For the sake of solving sustainability issues and analyzing the complicated service force states, eccentric compression experiments on self-compacting concrete-filled thin-walled medium-length steel tube columns with a circular cross-section were carried out in the present study. Thereafter, the influence of the eccentric ratios and the wall thickness factors on the mechanical behavior and failure characteristics of both the eccentrically loaded and axially loaded columns was comprehensively analyzed. Finally, prediction formulas for the ultimate load of the columns under eccentric compression were proposed, and a comprehensive comparison of the ultimate loads between the predicted values and experimental values was also conducted. The results indicated that the typical failure characteristics of the eccentrically loaded columns presented lateral deflection together with buckling, while the axially compressed columns displayed expansion and rupture at local positions. Moreover, the ultimate loads of the eccentrically loaded columns decreased by 43.0% and 34.5% in comparison to the columns under axial compression, with the wall thickness factor decreasing from 116.7 to 46.7, respectively. Meanwhile, the ratios of the ultimate loads calculated using design codes to the tested values were in the range of 0.70~0.90, which demonstrated that the design codes could predict the ultimate loads conservatively. Additionally, the ratios of the ultimate loads calculated using the proposed formulas to the tested values were within the range of 0.99~1.08, implying that the proposed formulas were more accurate than the design codes. At the same time, the initial stiffness of the columns under eccentric compression was correspondingly lower than that of the columns undergoing axial compression. The lateral deflections along the height of the columns were almost symmetrical at different loading levels. This study could provide a meaningful approach for designing columns and facilitate their application in civil industry. Concrete-filled steel tubes have been extensively researched and applied in civil infrastructure, for example, long-span bridges, ultra-high-rise buildings, urban viaducts, and military facilities, due to their high strength, outstanding ductility, excellent seismic performance, and convenient construction ,2. SteelOwing to their excellent advantages, research on concrete-filled steel tubes has been conducted worldwide ,9,10,11.The parameters of concrete-filled steel tubes undergoing eccentric loading examined in previous research including the strength of the materials, the ratio of the diameter to the thickness, the eccentricity ratio, the slenderness, and the cross-section shapes ,20,21,22In the past few years, concrete-filled thin-walled steel tube columns began to be researched and applied, following the fast development of high-strength steel tubes. The confinement on concrete is improved by high-strength steel tubes ,23,24,25Li et al. studied the relationships between displacement and load and the failure modes of axially loaded columns using both experimental and finite element methods . Liu et Self-compacting concrete was first developed in the 1980s, and it can be compacted by its own weight and need not extra vibration. It also presents advantages such as outstanding workability, good mechanical performance, and durability ,37,38,39Nevertheless, the primary research on the columns mostly concern the axially loaded behaviors. Wang et al. pointed out that the ACI code predicts the most conservative ultimate load of the axially loaded columns while the CECS code gives the most precise ultimate load of the same columns . It was s and Ac represent the area of steel tube and concrete, respectively, and e and r represent the load eccentric distance and outer radius of the columns, respectively. The values of the wall thickness factor of 116.7 and 46.7 correspond to wall thickness of 1.2 mm and 3.0 mm, respectively.Four of the SCCTST column specimens with circular cross-section were manufactured, wherein two of the columns undergo eccentric compressive load, and the other two columns withstand axial compressive load. The key parameters are the eccentric ratios and the wall thickness factor β, which is defined as the ratio of D/t. Steel tubes with wall thickness of 1.2 mm and 3.0 mm were adopted. Two kinds of eccentric ratios included 0 and 0.29. Outer diameter and length of the columns were designed as 140 mm and 700 mm, respectively. Two square endplates were welded on the columns’ ends. The thickness and side length of the square endplates were 20 mm and 180 mm, respectively. A square steel endplate was welded onto the bottom end of the columns before casting concrete, and it could function as a mold together with the steel tubes during the concrete casting process. The geometric center of the endplate and the steel tubes must remain in a vertical line to ensure the load can apply to the columns evenly. External vibration was not used during the whole casting process. The columns were cured in a laboratory with relative humidity and temperature of 95% and 20 °C, respectively, lasting for 28 d after casting the concrete. However, shrinkage about 2 mm was generated on the infill concrete after curing for 28 d. Therefore, high-strength cement paste was used to fill the uneven space generated by the concrete shrinkage. The top end was welded to another steel endplate before testing. Preparation for the SCCTST columns is shown in The mechanical performances of the steel tubes were tested by experiments which are listed in Both the concrete used to fabricate specimens to test the mechanical performances and the concrete used to fill in the steel tubes were mixed together. The concrete specimens used to test mechanical performances contained three cubic concrete specimens and six cuboid concrete specimens. The side length of the cubic specimens is 150 mm. Additionally, the dimensions of the cuboid are 150 mm × 150 mm × 300 mm. The concrete specimens were cured in the laboratory with similar conditions to the SCCTST columns, and plastic film covers were placed on top of the columns after concreting. The mechanical performances of concrete were tested according to the standard . Its modThe SCCTST columns under eccentric and axial compressive load after curing for 28 d were conducted by a universal testing machine with maximum load up to 3000 kN. The eccentric load was first exerted on the spherical hinges, as shown in Preliminary loading test was carried out before formal loading to ensure the load could compact on the endplates of the columns evenly. The loading amplitude in the preliminary loading test process was 15 kN, and the loading rate was 0.5 kN/min. Loads were applied to the columns continuously after the preliminary loading stage. During the formal testing process, one-fifteenth of the predicted ultimate load was set as the loading interval and the loading rate was 0.5 mm/min, then 3 min was maintained after each load interval had finished. The test was stopped after the load decreased to 70% of the ultimate load. The total loading time of one column was about 2 h. The data on loads, displacements, and strains during the loading process were automatically collected.No evident changes were present on the surface of the columns before loading to 80% of the ultimate load. And then, a small amount of bulking and buckling was generated on the surface of the columns corresponding to the columns withstanding eccentric compressive load. The bulking and buckling was more evident when loading to the ultimate load.The relations between displacement and load in the axial direction of the columns and the ultimate loads from experiments  and (2) are the proposed calculation formulas of the ultimate loads corresponding to different wall thickness factors 116.7 and 46.7, respectively.Theoretical calculation formulas on the ultimate loads of the columns subjected to eccentric compression were set up from fitting of the experimental data of load and displacement which are displayed in The ultimate load of the columns was obtained using calculation formulas of the design codes CECS 28:90  and DL/TThe descent phase of the curves on load–displacement of the axial compression columns is not evident, while the descent phase of the columns withstanding eccentric compressive load is clear and more gentlely. Meanwhile, the descent phase is more gently with thicker wall thickness. The initial stiffness tion (3) .(3)Kn=0ue corresponding to the ultimate load of the eccentric loading columns is larger than that of the axial loading columns. ue. As shown in y1 and εy2 stand for the yield strains of steel tubes corresponding to the wall thickness factor of 116.7 and 46.7, respectively, which are 1906 με and 1774 με, respectively.ue in the axial and transverse directions is correspondingly larger and smaller than that of the yield strain. This indicated that the confinement in the transverse direction is weak under the ultimate load. The average εue of the column A–N–T1 at the axial and the transverse directions is −2240 με and 1086 με, respectively. Compared with εy1, the average εue of A–N–T1 at axial and transverse directions is correspondingly increased by 17.5% and decreased by 43.0%, respectively. Additionally, the average εue of the column E–N–T1 at the axial and the transverse directions is −2359 με and 1022 με, respectively. Similarly, compared with the yield strain εy1, the average εue of E–N–T1 at axial and transverse directions is correspondingly increased by 23.8% and decreased by 46.4%, respectively. The average εue of the column A–N–T2 at the axial and the transverse directions is −2316 με and 1089 με, respectively. Compared with the yield strain εy2, the average εue of A–N–T2 at axial and transverse directions is correspondingly increased by 30.6% and decreased by 27.3%, respectively. The average εue of the column E–N–T2 at the axial and the transverse directions is −2958 με and 1263 με, respectively. Compared with the yield strain εy2, the average εue of E–N–T2 at axial and transverse directions is correspondingly increased by 66.7% and decreased by 28.8%, respectively.The average εue of the axially loaded columns is approximately increased upon increasing the wall thickness. Compared with A–N–T1, the εue at axial and transverse directions of A–N–T2 is increased by 3.4% and 18.7%, respectively. Compared with E–N–T1, the εue at axial and transverse directions of E–N–T2 is increased by 25.4% and 23.6%, respectively.The εue in the axial and transverse directions of the columns withstanding eccentric load is correspondingly larger and smaller than that of axially loaded columns. Compared with A–N–T1, the εue at axial and transverse directions of E–N–T1 is correspondingly increased by 5.3% and decreased by 5.9%, respectively. Compared with A–N–T2, the εue at axial and transverse directions of E–N–T2 is correspondingly increased by 27.7% and decreased by 2.0%, respectively. The εue withstanding the maximum load of E–N–T1 and E–N–T2 is 3.8 mm and 10.0 mm, respectively. The average lateral deflection fue of E–N–T2 is increased by 162.3% compared with that of E–N–T1.Equation 5) expresses the displacement ductility coefficient  columns .(5)μ=Δu expresseCompared with A–N–T1, the coefficient of displacement ductility of E–N–T1 is increased by 27.1%, as shown in In order to reduce energy consumption and analyze the complicated service states, SCCTST columns were first developed. And then, their failure modes and mechanical performances withstanding axial and eccentric compressive load were investigated. Thereafter, the influence of eccentric ratios and wall thickness factor on failure characteristics, relations between load and displacement, relations between load and strain, initial stiffness, displacements/strains corresponding to the ultimate loads, relations between load and lateral deflection, and coefficients of displacement ductility of the SCCTST columns were analyzed in depth. Finally, prediction formulas of the ultimate loads were proposed, and the calculated ultimate loads were compared with the tested values. Conclusions can be drawn as follows.Both lateral deflection and buckling were the main failure characteristics of the eccentrically loaded columns, while the columns withstanding axial load displayed bulking and rupture of the columns. The amount of bulking decreased upon increasing wall thickness.The descent phase of the relations between load and displacement of the eccentrically loaded columns was more gently compared with the axially loaded columns. The descent phase became more gently with increase of the wall thickness. In comparison with the axially loaded columns, the ultimate load of the eccentrically loaded columns decreased by 43.0% and 34.5%, respectively, corresponding to the wall thickness factors 116.7 and 46.7.Theoretical calculation formulas on predicting the ultimate loads of the columns subjected to eccentric compression were proposed, and the proposed curves coincided well with the tested curves. Meanwhile, the ratios of the ultimate loads calculated using design codes to the tested values were under the range of 0.70~0.90. This implies that the design codes can conservatively predict the ultimate loads. Additionally, the ratios of the ultimate loads calculated using the proposed formulas to the tested values were within the range of 0.99~1.08; it was demonstrated that the proposed formulas predicting the ultimate loads of the SCCTST columns withstanding eccentric compression are more accurate than those of the design codes.Initial stiffness of eccentrically loaded columns was reduced by 14.1% and 25.4%, respectively, compared with the axially loaded columns corresponding to wall thickness factors 116.7 and 46.7. When decreasing the wall thickness factor from 116.7 to 46.7, initial stiffness of the eccentrically loaded columns increased by 19.3%, while the displacements at the ultimate loads of the eccentrically loaded columns decreased by 18.1% and increased by 3.9%, respectively.ue of the columns withstanding eccentric load in axial and transverse directions was correspondingly increased by 23.8%/66.7% and decreased by 46.4%/28.8%, respectively. The εue was almost increased with increasing wall thickness.The strains developed nonlinearly with increases of the load. Compared with the yield strain, the average strain εLateral deflections of the columns withstanding eccentric load proximately increased linearly with load increasing up to 70% of the maximum load. After that, the increase rate of load was slower than that of the lateral deflection, and the relations between lateral deflection and load were nonlinear. The average lateral deflection corresponding to the ultimate load with wall thickness of 3.0 mm increased by 162.3% compared with that with the wall thickness of 1.2 mm. The lateral deflection along the columns’ height was proximately symmetrical at different loading levels. The symmetry of the lateral deflection and the ductility was more evident with increasing wall thickness.Quantity investigations on concrete-filled steel tubes have been conducted by experimental and numerical analyses. However, little studies have been carried out on the SCCTST columns subjected to eccentric compression because the mechanical behaviors of the SCCTST columns under these situations are considerably complex when applied to practical engineering. Thus, guidance for designing and optimizing the SCCTST columns withstanding eccentric compressive load for application in civil infrastructures should be founded in the future research.


Public health campaigns remain a central component in the fight to combat antibiotic resistance. Future campaigns should address the public’s understanding of antibiotic resistance and modifiable behaviors that may contribute to resistance.This study aimed to assess understanding of antibiotic resistance and evaluate antibiotic use themes among the general public. In March 2018, respondents that were ≥21 years old and residing in the United States were recruited from ResearchMatch.org and surveyed to collect data on respondent expectations, knowledge, and opinions regarding prescribing antibiotics and antibiotic resistance. Content analysis was used to code open-ended definitions of antibiotic resistance into central themes. Chi-square tests were used to assess differences between the definitions of antibiotic resistance and antibiotic use. Among the 657 respondents, nearly all (99%) had taken an antibiotic previously. When asked to define antibiotic resistance, the definitions provided were inductively coded into six central themes: 35% bacteria adaptation, 22% misuse/overuse, 22% resistant bacteria, 10% antibiotic ineffectiveness, 7% body immunity, and 3% provided an incorrect definition with no consistent theme. Themes that were identified in respondent definitions of resistance significantly differed between those who reported having shared an antibiotic versus those who had not ( Acinetobacter spp. (>56% resistant) and Klebsiella pneumonia (>57% resistant); 20% of Escherichia coli, the primary pathogen causing urinary tract infections, were resistant to first- and second-line urinary anti-infectives; also, gonorrhea, for which few treatment options remain, are now 60% resistant to ciprofloxacin. Antibiotic-resistant infections have been associated with increased morbidity and mortality; one study estimated that in 2019, there were 1.27 million deaths attributable to antibiotic-resistant bacterial infections [The increasing rate of antibiotic resistance is a global public health crisis that has been identified as one of the greatest threats to human health worldwide ,2. The efections . In the fections . The incA study of 2010 to 2011 healthcare data identified that antibiotics were prescribed during 154 million ambulatory care visits in the United States, representing 12.6% of all ambulatory visits during the timeframe [Despite the focus placed on public health education campaigns, research linking these efforts to changes in antibiotic use behavior is limited. Misconceptions surrounding antibiotics contribute to inappropriate use behavior, such as sharing of antibiotics, which in turn drives increasing antibiotic resistance . HistoriOf 1000 subjects that were invited to complete an inclusion screening form and participate in the survey panel, 770 persons responded to the invitation and 657 of these individuals met the inclusion criteria and completed the survey. Among the survey respondents, 45/50 US states were represented, with a majority of respondents living in a suburban geographic area. A total of 35% of respondents were aged 60 or older, 78% were female, and 89% identified as white . ApproxiNearly all respondents (99.5%) reported having taken an antibiotic in their lifetime, and over half of participants reported that they were moderately to extremely concerned about antibiotic resistance . A totalp < 0.01, p < 0.01). Respondents that were under 40 years of age, were more likely to have obtained or knew someone that had obtained an antibiotic without a prescription (33%) compared to respondents that were aged 40 and over ; yet, there was a larger proportion of respondents under 40 that accurately described resistance as bacteria adapting (46%) compared to participants 40 years or older .Respondents without a bachelor’s degree or higher were more likely to have shared an antibiotic (28%) compared to respondents with a bachelor’s degree or higher ; respondents who reported sharing an antibiotic were more likely to describe resistance with themes of antibiotic ineffectiveness (17% vs. 8%) and person immunity (10.5% vs. 7%) but were less likely to describe antibiotic misuse (17% vs. 23%), compared to those who did not report sharing antibiotics (p < 0.01). There were no significant differences in antibiotic resistance themes between those that had obtained or knew someone else that had obtained an antibiotic without a prescription.Themes that were identified in respondent definitions of resistance differed significantly between those who reported having shared an antibiotic versus those who had not (ibiotics . Respondp < 0.01).There was no association between sharing or obtaining an antibiotic and talking to one’s doctor about antibiotic resistance . RespondGlobal reports from the United Nations council and the World Health Organization continue to stress that raising awareness through public health campaigns is critical towards combating antibiotic resistance ,10,11. CPrior public health campaigns to educate the public regarding the effectiveness of antibiotics against bacterial versus non-bacterial infections were successful to a certain extent . Nearly Among respondents that requested an antibiotic, a little more than half had a doctor counsel them on antibiotic resistance. This suggests that prescribers are more likely to have conversations with patients about antibiotic resistance if the patient is seeking antibiotics. However, there was no significant difference between those that had a conversation about antibiotic resistance with their doctor and antibiotic resistance definition themes. Despite this, the patient-doctor conversation should be viewed as an important educational opportunity for discussing antibiotic resistance. Doctor patient conversations should focus on a clear definition of resistance and individual responsibilities of appropriate antibiotic use, regardless of whether or not antibiotic seeking behaviors are identified during the visit. Small interactions such as this play a significant role in increasing awareness of antibiotic resistance and should be a target for public health campaigns.The survey collected retrospective, self-reported data, which is subject to reporting and recall bias and, as such, may underestimate the true incidence of antibiotic use behaviors that were reported in this study. Participants self-selected to participate in potential studies with ResearchMatch.org and also self-selected to take part in our study. Participants were limited to English speaking US adults with access to a computer and the internet. Respondents included a higher proportion of age >40, females, white race, and received more education than the general population, thus these data may not be generalizable to other demographic groups. Further research is needed to better understand the antibiotic resistance knowledge and antibiotic use behaviors in younger populations, non-white racial groups, men, and persons who have not received a bachelor’s degree or higher levels of education. Still, this work highlights the ongoing need for continued effective public health education campaigns around antibiotic use.The SARS-CoV-2 pandemic has shown that previous methods for public health education may have been ineffective at preparing the general public for managing COVID-19 . The utiWe conducted a cross-sectional survey study of participants from across the United States. The participants were recruited from ResearchMatch.org, a national online clinical registry that matches participants that are interested in participating in research with researchers at institutions that have received research support from the US National Institute of Health’s Clinical and Translational Science Awards program. Inclusion was limited to English speaking participants 21 years or older that resided in the US with access to the internet. An email was sent to a random sample of 1000 eligible participants, via ResearchMatch.org inviting them to participate in a survey panel on combating antibiotic-resistant bacteria (CARB) during March 2018. If the respondents agreed to participate in the panel, they were sent an inclusion/exclusion criteria screening form, a study information sheet, and notification that completion of the survey indicated consent to participate in this study.The survey questions that were used in this study were developed by the study team to understand participant’s expectations, knowledge, and opinion regarding antibiotic prescribing and understanding of antibiotic resistance see . The surThe participants were asked to define antibiotic resistance as an open-ended survey question. Inductive content analysis was used to create central themes from the data. There were two rounds of thematic coding that were performed by a qualitative analyst; the first round reduced responses into phrases that were used by the respondent to describe resistance and a second round of coding grouped phrases into broader shared themes. Developing and final thematic categories were reviewed by the study team to ensure they were mutually exclusive and an accurate representation of the respondent’s definition. There were five mutually exclusive themes that were identified from the participant responses. Three categories reflect accurate concepts that were attributed to antibiotic resistance: ineffective antibiotics, bacteria adapting, and mis-/overuse of antibiotics. One category captures neutral responses with no other theme than “resistant bacteria” and two categories reflect incorrect responses, the person/body having antibiotic immunity and incorrect with no other consistent theme among respondents to be categorized beyond incorrect .p < 0.05 was considered statistically significant. Statistical analysis was performed using SAS v. 9.4 .Descriptive statistics  were used to describe participant characteristics. Chi-square tests were used to compare proportional differences in antibiotic use behaviors by respondent characteristics as well as antibiotic resistance definitions. Awareness of antibiotic resistance is growing at a rate much slower than the threat and consequences of antibiotic misuse. We must modify person-level antibiotic use behaviors that contribute to the spread of resistance. Public health campaigns remain a central component in the fight to combat antibiotic resistance, however the approach remains difficult, particularly given the complexity of the topic. Targeted campaigns for younger demographics and those without post-secondary education can go a long way in the fight to combat antibiotic resistance. These targeted campaigns should place greater focus on patient-provider conversations regarding the appropriate use of antibiotics and resistance. Finally, future research and public health initiatives should address patient motives for antibiotic requests and sharing. Given the global burden of infectious diseases and the morbidity and mortality associated with antibiotic-resistant infections, it is critical to engage the public as well as healthcare providers and public health officials in the global battle against antibiotic resistance.


Background: Evaluation of the adequacy of prophylactic antibiotics in surgery has been implemented as a national policy in Korea since August 2007, and the appropriate use of prophylactic antibiotics has improved. However, antibiotic prescriptions that are not recommended or discontinuation of prophylactic antibiotic administration within 24 hours after surgery are still not well done. This study introduced a program to improve the adequacy of prophylactic antibiotics for surgery and analyzed its effects. Methods: We retrospectively analyzed the effectiveness of the appropriate prophylactic antibiotic use program for surgery conducted at a university hospital in Seoul. The participants were patients aged ≥18 years who underwent any of 18 types of surgery. The program started was implemented in June 2020. First, a computer system was used to confirm the antibiotic prescription recommended for each surgery. It also assessed whether the number of days of administration was exceeded, whether antibiotics were prescribed in combination, and whether antibiotics prescribed for discharge medicine were checked in 4 steps. A pop-up window appeared in each patient record to enter the reason for the prescription. If the reason was appropriate, the prescription was allowed, but if not, the prescription was restricted. In addition, infectious diseases physicians and an insurance review team visited each department to conduct an education session. To analyze the effect 3 months before activity (January–March 2020) and 3 months after activity (October–December 2020), we compared the first antibiotic administration rate within 1 hour prior to skin incision, the recommended prophylactic antibiotic administration rate, and surgery type. The rate of discontinuation of prophylactic antibiotics within 24 hours after administration and the rate of prescription of prophylactic antibiotics at discharge were compared. Results: In total, 1,339 surgeries during the study period were included in the analysis. There were 695 cases before the introduction of the program and 644 cases after the introduction. The rate of first antibiotic use within 1 hour prior to skin incision was 93.1%–99.5% (P < .001), the rate of recommended prophylactic antibiotic administration was 85.0%–99.2% (P < .001), and the rate of discontinuation of antibiotic administration within 24 hours after surgery improved from 51.8% to 98.3% (P < .001), respectively. The prescription rate of antibiotics at discharge improved from 20.7% to 0.8% (P <.001) (Table 1). Conclusions: A computerized program to improve the adequacy of prophylactic antibiotic use in surgery combined with education of medical staff was very effective.Disclosure: None


Construction during cold weather can lead to freezing accidents in concrete, causing significant hidden threats to the project’s performance and safety by affecting the mechanical properties and durability reduction. This study aims to deduce the compressive strength and durability of the concrete containing nano- It has advantages such as convenience in construction, abundant source materials, good moldability, the low price2, high durability, and good bonding performance with reinforcing plates and steel bars3. Civil concrete structures experience millions of repeated load cycles during their service life4. It is highly believed that the growth of microcracks and deterioration of pore structure in concrete as a result of cyclic mechanical and thermal loading accelerate the damage accumulation of concrete5. Furthermore, concrete is simultaneously affected by environmental factors, such as freezing and thawing, deicing salts, 9. The integrated attack of environmental actions and mechanical loads results in early deterioration of concrete10, which can be extensively classified into two kinds of failure including drastic deterioration of the concrete’s durability (i.e. permeability) and major fatigue cracks’ unstable propagation5.Concrete is the most extensively utilized material in ports, houses, wharves, bridges, roads11. This is caused by freezing and thawing cycles, loss in mass13, and changes in mechanical14 and dynamic properties16. One of the major causes of reduction in the concrete durability is freezing and thawing, which is caused by fluctuations in temperature17. Freeze and thaw resistance is often a key index for evaluating the concrete’s durability. Moreover, the relative elastic modulus is measured along with strength loss rate and mass loss rate after freezing and thawing cycles to determine the frost resistance of concrete19.One factor that reduces the stability and durability of concrete is damage caused by freezing and thawing processes. Here, the hydraulic concrete structures are damaged in the cold regions, during day and night as a result of fluctuation in temperature. Freezing water increases it’s volume by 9%. This expansion causes pressure forces inside the concrete, which favors the formation of internal cracks. Water can penetrate into the concrete during the thawing procedure, through leak joints and cracks. Moreover, the penetrated water was frozen at the freezing stage, and the concrete’s strength was reduced owing to the formation of cracks. There is a close relationship between the freezing and thawing durability of concrete and its pore structure. The size distribution, volume, and radius of pores determine the pore solution’s freezing point and the quantity of ice formed in pores. Normally, within a certain temperature interval, greater internal hydraulic pressure is induced by more frozen concrete pore solution, thus, more severe frost damage20. It also reduces the strength of concrete. Moreover, pozzolans can result in a very compact microstructure of concrete, thus, improving frost resistance21. Also, pozzolans, admixtures such as silica fume, fiber materials, fly ash, and nano-materials can enhance the durability and frost resistance of concrete and preserve its strength.To minimize the damage caused by such processes, the composition of the concrete can be improved. For this purpose, the air-entraining agent is commonly utilized for concrete mixing design to enhance the concrete structures’ freezing-thawing resistance22. Nano-materials can significantly enhance the durability of concrete and mortar23. Several nano-materials represent great performance for improving the features of concrete like nano-clay24, nano-rice husk ash25, carbon nanotubes26, nano-33, nano-23, nano-34 enhancing the durability and mechanical characteristics of concrete.Nano-materials are ultra-fine with large surface area, particle sizes of 1-100 nm and small particle size, and higher surface energy with dimensional, volume, and surface effects35. Since hydrophilic NS has higher dispersion in water, it is mostly used in concrete36. NS may act as a nano-filler, occupying the voids between calcium-silicate-hydrate (C-S-H) gel particles. Moreover, NS is a pozzolan with a higher pozzolanic reaction rate owing to its large surface area to volume ratio, which indicates higher chemical activity. Concrete’s compressive strength can be enhanced using NS38. Moreover, adding NS can improve the tensile strength of the concrete39. Freezing and thawing resistance of the concrete is improved significantly by incorporating an optimum amount of NS into the concrete37. NS reduced the capillary voids in the hardened concrete. Therefore, adding NS enhances the durability of concrete against the freezing-thawing cycles40.NS as a white fluffy powder is made of amorphous silica powder. It represents strong surface adsorption, a large specific surface area, excellent chemical purity, large surface energy, and good dispersion as a result of its tiny particle size43 method resolve these discontinuities explicitly, but gained insufficient results, when it comes to crack branching, and further required highly specialsed code frameworks. A more recent approach, based on a so called phase-field, regularizes these discontinuities by introduction of an energy driven field-variable, blending between intact and broken material44. Further developments included the more physics based formulation of the crack driving energy and efficient treatment of the irreversibility of cracks46. Even if initially formulated for fracture within brittle materials, the phase-field based fracture models have been extended to ductile materials47 or multi-physical problems like thermo-mechanics49 or even multi-phasic continuas such as fluid-filled, porous structures50.As discussed previously, adding NS to concrete, significantly affects it’s mechanical properties and therefore the underling mechanisms, when it comes to damage. Within this context, evolving micro-cracks can lead to macroscopic failure. A mathematics description of such phenomena is challenging, as the evolution of a discontinuous displacement field has to be captured. Methods like the interface- or extended finite element51. Therefore, there is a significant impact of the freeze and thaw environment in this region. Owing to the effects of freeze and thaw damage, countermeasures are required to avoid the deterioration of reinforced concrete structures in bridges, main construction, and tunnels. Since a few studies investigated concrete properties under freezing and thawing cycles with the curing condition of Caspian seawater, in order to address this knowledge gap, the present work examined the effects of adding different dosages of NS on the compressive strength, water permeability, chloride ion penetration, crack formation in the concrete under different freezing and thawing cycles with Caspian seawater curing conditions.Due to the extensive use of concrete piers, breakwater decks, and retaining walls in the construction of ports and docks, studies on the mechanical properties and durability of concrete structures cured in seawater under freezing and thawing cycles is of great importance. On the southern coast of the Caspian Sea with occasionally heavy snowfalls, the average temperature is less than 052. The cement is produced by Khazar Cement Company . The fineness of cement was 3230 53 and the initial and final setting times were equal to 110 and 170 min, respectively. Also, the 7 and 28 day compressive strengths and the specific weight of cement were 415 In this study, a type II ordinary Portland cement is utilized as the main cementitious binder in accordance with ASTM C 150The size of NS particles with an average particle diameter of 25 nm, specific surface area of 193 54.Natural river sand with a fineness modulus of 2.64, specific gravity of 2.63, bulk density of 1720 55 is introduced in all the concrete mixtures as a weight percentage of the total cementitious materials. The superplasticizer was used to help disperse nanoparticles throughout the concrete mixture, increase compaction and improve the concrete workability. The characteristics of the superplasticizing admixture materials are given in Table A Type F polycarboxylate acid-based superplasticizer conforming with ASTM C494The water used for curing conditions in this study is obtained from the Caspian sea. To determine the chemical properties of Caspian seawater, samples of each of it were analysed. The results of the chemical analysis are given in Table Three series of concrete specimens, namely Series PC and NSC Series are cast and then subjected to the tests. PC denotes plain concrete and is regarded as control concrete. The water- to- binder (the sum of cement and nano-particles) ratio (W/C) used for all mixtures is 0.5. NSC1, NSC2, NSC3, NSC4, NSC5, NSC6, NSC7, and NSC8 denote the concrete containing 1 wt %, 2 wt %, 3 wt %, and 4 wt % , 5 wt %, 6 wt %, 7 wt % and 8 wt % nanosilica, by the weight of cement, respectively. The mix proportions for one cubic meter of concrete are presented in Table 57 by putting samples in a simple freezing and thawing chamber capable of attaining and maintaining the required temperature. The freezing and thawing process takes 5 hours to complete one cycle. Upon completion of one freezing and thawing cycle, the temperature changes from 4°C to -18°C and then back to 4°C. The samples was 150 mmThe freezing and thawing process on the PC and NSC series specimens is carried in accordance with ASTM standard C666/C666M58, a 200-ton hydraulic concrete pressure testing machine was employed. The specimens were filled up at 7, 14, 28, and 90 days at the rates of 100 In order to conduct compressive strength tests according to ASTM C3959. After making three specimens  system, which consists of the elastic energy of the undamaged solid and the fracture energy, based on Griffith theory61. To overcome difficulties within the minimisation due to the discontinuous displacement field62, introduced an order parameter, the phase-field, leading to a volumetric representation of the crack surface alongside with a spatially continuous displacement field.The numerical description of fracture processes is a challenging task, and part of ongoing research. Focusing on brittle materials63:45. As energy is dissipated during crack evolution, the internal energy of the undamaged solid is degraded with evolving fracture. Applying the so called degradation function 46The set of governing equations follows from minimisation of a total energy potential mentclass2pt{minimFor the solution of Eqs.  a standa62  to generate CSH gel. They also served as filler materials, which decreased porosity and improved early age strength73. Belkowitz et al.74 found that cement composite containing larger nano-40 performed an experiment to examine the correlations between the nano-Compressive strength test was done by loading specimens after 90 days curing and subjecting to uniaxial load until failure. Compressive strength of concrete containing NS increases as NS content approaches the threshold. A higher amount of NS over the threshold value reduces compressive strengthThe water penetration of concrete with various amounts of NS was studied for different freezing-thawing cycles to investigate the material changes resulting from the procedure. Figure Figure 73, Erdam et al.75, and Rezania et al.76 observed that the permeability reduction exhibited a declining pattern as the nanoparticle content increased. This was attributed to the challenges in dispersing the nanoparticles in concrete at higher dosages. The utilization of nano-77.The reduction of penetration depth is a consequence of the already discussed reduction of the permeability. This structure enables the absorption of the free water, which occurs in the mixing of the concrete. In addition, compared to PC, the interfacial transition zone thickness around the coarser size aggregate is less in concrete with NS. The reduction in water penetration caused by the inclusion of NS as compared to the reference concrete mix suggests that the capillary pores’ ability for interaction with adjacent ones was severely weakened by the pores’ increased filling of hydration products brought on by NS’s high pozzolanic reactivity. Elkady et al.As another important value for concretes, the chloride ion penetration at different cycles was investigated. Figure 65. With an increase in NS, the threshold and critical diameters of the pores as well as the big capillary porosity decreased65. Isfahani et al.78 and Jala st al.69 revealed that using nano-79. The resistance to penetration of chloride ions in the nano-80.The evaluation of the rapid chloride penetrability also shows a decrease of the passing charge with increasing proportion of NS in the concrete. The highest value is also reached with normal concrete, while the passing charge drops sharply up to a value of 6% NS and from there reaches a flatter descent. Furthermore, this evaluation also reveals an increase in passing charge with a higher number of freezing and thawing cycles. However, the differences between the cycles become smaller as the amount of added NS increases. The high NS dosage (3–8%) may cause concrete’s fast chloride penetrability to fall from a low grade to a very low rating when replacement levels drop. The volume of large pores and the total amount of porosity in the concrete can be decreased with an increase in NS content and fineness. As a result, deeper water penetration and chloride ion penetration are reduced by an increase in the percentage of NS. The lowering in the critical threshold diameter of pores and the finer microstructure brought on by the addition of NS can both contribute to the reduction of charge transferred inside the concreteBesides the experimental results, the resistance of concrete against cracks before and after freezing and thawing cycles will be further investigated by numerical simulations. We therefore apply the phase-field method, presented in section "The boundary value problem is derived from microscope images of a concrete sample. The observed inclusions are included in the FE mesh as cutouts. To avoid  boundary effects, a sufficiently large area around the inclusions is simulated. Since cracking is expected in the area of the inclusions, locally refined triangulations are used to capture this zones properly. The respective microscope image and the resulting mesh can be seen in Fig. 81 and the Poisson ratio Based on the so far described geometry, boundary conditions are chosen as follows: On the lower side of the domain vertical displacements are set to zero. Additionally the horizontal displacement is set to zero in the bottom-right corner. A further displacement condition is applied on the top of the domain. By prescription of a negative, vertical displacement the domain is compressed, leading to crack formation near the cutouts. For the simulation we chose Based on the described boundary value problem, crack propagation is calculated. The spatial distribution of the phase-field – 1 indicates an entirely damaged state – is shown in Fig. 82. This paper simulates a compression test for concrete with inclusions, but uses an anisotropic description of the concrete. Here, the spatial structure of the main vertical cracks, as well as larger areas in the 45° angle of the phase-field, is also visible. However, the simulation still shows significant blurring in the formation of the crack and the crack edges. This indicates that the so far considered mesh shows reasonable results for crack propagation, but these might still be improved with a finer mesh. For this reason, a convergence study will be performed to determine the appropriate mesh size and thus improve the accuracy of the results.The crack propagation is comparable to literature resultsThe determination of the optimal mesh fineness requires a convergence study based on subsequently refined meshes. Based on the mesh shown in Fig. First, the force-displacement curve is evaluated for six different refinements, as shown in Fig. Nevertheless, crack propagation by phase-field method is strongly mesh dependent. For this reason, the displacement at which the initial crack appears, is investigated. For each refinement, this displacement is graphically determined and plotted against the characteristic length of the elements in the refined mesh area, see Fig. For this reason, the spatial distribution of the crack and its accuracy at a given time are additionally investigated for different meshes. Figure Here, the distribution of the phase-field within the examined region is shown. Since the displacement is above the critical displacement, the formation of a crack is clearly visible. For further investigation of this crack, the isolines indicates phase-field values between 0.6 and 1.0. The spatial evaluation confirms the results of the previous analysis. In the results of the upper row, the crack is illustrated with clear contours. In addition, the isolines for all three evaluations show a very similar course. However, if the results are compared with the lower row and thus with the coarser meshing, a large difference becomes apparent. First, the crack is significantly smaller despite the same displacement. Furthermore, the crack is clearly less defined and has blurrier contours. The isolines also differ greatly in both shape and size from those with the finer meshing. The difference in isolines can also be clearly seen in Fig. The crack propagation simulation is based on Griffith theory, where it is not possible to measure the The curve clearly indicates that the crack length for the same displacement decreases significantly with an increase in the parameter. This development shows an almost linear behaviour over the range with a variation of -15% to 15% of the current value.An increasing number of freezing and thawing cycles in concrete leads to a reduction in compressive strength, as described in section "For all simulations within this section, the Dirichlet condition on the top-surface is replaced by an compressive force. First, the influence of a changed compressive strength on the force required for crack initiation is investigated. For this purpose, the compressive strength is varied in the range from 20 N/mmIn Fig. As a next steps, an evaluation of the force required to cause an initial crack for each composition of concrete with additional NS is performed. Figure 83. In our experimental and numerical studies, we found out, that:Adding NS caused a significant increase in compressive strength before and after freezing and thawing cycles. Samples showed an increase in compressive strength up to 6% NS. After this percentage, adding NS has a reverse effect on the compressive strength. The highest compressive strength of all samples was observed in NSC6, followed by NSC5 for different freezing and thawing cycles.When cement was replaced by NS  based on a homogenization approach. Together with the incorporation of cracking mechanisms calibrated to specialized fracture experiments, enables a better understanding of the impact of freezing and thawing cycles on the lifespan of real-world constructions.NS can enhance the microstructure of cement, thereby significantly enhancing the freezing resistance of concrete. In concrete containing NS, the microstructure and appearance of CSH gel are more uniform, compact, and arranged. Furthermore, NS results in fewer pores and tighter crystal couplingSupplementary Information.


Clostridioides difficile infection (rCDI) and to decolonize intestinal AROs. However, FMT has significant practical barriers to safe and broad implementation. Microbial consortia represent a novel strategy for ARO and pathogen decolonization, with practical and safety advantages over FMT. We undertook an investigator-initiated analysis of stool samples collected from previous interventional studies of a microbial consortium, microbial ecosystem therapeutic (MET-2), and FMT for rCDI before and after treatment. Our aim was to assess whether MET-2 was associated with decreased Pseudomonadota (Proteobacteria) and antimicrobial resistance gene (ARG) burden with similar effects to FMT. Participants were selected for inclusion if baseline stool had Pseudomonadota relative abundance ≥10%. Pre- and post-treatment Pseudomonadota relative abundance, total ARGs, and obligate anaerobe and butyrate-producer relative abundances were determined by shotgun metagenomic sequencing. MET-2 administration had similar effects to FMT on microbiome outcomes. The median Pseudomonadota relative abundance decreased by four logs after MET-2 treatment, a greater decrease than that observed after FMT. Total ARGs decreased, while beneficial obligate anaerobe and butyrate-producer relative abundances increased. The observed microbiome response remained stable over 4 months post-administration for all outcomes.Intestinal colonization with pathogens and antimicrobial-resistant organisms (AROs) is associated with increased risk of infection. Fecal microbiota transplant (FMT) has successfully been used to cure recurrent Pseudomonadota abundances and ARGs as well as obligate anaerobes and beneficial butyrate producers in individuals with high Pseudomonadota relative abundance at baseline. This study provides support for a randomized, controlled clinical trial of microbial consortia (such as MET-2) for ARO decolonization and anaerobe repletion.Overgrowth of intestinal pathogens and AROs is associated with increased risk of infection. With the rise in antimicrobial resistance, new therapeutic strategies that decrease pathogen and ARO colonization in the gut are needed. We evaluated whether a microbial consortium had similar effects to FMT on  Pseudomonadota (Proteobacteria) or Enterococcus and decreased abundance of obligate anaerobes and butyrate producers is associated with elevated risks of infection in these individuals  and is associated with decreased incidence of bloodstream infection in this population  is effective for the treatment of recurrent pulation , 16. Theeriaceae , 17-19eriaceae -22. FMeriaceae . Howevereriaceae . Two stueriaceae  and patieriaceae . Currenteriaceae , 25.Pseudomonadota and ARG abundance.Microbial consortia, consisting of a combination of bacterial strains isolated from healthy human donors, have been developed to overcome some limitations of FMT -29. InPseudomonadota, other pathogens, and ARO carriage with infection risk  had less than 10% Pseudomonadota relative abundance by 16S rRNA gene sequencing and were not subject to shotgun metagenomic sequencing in the current study. Participants were further selected for inclusion if they had high baseline Pseudomonadota (>10% relative abundance) measured by shotgun metagenomic sequencing and administration of a single course of therapeutic (MET-2 or FMT) relative to post-treatment sampling. A total 15/17 (88%) MET-2 for rCDI trial participants and 5/8 (62%) FMT for rCDI study participants met this inclusion criterion. Participant characteristics are outlined in Two individuals (participants 4 and 7) from the initial trial (n = 19)  (n = 4) (Pseudomonadota relative abundance for participants who received MET-2 (n = 13) was 44%  and for participants who received FMT (n = 5) was 55%  . At baseline, the most common and abundant Pseudomonadota genera in the MET-2 and FMT groups were Klebsiella, which included K. pneumoniae, K. oxytoca, K. variicola, K. michiganensis, and K. quasipneumoniae. Other species included Escherichia coli, Enterobacter cloacae complex, and Citrobacter spp.  in the MET-2 group  and 2.2%  in the FMT group . One participant (Participant 10) failed initial MET-2 therapy for rCDI   revealed(n = 15) , while t (n = 4) . Among pter spp. . At 1 moMT group  with a mbacteria  and Enteeriaceae   and γ-Proteobacteria by quantitative polymerase chain reaction (qPCR). Between baseline and 1 month post-administration, the median 16S rRNA stool density post-MET-2 or FMT increased by 1 log from 215 ng/µL  to 1,511 ng/µL  and 1.7 logs from 107 ng/µL  to 5,628 ng/µL , respectively, although the trend was not significant   to 0.0008 ng/µL  post-MET-2 administration , while no change in γ-Proteobacteria density between baseline  and 1 month post-FMT administration  was observed  and 3% , respectively, consistent with this hypothesis.It is possible that MET-2 or FMT administration is displacing  = 0.06) . The medobserved . As the Pseudomonadota abundance was 36% , where the most abundant family was Enterobacteriaceae   . There w samples .U-test, P = 0.16), where the median number of ARGs for participants who received MET-2 was 78  and for participants who received FMT was 91 . There was a decrease in the total number of ARGs by 1 month after the MET-2 and FMT interventions  between the total number of ARGs detected and Pseudomonadota relative abundance in the MET-2 interventional group  between the total number of ARGs detected and Pseudomonadota relative abundance in the FMT interventional group  , where participants 10 and 18 had an Enterococcus relative abundance of 21% and 0.2%, respectively, suggesting that the increase in ARGs conferring resistance to glycopeptides in the MET-2 group overall was not due to vancomycin-resistant Enterococcus (The number of ARGs categorized by drug class-associated resistance for the baseline and 1 month post-MET-2 or FMT interventions is shown in nd vanG)  were detipant 18 . The medrococcus .n = 73) outlined in the study by Zhang and colleagues . The median butyrate-producer relative abundances for MET-2 and FMT interventional groups were 0.002%  and 0.05% , respectively . There was an observed increase in obligate anaerobe (P = 0.0005) and butyrate-producer (P = 0.002) relative abundances between baseline and 1 month post-MET-2 and FMT samples.Because of their significance in ARO colonization resistance and intestinal epithelial barrier and systemic immune function, we quantified obligate anaerobes and butyrate-producer relative abundances. At baseline, the median obligate anaerobe relative abundances for the MET-2 and FMT interventional groups were 5%  and 20% , respectively  and FMT (n = 5), respectively. The medians of all measured outcomes remained lower than baseline and stable at the final sampling timepoints for both interventions.To assess stability of the treatment-associated changes in microbiome composition, undances , as wellbundance  and totabundance , were asPseudomonadota (Proteobacteria), we observed that administration of a microbial consortium (MET-2) was associated with decreased Pseudomonadota and ARGs. The observed changes were similar or greater in magnitude to the effect of FMT for these outcomes. Obligate anaerobe and butyrate-producer relative abundances by 1 month post-intervention increased in a similar manner to FMT. The γ-Proteobacteria absolute abundance, measured by qPCR, decreased in the microbial consortium interventional group along with non-significant increases in 16S rRNA density. In the FMT group, there was a trend toward increased 16S rRNA density with no change in γ-Proteobacteria density by 1 month post-administration, possibly due to transfer of donor-derived Pseudomonadota. In an exploratory longitudinal analysis, we observed that all microbiome outcomes, including Enterococcus relative abundance observed at 1 month, remained stable at 4 and 6 months after administration of the microbial consortium and FMT, respectively. Overall, our findings indicate that microbial consortium administration produces effects consistent with FMT.In this analysis of adults with rCDI colonized with Pseudomonadota and ARGs in the human gut microbiome. The results observed after MET-2 administration were similar to those after FMT administration in this study as well as to published studies using shotgun metagenomic sequencing to assess the effects of FMT on the gut microbiota composition of patients with rCDI. In published studies, multiple-log decreases in Pseudomonadota relative abundance have been documented, along with increases in anaerobic Bacillota (Firmicutes) and Bacteroidota (Bacteroidetes)  -22.E. coli bacteremia  risk-associated threshold.Our study has multiple limitations. This was not a randomized comparison of MET-2 and FMT, but a  2 years . Our resnfection -6. Hownfection , where Anfection . Althougng depth  and may ng depth  and pating depth ; it is uPseudomonadota and ARGs, while increasing obligate anaerobes and beneficial butyrate producers. Given the practical limitations and potential safety concerns of FMT, a trial of microbial consortia for pathogen and ARG decolonization is warranted.In conclusion, administration of a microbial consortium for rCDI in participants colonized with a high relative abundance of potential pathogens has similar effects to FMT for decreasing intestinal This is a study of participants 18 years or older with rCDI, defined as one or more recurrences of CDI, who participated in separate prospective cohorts evaluating the effects of either a microbial consortium (MET-2), which has been previously described , or FMT Pseudomonadota relative abundance in the baseline stool sample based on 16S rRNA gene and shotgun metagenomic sequencing and did not receive additional MET-2 or FMT within a month after initial administration. This study had research ethics approval.Briefly, both cohorts were on antibiotic therapies prior to the therapeutic intervention. Participants who received FMT underwent bowel preparation prior to FMT. FMT was administered via enema three times over the course of 7 days. Participants receiving MET-2 did not receive bowel preparation prior to the intervention. Initially, 10 MET-2 capsules were taken orally for 2 days, and then three capsules were taken orally for 8 days. In the current study, we selected individuals from either cohort with ≥10% °C for 3 minutes, 18 cycles at 95°C for 15 seconds, 50°C for 15 seconds, and 72°C for 15 seconds, followed by 5 minutes at 72°C. All reactions were performed in triplicate, assessed on a 1% TBE gel, and pooled to reduce amplification bias. Pooled triplicates were quantified using PicoGreen and combined by even concentrations. The library was then purified using Ampure XP beads and loaded onto the Illumina MiSeq at the Centre for the Analysis of Genome Evolution and Function at the University of Toronto.Stool sample collection and 16S sequencing from the MET-2 trial was described previously . BrieflyPseudomonadota relative abundance between baseline and approximately 1 month (30 days ± 10 days) post-intervention (MET-2 and FMT). The secondary outcomes included total ARGs as well as obligate anaerobe and butyrate-producer relative abundance between baseline and 1 month post-intervention (MET-2 and FMT). Lastly, exploratory longitudinal analyses of Pseudomonadota, Enterococcus, obligate anaerobe, and butyrate-producer relative abundances, as well as total ARGs and absolute abundance of γ-Proteobacteria up to 4 months in the MET-2 interventional group and 6 months in the FMT interventional group, were performed.The primary outcome was change in main v5.1.0 of the CARD  published previously , the reverse primer (5′-GGACTACCAGGGTATCTAATCCTGTT-3′), and probe (FAM-5′-CGTATTACCGCGGCTGCTGGCAC-3′-NFQMGB) . Density of γ-Proteobacteria in each fecal sample and DNA extraction negative controls were measured using qPCR with the forward primer (5′-TCGTCAGCTCGTGTYGTGA-3′), the reverse primer (5′-CGTAAGGGCCATGATG-3′) (E. coli DNA was amplified with each qPCR reaction. E. coli DNA concentration (ng/μL) was measured using the Qubit Fluorometer (Thermo Fisher) following the manufacturer’s instructions. The target DNA density in each sample was estimated based on the E. coli standard curve. For the 16S rRNA and γ-Proteobacteria qPCR reactions, the limit of detection was approximately 10−7 and 10−6 ng/μL, respectively, where a qPCR cycle threshold of ≥40 was considered no detectable target DNA.Total bacterial DNA was measured by targeting the 16S rRNA gene in each fecal sample and DNA extraction negative controls with the forward primer (5′-GATG-3′) , and proPseudomonadota content in each sample was summarized at the species level, and overall relative abundance was quantified at the phylum level. Enterobacteriaceae, γ-Proteobacteria, and Enterococcus relative abundances were also quantified. Obligate anaerobe and butyrate-producer diversity in each sample was summarized and relative abundance determined at the species level.Bergey’s Manual of Systematic Bacteriology volumes 2–5 to manually classify species-level taxa as obligate anaerobes and butyrate producers based on descriptors in the manuals such as “strictly anaerobic,” “anaerobic,” or “obligate anaerobe” as well as “produces butyrate,” “forms butyrate,” or “butyric acid is an end product”  and up to 4 or 6 months post-intervention for MET-2 and FMT recipients, respectively.U-test was used to compare groups. The non-parametric Spearman’s correlation was performed to test the relationship between total ARGs and Pseudomonadota abundance. Statistical analyses were performed in GraphPad Prism v9.0.3. Statistical analyses were not performed between timepoints for the individuals receiving FMT.Samples were grouped by intervention received (MET-2 or FMT) and stratified by timepoint. To compare relative abundances between baseline and 1 month post-intervention samples, 0.000001 was added to relative abundances for all taxa (to account for zeros), then log transformed. Pairwise analyses were performed using the non-parametric Wilcoxon matched-pairs signed-rank test on log-transformed relative abundances, DNA density, and total number of ARGs within interventional groups between the baseline and 1 month post-intervention timepoints. The non-parametric Mann-Whitney NuBiyota is the manufacturer of the microbial consortium (MET-2) assessed in this study. The company funded the original MET-2 trial , but did


The compressive strength of the specimens after dry–wet cycles in different environments generally increased first and then decreased, reaching a peak at the seventh dry–wet cycle, and the compressive strength of the specimens under chloride salt solution decreased more than that under clear water solution. Thes provided new concrete materials for the construction of highways and tunnels in coastal areas. Under the premise of ensuring the strength and durability of concrete, it is of great practical significance to explore new roads for energy conservation and emission reduction.In order to study the mechanical properties of rice husk ash–rubber–fiber concrete (RRFC) under hygrothermal environment, the optimal group was selected by orthogonal test. The mass loss, relative dynamic elastic modulus analysis, strength analysis, degradation degree analysis after cyclic loading and internal microstructure analysis of the optimal group of RRFC samples after dry–wet cycles under different environments and temperatures were compared and analyzed. The results show that the large specific surface area of rice husk ash optimizes the particle size distribution of RRFC specimens, reacts to form C-S-H gel, enhances the compactness of concrete, and forms a dense structure as a whole. The presence of rubber particles and PVA fibers effectively improves the mechanical properties and fatigue resistance of RRFC. The comprehensive mechanical properties of RRFC with rubber particle size of 1–3 mm, PVA fiber content of 1.2 kg·m Mn beings . The hign beings ,18,19.Due to the shortcomings of self-weight and low tensile strength of concrete, many scholars have made up for these shortcomings by adding various fibers ,21,22. JAlthough rubber concrete has many advantages such as low density, high energy consumption and good toughness, previous research results show that the weakening effect of rubber particles on concrete strength cannot be ignored, which has indeed become a bottleneck restricting the promotion and application of rubber concrete. Therefore, this paper also considers that the building structures such as highways and tunnels in coastal areas are seriously affected by hot and humid environment , chlorinThe cement used in the test is P·O 42.5 ordinary Portland cement produced by the Bagongshan Cement Plant in Huainan City; the rubber particles cut and crushed from waste tires were selected, and the average particle sizes were 0.4–0.6 mm, 1–2 mm and 2–4 mm, respectively. The rice husk ash is grade I fly ash produced by the Huainan Pingwei Power Plant. The main chemical composition is shown in In this paper, aiming at examining the two problems of solid waste recycling and fiber-reinforced concrete characteristics, the rice husk ash–rubber–fiber concrete is studied. The main research contents are as follows:2 solution at (20 ± 2) °C for 28 days.(1) According to the standard design C30 ordinary concrete mix, efore the test block is made, the concrete wet mixer with the reference mix ratio is first used to reduce the test error. During the production, the pre-weighed coarse aggregate, fine aggregate, rubber particles, rice husk ash and PVA fiber were mixed and stirred for 2 min, then cement was added and stirred for 1 min, and then the uniformly mixed water and water reducer were injected into the mixer and stirred for 3 min. In order to prevent the rubber floating, the concrete was poured into the mold in three rounds and placed on the vibration table to vibrate and compact until no bubbles were generated, and then the surface was flattened. Then, the concrete was cured in a curing room with a temperature of (20 ± 3) °C and a relative humidity of 70%. After 24 h of curing, the specimens were removed and then placed in a saturated Ca(OH)9(33) orthogonal test table was finally selected, see (2) The rubber particle size (factor A), rice husk ash content (factor B) and PVA fiber (factor C) were set as the three factors of the test, and each factor was set at three levels. The three-factor three-level orthogonal test was carried out, and the test results were analyzed by the efficacy coefficient method to obtain the best factor–level combination. The orthogonal test factors–levels are listed in (3) According to the optimal mix ratio obtained by the orthogonal test, a cylindrical rice husk ash–rubber–fiber concrete test block with a diameter of 50 mm and a height of 100 mm was prepared. After grinding and drying, the dry–wet cycle test was carried out in different environments. The specimens were divided into six groups and placed in a constant temperature water bath at 20 °C, 60 °C and 80 °C, respectively. Two solutions were set for each temperature gradient, including water and a 5% NaCl solution. In order to accurately investigate the influence of hygrothermal environment on the fatigue performance of RC, the dry–wet cycle test (soaking 16 h + drying 6 h + cooling 2 h) was used to simulate the hygrothermal environment under laboratory conditions. The number of dry–wet cycles was 0, 7, 14, 28 and 56, respectively. The dry–wet cycle test process is shown in According to the standard for test methods of physical and mechanical properties of concrete (GB/T50081-2019), the calculation formula of uniaxial compressive strength stress of RRFC cylinder is as follows:N); 2).In the formula, The uniaxial compressive strain calculation formula of RRFC cylinder is as follows:ε is the uniaxial compressive strain (MPa) of the concrete cylinder test block; L is the length of concrete cylinder after deformation (mm); L0 is the original length of concrete cylindrical test block, L0 = 100 mm.In the formula, (4) The microstructure and material composition of the interface area of the optimal group of concrete aggregate were analyzed. The internal damage of concrete was reflected by non-destructive ultrasonic testing technology ,41 and sThe mix ratio and strength results of each group of concrete tests are shown in The efficacy coefficient of each index of RRFC was calculated by using the satisfactory value and the allowable value of each index in i is the evaluation index, i = 1,2,3; i index of RRFC specimen; i. i index.In the formula, According to the above Formula (3), the efficiency coefficient value is calculated and analyzed, and the results are shown in −3, and the content of rice husk ash is 15%. According to the optimal ratio, concrete test blocks were made and subsequent tests were carried out.According to the analysis results of the efficacy coefficient method in mW of RRFC test block under different dry–wet cycles was calculated by the following formula:mW is the concrete quality change rate/%; m0 is the initial mass of concrete test block/kg; nm is the mass/kg of the concrete test block after n dry–wet cycles.The quality of RRFC concrete is constantly changing under the double damage of chloride erosion and dry–wet cycle. The mass of concrete before and after the dry–wet cycle test was weighed, and the mass change rate ∆The curve of the mass loss rate of RRFC test block with the number of dry–wet cycles in different environments is shown in 2 in rice husk ash and Ca(OH)2 in the process of cement hydration in the early stage of the dry–wet cycle, which generates a large number of C-S-H gel to fill the holes and increase the quality. With the progress of the dry–wet cycle, water molecules are continuously immersed and baked inside the concrete, and the holes inside the concrete test block are increasing, even penetrating into cracks. The cementation force of the internal structure is weakened, and some internal particles are brought to the external environment, resulting in the continuous reduction in concrete quality. In the chloride salt solution, the mass of the specimen increased with the increase in the number of dry–wet cycles in the early stage of the dry–wet cycle, and the mass of the specimen reached the maximum peak at 28 dry–wet cycles. The reason is that the dry–wet cycle in the salt solution consists of the C-S-H gel produced by rice husk ash and Ca(OH)2, and it also contains the impurities and NaCl in the solution that are attached to the internal holes and surfaces of the concrete test block. The chloride salt forms salt crystal erosion damage to the concrete, and the crystallization accumulates in the cracks of the internal holes of the concrete; in this way, the quality of the concrete is increasing.It can be seen from When the number of dry and wet cycles is the same, the higher the solution temperature, the greater the mass loss rate of the specimen. When the temperature of the clear water solution is 80 °C, the mass loss of the test block is the largest, and the mass loss rate is 1.62%. The temperature of the clear water solution is 60 °C, and the mass loss is the smallest at 20 °C with the mass loss rate of 1.38%. This is because the dry–wet cycle itself has a certain deterioration effect on the concrete specimen, and the increase in the temperature leads to the acceleration of the crystallization erosion diffusion of the chloride salt on the concrete specimen, which accelerates the deterioration rate of the concrete specimen, and the deterioration damage is more serious.drE is relative dynamic elastic modulus/%; dtE and dE0 are the dynamic elastic modulus/MPa of the specimens after different dry–wet cycles and without dry–wet cycles. tT and T0 are the sound time/s of the specimens after different dry–wet cycles and without dry–wet cycles. tV and V0 are the ultrasonic wave velocity/m·s−1 of the specimens after different dry–wet cycles and without dry–wet cycles.The relative wave velocity of RRFC was measured by NN-4B non-metallic ultrasonic testing analyzer manufactured by Beijing Kangkerui Company , and the relative dynamic elastic modulus of concrete specimens was calculated. The calculation formula is as follows:It can be seen from It can be seen from fK of RRFC specimens after different dry–wet cycles is calculated by the following formula:fnK is the compressive strength corrosion resistance coefficient/% of concrete specimens after n dry–wet cycles; nf is the compressive strength/MPa of concrete specimens after n dry–wet cycles; f0 is the compressive strength/MPa of the specimen before the dry–wet cycle.The compressive strength corrosion resistance coefficient It can be seen from 2 reacts with Ca(OH)2 generated during the hydration reaction to form C-S-H gel, which fills holes and gaps, improves the compactness, alleviates the damage caused by the dry–wet cycle process, and improves the compressive strength and corrosion resistance of the RRFC specimen. As the number of dry–wet cycles increases, the compressive strength of the specimen gradually decreases, and the corrosion resistance coefficient continues to decrease. The higher the solution temperature, the greater the compressive strength damage of the specimen, the greater the decrease in the corrosion resistance coefficient, and the lower the residual compressive strength. After 56 dry–wet cycles, the compressive strength of the specimen reached 29 MPa and the corrosion resistance coefficient was 0.78 when the solution temperature was 20 °C. When the solution temperature was 60 °C, the compressive strength of the specimen reached 28.2 MPa, and the corrosion resistance coefficient was 0.75. When the solution temperature was 80 °C, the compressive strength of the specimen reached 26.7 MPa and the corrosion resistance coefficient was 0.71.In the clear water solution, the compressive strength of RRFC specimens increased with the increase in the number of dry–wet cycles and peaked at the seventh time. In the early stage of the dry–wet cycle, the incompletely hydrated cement inside the concrete specimen continues to undergo hydration reaction, so that the hydration reaction is carried out thoroughly, the cementation force is enhanced, and the compressive strength of the specimen is enhanced. The rice husk ash in the specimen has high pozzolanic properties. The highly active SiO2 in the rice husk ash reacts with Ca(OH)2 to form C-S-H gel to fill the pores, and the chloride salt forms crystals attached to the surface and inside of the concrete, filling some pores and cracks and improving the compactness. At this time, the tensile strength provided by the PVA fiber in the specimen is greater than the expansion force generated by the chloride salt crystallization, so the compressive strength of the concrete specimen increases and the corrosion resistance coefficient increases. However, with the increase in dry–wet cycles, the compressive strength of the specimens gradually decreased, and the corrosion resistance coefficient continued to decrease. The higher the solution temperature, the greater the compressive strength damage of the specimen, the greater the corrosion resistance coefficient, and the lower the residual compressive strength.In the chloride solution, the compressive strength of RRFC specimens increased with the increase in the number of dry–wet cycles and reached the peak at the seventh time, and the peak compressive strength was significantly greater than that in the clear water solution. This is because in the chloride solution, not only the cement hydration reaction is more thorough and complete, but also the highly active SiOWhen the RRFC test block reaches the corresponding dry–wet cycle times  in different hot and humid environments, the uniaxial compression test and cyclic loading and unloading test are carried out to analyze the fatigue damage law.The uniaxial compressive strength stress and strain of the optimal factor level combination are calculated by using Formulas (1) and (2). The uniaxial compressive stress–strain curve is shown in It can be seen from The cyclic loading and unloading test was carried out on the RRFC specimen after the dry–wet cycle, that is, 60% of the uniaxial compressive failure load of the specimen itself was taken as the upper limit of the loading load, and the lower limit of the unloading load was 100 N. A loading–unloading process was used as a cycle, and a total of 50 cycles was carried out. The test results are transformed into stress and strain by Formulas (1) and (2). During the pouring process of concrete specimens, a small amount of pores and cracks inevitably occurs, resulting in the inhomogeneity of concrete materials, and the strength and deformation of different parts of the specimens also shows differences. Therefore, the deformation of RRFC specimens during compression includes reversible elastic deformation and irreversible plastic deformation. The specific situation is also determined by the stress level and the history of unloading and unloading, such as the upper limit of loading stress and the number of cyclic loadings and unloadings. This feature shows that the loading curve and the unloading curve cannot coincide with each other on the stress–strain curve of the specimen, forming a hysteresis loop.As shown in 3A·CaCl2·10H2O  generated by the reaction are greater than the tensile strength caused by the polyethylene fiber, resulting in the increase in holes and gradual penetration into gaps. The compressive strength of the specimen decreases significantly and the corrosion resistance coefficient decreases. The higher solution temperature accelerates the thermal movement of chloride ions and water molecules in the solution inside the concrete. The diffusion rate of chloride ions increases and the range becomes wider; the erosion rate increases exponentially, resulting in an increase in the internal solubility of the concrete specimen, a decrease in compactness, and internal structure damage. This explains the reason why the macroscopic mechanical properties of the RRFC specimens began to decrease in the middle of the dry–wet cycle in chloride solution and the decrease was significantly greater than that of the specimens in the clear aqueous solution environment.It can be clearly seen from Based on the orthogonal test scheme, the feasible ratio combination of new green concrete is explored. At the same time, the dry–wet cycle test and cyclic loading–unloading test of the RRFC specimens under the optimal ratio were carried out, and the damage and deterioration law of the specimens after the dry–wet cycle test was analyzed. The following conclusions were drawn:−3, and the rice husk ash content is 15%.(1) The compressive strength of RRFC specimens is between 29.1 MPa and 37.6 MPa, the splitting tensile strength is between 3.2 MPa and 4.5 MPa, and the flexural strength is between 4.6 MPa and 5.8 MPa. Its mechanical properties are mostly better than those of the C30 ordinary concrete, and the maximum increase is 17.5%, 26.7% and 15.7%, respectively. The optimal factor level combination of RRFC specimens is A2B2C3, that is, the rubber particle size is 1–3 mm, the PVA fiber content is 1.2 kg·m(2) The best ratio of RRFC specimens was placed in clear water solution and chloride solution at different temperatures for 56 dry–wet cycles. It was found that the compressive strength of the specimens under the dry–wet cycles in different environments increased first and then decreased, and reached the peak in the seventh dry–wet cycle. When the number of dry and wet cycles is the same, the compressive strength of the specimen under the chloride solution is lower than that of the clear water solution, and the higher the solution temperature, the more serious the damage of the specimen. There is a significant correlation between these deterioration damage indexes and the change law of compressive strength of specimens, which proves that the change in mechanical properties of RRFC specimens is closely related to the deterioration damage of specimens under dry–wet cycle erosion.(3) The cyclic loading–unloading stress–strain curve of RRFC specimen shows two stages of sparse first and then dense. The total strain of the specimen changes little, and the deformation mainly occurs in the first cycle. As the number of cyclic loading–unloading increases, microcracks appear inside the RRFC specimen. At this time, the specimen is dominated by elastic deformation, and the hysteresis loop area decreases. The axial peak strain and residual strain of the RRFC specimen increase continuously during the repeated loading and unloading process. The increase in the axial peak strain in the first five cycles is the most obvious; then, it gradually slows down and tends to be stable, reflecting the trend of the hysteresis curve from sparse to dense.2 in rice husk ash reacts with Ca(OH)2 to form C-S-H gel, which enhances the compactness of concrete, reduces the concentration of Ca2+, promotes the hydration reaction of cement, and continuously forms honeycomb products during the hydration reaction and the surrounding plate-like area increases, so that the specimen forms a dense structure as a whole.(4) The large specific surface area of rice husk ash optimizes the particle gradation of RRFC specimens, exerts the filling effect, and makes the interior of the specimens denser. At the same time, a large number of highly active SiO(5) The excellent ductility of rubber particles effectively alleviates the damage caused by the immersion and drying of water molecules and the expansion force caused by chloride crystallization in the dry–wet cycle erosion. In the process of cyclic loading and unloading, the damage caused by repeated loading and unloading is effectively alleviated, and the stress redistribution inside the specimen is optimized, so that RRFC exhibits excellent fatigue resistance. The PVA fiber forms a random three-dimensional space grid in the RRFC specimen, which effectively hinders the migration channel and crack development of chloride ions, alleviates the stress concentration phenomenon, prevents the floating of rubber particles, and improves the mechanical properties and fatigue resistance of the specimen.(6) Due to the limitation of conditions, only the RRFC specimens with the best ratio were selected for the dry–wet cycle test and cyclic loading–unloading test under different solutions, while the durability and fatigue resistance of RRFC specimens with other dosages need further exploration and research.