded to the concrete and acted as internal stiffeners for the Slender CFST beam’s cross-section, which delayed the outward buckling failures at their top flanges. For example, the use of recycled aggregate to replace raw aggregate at a proportion of up to 70% resulted in slightly lower flexural stiffness and strength capacity values (−7.2% to −10.7%) compared to those obtained using normal concrete.➢Generally, it is worth highlighting that the suggested fabricated steel tube beams’ self-weight was increased substantially due to the effect of concrete infill materials. In turn, the flexural strength capacities of these beams were remarkably enhanced, by approximately 409% and 363%, when using normal concrete and 70% recycled concrete mixtures, respectively. These findings are very important from a structural engineering point of view as, regardless the increment of the beams’ self-weight, they can be used to prospectively determine the scenarios in which this composite system would be reliable for the targeted purpose of construction projects. Cost also played a vital role in the construction design process, which was demonstrated when we compared the cost of the concrete and steel sections in the local market.➢The flexural behaviour of tested CFST beam was accurately simulated using the ABAQUS software. The results obtained from the non-linear analyses of FE CFST models that were prepared for investigation of various parameters confirmed that slightly increasing the thickness of the tubes in these models had a major influence on their flexural strengths and stiffnesses as compared to the effects of other parameters. In contrast, a limited degree of influence was achieved when the compressive strengths of the concrete infill material and/or the yielding strengths of the steel tubes were increased.➢Lastly, the newly developed analytical method achieved the best prediction of the flexural strength capacities of the internally stiffened CFST beams that were tested and analysed in this study, since it was able to independently consider the influence of internal steel stiffeners along with the effects of the properties of steel tubes and concrete. However, this method was found to only be reliable for the internally stiffened rectangular CFST beams.The conclusions of the investigated CFST beams are summarized as follows:It is worth highlighting the main research limitation of the current investigation, namely that the uncertainties related to this model could be further examined as they are very significant in terms of the parameters of structural behavior. In addition, further experimental/numerical investigations, other than the rectangular cross-sections under static/dynamic loading scenarios, could be conducted on the stiffened CFST beams.


The growth of the construction industry has led to the greater consumption of natural resources, which has a direct or indirect negative impact on the environment. To mitigate this, recycled or waste materials are being used as a partial substitute in the manufacture of concrete. Among these waste materials is cement kiln dust (CKD), which is produced during cement production. This study investigated the potential benefits of replacing part of the cement with CKD in two construction applications, i.e., plain concrete and cement blocks. This reflects positively on cost, energy, and the environment, since putting CKD in a landfill damages agricultural soil and plant respiration. In this study, an experimental program was carried out to study how replacing various percentages of ordinary portland cement (OPC) with CKD affected the compressive strengths, the tensile strengths, and the air contents of concrete and cement blocks. Although the results showed that the compressive and tensile strengths decreased as the amount of CKD increased, the air content of the concrete increased, which showed that 5% CKD was suitable for such applications. The results were used to propose two equations that approximate the concrete and cement block compressive strengths according to the CKD replacement percentage. Over the past few decades, the demand for construction materials has increased due to the worldwide growth of construction projects. Unfortunately, this demand is fulfilled by the overconsumption of natural resources endangering the environment . AccordiMałek et al.  investigExperimentally, Chalangaran et al.  improvedOne of waste materials that researchers have used in concrete is CKD, a fine powdery material resulting from cement manufacture. Studies showed that the greatest health danger in cement production comes from dust, and several studies have been conducted by references ,9,10,11 The environmental concerns related to portland cement (PC) production and emission and the disposal of CKD are becoming progressively significant, because 80% of CKD ends up in landfills. The extreme contamination of the surrounding environment highlights the need to find more environmentally friendly ways of disposal.Using CKD as a partial replacement in PC is currently fraught with difficulties, and many of its applications continue to be investigated, for example, as a component in cement, an agricultural fertilizer, a soil and wastewater stabilizer, a partial replacement of soda in glass production, an antistripping agent in asphalt, and a subgrade for highway construction as stated by Shervan .Maslehuddin et al. ,14 studiRavindrarajah et al.  studied Abo-El-Nien et al.  studied Al-Harthy et al.  investigHeikal et al.  studied This research effort was designed to open new industrial areas for recycled CKD. Two main construction applications were studied in this experimental work program. The first was the effect of CKD replacement on plain concrete strength and air content. In this application, three different groups were investigated. The first group consisted of concrete samples tested for concrete compressive strength after being prepared with 0%, 2%, 5%, 8%, 10%, 15%, and 20% CKD replacements. The second group consisted of concrete samples prepared with 0% and 5% CKD replacements and tested for tensile strength. To test the effect on air content, the third group included concrete samples prepared with 0%, 5%, 10%, 15%, and 20% CKD replacements.The second construction application was related to hollow cement blocks. Cement block specimens were prepared with 0%, 10%, 15%, 20%, and 25% CKD replacements and tested to study their effect on compressive strength and water absorption. The values are represented in the database to form equations that reflect the impact of the CKD% on the compressive strength.An experimental program was conducted to study the influence of replacing a percentage of OPC with CKD in 120 specimens divided into two groups: the specimens of the first group were used to measure the most important parameters of concrete, and those of the second group were used to scale the effect on cement blocks. The amount of CKD in the mix was expressed as a percentage of the total weight of cement in the mix. The types of test and specimen numbers and details are listed in The materials used in this research were untreated raw CKD collected from electrostatic precipitators and OPC products from a Madina cement factory . A comparison between the chemical compositions of CKD produced from the Madina cement factory with the CKD limits standard in the UK is illustrated in The percentage of sulfate, as well as alkalinity, chloride, and silica concentrations, was within acceptable limits, according to this analysis. On the other hand, the chemical composition of cement varied based on raw materials and the manufacturing processes used. The quantity of decarburization of the calcium carbonate in the clinker-making raw materials was reflected in the level and variability of the loss on igniting the CKD.The concrete mixture can be designed in a number of ways, but the British Standard (BS) mix was used in this study since it is concerned with cube compressive strength. Using the coefficient of variation and the lowest strength as a percentage of the mean strength, the BS technique defined the characteristic strength. This approach also took into account the influence of the fine aggregate on the determination of the fine-to-total aggregate content in the mix by ensuring that the aggregate grading followed the grading zones.w/c) ratio of 0.5) that is thoroughly compacted, correctly cured and cast with various types of cement and coarse aggregate and tested at various ages. The specified quantities are sufficient just for plain concrete.The approach, suitable for OPC (type I), uses a hypothetical concrete mix with a moderate cement content (a water/cement (w/c ratio (0.48), the cementitious material content (250 kg/m3), and the fine/total aggregate ratio (0.33) were all components. The relative density and the bulk density of the aggregate were measured and found to be 2.65 and 1645 kg/m3 for coarse and 2.70 and 1750 kg/m3 for fine aggregate.The fine and coarse aggregates used in the mix were graded using sieve analysis in accordance with BS 882:1983. The coarse aggregate size varied from 20 to 5 mm sieve size, while the fine aggregate size ranged from 5 to 0.61 mm. The The design, treatment, and control conditions of the concrete mixes, with and without CKD, were the same according to BS 1881-108 . To ensuA traditional slump test was used to determine the consistency of fresh concrete and the temperature. Specimens of a 150 mm cube were prepared from each concrete mix to be tested in compression after 28 days. During the concrete placement, a vibrating table was used to verify that the concrete was fully compacted. After 24 h, the cube specimens were demolded and submerged in water, until they were examined. Six cubes (150 mm × 150 mm × 150 mm) were cast from each mix and cured in clean water for 28 days. Compression tests were performed on standard cubes according to BS 1881-116 .The crushing load was measured using a Universal Hydraulic Testing Machine with a capacity of 2000 kN to evaluate the compressive strength of a concrete sample as illustrated in The compressive strength results found experimentally for the 42 cubes were averaged and are listed in The CKD describes fine-grained, extremely alkaline particulate material mostly made of oxidized, anhydrous, micron-sized particles. The bulk of prior research has found that fine CKD particles have greater sulfate and alkali concentrations and less lime content . As a reThis study was performed to investigate the influence of replacing cement with CKD up to 5% on concrete tensile strength. Concrete mixes with and without CKD were mixed, treated and controlled under the same conditions. The components were combined in a dry condition for about a minute. For a further two minutes, all of the ingredients were mechanically combined to guarantee the homogeneity of the mix.The conventional slump test measured the consistency of fresh concrete. Standard cylinders with a diameter of 150 mm and a height of 300 mm were prepared from each concrete mix according to ASTM C31 [All the molds were placed on a vibrating table while placing the concrete to ensure full compaction, and 6 cylinders were cast from each mix. After 48 h, all cylinder specimens were demolded and immediately submerged in potable water for 28 days. As shown inIn this study, a total of 12 cylinders were tested to investigate their tensile strengths after replacing cement with CKD. The main factor considered in this study was the percentage of CKD replacement (0% and 5%). The results are listed in The gross air contents of 15 concrete specimens were determined using the same mix that was previously used to determine compressive and tensile strength. The tests were performed using the pressurized technique according to ASTM C231  for fiveThe results are recorded in These data showed that up to 5% CKD replacement can be ignored. When it was increased to 10%, the air content increased by 24%. In the last two cases, i.e., 15% and 20% CKD replacements, the air content rose by 33% and 43%, respectively, compared to the control mix.N/mm2). The expression for R is also given by R = (Vc + kVd)/Vw, where Vc, Vd, and Vw are the volumes of cement, kiln dust, and water, respectively, and k is the cementing efficiency factor and written as:3); 3); w/c; and The results of this investigation for the concrete compressive strength effect were in accordance with the results of a previous study ,33. Accok, w/c ratios, and the strengths after 28 days were plotted to derive the strength and w/c relationship curve [w/c ratios for mixtures with different CKD percentages.To obtain ip curve . The resN cement: 53.5 N sand: 113 N coarse aggregate. To reach a uniform mixture, the ingredients were mixed in a dry state for about three minutes, after which water was gradually added. The blocks were mixed and formed mechanically as shown in The study was conducted according to ASTM C140 . Twelve In this part of the investigation, four different percentages of CKD were used: 10%, 15%, 20%, and 25%. The blocks with and without CKD were treated, controlled and cured under the same conditions until compression testing after 28 days, as shown in 2, respectively.The results of the compression test are listed in By applying the regression analysis reported by reference  to the eThe present study was concerned with an analysis of the percentage of water absorption of hollow cement blocks (200 mm × 200 mm × 400 mm) with and without CKD conducted with respect to ASTM C140 .The sequence of block formation was performed using the same procedure described in the previous section. The blocks were kept in an electronic oven under 100 °C for 24 h, weighed, subjected to the same drying conditions in the oven for half an hour and then reweighed to ensure that the weight did not change. The blocks were immersed in water for 24 h and then weighed at the end of that time.The results from both stages are shown in It can be seen that having more than 5% CKD had a significant impact on the sample properties. Therefore, it is recommended that a replacement of 10% CKD can be used with an acceptable reduction in concrete and block strength.CKD has a detrimental impact on compressive strength, as evidenced by the fact that as the amount increased, the compressive strength of the concrete and cement block specimens decreased. An equation corresponding to each was presented to anticipate this reduction.Regarding the concrete tensile strength, there was no significant difference between 0% and 5% CKD, which was only approximately 3%.In the concrete mix, the percentage of air content from 0% to 5% CKD replacements made no difference; however, when CKD was increased to 10%, 15%, and 20%, it increased by 24%, 33%, and 43%, respectively.The percentage of water absorption due to partial replacement by CKD in cement blocks can be increased up to 25% within the allowed limits.This research demonstrates that CKD can be used as a primary component in concrete  and cement block products.The effects of CKD in plain concrete on compressive strength, tensile strength, and air content were studied, while the effects of CKD in cement blocks on compressive strength and water absorption were investigated. The experiments revealed the following:


IgG4-related disease is a rare immune-mediated disease that can involve many organs in the body. The lymph node is also where IgG4-related diseases occur, but its histological structure is different from that of other organs. For this reason, pathologists have difficulty diagnosing IgG4-related lymphadenopathy. If there were specific imaging findings of IgG4-related lymphadenopathy, it would be of great help to pathologists. A 64-year-old male visited our hospital with right ankle pain. On physical examination, the right lower extremity showed severe swelling with wound dehiscence, and infection was suspected. On CT  taken at the lower extremity, multiple enlarged lymph nodes were incidentally noted in the right inguinal area. On ultrasonography, a “starry night sign” resembling hyperechoic follicles was observed in the enlarged lymph node. A core needle biopsy was performed, and IgG4-related lymphadenopathy was diagnosed. Laboratory examination showed hypergammaglobulinemia with marked elevated serum IgG4, corresponding to IgG4-related disease. Chest and abdominal imaging were evaluated, but there was no extranodal IgG4-related disease. IgG4-related lymphadenopathy showed a very unique ultrasonography imaging finding. The cortex was filled with diffusely scattered hyperechoic foci and some bright foci gathered to form a follicle. This imaging finding may help diagnose IgG4-related lymphadenopathy. Immunoglobulin G4 (IgG4)-related disease is a recently discovered, rare immune-mediated condition with infiltration by abundant IgG4-positive plasma cells . The panWhile extranodal IgG4-related diseases characteristically show specific pathologic findings such as dense lymphoplasmacytic infiltration, storiform fibrosis, and obliterative phlebitis in a hematoxylin and eosin stain ,5,6,7, IFor evaluation of lymphadenopathy, ultrasound (US) is the modality of choice to evaluate superficial regions including the head and neck, axilla, and inguinal area ,9,10. ItIn the present case, we describe computed tomography (CT), magnetic resonance (MR), and characteristic US imaging findings of a patient with right inguinal and popliteal lymph nodes as the only affected site for an IgG4-related disease.Our study was approved by our Institutional Review Board, and informed consent was waived. A 64-year-old male came to the emergency room at our institution for right ankle pain. He was diagnosed with psoriasis 22 years ago and had a history of 4 surgeries on the right ankle for fracture and septic arthritis within the last 3 years. On physical examination, the right lower extremity showed diffuse and severe swelling with redness and heating sensation, and there was wound dehiscence at both the medial and lateral ankle. The range of motion of the right ankle was near full, and motor and sensory abilities were normal.Laboratory examination showed a normal range of white blood cell counts (5.51 k/µL) and eosinophils (0.19 k/µL). C-reactive protein (42.74 mg/L) and erythrocyte sedimentation rate (77 mm/hr) were elevated, suggesting inflammation. In addition, hemoglobin level (11.0 g/dL) and creatinine (0.44 mg/dL) were low.The patient underwent right lower extremity CT for the evaluation of cellulitis. Chronic osteomyelitis with acute aggravation was suspected in the distal tibia and calcaneus with diffuse subcutaneous swelling extending from the foot to the distal thigh. In addition, there were multiple enlarged round-shaped lymph nodes in the right external iliac and inguinal areas with a shorter diameter of 0.8–2.1 cm . BecauseHistology showed follicular hyperplasia with many plasma cells . ImmunohConsequentially, chest CT, abdominal CT, and pelvic MR  were taken to look for other affected organs. There were no organs around the external iliac and inguinal chain to suspect an IgG4-related disease. Size of pancreas was normal, and there was no evidence of involvement in the hepatobiliary tract, kidneys, retroperitoneum, salivary glands, or lung parenchyma. On MRI, the cortex was very thick in the right inguinal and external iliac lymph nodes, and the signal was decreased on T2WI compared to the lymph nodes on the contralateral side . No follThe patient underwent below-knee amputation for ankle osteomyelitis and cellulitis. Systemic corticosteroid therapy was recommended to the patient after controlling the infection of the lower leg, but the patient refused treatment, and follow-up was lost.In this case, the patient showed multiple enlarged lymph nodes of the unilateral inguinal and external iliac chain. In ultrasonography for inguinal lymph nodes, a characteristic appearance of a “starry night sign” was seen. A biopsy was performed on the inguinal lymph node, and immunohistochemical staining revealed many IgG4-positive plasma cells. On hematologic examination, serum IgG4 was markedly increased.IgG4-related diseases are immune-mediated fibroinflammatory diseases that may cause irreversible organ damage, resulting in life-threatening events. IgG4-related diseases can involve nearly all organ systems, including the pancreas, hepatobiliary tract, lacrimal glands, salivary glands, retroperitoneum, kidneys, thyroid, muscle, and lymph node ,3,12. CoThe lymph node is an organ frequently involved in IgG4-related disease ,6,11. FiA proper radiologic feature of IgG4-related lymphadenopathy may be helpful because it is not easy to diagnose IgG4-related lymphadenopathy. The characteristic morphologic features of an IgG4-related disease are known to be as follows: dense lymphoplasmacytic infiltration, storiform fibrosis, and obliterative phlebitis ,5,6,7. HThe “starry night sign” in the present case is thought to be reminiscent of a follicle visible inside the lymph nodes on pathological tissue. However, since we performed a core needle biopsy rather than resection, there was a limitation on matching pathological tissues and US imaging findings directly, and further evaluation with a larger cohort is required. CT and MR imaging only demonstrated multiple enlarged lymph nodes with a round/oval shape, fatty hilum, and cortical thickening without the internal follicles mentioned above.In conclusion, we present a rare case of IgG4-related disease with involvement localized only to a lymph node, which showed a unique ultrasound finding of a starry night sign. When a starry night sign is seen in an enlarged lymph node, IgG4-related lymphadenopathy could be considered, and this imaging finding may help in diagnosing IgG4-related lymphadenopathy.


This study investigates the use of crushed glass waste as partial cement replacement in ordinary concretes. Six concrete mixes were designed and prepared: a reference without substitution and five substitution percentages of crushed glass waste ranging from 5% to 25%. The made concrete mix design underwent different tests, namely: slump test, mechanical strength, thermogravimetric analysis (TGA), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) determination and finally, water porosimetry, in order to evaluate the influence of the use of crushed glass waste on the properties of fresh and hardened concrete. Mechanical strengths results show that the use of 15% of the crushed glass waste improves the mechanical strength. TGA analysis confirms this result by highlighting a higher hydration degree. The latter contributes to the reduction of the porosity and, consequently, the mechanical strength increases. Also, it can be caused by the increasing amount of chromium which, if added a little, accelerates the hydration of C3S and leads to an increase of the mechanical strength. The BET technique and porosimetry tests showed that the use of crushed glass waste reduces the global porosity of concrete. This is due to the filling effect of the glass powder. The comelm (t): the water mass related to the cement at the instant « t » [kg];mc: the anhydrous cement mass added to the sample [kg];m145°C→1100°C(t): sample mass loss between 145 °C and 1100 °C in [kg];Δm600°C→800°C(t): sample mass loss between 600 °C and 800 °C in [kg];Δd,m145°C→1100°C(t): instrument drift between 145 °C and 1100 °C in [kg];cm: the anhydrous mass of cement introduced into the sample in [kg];LOI: ignition loss of the anhydrous cement in [%];samplem: Initial mass of the sample in [kg];W/C: water/cement ratio [%];S/C: sand/cement ratio [%];A/C: mineral addition/cement ratio [%];Wel(∞): amount of water required for complete hydration of the cement [%]. This amount of water is estimated according to the composition of the cement by Bogue equations.The TGA is used to study the influence of the addition of glass powder on the hydration degree of the studied materials. The device used in our study is the SETARAM type TG-DTA 92. The hydration degree α (t) of cement is then calculated from Equation (2) ,30:(2)α 2 (g/g of cement) present in the cement paste is calculated from the mathematical expression (6) [m400°C→500°C(t): sample mass loss between 400 °C and 500 °C in [kg];Δd,m400°C→500°C(t): instrument drift between 400 °C and 500 °C in [kg];The mass content of Portlandite Ca(OH)sion (6) :(6)mCa2.A diffractometer type X’PERT PRO PANalytical was used to analyze the mixes studied in the form of fine powders < 100 µm. The measurement conditions are as follows: 10° < 2subM”. Always saturated, the samples are then weighed in air and thus the mass of the saturated samples obtained “airM”. At this stage, the sample is placed in an oven at a temperature of 105 °C, until the mass of the sample stabilizes, which will then be assumed to be dry. If this mass stabilization is achieved, then the mass of the dry sample is obtained “dryM”. The porosity “ε” is then calculated as follows:Open porosity is considered as an essential parameter with respect to the concrete’s durability. Water porosimetry was carried out according to the AFPC-AFREM procedure . To do tSorption measurements combined with Brunauer–Emmett–Teller (BET) theory allow the determination of the specific surface area and pore size distribution from desorption isotherms. The test involves placing a sample in a closed volume, with a certain gas pressure, where an increase in the mass of the solid is observed accompanied by a decrease in the gas pressure. This increase in mass, which is proportional to the quantity of gas adsorbed, depends on the temperature T, on the pressure of the gas P and on the chemical nature of the solid/gas pair. During the test, the amount of adsorbate retained on the surface of the solid equilibrates as a function of the pressure of the gas (Activity in the gas phase). The representation of the set of equilibrium states corresponding to pressures between 0 and the saturated vapor pressure (P0) is called the sorption isotherm. This curve is characteristic of the adsorbent/adsorbable couple studied. Before starting the analysis, the samples are degassed at 200 °C for 1 h and then weighed. For all samples, the measurements were carried out with nitrogen, the latter acts as the adsorbable at its normal liquefaction temperature. The activity in the gas phase expressed in grams or mol of adsorbent per unit mass of solid adsorbent is represented as a function of the relative pressure P/P0. The interpretation of adsorption-desorption isotherms by the BET method makes it possible to determine the average pore size distribution and the specific surface area of the sample.d: the average pore diameter;R: the gas constant;V: nitrogen molar volume;T: nitrogen temperature;γ: the surface tension of nitrogen;θ: the contact angle.An estimation of pore size distribution can be obtained from desorption isotherms by using Kelvin formula and Laplace equation, which aim at determining the average pore diameter ,33.(8)dAs: the specific surface area;mn: the number of moles of adsorbate in a monolayer;m: the sample mass in grams;a: the cross-sectional area of the adsorbate molecule of nitrogen;A: Avogadro’s number.NThen, the specific surface area is obtained according to the following formula (9):Slumps of fresh concrete with Abrams cone are presented in 2/g, compared to that of cement (3310 cm2/g) and consequently leads to low slumps. Also with the increase in the glass volume in the mixture results in an important frictions between solid grains due to the angular shape  that provide the concretes strength. Also, it can be caused by the excess of the amount of chromium supplied by the glass powder. The addition of chromium to cementitious materials with moderate quantities causes an increase in the mechanical strength. When the amount of chromium exceeds a certain percentage, it causes an opposite effect and consequently slows down the hydration of the cement grains ,36.To better illustrate the improvement of strength of mixed concrete B5%; B10% and B15% comparing to BT; B20% and B25%, TGA analyses were performed. Hydration degrees and amount of portlandite obtained from thermogravimetric analysis at 28 days of cure are given in The histogram of hydration degrees given in From a percentage of 15%, it has been observed that the hydration degree and compressive strength decreases in spite of the increase in the glass powder amount. It can be seen in Also, it can be caused by the excess of the amount of chromium which slows down the hydration of the cement grains when its amount exceeds a certain percentage ,36. To bThe spectrograms obtained were treated using X’Pert High Score software to determine crystalline phases using ICDD “International Centre for Diffraction Data” cards See .2) and ettringite that are the result of hydration reactions. Also the presence of anhydrous cement grains in the mixtures. The results of XRD measurements were analysed using the Rietveld method [The spectrograms obtained from XRD analysis show the presence of portlandite (Ca(OH)d method . It was d method . The amod method ,34. The d method ,40 and/od method  which arAccording to XRD results, we can conclude that, the addition of 15% of glass powder in concrete decreases considerably the amount of portlandite due to pozzolanic reactions of silica and portlandite. This phenomenon is considered as an advantageous gain limiting the concrete degradation after its curing toward sulphate attacks and chloride ions .The specifications for the formulation of concretes take into consideration the mechanical properties as well as the fresh properties of these materials. The material’s porosity is the first indicator of concrete durability towards external aggressions. 2 equal to 0.9835.From the results illustrated in The average pore diameter of the reference concrete BT is almost 162 nm, whereas that of concrete containing 15% of glass powder is 95.3 nm. This is due to (i) the pozzolanic potential of glass powder to produce more C-S-H which densifies the structure of the concrete and improves its connectivity, and (ii) to the filling effect of the glass powder particles due to its high fineness compared to that of cement, thereby reducing capillary pore size and concrete porosity. Beyond a substitution percentage of 15%, a significant increase in the average pore diameter accompanied by an increase in porosity is observed. This is mainly due to an insufficient amount of cement which serves to maintain the compactness of the mix from the initiation of hydration process .3. Most of this price is the cost of the cement which is about from 30% to 35% of this price (c.a. 30 Euro/m3). The cost of the waste glass powder has been assumed as 10% of replaced cement price which is about 3 Euro/m3. The calculation of price of prepared concrete mixtures with waste glass powder and the decision ranks of the compressive strength and the cost of the cementitious composite mixtures are presented in In order to choose the most effective cementitious composite mixture the ranking method has been selected. The two analysed properties were cost of the material and compressive strength of concrete for all of the investigated mixtures including the reference sample. The assumption of the price of concrete was made based on average market values of concrete in European Union which is about 100 Euro/m3.Analysing the results presented in Presented in this article the laboratory tests proved that there is possible to obtain a mixture by incorporating the waste glass powder into the concrete, which has positive effect in terms of physico-mechanical properties. It has been proved by performing the analyses of the compressive strength, hydration degree and porosity. It was observed that both properties (hydration degree and porosity) strongly correlate with the compressive strength of cementitious composite with waste glass powder. Also the second goal was achieved, because using for this purpose waste glass powder obtained in the process of utilization of the glass bottles decreases the price of the concrete and it is environmentally friendly. It has been evaluated using the ranking method and proved the positive effect of the economical aspect, in terms of quality/price, of using waste glass powder as an admixture.The incorporation of glass powder directly influences the mechanical strength at 7 and 28 days of age. Replacing cement with dosage of 5%, 10% and 15% of cement by waste glass powder increases the value of compressive strength obtained at 7 and 28 days of age. Replacement of 15% cement by glass powder shows the highest compressive strength in comparison to the other substitution percentages. This is may have considered as the optimal dosage;TGA analysis shows that cement replacement by glass powder with dosage 15% and less increases the hydration degree of concrete. This is due to a small amount of chromium oxide contained in glass powder. These compounds accelerate the hydration reactions of cement particles. However, increasing the dosage of waste glass powder more than 15% has an opposite effect and the rapid decrease of the hydration degree was observed;XRD analysis of concrete mix design B15% highlighted the decrease of the intensities of portlandite peaks and confirmed the pozzolanic potential of glass powder that is considered as an advantage to limit the concrete degradation after its curing toward sulphate attacks and chloride;The results of BET analysis have shown that the cement replacement by glass powder up to 15% has reduced considerably the average pore diameter and therefore the concrete porosity.Results obtained through this study, highlight the following main points:It would be desirable to complete this study by further investigations on the microstructure morphology of the obtained concrete and its relationship with permeability, which governs aggressive agent penetration within the concrete . This wo


With the onset of the coronavirus disease 2019 (COVID-19) pandemic, pediatric primary care delivery changed rapidly. Prior studies have demonstrated a reduction in ambulatory encounters and antibiotic prescriptions with the pandemic onset; however, the durability of these reductions in pediatric primary care in the United States has not been assessed. We conducted a retrospective cohort study to assess the impact of the COVID-19 pandemic and associated public health measures  on antibiotic prescribing and encounter volume in 27 pediatric primary care practices, and the duration of these changes. Patients under age 19 with an encounter from January 1, 2018 through December 31, 2020 were included. The primary outcome was monthly antibiotic prescriptions per 1000 patients, in the overall population and a subset of encounters with infectious diagnoses, including respiratory tract infections (RTIs). Interrupted time series (ITS) analysis was performed.There were 60,562 total antibiotic prescriptions from April to December in 2019 and 14,605 antibiotic prescriptions during the same months in 2020, a 76% reduction. The reduction in RTI encounter prescriptions accounted for 91.5% of the overall reduction in prescriptions from 2019 to 2020. Using ITS analysis, there was an immediate decrease from 31.6 to 7.4 prescriptions/1000 patients (predicted means) in April 2020  . This was followed by a stable rate of antibiotic prescriptions that remained flat through December 2020. For RTI encounters, a similar pattern was seen, with a decrease by 21.8 prescriptions/1000 patients; 95% CI: -29.5, -14.2) . Encounter volume also decreased immediately, and while overall encounter volume began returning to a pre-pandemic baseline volume toward the end of the study period, RTI encounter volume remained persistently lower through December 2020 .Figure 1. Antibiotic prescriptions per 1000 patients prescribed by month from January 2018 to December 2020, overall and for disease-specific subgroupsRTI = respiratory tract infection; UTI = urinary tract infection; SSTI = skin and soft tissue infection. Months are numbered sequentially, starting with January (number 1). Dashed line indicates first full month of the pandemic, April 2020.Interrupted time series analysis for antibiotic prescriptions per 1000 patients by month from January 2018 to December 2020 for (A) all antibiotics as well as antibiotics prescribed at encounters with (B) respiratory tract infections (RTIs), (C) urinary tract infections (UTIs), and (D) skin and soft tissue infections (SSTIs)Intervention starts in April 2020 (dashed line). Months are numbered sequentially, starting with January (number 1). Dashed line indicates first full month of the pandemic, April 2020.Antibiotic prescriptions per 1000 billed encounters by month from January 2018 to December 2020 for (A) all encounters, as well as antibiotics prescribed at encounters with (B) respiratory tract infections (RTIs), (C) urinary tract infections (UTIs), and (D) skin and soft tissue infections (SSTIs)Months are numbered sequentially, starting with January (number 1).Dramatic reductions in antibiotic prescribing in pediatric primary care during the COVID-19 pandemic were sustained through 2020, primarily driven by reductions in RTI encounters.All Authors: No reported disclosures


Recently, filamentous fungi have been recognized as high-potential microorganisms for this application as their hyphae grow in an interwoven three-dimensional network which serves as nucleation site for CaCO3 precipitation to heal the crack. This potential is corroborated by the current state of the art on fungi-mediated self-healing concrete, which is not yet extensive but valuable to direct further research. In this review, we aim to broaden the perspectives on the use of fungi for concrete self-healing applications by first summarizing the major progress made in the field of microbial self-healing of concrete and then discussing pioneering work that has been done with fungi. Starting from insights and hypotheses on the types and principles of biomineralization that occur during microbial self-healing, novel potentially promising candidate species are proposed based on their abilities to promote CaCO3 formation or to survive in extreme conditions that are relevant for concrete. Additionally, an overview will be provided on the challenges, knowledge gaps and future perspectives in the field of fungi-mediated self-healing concrete.Concrete is the most used construction material worldwide due to its abundant availability and inherent ease of manufacturing and application. However, the material bears several drawbacks such as the high susceptibility for crack formation, leading to reinforcement corrosion and structural degradation. Extensive research has therefore been performed on the use of microorganisms for biologically mediated self-healing of concrete by means of CaCO Reinrability . As cracrability , the prombustion . In othe2 and portlandite (Ca(OH)2)  carbonation and (ii) the further hydration of unhydrated cementitious material near the cracks , 10. Car3) is considered as one of the most suitable self-healing products [3 on sand grains [3-producing biomineralization, they are considered to be efficient strengthening [3 and healing of the crack [3 precipitation takes place at the microbial cell wall surface that serves as nucleation site [Thanks to its efficient bonding capacity and high compatibility with cementitious materials, given its autogenous presence, calcium carbonate  influence on the survival and growth of the fungal spores, as they will not be incorporated in the concrete mix.The concrete structures targeted for applications with fungi-mediated self-healing are the ones subjected to or in contact with water and salts such as chlorides, which can be harmful to the steel reinforcement, and where access for repair or maintenance is limited. Examples of such structures are water-retaining walls, bridges, marine structures, wastewater treatment plants, tunnels and underground parking garages. However, existing structures can be targeted as well, in which case cracks could be healed by means of a repair mortar or spray containing fungal spores (and possibly nutrients), as already done with bacteria. This investigation will already give first insights on CaCO3 precipitation in concrete are explained, applications of biomineralization processes in practice are given and a list of potential candidates is identified. Finally, the challenges, knowledge gaps and future perspectives for fungal-based self-healing concrete are discussed.In this review, we present a comprehensive overview of the state-of-the-art of microbial self-healing of concrete, thereby drawing a conceptual framework, which is required to summarize and further explore the potential of filamentous fungi for this biotechnological application. The review paper starts with the state-of-the-art of bacteria-based self-healing concrete, followed by fungi. From this point onwards, the focus is placed on fungi only. Conceptual principles and hypotheses on fungal CaCOBacillus species are used [2)2) into ammonium (NH4+) and carbonate (CO32−), which then react with Ca2+-ions that are sequestered by the bacteria from the concrete environment and deposited on their negatively charged cell wall surface. The reaction subsequently leads to the precipitation of CaCO3 at the cell wall surface.The use of bacteria in concrete self-healing by means of MICP is well-established. Typically, endospore-forming chemoorganotrophic are used . Two maj4+ is known to be an environmental pollutant and poses a health risk for animals and humans [2 production and calcium carbonate precipitation [However, not all bacteria are capable of synthesizing urease and, depending on the application, the growth and survival of many ureolytic bacteria can be inhibited . Furtherd humans . Therefopitation , is a mopitation , 37–40. ., bacterial spores were encapsulated into hydrogels: the bacterial and non-bacterial series resulted in a maximum healed crack width of respectively 0.5 mm and 0.3 mm and in a decrease in water permeability of respectively 68% and 15–55% on average [The direct addition of bacterial spores and nutrients to the concrete mix has been shown to result in a decreased intrinsic compressive strength of the material and in a loss of viability of the spores . The red average . The use average , a susta. used silica gel to immobilize ureolytic bacteria while at the same time filling the cracks before the start of CaCO3 crystal precipitation inside the matrix [Besides adding bacterial spores in the concrete mix, existing concrete infrastructures can be targeted as well by applying a spore-enriched repair mortar or repair spray in the crack. In the latter case, the previous stated issues related to the mechanical forces, pore diameter size, alkaline environment and the limited availability of oxygen and nutrients do not apply, thus increasing the chances for an effective self-healing procedure. Van Tittelboom et ale matrix . After pe matrix .The study of bacteria-based self-healing of concrete has gone beyond lab-scale experiments. Successful field trials have been performed for different types of structures and repair techniques , 33. TheTrichoderma reesei and Aspergillus nidulans were investigated [Umbelopsis dimorpha and Pseudophialophora magnispora [T. reesei and A. nidulans belong to the phylum Ascomycota, which differs from the phylum Basidiomycota in many aspects besides morphological features, as recently discussed from a phylogenetic perspective [Despite successful developments in the use of bacteria for biogenic crack repair in concrete, applications are not yet far-reaching. An extension towards other microbial hosts is the way forward and given the versatile lifestyles and morphologies of filamentous fungi, these appear to be promising candidates to target. Recently, pioneering studies have been performed with different fungal strains to investigate their eligibility for the concrete self-healing application , 23, 35.gnispora . These sspective , 43. Forspective , 45.T. reesei germinated on concrete and resulted in the growth of mycelium, which grew equally well with or without concrete [A. nidulans [pacC gene encoding a pH regulatory transcription factor thereby generating an alkalitolerant phenotype compensating for the alkaline concrete environment [A. nidulans is a biosafety level 1 fungus, and its genetic engineering opens new prospects for applications within the context of the circular economy such as concrete self-healing [Fusarium oxysporum was also able to grow on a layer of hardened concrete and precipitate CaCO3, SEM images and FTIR (Fourier Transform Infrared Spectroscopy) spectra confirmed spore germination and the presence of CaCO3 and calcium oxalate monohydrate, resulting from the fungal metabolism [T. reesei, A. nidulans and F. oxysporum are Biosafety Level 1 (BSL 1) fungi [Initial growth set-ups were made to investigate the compatibility of fungal growth with the concrete environment and in case growth was observed, X-ray diffraction (XRD) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM–EDX) were used to determine if calcite precipitation had occurred , 15. XRDnidulans , however-healing . Howevertabolism . FTIR istabolism . Notably1) fungi .3 through either induced biomineralization (metabolism-dependent) and/or organomineralization (metabolism-independent) processes , (ii) the sequestration of cytoplasmic Ca2+ into specific organelles (Ca2+organelles) and (iii) binding to calmodulins (CaM) and calcineurins (Ca2+proteins) [2+-ATPase are transporters capable of sequestering calcium and directing it to different organelles, such as vacuoles, Golgi and ER, decreasing cytosolic calcium levels [2+ levels, forming a Ca2+/CaM complex. This complex becomes the binding target for several other proteins that activate specific kinases and initiate signalling cascades [2, oxidation of organic acids, nitrate assimilation or urea mineralization [2+ concentrations may result in cytotoxicity [3 to decrease the excess of intracellular Ca2+ concentration [Fungi are involved in the promotion of mineral precipitation of CaCOses Fig. . Inducedkalinity  Fig. 2)3 throughell wall , 51. Calroteins) . The pumcascades . Calcinelization . Overalllization –55. Impotoxicity . Fungi mntration  and thus3 precipitation through organomineralization relies on their metal-uptake or biosorption capability thanks to the presence of chitin, a long-chain N-acetylglucosamine polymer, in their cell walls, which confers structural rigidity to the cell [2+-ions , thus reducing the activation energies required for nuclei formation [2+-ions will then react with CO32−-ions resulting in the precipitation of CaCO3 on the hyphae. This process is metabolism-independent and could thus occur for both metabolically active and inactive fungi [Fungi-mediated CaCOthe cell . Chitin the cell –59 , thereby representing an extreme habitat in which growth of most other organisms is restricted [Paecilomyces lilacimus and Chrysosporium spp., which are able to grow at a maximum pH value of 11 [A special focus can be placed on alkaliphiles, which grow well at pH values higher than pH 9, with optimal growth typically observed at a pH value between 10 and 13, whereas slow or no growth is observed at near-neutral pH values , 79. Alkstricted , 80. Exaue of 11 .Neurospora crassa mediates the formation of calcite in urea- and calcium-containing media [Penicillium chrysogenum CS1 was isolated from cement sludge and shown to promote the formation of biosandstone by calcite precipitation [Another criterium for species selection is the inherent metabolic capability of performing MICP, such as the presence of urease. For example, it was demonstrated that the ureolytic fungus ng media : here, mpitation . For thePlectosphaerella cucumerina, Clonostachys rosea, Cephalotrichum oligotriphicum and C. guizhouense were isolated [Based on the poor nutritional status of the concrete environment, oligotrophic fungi could be selected. For example, oligotrophic fungi can be found in natural habitats such as caves, characterized by constant low temperature, high humidity, lack of organic matter and darkness . This tyisolated . Interes. investigated the microbial diversity of moonmilk, a type of speleothem found in limestone caves. Speleothems are secondary deposits in caves and are composed of one or a mixture of the minerals calcite (CaCO3), aragonite (CaCO3) and gypsum (CaSO4·2H2O) with calcite the most prominent [Mortierella to be dominantly present in moonmilk.Park et alrominent . As recerominent , the autAspergillus, Aureobasidium, Cephalosporium, Fusarium, Monilla and Penicillium [Another oligotrophic environment are rock substrates due to the scarcity of nutrients and moisture and their exposure to solar radiation . Epi- anicillium .. isolated two ascomycota fungi from a calthemite straw stalactite growing from a concrete ceiling of a building, Paecilomyces inflatus and Plectosphaerella cucumerina [P. inflatus and pure calcite in the presence of P. cucumerina [Finally, anthropogenic habitats could be explored for the presence of fungal species with potential for concrete self-healing. Pasquale et alcumerina . After lcumerina .3 formation with the fungi T. reesei, A. nidulans and F. oxysporum, the current state-of-the-art is still lacking in-depth and more elaborated research. The methods by which fungal spores can be implemented in the concrete mix remain unexplored; up till now, no literature exists on the addition of fungal spores during the mixing process of concrete. Both direct addition and encapsulation methods can be considered, each giving rise to new research questions. Can fungal spores survive the harsh concrete environment? How should the nutrients be added? Which concentration of fungal spores (and nutrients) can be added without compromising concrete’s mechanical properties? In case of encapsulation, which techniques can be applied to fungi? Can the protective barrier simultaneously act as a nutrient? Additionally, concrete can have many different compositions, each of them affecting the spores’ survivability and growth capabilities in a different way, thus imposing an additional challenge. As a result of this knowledge gap, the organism’s influence on the mechanical, physical and chemical properties of concrete has not yet been investigated, neither the organism’s growth capabilities when surrounded by a concrete environment. Consequently, no research exists on the crack width that could possibly be healed with the help of fungi. However, thanks to their high biomass yield and growth rates, it is aimed to heal cracks with a width larger than 1 mm. Nevertheless, the potential of various eligible fungal candidates remains undetermined and currently only three fungal species have shown favourable results. The fungal growth rate and the associated CaCO3 precipitation rate in concrete remain unknown as well, although they play a crucial role in the protection of the concrete material against the entry of water.Despite the promising initial proof of concept studies demonstrating growth and CaCO3 precipitation upon crack formation. Results can be compared with direct addition of the spores. This kind of research will allow the investigation of other knowledge gaps, such as the maximum crack width that can be healed and the efficacy of the precipitated CaCO3. Furthermore, research on bacteria-fungi interactions for CaCO3 precipitation is inexistent but could potentially mediate challenges encountered with both bacteria and fungi. In nature, bacteria and fungi co-inhabit in harsh and stressful environments [3 has been described in the literature  their capability of forming extensive network-like structures, (ii) their high biomass yield providing abundant nucleation sites for CaCO3 precipitation both directly and indirectly, (iii) their nutritional versatility, (iv) their capability of growing in harsh environments relevant for concrete, (v) superior wall-binding and metal-uptake ability because of the presence of chitin in their cell walls, and (vi) the inherent hydrophobicity of fungal cells.This review provides conceptual principles and insights into the potential of fungi for self-healing of concrete cracks with a focus on fungal biomineralization processes, while providing an overview of potential fungal candidates suitable for the application. In contrast to bacteria, filamentous fungi grow in extensive mycelium networks with branched filamentous-shaped hyphal structures that enable to fill and deposit CaCO


Aptly enabled by recent developments in additive manufacturing technology, the concept of functionally grading some cementitious composites to improve structural compression forms is warranted. In this work, existing concrete models available in Abaqus Finite Element (FE) packages are utilized to simulate the performance of some cementitious composites numerically and apply them to functional grading using the multi-layer approach. If yielding good agreement with the experimental results, two-layer and three-layer models case combinations are developed to study the role of layer position and volume. The optimal and sub-optimal performance of the multi-layer concrete configurations based on compressive strength and sustained strains are assessed. The results of the models suggest that layer volume and position influence the performance of multi-layer concrete. It is observed that when there exists a substantial difference in material strengths between the concrete mixes that make up the various layers of a functionally graded structure, the influence of position and of material volume are significant in a two-layer configuration. In contrast, in a three-layer configuration, layer position is of minimal effect, and volume has a significant effect only if two of the three layers are made from the same material. Thus, a multilayered design approach to compression structures can significantly improve strength and strain performance. Finally, application scenarios on some structural compression forms are shown, and their future trajectory is discussed. The support for automation and complexities in design, in the architecture, engineering, and construction (AEC) industry, underpinned by a fast-paced concrete science and a materials engineering niche, are driving significant and rapid research in additive manufacturing (AM)  and consECC, a special class of concrete mix, is renowned for its tensile strain-hardening behavior and tensile ductility because constituent materials like fiber, fly ash, and microsilica  are beinA performance-driven approach (PDA) is required in structural design and infrastructure construction to reap the benefits of the multitude of materials studied and developed over time. PDA is simple, conforming structural design and material used to a set of the performance function. While the concept of PDA is not new, the reluctance to apply it in real projects lingers . Often tThe urgent need to cut down global carbon emissions coupled with advances in AEC has led to a significant rise in interest in functionally graded concrete (FGC) ,30. FGC,The mechanical performance of a new concrete structure or mix is primarily studied by experimentation. These tests make it possible to evaluate the structural performance of materials in basic geometries of cubes, cylinders, and rectangular beams. Considering the current AM technology, the compressive performance of 3D printed concrete cubes is expected to be lower than mold cast samples because of the inadequacies of the filament layer interface, zero compaction approach, and unavoidable voids that develop during the printing process ,6,40. MoExisting FE tools, such as Abaqus CAE, can utilize experimental data from concrete testing, converted into model inputs, enabling design, analysis, and numerical performance evaluation and prediction. Many studies have been carried out on the flexural performance of FGCs. However, very few studies consider the application of FGC in compression forms, and none exists on the compressive performance of multilayered cementitious composites. In this work, glass fiber and microsilica dominant cementitious composites are developed and test their performance tested. These materials are modeled in Abaqus, and their results are compared to experimental performance. The validated material model is applied to numerical studies on FGC in compression by the multi-layer approach. The rest of the paper is presented as follows: To manufacture and assess the mechanical performance of 3D concrete samples, the concrete mixes’ pumping and shape retention requirements had to be satisfied, ensuring minimal geometric deviation of hardened samples. Therefore, the mixes’ shape retention index (SRI) is determined as the ratio between the bottom width of an extruded paste filament and the printer nozzle’s width. The ingredients used include: fine granite aggregates, with particles up to 98% passing 2 mm sieve and a specific gravity of 1.95. GF, OPC, Grade 42.5, microsilica, rapid hardening cement with a specific gravity of 3.1, water reducing agent (polycarboxylic acid series) with a water reduction rate of 20–25%, and expansion agent: alkali content 0.4% fineness 10% powder were also used. The chemical composition of the microsilica used in the mix is shown in 3 of rapid hardening cement, 0.1% vol. water reducing agent, and 0.35% vol. sulphoaluminate-based expansion agent is utilized in the mix to compensate for the shrinkage caused in concrete due to hydration, and 270 kg/m3 of water was used. After sufficient consistency is attained, the mix is introduced into the 3D printer’s material hopper, i.e., uniform rheology that satisfies good 3D printing buildability thorough mixing of the concrete mix materials to attain a suitable viscous blend that minimizes bulging or collapse in its fresh state and geometric deviation of hardened samples.The 3D modeled cube is transferred to the 3D printer software  interface and oriented to an appropriate print direction, as shown in Then, the printing is executed using a robotic arm, extrusion type concrete 3D printer by CIIC, Model HC1008 , as illustrated in After printing, a normal curing method was applied. The specimens were left to harden for 24 h at room temperature while covered with plastic sheets to minimize evaporation. Afterward, the specimen was cured in a water bath for 28 days at about 28 °C. A compressive strength test on the cube samples was carried out by loading them perpendicular to the print direction, the Z-direction, as shown in Concrete can be modeled in commercial FE software using applied damage theories. The ability to transform experimental data into numerical material models has improved studying complex isotropic materials like concrete. Concrete damage models (CDM) can simulate concrete degradation resulting from the microstructural coalescence of micro-cracks under applied load. The behavior of the degrading concrete under load can be evaluated using failure theories such as the continuum damage mechanics theory (CDMT). CDMT is concerned with the representation of the failure of materials, modeled as a continuous mass rather than as discrete particles to illustrate the initiation, propagation, and fracture of solid materials without resorting to microscopic constitutive details that are complex for practical engineering purposes such as analysis and predictions ,47. OfteOne of the popular CDMs, based on CDMT, is concrete smeared cracking (CSC). Smeared crack models adopt cracking as distributed effect with directionality. The cracked material is simulated as a continuous medium with anisotropic properties arising with each crack opening at each integration point . VariousWhen concrete is loaded in compression beyond its elastic regime in the CSC model, it develops inelastic non-recoverable strains. If it is unloaded before the failure point, the reloaded elastic response will be softer than the initial. However, the model assumes that the post-failure response in tension is governed by damaged elasticity, not unrecoverable or permanent straining (plasticity), thus allowing cracks to close and open when the loading changes from a tensile to a compressive state and vice versa. Tensile degradation is determined by a crack detection surface, as shown in Another CSC-based concrete model is the MFC model available in Diana FEA V10.5. It is a combination of three concrete models: the Total Strain crack model (TSM), the elastoplastic damage model (EPM), and the Maekawa Cracked concrete (MCC) curves. TSM is based on CSC and developed along the lines of MCFT. The basic building block is hypo-elasticity, where the loading and unloading behavior is along the same stress–strain path as shown in The EPM is based on a fracture parameter denoted as “K,” which ranges from 0 (complete damage) to 1 (intact state). K reduces the shear modulus of the concrete. Including defects, K represents the degradation of the shear elastic strain energy of the concrete. Once the elastic strain vector denoted as “F” is determined at any integration point, K is calculated as a function of the invariants of the elastic strain tensor and some elastic variables. The calculated factor reduces the shear modulus at that point, and the model moves to the next integration step. However, to calculate the resulting damage shear modulus, the precise stresses and the elastic-moduli matrix of the damaged concrete are formulated primarily as a function of the damage parameter (of the invariants of the elastic strain tensor). Plastic hardening denoted by “H” is defined by the second strain invariant and a user-defined correction factor for plastic evolution. Plastic dilatancy, also known as plastic flow, results from shear plastic dislocation along the lines of the internal defect, and it is a function of the first strain invariant and K. When MFC is selected in Diana FEA for compression models, EPM is applied until the first crack occurs in an integration point. When cracking occurs at an integration point, the model changes to a non-orthogonal Total Strain crack model. The parameters F, K, and the compressive and tensile stresses and strains at the integration point, being the controlling parameters for both models, are transferred .The MCC curves are shown in The CDP model, available in Abaqus CAE, is multi-hardening plasticity and isotropic damaged elasticity-based model . The Druothesis. . The defd” asd” varies from zero to one, with zero corresponding to an intact state and one corresponding to the total failure of the model. The expression is valid in the tension and compression phases of the cycle. The variable connoting degradation “d” is a function of the stress and uniaxial damage variables The CDP assumes the failure mechanisms for failure are tensile cracking and compressive crushing. Failure is regulated by plastic strain in tension A comparison of the models is presented in The numerical models are only developed using the CSC and CDP modeling theories in the Abaqus Computer-Aided Engineering, FE software. The simulation and experimental results are compared to validate the performance of both models. See the In contrast, the CSC model predicts the elastic performance to a good degree but fails to capture the post-failure softening adequately. In general, the performance of both models is satisfactory. In Multilayering in this case and study refers to a heterogeneous array of concrete mixes within a given structural form and should not be mistaken for layered 3DCP. For a cost-efficient and high-performance concrete structure, multilayering may often be required. The influence of layer volume can be observed in three categories: from Case 1 (MC2-and C) in In The overall trend observed in Case 2 differs from Case 1 even though the peak strengths of GFC-1 and MC-2 are not far apart, further indicating that the difference may be owed to the stress–strain behavior of the individual materials, as opposed to the peak strength alone. Both GFC-1 and C individually exhibit a sudden drop in peak strength, fracturing similarly, unlike MC-2, which gently declines in strength. This factor may be responsible for the difference in overall trend between the cases. To study the influence of layer position, the material volumes from Cases 1 to 3 are reversed. In the study of layered concrete, it is justified to question what may lie beyond the bi-layer configurations and study the influence of multilayering in three or more layers or finely tuned functionally graded concrete. This study thus further examines a three-layer concrete matrix as presented in The concrete matrix is divided into equal volumes, approximately 33.33% each, as shown in Highly compressive structures such as bridges and tunnels can be designed using the PDA with lessons from multilayering. As a result, they can be high-performance-based and cost-efficient. In addition, the nature of arched structures is such that the loads are efficiently transferred, and failure modes are predictable . As suchThe addition of glass fiber to concrete can improve the strain performance as multi-strength peaks and fairly extended strains. However, the addition of glass fiber to 3D printed concrete will influence printability and reduce the mechanical performance of the resulting printed concrete by the unavoidable imperfection of surface and internal voids.The addition of microsilica to concrete has the effect of a stretched-out post-failure regime. In other words, it considerably reduces the brittle failure of concrete by sustaining a large strain at maximum load. However, in 3d printing, microsilica can result in a highly cohesive mix, lacking adequate followability, thus yielding a highly stratified sample after printing resulting in print imperfections such as bulking or necking.Although experimental and theoretical frameworks are the foundations of engineering research, numerical tools and FE analysis have played a significant role in civil engineering design, analysis, and prediction in recent years. They help reduce cost and maximize efficiency. Multilayered concrete as a subset of functionally graded concrete, with increasing applicability in 3D printing concrete, also seeks to maximize structural efficacy by creating high performance, fit for purpose, concrete layer configuration. This study has briefly summarized the underlying principles of some existing FE numerical tools and applied them. Experiments on single-material 3D printed cubes using some cementitious composites mixes are conducted. The stress–strain data are converted to numerical input to enable the numerical performance evaluation of multilayered concrete cubes. The FE models are validated against the experimental results. The major conclusions on the material’s performances are as follows:For a two-layer configuration, the difference in the respective material strengths greatly influences the role of position and material volume. In other words, when the difference in material strength is high , the stress–strain plot flips with position interchange, as shown in Cases 1 and 4 in When the stress–strain performances of the combined materials are similar, the resulting stress–strain plot amplifies the weaknesses and strengths of the source materials.The stress–strain behavior of the outer layer of concrete sample influences to a great extent the post-failure performance of the sample. Thus, in multilayering of concrete, the post-failure performance objective should influence the choice of materials regarding positioning. In addition, the peak strength should guide decision-making regarding volumetric ratios.A three-layer configuration model is influenced by volume if two of the three layers are allotted the same material. Furthermore, layer position has minimal to zero influence on the concrete models’ performance, provided each layer is allotted a different material and has equal volume.On the multilayering front, the layer volume and position influence the performance of multi-layer concrete because stress distribution varies across the concrete matrix. Damage is usually more pronounced at the outer surface than the inner because the inner matrix is confined by the outer. As a result, under compressive loads, the outer surfaces fracture more visibly. When the effects of layer volume and position from a holistic perspective are considered, the following conclusion is drawn:The application of multilayering in scaled structures is yet to be accessed. In service, some of the challenges of multilayering are stresses–strains transfer between layers, layer interface debonding, and cracking due to stress localization, while in numerical work, modeling interlayer boundary conditions to account for variation in stiffnesses is a challenge. For this study, a simple “tie-constraint” was applied. The stress contribution from layers and the effect of the interlayer boundary condition are presented in the


The present study aimed to characterize the serum levels of coinhibitory checkpoint molecule, T cell immunoglobulin and mucin-containing-molecule-3 (TIM-3), and its ligand, galectin-9 , among IgG4-related disease in patients with IgG4-RD patients with various organ involvements.Immunoglobulin G4-related disease (IgG4-RD) is characterized by increased serum IgG4 concentration and infiltration of IgG4Serum samples were collected from untreated 59 patients with IgG4-RD, 13 patients with rheumatoid arthritis, and 37 healthy controls (HCs). HCs lacked chronic medical diseases or conditions and did not take prescription medications or over-the-counter medications within 7 days. Patients with IgG4-RD (n = 57) were subdivided into those with visceral involvement (n = 38) and those without visceral involvement (n = 21). Serum levels of Gal-9 and soluble TIM-3 (sTIM-3) were determined using enzyme-linked immunosorbent assay (ELISA). The results were compared with the clinical phenotypes of IgG4-RD.In untreated patients with IgG4-RD, serum levels of Gal-9 and sTIM-3 were significantly higher than in RA patients as well as in healthy controls. There were significant correlations between the serum levels of Gal-9 or sTIM-3 and serum levels of IgG, BAFF, or sIL-2R. However, there was no significant correlation between the serum levels of Gal-9 or sTIM-3 and serum IgG4 concentrations. Serum levels of sTIM-3 were significantly higher in a subset of patients with visceral involvements than in those without visceral involvements. However, there was no significant difference in the serum levels of Gal-9 between IgG4-RD patients with and without visceral involvements, although both Gal-9 and sTIM-3 were elevated in untreated IgG4-RD patients, and the levels of these checkpoint molecules remained unchanged after steroid therapy.Serum levels of Gal-9 and sTIM-3 were significantly elevated in untreated patients with IgG4-RD. Furthermore, serum levels of sTIM-3 were significantly higher in IgG4-RD patients with visceral involvements. These checkpoint molecules could be a potentially useful biomarker for IgG4-RD and for assessing the clinical phenotypes of IgG4-RD. Immunoglobulin G4-related disease (IgG4-RD) is characterized by multi-organ involvement and elevated serum IgG4 levels . The mosGalectins, a protein of the conserved lectin protein family, are important regulators of immune homeostasis. Galectins are also recognized as checkpoint molecules that regulate T cell development by the regulation of thymocyte apoptosis and can be potential regulators of bone marrow B cell development . Thus faA total of 59 patients with IgG4-RD were included in this study. All IgG4-RD patients were diagnosed at the Department of Rheumatology of Fukushima Medical University and the Department of Immunology and Rheumatology of Nagasaki University between February 2007 and November 2020. The clinico-demographic data were retrospectively collected from Medical Records. In those 59 patients, post-treatment data were collected from patients. As controls, 37 healthy controls (HCs) were included. HCs lacked chronic medical diseases or conditions and did not take prescription medications or over-the-counter medications within 7 days. An additional independent set of 13 patients with untreated rheumatoid arthritis (RA) was included to compare the value of Gal-9 and sTIM-3. Among the 13 patients of RA, 7 (53.8%) were female, and their median age was 65 years (17–88). The serum samples of these patients were properly stored at −20 °C.This study was conducted in accordance with the principles of the Declaration of Helsinki. Ethical approval for this study (No.29317) was provided by the Ethics Committee of Fukushima Medical University.Laboratory study included white blood cell count (WBC), hemoglobin (Hb), platelets (PLT), serum immunoglobulin G (IgG), serum immunoglobulin G4 (IgG4), the ratio of IgG4/IgG, C-reactive protein (CRP), compliment 3 (C3), compliment 4 (C4), soluble interleukin 2 receptor (sIL-2R), and lactate dehydrogenase (LDH). All patients underwent contrast-enhanced computed tomography (CT) or plain CT scan, and some patients were evaluated by ultrasound, radiography, magnetic resonance imaging, and positron emission CT.We diagnosed IgG4-RD based on the 2019 ACR/EULAR classification criteria for IgG4-RD. The 2019 ACR/EULAR classification criteria for IgG4-RD include clinical, serological, radiological, and pathological findings. A patient is classified if a cumulative score of 20 or more points is obtained .Furthermore, IgG4-RD patients were divided into two groups depending on the presence or absence of visceral involvement. Visceral involvement is defined as the complication of the lung pancreas, bile duct, kidney, retroperitoneal fibrosis, aorta, and prostate.The serum concentrations of Gal-9, sTIM-3, and B cell-activating factor of the tumor necrosis factor family (BAFF) were measured using an enzyme-linked immunosorbent assay kit  according to the manufacturer’s instruction.U test. The comparisons between the categorical variables were analyzed by Fisher’s exact test. Correlations between continuous variables were analyzed by Spearman’s rank correlation test. Paired data were analyzed by non-parametric tests using the Wilcoxon signed-rank test. The Kruskal-Wallis test was used for continuous variables for comparisons among the three groups. Post hoc pairwise analyses between the two groups were performed by the Games-Howell test. The prognostic factors for higher levels of Gal-9 and sTIM-3 were identified using a stepwise multiple logistic regression model. All data entry and statistical analyses were performed using SPSS Statistics version 22.0 . In all the analyses, a two-tailed p < 0.05 was considered statistically significant.The results were non-normally distributed and are presented throughout the manuscript with median and 25–75th centiles  and were compared by the Mann-Whitney The demographic, clinical, and laboratory characteristics of the enrolled IgG4-RD patients have been summarized in Table In order to evaluate possible role in checkpoint molecules in IgG4-RD, we compared the serum levels of Gal-9. As shown in Fig. We performed the correlation analysis among several laboratory markers, including checkpoint molecules and BAFF in IgG4-RD patients. Since BAFF has been reported to be a biomarker for IgG4-RD , we measp = 0.004), kidney , and retroperitoneum  involvement was independently associated with high sTIM-3 levels in patients with IgG4-RD. However, the presence of kidney involvement did not affect IgG4-RD RI -4, IL-5, IL-13, and IL-21) and the regulatory T cell-mediated cytokines (IL-10 and transforming growth factor-β) in IgG4-RD patients . TherefoTIM-3 acts as a co-inhibitory receptor that is expressed on exhausted T cells. TIM-3 was initially thought to be expressed only by T cells; it has now been proven that TIM-3 is expressed by multiple cell types, including DCs, macrophages, and Tregs , indicatTfh is a critical regulator of immune responses in inflammatory disorders –31. ChecAlthough the serum concentrations of sTIM-3 were associated with visceral involvements of IgG4-RD, the levels were not modulated by steroid treatment. Steroid is effective for most patients with IgG4-RD ; howeverAdditional studies are required to clarify the roles of circulating checkpoint molecules in the pathophysiology of IgG4-RD and their relationship to the clinical phenotypes. Furthermore, it is necessary to elucidate whether more aggressive treatment such as B cell depletion treatment may affect the upregulated immune checkpoint molecules in IgG4-RD.There are certain limitations of this study. The sample size was relatively small, and larger scale studies are necessary to confirm the present finding. Checkpoint molecule profiles in other potential controls, such as those with Sjögren’s syndrome or lymphoproliferative disorders, were not compared with the profiles in IgG4-RD patients in the present study. This study was a cross-sectional analysis for untreated IgG4-RD patients. Therefore, clinical manifestations that occurred during the disease course were not completely surveyed. We enrolled only Japanese patients with IgG4-RD; therefore, non-Japanese patients with IgG4 were not included, and further studies on non-Japanese patients with IgG4-RD are warranted. The mechanism through which the Gal-9/TIM-3 pathway contributes to the pathogenesis of IgG4 was not clarified because the functional analysis by in vitro cannot be performed. However, TIM-3 biology is complex in terms of broad expression by different types of immune cells and multiple ligands. Given the variety of TIM-3 ligands, it is possible that binding to other ligands might facilitate the functions of TIM-3. Moreover, it will be necessary to address whether sTIM-3 acts as an agonist or an antagonist to understand the role of sTIM-3 in IgG4-RD.We demonstrated that serum sTIM-3 and Gal-9 levels were elevated in IgG4-RD patients. With respect to the relationship with the clinical phenotypes, the serum sTIM-3 levels were significantly higher in patients with visceral involvements than in those with disease limited to the lacrimal or salivary glands. These data suggest that the circulating checkpoint molecules are involved in the pathophysiology of IgG4-RD and their relationship to its patterns of organ involvement.