This study takes the aeolian sand concrete as a research object, uses the relative dynamic elastic modulus to study its macro characteristics, and combines nuclear magnetic resonance、scanning electron microscope to study its pore characteristics and micro morphology under the action of prestress, freeze-thaw and salt intrusion. The results show that with the increase of the amount of aeolian sand, the dynamic elastic modulus of aeolian sand concrete shows a pattern of first decreasing, then increasing, and then decreasing; when no prestress is applied, the porosity of aeolian sand concrete first increases, then decreases, and then continues to increase. Among them, the porosity of aeolian sand concrete with a 40% content of aeolian sand decreases by 0.06% compared to that with a 0% content of aeolian sand, and decreases by 0.003% compared to that with a 60% content of aeolian sand; with the increase of prestress, the porosity of aeolian sand concrete with the same amount of aeolian sand increases gradually with the increase of damage degree. The porosity of concrete with 40% aeolian sand content increases by 0.33% when the damage degree is 0.0 compared to 0.3, with a 6.31% increase in the number of multi damage pores; under the coupling effect of multiple factors, when the amount of aeolian sand is 40%, the damage degree of the four groups of aeolian sand concrete before and after the coupling effect is 0.0, 0.1, 0.2, and 0.3, respectively, increases by 25.8%, 32.2%, 73.8%, and 85.8%, respectively; under the coupling effect of multiple factors, the content of aeolian sand is 60%, the damage degree is 0.2 and 0.3 groups, and the content of aeolian sand is 20%, the damage degree is 0.3 groups, which does not meet the standard requirements; under the coupling action of stress, freeze-thaw, salt intrusion and the amount of aeolian sand, the filling effect of aeolian sand on the internal pores of aeolian sand concrete decreases first, then increases, and then decreases with the increase of the amount of aeolian sand. The filling effect is further weakened after the action of stress. After the superposition of freeze-thaw and salt intrusion, the coupling effect of water and salt solution in frost heaving medium makes the variation law and range of physical and chemical characteristics of aeolian sand concrete show a great difference. Domestic and foreign scholars have also conducted a large number of experimental and theoretical studies on the deterioration characteristics and mechanism of concrete after stress damage, such as: Zhou Zhijun et al . Studiedan et al . Studiedan et al . Studiedan et al . Studiedan et al  and othean et al . Studiedan et al . Studiedan et al  and othean et al . Studiedan et al . Tested an et al . StudiedTo sum up, scholars at home and abroad have studied the deterioration process of concrete under uniaxial, biaxial and bending stresses, and made clear its superimposed influence on the coupled erosion effects such as salt intrusion and carbonation, and pointed out that when stress is coupled with other erosion effects, concrete deterioration presents phased changes, and the promotion or suppression of concrete deterioration also depends on the superimposed effect, based on damage theory-Fick’s law Octahedral theory established the deterioration model under the coupling effect of stress and erosion. However, the existing research often focuses on the traditional concrete materials, and the coupling factors are also common in the two factors coupling. The damage mechanism research is also dominated by the deterioration mechanism under the action of a single factor. There are still significant deficiencies in the research and development of green new building materials, as well as in the study of the deterioration mechanism of concrete materials under the coupling of multiple factors, which is in line with the harsh environment in the western region.In view of this, this study uses aeolian sand widely distributed in Western China as raw material to replace river sand to prepare a new green building material, namely aeolian sand concrete, and discusses its degradation process under multiple factors in the harsh environment of the western region , so as to clarify its degradation characteristics and mechanism, which is not only conducive to the development of aeolian sand resources, the economic development of aeolian sand, and the research and development of new building materials, it is also conducive to protecting river sand resources, promoting social development and environmental protection, which is of great social, economic and practical significance.3, a bulk density of 1650kg/m3, and a particle size range of 4.75~20.0mm; the mixing water is ordinary tap water; the water reducing agent adopts polycarboxylic acid sc-40 high-efficiency water reducing agent of Inner Mongolia Rongshengda new materials Co., Ltd., with a water reducing rate of 26%; the air entraining agent is sj-3 high-efficiency air entraining agent, grade II fly ash of Inner Mongolia Jinqiao power plant and Jidong P•O42.5 cement. Some physical and chemical property indexes are shown in Tables The fine aggregate used in the study is from the sand field around Hohhot, with a fineness modulus of 2.91 and a particle size range of 0.075~4.75mm; aeolian sand is taken from the Kubuqi Desert in Inner Mongolia, China, with a fineness modulus of 0.72. The coarse aggregate used in the test is egg gravel, with an apparent density of 2669kg/mIn accordance with the relevant provisions of concrete mix proportion design in the code for hydraulic concrete construction (SL677-2014), code for mix proportion design of ordinary concrete JGJ55-2011) and ACI method of proportion, and in order to ensure that the aeolian sand concrete can obtain high slump and fluidity for engineering practice, equivalent replacement shall be carried out according to the aeolian sand content of 0%, 20%, 40%, 60%, 80% and 100%, the strength grade of the benchmark aeolian sand concrete is generally C25, and its mix is shown in According to the standard for test methods of long-term performance and durability of ordinary concrete >  , measure the initial relative dynamic elastic modulus, and define the damage degree at this time as 0.0. Apply axial loads respectively by universal testing machine. When the relative dynamic elastic modulus decreases by 5%, stop loading, and define the damage at this time as 0.1, and so on, the relative dynamic elastic modulus of aeolian sand concrete with damage degree of 0.2 and 0.3 is 90% and 85% of the initial value respectively.② Apply freeze-thaw and salt intrusion: select concrete specimens of aeolian sand with different amounts of aeolian sand and different degrees of damage. After 24 days of standard curing, immerse them in (full immersion method) the freeze-thaw medium (5.0% NaCl solution) with a temperature of 15 ~ 20°C. After 4 days, wipe the surface moisture of the soaked specimens, and further determine the relative dynamic elastic modulus at this time. Then, use the "quick freezing method)" to carry out the freeze-thaw and salt intrusion coupling test of aeolian sand concrete.③ Test and analysis: under the coupling effect of stress, freeze-thaw and salt intrusion, the relative dynamic elastic modulus of aeolian sand concrete samples with different amounts of aeolian sand is measured with 25 freeze-thaw cycles as a cycle. When the relative dynamic elastic modulus drops to 60% of the initial value, the test is terminated, and then the micro pore structure after prestressing and the coupling effect of stress, freeze-thaw and salt intrusion is measured by NMR, Sigma500 field emission scanning electron microscope was used to measure the micro morphological characteristics before and after the coupling condition.The compressive strength and splitting tensile strength of aeolian sand concrete are measured according to the standard for test methods of mechanical properties of ordinary concrete GB/T50081-2002, as shown in Figs According to Figs It can be seen from At the same time, it can be seen from On the basis of the study on the mechanical properties of aeolian sand concrete and the pore characteristics after prestress, the concrete with damage degrees of 0.0, 0.1, 0.2 and 0.3 and the content of aeolian sand of 0%, 20%, 40% and 60% was first soaked in 5.0% sodium chloride solution for 4 days, and then put into the freeze-thaw test box with 5.0% sodium chloride solution as the freeze-thaw medium for stress, freeze-thaw and salt intrusion coupling tests, taking 25 freeze-thaw cycles as a cycle, measuring the relative dynamic elastic modulus of aeolian sand concrete. When the relative dynamic elastic modulus drops below 60% of the initial value or the freeze-thaw cycle is 200 times, the test is terminated, and samples are taken for NMR, field emission scanning electron microscope. The test results are shown in Figs It can be seen from Figs It can be seen from Tables This is due to the unique physical and chemical characteristics of aeolian sand concrete different from ordinary concrete under the coupling action of stress, freeze-thaw, salt intrusion and the change of aeolian sand content. When aeolian sand replaces river sand, if the replacement proportion is less, aeolian sand, as a super fine sand, requires more water in the concrete slab and process, and because the amount of aeolian sand is less, its effect on filling the pores in the concrete is poor, resulting in an increase in the overall porosity. Therefore, when the amount of aeolian sand is 20%, the porosity of aeolian sand concrete increases, and the relative dynamic elastic modulus and irreducible fluid saturation decrease within the same damage degree; with the increase of the replacement proportion of aeolian sand, the filling effect of aeolian sand on the internal pores of concrete increases, so when the content of aeolian sand is 40%, the porosity of aeolian sand concrete in the same damage degree decreases, and the relative dynamic elastic modulus and irreducible fluid saturation increase; at the same time, when the amount of aeolian sand is large, the filling effect of aeolian sand on the pores in the concrete has reached saturation, and the excess aeolian sand needs more water during the preparation of concrete, resulting in the formation of aeolian sand particles including incomplete mixing in the concrete. Therefore, when the amount of aeolian sand is 60%, the internal porosity of aeolian sand concrete increases significantly, and the relative dynamic elastic modulus and bound fluid saturation decrease significantly.When the stress is superimposed, it is only the mechanical damage to the original concrete, which reduces the physical and chemical properties of aeolian sand concrete to a certain extent, but does not change the change rules of the physical and chemical properties such as the relative dynamic elastic modulus and porosity of aeolian sand concrete caused by the change of the content of aeolian sand; when the freeze-thaw and salt intrusion are superimposed, the change law and range of physical and chemical properties of aeolian sand concrete show great differences. This is because under the action of freeze-thaw and salt intrusion, the freeze-thaw medium gradually erodes into the interior of aeolian sand concrete, and the water in the freeze-thaw medium freezes and melts under the action of freeze-thaw, while the volume of water expands when it freezes, destroying the internal pores of aeolian sand concrete, make it transform from harmless and less harmful pores to more harmful and harmful pores with larger pores. At the same time, the salt in the freeze-thaw medium enters the interior of aeolian sand concrete with the pores generated by water frost heaving and melting under the action of capillary, infiltration and diffusion –19, and With the increase of the amount of aeolian sand, the relative dynamic elastic modulus of aeolian sand concrete decreases first, then increases, and then decreases. The porosity increases first, then decreases, and then continues to increase. The porosity of aeolian sand concrete with 40% of aeolian sand is 0.06% lower than that with 0% of aeolian sand, and 0.03% lower than that with 60% of aeolian sand, and the pore changes are mainly concentrated between harmless pores of 20-50nm, up to 27.05%.With the increase of prestress, the porosity of aeolian sand concrete with the same amount of aeolian sand presents a gradual increase trend. When the damage degree of aeolian sand concrete with 40% of aeolian sand is 0.0, the porosity is 1.598%, while when the damage degree is 0.3, the porosity increases to 1.928%, with an increase of 0.33%, in which the number of more harmful pores increases by 6.31%, and the irreducible fluid saturation decreases by 2.371%.This indicates that pre-stressing causes the transformation of less harmful pores with smaller internal pore sizes into harmful pores with larger pore sizes, resulting in larger pores and a decrease in compactness in aeolian sand concrete.Under the action of stress, freeze-thaw and salt intrusion, when the content of aeolian sand is 60%, the damage degree is 0.2 and 0.3, it decreases to 58%, 54% .And when the content of aeolian sand is 20%, the damage degree is 0.3, it decreases to 59% of the initial value, and the other groups meet the standard requirements; when the content of aeolian sand is 40%, the damage degree is 0.0, 0.1, 0.2 and 0.3. The relative dynamic elastic modulus of aeolian sand concrete decreases by 23.8%, 24.4%, 26.0% and 38.8% respectively, the porosity increases by 25.8%, 32.2%, 73.8% and 85.8% respectively, and the irreducible fluid saturation decreases by 5.3%, 25.8%, 27.7% and 41.2% respectively, meet the standard requirements.Under the coupling action of stress, freeze-thaw, salt intrusion and the amount of aeolian sand, the filling effect of aeolian sand on the internal pores of aeolian sand concrete decreases first, then increases, and then decreases with the increase of the amount of aeolian sand. The filling effect is further weakened after the action of stress. After the superposition of freeze-thaw and salt intrusion, due to the combined influence of water and salt solution in the frost heave medium, the variation law and range of physical and chemical properties of aeolian sand concrete show great differences.


Dairy cows are regularly handled when moved to the milking parlor and during other routine procedures. Low-stress handling methods are important in avoiding negative welfare states for dairy cattle. Tail twisting is used by some handlers to prompt cattle movement. However, when used inappropriately with excessive force, tail twisting can lead to a broken tail. The aim of this cross-sectional study was to determine cow-level factors that may be associated with the prevalence of broken tails in dairy cattle. A subset of 229 Holstein dairy cows (68 primiparous and 161 multiparous) at a single dairy were assessed for broken tails from the larger herd . Tails were visually assessed for the presence of fractures by a single trained observer. A tail was classified as unfractured if it laid straight when at rest and as fractured if there were deviations in the tail when at rest. Poisson regression models were used to identify associations between cow-level characteristics and broken tails and compute adjusted prevalence ratios (PR). The prevalence of broken tails was 45.8% (105/229) at the time of assessment. Multiparous cows had a greater prevalence of broken tails than primiparous cows . The prevalence of broken tails was also greater for cows treated for mastitis ≥2 times than cows treated once for mastitis  and cows never treated for mastitis . Results from this study indicated that the longer a cow was present on the farm and the more times she was treated for mastitis, the more likely she was to experience a broken tail. These findings suggest that the relationship between dairy cow handling, health, and welfare is a multifactorial issue. Dairy cows are regularly handled when moved to the milking parlor multiple times per day and during routine management practices. Therefore, low-stress handling methods are important to avoiding negative welfare states for dairy cattle. Tail twisting is used by some handlers to prompt cattle movement. The use of tail twisting as a handling method to prompt forward cattle movement involves releasing the tail after the animal moves forward and never involves continuous twisting of the tail . If tailCurrent conjectures regarding the cause of broken tails include facility design  and incorrect handling. It is possible that improper handling, rather than facility design, is the primary cause of broken tails. During some animal welfare assessments on dairy farms, tails are assessed as part of the evaluation criteria and are generally considered to be broken or not broken. The All procedures involving live animals in this study were approved by the Colorado State University Animal Care and Use Committee. The approved protocol number was 09-175A-01.A subset of 229 cows from a dairy herd consisting of 1,356 lactating and nonlactating Holstein cows were assessed for locomotion score and fractured tails. The dairy was located in the Western Plains region of the United States. Data for this cross-sectional study were collected during a single visit to the dairy in June 2009. This study was originally designed to assess biochemical markers of energy balance  and inflammation . During blood collection by tail venipuncture, a trained observer noted that many animals had fractured tails. Thus, the prevalence of broken tails was included as an outcome of interest. Cows were included for broken tail analysis if they were scheduled to have blood collected on the final day of data collection (over a 2 d period of data collection).Cows were housed outdoors in dry lots with gravel and soil substrate without access to shade or stalls. No automatic manure scrapers were present at this facility. A TMR formulated for the appropriate stage of lactation was provided ad libitum by fenceline feed bunks. Ad libitum access to water was also provided within each pen. Animal records were maintained by herd management in DairyComp305 software  and transferred to an Excel spreadsheet (Microsoft Corp.).All dairy cattle were visually assessed for broken tail and locomotion score by a single trained observer. Tails were classified as unfractured if they laid straight when at rest and as fractured if there were any noticeable deviations when at rest. Tails were considered at rest when the entire tail hung directly toward the ground and the switch of the tail was not moving. Our definition of a fractured tail aligned with the definitions of level 2, 3, and 4 tail fractures outlined by P < 0.05.All analyses were performed using SAS software . Raw data were visually screened at the individual animal level for data distribution and outliers using the UNIVARIATE procedure in SAS. Statistical significance was declared at P < 0.20) were included in the multivariable model. Manual backward removal was performed and variables with P < 0.05 were retained in the final model. Interactions were tested between biologically relevant variables and removed from the model if P > 0.05. Confounding was assessed and a variable was retained in the final model if its removal changed the coefficients by >20%. The prevalence ratio (PR) of broken tails (broken vs. unbroken) was analyzed using a Poisson regression model with robust error variances (PROC GENMOD), including a log-link. Standard errors were corrected for overdispersion by adding the “pscale” option to the model statement  and each explanatory variable using a Poisson regression model (PROC GENMOD). Continuous variables were visually assessed for normality and outliers, and were categorized if they did not meet the assumptions of normality. Parity was categorized into primiparous (parity = 1) and multiparous (parity ≥2). Total lifetime mastitis treatments were categorized into never treated for mastitis, treated for mastitis once, and repeated mastitis treatments . No outliers were detected in the data set. Variables of interest were tested at the univariable level if they were expected to be biologically relevant to the prevalence of broken tails and included parity, DIM, locomotion score, total lifetime mastitis treatments, and predicted 305-d milk production. Explanatory variables associated with the dependent variable (tatement . Cow wasThe study population included 29.7% primiparous and 70.3% multiparous dairy cattle. The population of cows included in the analysis for broken tails was representative of the entire population . MultipaThe objective of this study was to evaluate cow-level factors associated with broken tails in dairy cattle. In this study, we found that multiparous cows had a greater PR of broken tails than primiparous cows. Multiparous cows are at an increased risk for culling for a variety of reasons, including infertility, mastitis, skeletal injuries, and lameness . Older aCows with repeated mastitis treatments also had a greater PR of broken tails than cows treated once or never treated for mastitis . Of the Broken tails are included as an animal-based measure of dairy welfare assessments . At the A primary limitation of our study is that a cross-sectional sample of a single dairy was observed, and only a subset of the animals in this herd were assessed for broken tails; the result of this was a relatively small sample size. Only cow-level factors could be evaluated; as such, facility and management factors could not be assessed. Because animal handling was not evaluated, the frequency of tail twisting is unknown. Additionally, the facility design of this dairy may not be generalizable to dairies outside of the Western Plains region of the United States, where this study took place. Since the time of data collection, guidance has indicated that palpation of the tail should occur during assessments of tail damage . It is aThis study aimed to identify cow-level factors associated with the occurrence of broken tails on dairy farms. Multiparous cows had a greater prevalence of broken tails than primiparous cows. Cows with repeated mastitis treatments were also more likely to have a broken tail than cows treated once or never treated for mastitis. There are still gaps in our knowledge considering the prevalence and implications of broken tails in dairy cattle. Further research is needed to deepen our understanding of how and why tails are broken, the welfare implications of broken tails, and how broken tails can be prevented on dairies. Future studies could include quantifying the occurrence of tail twisting to prompt forward movement on dairies or the occurrence of forceful tail twisting on dairies and how often this technique results in a broken tail.


Finally, the differences between the age- and temperature-based compressive-strength prediction models were analyzed according to the corresponding microstructures.The ultrasonic pulse velocity (UPV) technique, which is an efficient technique for concrete quality evaluation, can be affected by several factors. Many studies have proposed compressive-strength prediction models based on UPV in concrete; however, few studies have investigated the factors resulting in statistically different UPV results for different models. This study examined the difference between compressive strengths of various concrete specimens calculated by age-dependent and temperature-dependent UPV-based prediction models. Furthermore, a statistical analysis was conducted to evaluate the influence of aggregates and water/cement ratio (design compressive strength), which are said to affect UPV, on the compressive-strength prediction models. The experimental results revealed that the residual compressive strength of concrete after high-temperature exposure was about 9.5 to 24.8% higher than the age-dependent compressive strength. By contrast, after high-temperature exposure, UPV tended to be about 34.5% lower. The compressive strengths and UPVs were significantly different with respect to high temperature, aggregate density, and design compressive strength. The compressive-strength prediction model derived from the regression analysis showed a high R Sound waves whose frequencies are beyond the audible range are called ultrasound. The transmission of sound through a medium is driven by the kinetic energy of vibrating particles in the medium and the resulting motion of the surrounding particles . The traPrevious studies conducted on the prediction of concrete strength using UPV primarily employed two approaches: the analyses of (1) compressive strength and UPV with respect to concrete age and (2) residual strength and UPV after exposing the concrete to high temperatures. Conceptual diagrams of the concrete matrix during curing and after high-temperature exposure are shown in As evident from Equation (1), UPV is proportional to the square root of the elastic modulus, which is primarily influenced by the number of coarse aggregates and the water/cement (W/C) ratio. Aggregates account for approximately 70% of concrete by volume, and the W/C ratio affects the compressive strength.However, UPV in concrete after high-temperature exposure exhibits a different trend. Concrete exhibits higher strength at high temperatures than at room temperature for the same UPV range see . This isSeveral researchers have proposed compressive-strength prediction models for concrete. However, few studies have investigated the differences between compressive-strength prediction models based on the analysis of age-specific and residual mechanical properties after high-temperature exposure. Moreover, the validation of these models remains sparsely documented. Additionally, for an accurate compressive-strength prediction model for concrete, it is essential to determine the distribution pattern of the data and select a regression model that can be effectively fitted to this distribution. In addition, a wide distribution of data may entail data classification prior to the selection of a suitable model. The majority of previous studies either classified the data from a material-centric perspective or developed compressive-strength prediction models based on the entire dataset. Few studies have analyzed the factors leading to different results obtained by different compressive-strength prediction models.This study evaluated the differences between the concrete compressive-strength prediction models based on age and high-temperature exposure. Subsequently, we employed hypothesis testing, a statistical analysis technique, to evaluate the significant differences between age-specific and temperature-exposure-based compressive strengths and UPVs. The null hypothesis stated that there is no statistically significant difference in concrete compressive strength and UPV depending on the set factors . The alternate hypothesis stated that there is a significant difference depending on each set factor.Finally, in this study, an analysis was conducted to propose a model for accurate prediction of compressive strength of concrete according to the high temperature using UPV. In addition, an error test was performed to evaluate the factors that significantly influence the strength prediction model. Scanning electron microscopy (SEM) was used to observe the matrix structure, which was used to evaluate the patterns followed by different UPVs at the same compressive strength. Furthermore, to evaluate the effect of the aggregate and W/C ratio, experiments were conducted with normal-aggregate, light-aggregate, normal-strength, and high-strength concrete materials.t-test, regression analysis, and error test were conducted to statistically analyze the results.The experimental plan followed in this study is presented in 3 and fineness 320 m2/kg was used. For preparing the NAC, granite-type coarse aggregates of density 2680 kg/m3, fineness modulus 7.03, and water absorption ratio 0.68% were used. For preparing the LAC, an artificial lightweight aggregate  of density 1470 kg/m3, fineness modulus 6.39, and water absorption ratio 8.68% was used. River sand of density 2540 kg/m3, fineness modulus 2.54, and water absorption 1.60% was used as the fine aggregate. Polycarboxylic-based super plasticizer was added to improve the workability of high-strength concrete.The physical properties of the raw materials and chemical composition of cement are listed in The mix proportions used in this study are listed in Cylindrical concrete specimens of dimensions 100 × 200 mm were fabricated to evaluate the mechanical properties of concrete based on age and high-temperature exposure . The speThe test and analysis methods followed in this study are outlined in t-test was conducted under the assumption of equal and unequal variances to evaluate the significant differences between the groups. Subsequently, the compressive-strength prediction model was proposed through regression analysis of compressive strength and UPV data. Finally, the reliability of the model was demonstrated via an error test.To statistically analyze the compressive strength and UPV, each concrete sample was first set and classified into a group according to its type, design compressive strength, and high-temperature history . An F-teAll concrete specimens used in this study were prepared using the same binder; hence, dehydration-driven degradation of the cement chemical components occurs at the same temperature ranges shown in Thereafter, the two compressive strengths were similar. HNAC60, LAC30, and HLAC60 showed approximately 20.18%, 24.82%, and 9.53% higher compressive strength after high-temperature exposure compared to their corresponding age-specific compressive strengths. The specimens subjected to high-temperature history were heated after an age of 91 days. After the generation of hydration products and strength development resulting from the hydration reaction had converged, the strength decreased, owing to structural degradations such as interface cracks, matrix collapse, and voids. However, the lower age-specific compressive strength compared to the temperature-dependent residual compressive strength is attributed to insufficient data on the generation of hydration products and strength development during concrete hydration. After high-temperature exposure, the compressive strength of the specimens increased slightly in the range of approximately 200–300 °C, as reported previously for high-temperature concrete properties . Alonso The results for UPV showed a different trend than that of the compressive strength. The age-specific UPV tended to be higher than the residual UPV after high-temperature exposure. NAC30 and HNAC60 showed high UPVs of approximately 66.22% and 57.25%, respectively, whereas LAC30 and HLAC60 showed low UPVs of approximately 31.62% and 29.87%, respectively. Zhang et al. investigated the cracks developed and UPV in concrete after exposing the concrete to high temperatures. They reported that the UPV decreased because the ultrasonic waves were delayed owing to their refraction, diversion, and reflection at the cracks and aggregate–paste interface . In partt-test for significance evaluation. Through the F-test, it is possible to evaluate the degree of dispersion, that is, the expression range of mechanical properties and the range of degradation due to high temperature. Through the results of the F-test, a t-test was performed to evaluate the significance between groups, and it is possible to quantitatively evaluate whether it is a factor that significantly affects the intensity prediction model according to the results of the significance evaluation.Although many researchers have proposed a concrete strength prediction model, the difference between the strength prediction model and its verification for the history of high temperature is insufficient. In this study, a statistical analysis method—hypothesis testing—was used to evaluate significant differences in mechanical properties according to high-temperature history and to evaluate the significance of aggregate density and design compressive strength . The nult-test. The significance level is the probability of perceiving the difference as significant when it is not. Typical significance levels used in hypothesis testing are 0.05, 0.01, and 0.001. In this study, the significance level was set as 0.05, as commonly practiced. If the p-value is greater than 0.05, the null hypothesis is accepted; if it is smaller than 0.05, the alternative hypothesis is accepted. The F-test results revealed that the age-specific and temperature-specific compressive strengths and UPVs exhibit equal and unequal variance, respectively. Variance measures the deviation of data from the mean and indicates the range of the data. After high-temperature exposure, the value of UPV varied within a wide range compared to the age-specific UPV. This is because cracking severely reduced the UPV. The t-test results showed that the age-specific and temperature-specific compressive strengths were not significantly different, except for HNAC60. By contrast, the UPVs showed significant differences with p-values below 0.05. The t-test results were likely influenced by the low range of UPV after high-temperature exposure. The compressive-strength prediction model for concrete based on age and temperature is likely to exhibit different UPVs at the same compressive strength.p-value of 0.04114, which is less than 0.05 ; however, the values appeared to converge after high-temperature exposure. This is because of crack formation resulting from the difference in thermal-expansion characteristics of the aggregates and UPV reduction properties.The F-test results between different aggregate-density groups revealed equal variance, except between the compressive strengths of HNAC60_BA and HLAC60_BA and those of HNAC60_HT and HLAC60_HT. The degree of variance is expected to be different between the compressive strengths of high-strength and normal-strength concretes because LAC exhibits a lower strength than NAC, owing to the limited aggregate strength. The t-test results showed significant difference, except between the UPVs of NAC30_HT and HNAC60_HT and those of LAC30_HT and HLAC60_HT.The F-test results for different design-compressive-strength groups exhibited equal variance, except between NAC30_BA and HNAC60_BA. This is because HNAC60 has a wider range of compressive strengths than NAC30, owing to the high strength expression with respect to age. The The concrete samples with relatively high design compressive strength before heating (20 °C) showed a high UPV; however, the UPV possibly converged owing to the formation of numerous cracks and voids after high-temperature exposure.Various forms of compressive-strength prediction models for concrete have been proposed in the literature, including linear, exponential, quadratic, and power functions. The forms were derived by first setting UPV and compressive strength as the independent variable and dependent variable, respectively. Subsequently, regression analysis was conducted, and the regression model was derived ,42,43,442 (R-squared) is an indicator of the linearity of the data, and R2 quantifies the extent to which the independent variables explain the variation in the dependent variable. Without considering the high-temperature exposure of aggregates, Pearson’s R2 and R2 were approximately in the range 0.56–0.67 and 0.26–0.45, respectively, which are very low values. 2 and R2 values. 30_BA samples exhibited low values due to the difference in UPV, even though the difference between the compressive strengths of NAC30 and LAC30 was non-significant. Moreover, 60_HA samples exhibited low Pearson’s R2 and R2 values, likely owing to the significant difference between the compressive strengths of HNAC60 and HLAC60.2 and R2 values, whereas NAC_HT and LAC_HT exhibited relatively low values. After high-temperature exposure, the residual UPV did not show a significant difference, whereas the residual compressive strength did. The low value may be attributed to the different compressive strengths observed for the same range of UPV. Hence, the design compressive strength must be considered in developing a temperature-based compressive-strength prediction model for concrete.2 and R2 when the factors set in this study were not considered. The values exhibited by the regression analysis model developed for HA samples were particularly low. Individual analysis of multiple factors may be required for a more accurate evaluation of the structural and material safety of concrete after high-temperature exposure. The regression model produced relatively low Pearson’s R2 value, ranging from approximately 0.87 to 0.94. Pearson’s R2 for the temperature-based compressive-strength prediction model was also high, which was approximately in the range 0.94–0.96. The regression model for the age-specific mechanical properties of concrete showed a relatively high R2 when the design compressive strength was not considered. However, we believe that design compressive strength needs to be considered for accurate strength prediction.Even with the same compressive strength, different matrix structures depending on the high-temperature history have a great influence on UPV. This study can bring about the economic benefits of securing structural safety and evaluating the exact degree of repair and reinforcement of buildings after a fire, and it is believed that UPV can be used to contribute to engineers and researchers who consider the accurate strength prediction and quality evaluation of concrete.The residual compressive strength of the concrete after high-temperature exposure tended to be in range 9.53–24.82%, higher than the compressive strength of the aged concrete. The higher compressive strength of the concrete after high-temperature exposure compared to the age-specific compressive strength is attributed to insufficient formation of hydration products and strength expression. This is because the formation of cracks and voids reduced the strength, while the formation of hydration products and strength development converged to some extent.The UPV of the aged concrete tended to be 29.87–66.22% higher than the residual UPV displayed after the high-temperature exposure of the concrete. The UPV reduced by the formation of cracks and voids is believed to be more sensitive to the severely degraded matrix structure of the concrete exposed to high temperature.The significance test results suggested that the compressive strength and UPV were significantly different owing to high-temperature exposure, aggregate density, and design compressive strength. In particular, consideration of the set factors is critical for evaluating the mechanical properties of HNAC and HLAC.2 when the age-specific and temperature-specific data of the concrete were not separated. The error test result showed that the average error converged to almost zero when the compressive-strength prediction model considered all the factors set in this study.The regression analysis results showed a very low RWhen SEM analysis was performed based on the same compressive strength in the compressive-strength prediction model for concrete by age and after high temperature, the difference in UPV increased in the lower compressive strength range. This appears to be due to the effect of severe cracks and voids that occur in concrete after high temperature, which resulted in a very low UPV compared to the compressive-strength prediction model for concrete by age.This study analyzed age-based and temperature-based compressive-strength prediction models for concrete using UPV. Additionally, this study evaluated the factors that lead to significant differences through statistical tests. The results of the experiments and analysis are summarized as follows:In this study, different UPVs at the same compressive strength were demonstrated through statistical and SEM analysis results, but additional micro-analysis such as quantitative quantity of hydration products, porosity, and visual analysis of cracks is considered necessary to prove clearer experimental results and hypotheses.


This study investigated changes in the interfacial properties of epoxy-coated concrete exposed to various conditions, regarding the epoxy type, coating equipment, and exposure environment and period. The measured coating thickness and pull-off bond strength exhibited diverse trends, depending on the exposure period and conditions. In the real sea (RS) environment, the average bond strengths for bisphenol A (BPA) (E1), BPA with zinc powder (E2), and BPA with cresyl glycidyl ether (E3) were 1.26, 1.93, and 1.92 MPa, respectively. The coating method did not significantly affect the measured coating thickness and strength values. The conventional roller (D1) exhibited the highest thickness variation, with a value of 214.45 μm. The RS condition significantly increased the coating thickness (34% to 158%) compared to the tap water (TW) condition. The exposure conditions had little impact on bond strength except for E3, which showed an increased strength (2.71 MPa) over 7–91 days, especially under RS conditions, while E2 remained constant at approximately 1.82 MPa. This study offers insights into factors influencing marine concrete coating performance and discusses limitations and future work. Hang et al. [Marine concrete structures face exposure to harsh and aggressive environments, such as chloride and sulfate attacks, which can significantly impact their service life. Underwater coatings are recognized as an economical and rapid repair method for preventing water and moisture infiltration into the concrete. Numerous studies have been conducted to develop effective repair strategies for concrete structures with surface protection, with some focusing on specific coating types ,9,10,11.g et al.  describeg et al.  reportedg et al. ,14,15,16g et al. . Furtherg et al. ,19.The coating method, encompassing coating tools, the coating procedure, and the type of pre-treatment, plays a significant role in shaping the interfacial bond properties between the coating and the substrate. Sadowski et al.  affirmedIn their respective studies, Al-Kheetan et al.  examinedThis study experimentally investigated the significant factors, including the epoxy resin type, coating equipment, exposure time, and exposure conditions, that must be considered when applying coatings to marine concrete structures. This study considered three different epoxy resins and coating equipment options, based on the results of previous studies. In addition, the effects of the exposure period and conditions on the measured pull-off bond were evaluated. The investigated test variables, materials, and experimental procedures are summarized in the following sections.The majority of the prior research on concrete surface repair has primarily concentrated on conventional, land-based structures, with less emphasis on marine structures. This discrepancy can be ascribed to the limited understanding of underwater coating materials, their suitability for real marine environments, and the reliability of experimental outcomes. Experimental studies that specifically addressed the bond performance of underwater coatings in real sea conditions are currently limited in the literature. Such research would hold significant value for individuals engaged in the repair and retrofitting of submerged concrete structures. In addition, studies on the development and performance evaluation of coating materials for underwater operations are limited, and the time-dependent interfacial adhesion between applied coatings and substrates has not been systematically investigated. Therefore, this study performed experiments to determine the bond strength between underwater coatings and concrete substrates. The results presented in this paper are part of an ongoing research project and are expected to greatly contribute to the maintenance of marine concrete structures located in actual marine environments.A 300 mm × 300 mm × 30 mm rectangular concrete substrate was prepared. A mixer truck and electric concrete vibrator were used to cast the concrete. The adopted water-to-cement ratio (w/c) was 0.24, and ordinary Portland cement (OPC) was used. The prepared specimens were water-cured for 28 d under controlled temperature and humidity conditions. Subsequently, the surface was water-jetted and relocated to the laboratory or onsite for surface coating. The compressive and splitting tensile strengths of the substrate concrete were measured according to the ASTM C39 and ASTM C496, respectively . At leas2). One-way analysis of variance (ANOVA) and Tukey’s honest significant difference (HSD) tests were used for the statistical analysis of the measured values to determine whether there were statistically significant differences in the means of the results. The null hypothesis for the ANOVA was that each group would have similar values and not exhibit significant differences. In contrast, the HSD test was used to detect differences between any pair of groups.After establishing the appropriate test duration for each exposure condition, the coated specimens were extracted. The specimens were then initially cut into small rectangular sizes of 20 mm × 20 mm × 20 mm to capture scanning electron microscopy (SEM) images and observe the changes at the interface between the coating and substrate. These images were captured using an EM-30AX device manufactured by COXEM, Daejeon, Republic of Korea, following the completion of the proper curing, grinding, and polishing processes. Images were captured at two exposure periods of 7 and 91 d, and two different magnifications (×100 and ×1000) were used at the same location. The presence of separations, residual voids, and cracks near the interface was visually inspected to investigate the interfacial bond behavior. The coating thickness was measured according to the ASTM D6132 . A commeThe coating thickness was measured according to the ASTM D6132 procedure; The measured strengths varied significantly, as shown in p-value of less than 0.0001 (p = 0.0001) and between E1 and E3 (p = 0.0001). However, no significant difference was observed in the mean coating thickness between E2 and E3 (p = 0.3222). The mean bond strengths of E1, E2, and E3 were 1.26, 1.93, and 1.92 MPa, respectively, as shown in p < 0.0001), as shown in The mean thickness values for E1, E2, and E3 were 117.54, 204.60, and 227.40 µm, respectively, as shown in n 0.0001 . TherefoSEM was used to investigate the internal porosity within each epoxy coating, and the results from SEM under the RS condition confirmed that E1 had larger internal pore sizes than E2 and E3, as shown in p-value of 0.787 further supported this conclusion. Notably, D1 exhibited the highest variation with an S.D. of 123 µm, which was unexpected considering that D1 was initially anticipated to have a stable thickness compared with other methods based on previous findings [findings ,21,22. Tfindings ,41,42. Tp-values for E1 and E2 were greater than 0.05, suggesting no significant changes in the strength values. These results also reaffirmed the insignificant correlation between strength and thickness. Furthermore, the bond strength values were found to be similar under all conditions at the 0.05 significance level, with the coating method having no significant effect. Overall, it can be inferred that the exposure condition can significantly influence the coating thickness, resulting in potentially thicker and more dispersed coatings compared with conventional conditions. Furthermore, within the range of this study, the exposure conditions had a limited impact on the measured bond strength, except for E3.Neither E1 nor E2 exhibited significant changes or trends in strength during the exposure period c,d. By cE3 exhibited a slight increase in bond strength with an increased exposure period, especially in the RS condition, while E1 and E2 showed constant values. The two additives, zinc powder and cresyl glycidyl ether (CGE), resulted in performance variations among the three coatings. As mentioned previously, while zinc powder tends to increase viscosity and lead to a thicker consistency, CGE may not directly increase viscosity like zinc powder. However, it can influence the curing process and the final properties of the epoxy, potentially affecting its flow characteristics. These results are consistent with those of Park et al. , who repOverall, this study confirmed that the exposure period and conditions had a combined effect on the early strength gain, suggesting that further long-term investigations are necessary.This study aimed to establish and conduct an experimental program to investigate the significant factors influencing the surface protection of marine concrete structures. The coating performance was assessed by measuring both the coating thickness and bond strength. It was observed that the exposure conditions and period significantly influenced the coating thickness and strength. The results also indicated a high degree of variability. However, it is imperative to emphasize the need for further research in underwater coatings for marine structures. These structures are constantly exposed to harsh underwater environments, which can result in material corrosion and degradation over time. Continuous research efforts can play a pivotal role in the development of and improvement in coatings that offer effective corrosion protection, thereby extending the lifespan of these structures and ultimately reducing maintenance costs ,51,52,53In this study, we noted significant variability in the test results, primarily stemming from uncontrolled conditions and human errors. To mitigate this variability in underwater coatings and ensure reliability, a multifaceted approach is essential. This encompasses factors such as meticulous material selection, precise application techniques, stringent quality control measures, and continuous maintenance. In particular, the proper surface preparation of target structures and thorough training for applicators play pivotal roles in achieving the desired performance. Regular monitoring and maintenance are equally vital to secure long-term effectiveness. The high variability in the results can be considered a limitation of this study, as it may hinder the proper selection of coating materials and methods, considering their appropriate application areas. Similarly, reducing the high variability in underwater coatings and achieving reliability involves factors such as proper material selection, application techniques, quality control measures, and ongoing maintenance. These limitations should be properly addressed through ongoing testing and future research.Within this research, it was further affirmed that the exposure conditions had the most substantial influence on both the thickness and strength, while the effect of the coating method was deemed negligible following a thorough statistical analysis. Specifically, the differences between the maximum and minimum mean thickness and strength values were 83% and 37% higher in the RS condition compared to the TW condition, while no significant difference in the coating method was observed at the 0.05 significance level. This contradicts the results obtained in previous laboratory testing. Hence, it is evident that conducting tests in authentic sea conditions is indispensable. This is because the performance of underwater coatings on concrete structures can exhibit substantial variations between controlled laboratory settings and the real sea environment. In addition, within the scope of this study, E3 can be recommended to ensure proper bonding performance for underwater structures, while the coating method could not be optimized.Additional research is required to gain a deeper understanding of the wear resistance and fatigue characteristics of underwater coatings through long-term investigations. Conducting extended studies is essential to enhance the performance assessment of underwater coatings. It is worth noting that short-term studies may not provide a precise reflection of the long-term performance of these coatings. Over time, various environmental factors, such as saltwater corrosion, biofouling, and other wear and tear, can significantly affect the effectiveness of these coatings. Long-term studies provide a more realistic simulation of the actual conditions these coatings will face in practice, while allowing for a comprehensive assessment of the durability and robustness of underwater coatings. This encompasses the evaluation of their resistance to deterioration, the preservation of their protective properties, and their ability to endure prolonged exposure to the demanding conditions underwater. Extended testing proves invaluable in uncovering any latent weaknesses or vulnerabilities in coatings that might escape notice in shorter-term investigations. This, in turn, leads to refinements and enhancements in the formulation and application of these coatings, ultimately bolstering their long-term performance. In summary, continuous research into underwater coating technologies is imperative, to tackle the distinct challenges presented by marine environments, extend the longevity and efficacy of marine structures, and adhere to evolving environmental and regulatory standards, ensuring that these coatings retain their effectiveness, safety, and environmental sustainability over time.BPA  had the lowest coating thickness and bond strength, whereas BPA with zinc powder (E2) and BPA with cresyl glycidyl ether (E3) demonstrated similar values.The impact of the chosen coating method on the measured thickness and strength values appeared to be minimal, and notably, the conventional roller (D1) had the highest thickness variation. This might be attributed to the possibility that the other factors had a more significant influence than the coating method.Under RS conditions, there was a noticeable increase in coating thickness compared to the controlled condition. As for bond strength, the exposure conditions had only a limited effect, except for E3.Thickness values remained relatively stable regardless of the exposure period, and E3 demonstrated an upward trend in bond strength with increasing exposure time, particularly under the RS conditions.The relationship between the measured thickness and bond strength appeared unclear, and this pattern aligns with findings from previous studies.This study conducted experimental investigations into the alterations in the interfacial bond properties of BPA epoxy resins when applied to underwater concrete. It specifically examined the impact of various epoxy types, coating techniques, and exposure conditions and durations on both the coating thickness and bond strength. The following conclusions have been derived from the test results and subsequent analyses:The measured thickness and strength values exhibited high variability, which could be attributed to environmental factors . This study offers valuable insights into the key factors that need to be considered when applying coatings to marine concrete structures, thereby contributing to the ongoing research and development of underwater coating technologies.


IgG4-related disease (IgG4-RD) is a condition that was first described recently, and is capable of affecting any organ of the body. Diagnosis is based on the correlation of clinical findings with histopathological findings and elevated serum IgG4. Treatment involves corticosteroids and rituximab for the most severe cases. We report the case of a symptomatic patient diagnosed of IgG4-RD whose diagnosed was guided by elevated serum IgG4 levels. IgG4-related disease (IgG4-RD) is a recently-described clinico-pathological condition with a wide range of clinical manifestations. Clinical signs include neoplasms, a dense lymphoplasmacytic infiltrate rich in IgG4-positive plasma cells, fibrosis arranged in a storiform pattern, obliterative phlebitis and, most commonly, elevated serum IgG4 concentrations . The preThis entity was first described in 2001, when autoimmune pancreatitis in a patient correlated with elevated serum IgG4 levels and numerous IgG4-rich lymphoplasmacytic cells . The terIgG4-RD is generally diagnosed when patients are in their 60s or 70s and is more frequent in men. The organ most commonly involves is the pancreas, although IgG4-RD can involve any site in the body , [6], 7, includiPresentation is subacute and patients rarely exhibit constitutional symptoms, with a predominance of symptoms of organ dysfunction. Patients commonly have a previous history of rhinitis, asthma, nasal polyps and athopy .Diagnosis may be challenging as symptoms are nonspecific and are related with other more common diseases. Symptoms and laboratory findings may guide the clinician to further appropriate imaging studies and reach a diagnosis.A 29 year-old patient with a history of allergic rhinitis seen in Primary Care in December 2015 for a 6-month history of asthenia and a weight loss of 10 kg.Physical examination was unremarkable. Laboratory tests showed biochemical alterations in blood, namely: elevated creatinine levels , eosinophilia , elevated cholestatic enzymes gamma-glutamyl transferase (GGT) enzyme concentrations  and alkaline phosphatase , and a protein concentration of 9.2 g/dL (reference range: 6.6–8.7 g/dL). Although bilirubin was not tested, the index of jaundice was within normal limits.Laboratory values and clinical symptoms led to patient's referral to the Outpatient Unit of Internal Medicine. Differential diagnosis with vasculitis, a lymphoproliferative and parasitic process was performed.Laboratory findings included elevated IgG concentrations  and IgE . Other parameters were within normal limits, including autoimmunity markers , serology , CA19-9 , adenosine deaminase, cryoglobulins, complement and Mantoux test.The radiological study included a thoraco-abdomino-pelvic CT scan, which demonstrated multiple large adenopathies and a renal and periportal lymphomatous infiltration, with a lymphoproliferative process as first diagnostic optionInterconsultation with the Units of Nephrology and General Surgery was performed for a renal biopsy and surgical exeresis of an inguinal node for histopathological examination. Results were negative for a lymphoproliferative process, although they demonstrated significantly elevated lymphoplasmacytic cell levels. Samples were sent to the referring center for immunohistochemistry testing. The results obtained supported the suspicion of an IgG4-related disease.Testing for IgG subclass levels yielded a total IgG concentration of 2.225 mg/dL, IgG1 of 1.432 mg/dL (reference range: 382–929 mg/dL); IgG2 of 816 mg/dL (reference range: 242–700 mg/dL); IgG3 of 184 mg/dL (reference range: 22–176 mg/dL) e IgG4: 652 mg/dL (reference range: 4–86 mg/dL).Final diagnosis was performed based on the finding of very elevated IgG4 levels and after other pathologies had been excluded.During the study period, three bolus units of methylprednisolone 125 mg and oral prednisone (10 mg/day) were administered. When diagnosis of IgG4-RD was confirmed, rituximab therapy was started in November 2016 . The reason for this therapy was that clinical response to corticosteroids was only partial and resulted in the activation of herpes zoster, high blood pressure and cushingoid habitus. In May 2017, the other two cycles were administered.The clinical status of the patient improved progressively, creatinine returned to normal levels and IgG4 was reduced to values below 135 mg/dL after the first four cycles of rituximab. Adenopathies and infiltration decreased in size.IgG4-RD is a recently described entity with a challenging diagnosis. This disease is increasingly considered in the differential diagnosis of a variety of symptoms of organ or systemic dysfunction , 11]..11].The etiopathogenesis of the disease and the role of IgG4 are unclear, being the hypothesis of an autoimmune disease the most widely accepted .Final diagnosis is based on the immunohistochemical analysis of a biopsy of the organ involved. However, laboratory plays a crucial role in the diagnosis of IgG4-RD. Thus, a range of non-validated diagnostic criteria have been proposed by different research groups, where IgG4 levels >135 mg/dL are highly suggestive of IgG4-RD , 12], , . I. I16]. IThe etiopathogenesis and the role of IgG4 in this disease are not clearly understood. The diagnostic value of serum IgG4 levels has not been sufficiently proven. However, its use in the adequate clinical setting, especially if concentrations double the reference limit can be useful to guide the clinician to further appropriate imaging studies and reach a diagnosis. Further evidence is needed to support the recommendation of using serum IgG4 levels as a prognostic marker and as an indicator of response to therapy.Although the diagnostic value of other biomarkers is under study, further studies are needed to provide robust evidence .The patient was young and exhibited nonspecific clinical symptoms, and histopathological and laboratory findings were crucial to obtaining the diagnosis of IgG4-RD after only 6 months after the onset of clinical symptoms. The mean time to diagnosis is 4–5 years, especially as this entity mimics other diseases. Fortunately, IgG4-RD is increasingly included in differential diagnosis.


Antibiotic resistance is one of the biggest threats to human health, food security, and development. This study aimed to examine the level of knowledge and awareness regarding antibiotic resistance while comparing students from health sciences to students in other disciplines. A cross-sectional study was conducted based on the “antibiotic resistance” questionnaire developed by the World Health Organization. A total of 371 students participated in the study. All respondents had taken antibiotics in the past. A tenth had taken them on their own without a prescription, and 14% had not received an explanation regarding the use of antibiotics. The average for the knowledge questions was 15.49 ± 5.35 (out of 27). Many students mistakenly associated antibiotics with viral diseases. Despite these misconceptions, there was a high level of awareness and understanding regarding the ways to treat antibiotic resistance. Still, the awareness of the severity of antibiotic resistance was not high. Differences were found between the disciplines in general knowledge and the level of awareness and understanding about the ways to treat antibiotic resistance, where health science students had the highest scores, followed by social science students and finally, computer and management students. No differences were found in the perception of the severity of the phenomenon. This information is essential to developing educational interventions to improve knowledge, attitudes, and practices regarding antibiotic use among students, especially those unrelated to the health sciences. Antibiotics have been one of the most significant medical breakthroughs in modern medicine , enablinAntibiotic resistance has been reported throughout the world . A contrStudies have identified several public misconceptions regarding antibiotic use and resistance . Many inAnalyses of students have reported improper antibiotic use and a lack of knowledge about antibacterial substances . A surveAlthough the issue of antimicrobial resistance is not new, it has long been assumed that this problem could be solved by the continuous development of novel drugs. However, antibiotic development has declined alarmingly over time . ReturniThis study seeks to examine the levels of knowledge, awareness, attitudes, and behaviors of students in Israel related to antibiotic resistance and the relationships among these variables while also comparing the knowledge and awareness of students in the health sciences to those of students from other disciplines. These research findings can assist policymakers in public health and infectious diseases in formulating an outreach program to improve the public knowledge and understanding of antibiotic resistance and how people can influence and mitigate this threat to global public health. No similar studies have been conducted to date in any academic institutions in Israel.2 tests and one-way ANOVAs. Participant characteristics are summarized in In total, 371 individuals participated in the study, of whom 74% were women, 57% were in relationships, and 27% had children. Most participants were Jewish (92%) and Israeli-born (86%). The mean age of the respondents was 28 ± 8.58 years. The differences between disciplines were analyzed using χ2 tests. The pattern of antibiotic usage among study participants is presented in Differences between disciplines regarding antibiotic usage were analyzed using χThe relationships between knowledge and attitudes were analyzed using Pearson correlations. We found positive and significant relationships between the levels of knowledge and attitudes, as shown in The differences between disciplines in the study variables were analyzed using one-way ANOVA tests. (349) = 25.43, p < 0.001), with an explained variance of 13%. Awareness of the severity of antibiotic resistance is the best predictor of the level of awareness and understanding regarding the ways to treat antibiotic resistance , followed by general knowledge .The results of the multiple linear regression model developed to predict the level of awareness and understanding regarding approaches to treating antibiotic resistance are presented in This study was a cross-sectional analysis of students enrolled at Ashkelon Academic College in 2023 (about 4000 students). After receiving approval from the Ashkelon Academic College Ethics Committee , the questionnaires were programmed using Qualtrics  and distributed to the students through email on 12 January 2023. A reminder to complete the questionnaire was sent in the same manner after two weeks. On 11 February 2023, the questionnaire was closed to further participants in the program. The average time taken to answer the questionnaire was 6.1 ± 2.13 min. The introductory page of the questionnaire contained an explanation of the ideas and aims of the questionnaire. Submission of the completed questionnaire represented students’ informed consent to participate in the survey. The students could stop responding to the questionnaire at any stage and had the option to elect not to answer certain questions. No questions were defined as compulsory. There were 524 entries to the questionnaire, of which 371 students filled out at least 90%. Hence, the response rate is 71% of all entries and 9% of the research population. They were divided into 3 groups (disciplines) according to the department they studied in: health sciences, social sciences, and computers and management.Demographic information: Gender, age, marital status, religion, department, and year of study.Practice: Three questions: When did you last take antibiotics? Did you get a prescription from a doctor? Did a doctor/nurse/pharmacist explain how to take the antibiotics?Knowledge about the use of antibiotics: Three questions in which respondents were asked to indicate whether, in their opinion, the statement was correct or incorrect or whether they did not know. For example, “You should stop taking antibiotics when you feel well”. The number of correct responses to each statement was totaled to calculate the knowledge score.Knowledge about the necessity of antibiotics for 12 medical conditions: Only 3 of the 12 indicated knowledge of conditions that require antibiotic treatment . The number of correct responses to each statement was totaled to calculate the knowledge score.Familiarity with four terms related to antibiotic resistance: Respondents were asked to indicate whether or not they were familiar with the following terms: antibiotic resistance, superbugs, antimicrobial resistance, and antibiotic-resistant bacteria.General knowledge about antibiotic resistance: Eight questions asking respondents to indicate whether, in their opinion, the statement was correct or incorrect or whether they did not know. For example, “Antibiotic resistance is an issue in other countries but not in Israel”.The level of awareness and understanding regarding approaches to treating antibiotic resistance: Seven questions asking respondents to indicate to what extent they agreed with the given statements on a Likert scale ranging from 1  to 5 (a very large extent) For example, “People should use antibiotics only when prescribed by a doctor”. The average of the answers was calculated for each participant. Cronbach’s α for reliability was 0.73.Awareness of the severity of antibiotic resistance: Five questions asking respondents to indicate to what extent they agreed with the given statements on a Likert scale ranging from 1  to 5 (a very large extent). For example, “Antibiotic resistance is one of the biggest problems the world faces”. The average of the answers was calculated for each participant. Cronbach’s α for reliability was 0.75.A professional translator translated the anonymous, closed, self-completed WHO questionnaire, “Antibiotic Resistance: Multi-country public awareness survey”  from Eng2 tests and one-way analyses of variance (ANOVAs) as appropriate. A linear regression model was used to test the prediction of the level of awareness and understanding regarding the ways to treat antibiotic resistance. All reported p-values were based on two-sided tests and were considered significant when the values were below 0.05.The data were analyzed using SPSS 29.0 . Relationships between the variables were examined using Pearson correlation analyses. Differences between groups of students were analyzed using χThe current study sought to explore knowledge, attitudes, and practices among higher-education students related to antibiotic use and resistance. To the best of our knowledge, this is the first such study conducted among Israeli higher-education students. The overall knowledge level among these students was moderate, and the level of awareness was unsatisfactory, with students from health science disciplines scoring higher than students from social science and computer and management disciplines.We found that half of the participants reported having used antibiotics in the year prior to the study ,28. In cWe also found that, overall, the level of knowledge and attitudes regarding antibiotic resistance were low. Participant knowledge about the necessity of antibiotic use for the treatment of different medical conditions was rather low (average: 5.75/12), as was the level of knowledge about antibiotic resistance (average: 4.91/8). Comparably, in previous studies, low levels of knowledge about antibiotic resistance were documented among students in different countries ,32,33,34With respect to the familiarity with the four terms related to antibiotic resistance, the average level of knowledge was relatively low (2.52/4). This is consistent with previous research ,39. StudAll three groups of students demonstrated a similar level of recognition of the severity of the phenomenon of antibiotic resistance, without significant differences among disciplines, and with all agreeing that antibiotic resistance is a serious problem. These findings are similar to previous studies’ findings ,28. It, Moreover, the results of the developed multiple linear regression model indicated that the awareness of the severity of antibiotic resistance is the best predictor of the level of awareness and understanding regarding approaches to treating antibiotic resistance, followed by general knowledge. Previous studies in the field of health behavior have suggested that attitudes are a stronger predictor of behavior than knowledge .The current study has some limitations. First, it was conducted only at Ashkelon Academic College and may not be a representative sample. Second, the groups are not demographically similar, which may cause bias. Third, no causal inferences could be drawn due to its cross-sectional design. Another limitation of the study may be the social desirability bias among the participants.These findings provide important insights into the level of understanding of antibiotic resistance among students, which will be helpful when designing interventions aimed at raising knowledge and awareness of antibiotic resistance, its implications, and ways to mitigate it. In order to successfully incorporate lessons related to antibiotic resistance and other public health issues into the higher-education curriculum of non-health disciplines, effective and productive collaboration is required from all the stakeholders: clinicians, universities, governments, drug industries, and the public. All these groups should formulate interventions to address misconceptions regarding how people contribute to antibiotic resistance, and health authorities must improve the oversight of access to antibiotics. A new plan in Israel to fight antimicrobial resistance is currently being considered by the Public Health Services, based on a “one health” approach with a strong emphasis on antimicrobial resistance in food-producing animals . This na


In order to evaluate the feasibility of surface coatings in improving the performance of RCC under salt spray conditions, sodium silicate (SS), isooctyl triethoxy silane (IOTS), and polyurea (PUA) were used as surface coatings to prepare four types of roller-compacted concrete (RCC): reference RCC, RCC-SS, RCC-IOTS, and RCC-PUA. A 5% sodium sulfate solution was used to simulate a corrosive marine environment with high temperatures, high humidity, and high concentrations of salt spray. This study focuses on investigating various properties, including water absorption, abrasion loss, compressive strength, dynamic elastic modulus, and impact resistance. Compared to the reference RCC, the 24 h water absorption of RCC-SS, RCC-IOTS, and RCC-PUA without salt spray exposure decreased by 22.8%, 77.2%, and 89.8%, respectively. After 300 cycles of salt spray, the abrasion loss of RCC-SS, RCC-IOTS, and RCC-PUA reduced by 0.3%, 4.4%, and 34.3%, respectively. Additionally, their compressive strengths increased by 3.8%, 0.89%, and 0.22%, and the total absorbed energy at fracture increased by 64.8%, 53.2%, and 50.1%, respectively. The results of the study may provide a reference for the selection of coating materials under conditions similar to those in this study. The service life of marine concrete structures is contingent upon concrete durability, often impacted by environmental factors, particularly in harsh conditions ,2. The sConcrete surface coatings, essential for protecting structures in corrosive environments ,8,9, falMehdi et al. . identif2 or nano-TiO2 suspensions into an acrylic emulsion.Additionally, Shi et al.  observedThe cost-effectiveness and environmentally friendly nature of surface coatings have led to widespread use in various protective engineering applications ,26. HoweIn this study, sodium silicate (SS), isooctyl triethoxy silane (IOTS), and polyurea (PUA) were used as the surface coatings. Roller-compacted concrete (RCC), commonly used for airport runways, was prepared with and without a surface coating. Since the abrasion resistance and impact resistance requirements of the airport runways are higher than those of other ordinary building structures, these two properties of RCC, exposed to salt spray, were tested in this study. The microstructures and pore size distribution were also measured. The objective of this study was to evaluate the feasibility of surface coatings in improving the performance of RCC used in island airport runways under salt spray conditions.The chemical composition of 42.5-grade Portland cement was detailed in The size of the prismatic specimen was 100 mm × 100 mm × 400 mm, and the side length of the cubic specimen was 150 mm. Concrete mixture was poured into the test molds in three layers, and each layer was compacted with a vibrating hammer for 30 s. After 24 h, the specimens were demolded and cured under the standard conditions.The treatment process of the coating materials was carried out in accordance with the manufacturer’s recommendations for use.In the case of treating RCC with sodium silicate (RCC-SS), the process occurs at 7 days of curing. After removing the specimens from the curing room, their surfaces were brushed with a wire brush. Subsequently, sodium silicate, dissolved in warm water, was evenly sprayed onto the specimen surfaces. This treatment was repeated every two hours for a total of four applications. Finally, the treated specimens were returned to the standard curing chamber and allowed to cure until reaching 28 days.For RCC treated with isooctyl triethoxy silane (RCC-IOTS), the process was initiated at 28 days of curing. After removing the specimens from the curing room, their surfaces were brushed with a wire brush. Isooctyl triethoxy silane was sprayed onto the specimen surfaces and left for 6 h before a second round of spraying was conducted.In the case of RCC treated with polyurea materials (RCC-PUA), components A and B were mixed in a ratio of 1:0.45, and a specified amount of butyl acetate was added as a diluent. The treatment was also carried out at 28 days of curing. After removing the specimens from the curing room and brushing their surfaces with a wire brush, the polyurea mixture was uniformly sprayed onto the specimen surfaces. The specimens were then left at room temperature until the polyurea mixture hardened.In this study, there was one group of reference specimens (without surface treatment) and three groups of surface-treated specimens, which were RCC-SS, RCC-IOTS, and RCC-PUA. The above four groups of specimens were subjected to the performance tests mentioned below, and each group of specimens contained three specimens. The average of the test results of the three specimens was used for comparative analysis. Cubic specimens are used in the water-absorption tests, mass change, and abrasion tests. Prismatic specimens are used in the dynamic elastic modulus and impact tests. The compressive strength of the specimen is determined by using the prisms that break in the impact test, and a 100 mm × 100 mm × 10 mm steel plate is placed on the upper and lower surfaces, respectively, along the length of the specimen, so that the area of the compression surface of the specimen is 100 mm × 100 mm.2SO4 (w/w) was used for salt spray, and the deposition rate was 1.2 mL/(80 cm2·h). After the specimen reached the age of maintenance, the specimen was uniformly arranged in the specimen holder to ensure that the upper surface of the specimen was horizontal and the interval between the specimens was more than 100 mm. Each cycle started with 4 h of salt spray at 26.5 °C with 96% humidity, followed by 2 h of drying conditions without salt spray at 50 °C. In order to minimize the effect of salt spray inhomogeneity on the results, the left, right, front, and rear specimens were repositioned every 5 salt spray cycles.Salt spray conditions in the South China Sea were simulated via indoor salt spray tests. RCC underwent corrosion tests in an automatic machine see  followinAbrasion resistance, assessed using JTG E30-2020 , was meaFor impact resistance testing, the study employed a drop hammer impact tester  and (2)). The volume expansion of ettringite leads to the expansion of existing cracks and the creation of new cracks in the concrete, ultimately reducing the strength of the concrete under sulfate attack ,38.Na2SThe initial physical sulfate attacks tend to augment the weight of concrete. However, subsequent physical and chemical assaults typically lead to concrete cracking and mass loss.The mass change rate of RCC under salt spray cycles is given in For RCC treated with IOTS, the mass loss rate of the specimens subjected to 50 cycles of salt spray is 0.03%. After 100 cycles of salt spray, the rate of mass change of the specimens first approaches zero and then increases with the number of salt spray cycles. At 300 cycles of salt spray, the mass increase rate is 0.15%, which is only about 50% of the control RCC subjected to the same number of salt spray cycles. For RCC-PUA, the rate of mass loss of the specimens remains at approximately 0.04% as the number of salt spray cycles increases.Therefore, both RCC-IOTS and RCC-PUA surface coatings exhibit favorable resistance to salt spray corrosion when considering the criterion of mass change in a specimen under salt spray cycles.The use of concrete in runway construction exposes it to rubbing, scraping, skidding, and sliding due to the impact loads from surface movement. These actions contribute to the deterioration of concrete surfaces. Surface fractures lead to a reduction in concrete thickness, resulting in a smoother surface and an increase in dust accumulation. These factors collectively weaken the concrete, posing a threat to flight safety. Therefore, it is imperative for concrete runways to possess adequate abrasion resistance—a property that shields the hardened concrete surface from wear caused by abrasive forces. Ensuring the abrasion resistance of concrete runways and pavements is crucial in preventing surfaces from becoming overly polished, thus maintaining optimal skid resistance.The surface changes of the reference RCC with 300 cycles of salt spray are shown in The abrasion loss per unit area of RCC with 30 and 90 rotations of the grinding head are presented in 2 and 2.26 kg/m2, respectively—indicating reductions of 4.4% and 34.3% compared to the control RCC. Wu et al. [Both RCC-IOTS and RCC-PUA exhibit significantly lower abrasion losses per unit area. After 90 cycles of grinding head rotation, RCC-IOTS and RCC-PUA experienced abrasion losses of 3.29 kg/mu et al.  also notu et al.  observedThe percentage change in dynamic elastic modulus of RCC with 300 cycles of salt spray is shown in The relative change in the compressive strength of RCC with surface coatings after 300 cycles of salt spray is depicted in In the drop hammer impact test, each impact’s energy is controlled at 13 J, and continuous impact loads are applied until the fracture of the specimen occurs. The reference RCC followed with a peak impact force of 20.7 kN, while RCC-SS and RCC-IOTS show similar peak impact forces at around 19.2 kN, with two peaks observed. The second peak is likely attributed to the loosening of the surface layer of the specimens due to corrosion. When the impact force is applied, the loose surface concrete becomes compacted and comes into contact with the non-corroded and harder concrete in the interior. In addition, some of the following factors may also cause a second wave peak ,43: (1) Elemental analysis of the fillers in the internal pores shows sodium (Na) contents of 4.6%, 3.4%, 2.8%, and 0.5% for the control RCC, RCC-SS, RCC-IOTS, and RCC-PUA, respectively. Furthermore, this study revealed that surface coatings, particularly PUA, can effectively deter the infiltration of sodium sulfate into concrete. After 300 salt spray cycles, concrete treated with PUA exhibited the lowest sodium (Na) content.In addition, clear microcracks are observed in the internal and edge regions of the pores in the uncoated RCC, which indicates that the internal pores have suffered damage after 300 cycles of salt spray. Although the pores of RCC-SS and RCC-IOTS are filled with crystals and no significant microcracks are found, the changing trend of the pore size distribution see  indicateThere are three main types of hydrophobic surface treatments: (1) surface coatings, which form a continuous film of varying thickness on the surface; (2) pore filling, which acts as a localized pore barrier; and (3) impregnation or pore lining, which involves lining the pores along the entire surface of the concrete.The SS coating undergoes hydrolysis at room temperature, forming an interconnected network structure, as shown in the following reaction:2, generating hydrated calcium silicate gel that fills the concrete pores, making it more compact and enhancing the durability of concrete [The resulting thin film material adheres to the concrete surface, creating a separation between the concrete and its surrounding environment. However, due to the solubility of Na+ in water, the water glass-formed film generally exhibits moderate impermeability. Nevertheless, when the surface water glass penetrates into the interior of the concrete, it reacts with the cement hydration product Ca(OH)concrete ,45. TherThe chemical molecular structure of IOTS is shown in 2, ettringite, and quartz sand through -OH group reactions. Subsequently, the two -OH groups of IOTS form Si-O-Si bonds via condensation and release water in the process. As a result, a continuous self-assembled molecular film of IOTS is formed on the surface of the hydrated products. The presence of -CH3 and -CH2 groups in IOTS effectively reduces the surface energy of the cement matrix and significantly improves its hydrophobicity [This phenomenon is consistent with Wenzel’s theory, which suggests that rough mortar samples can be changed to hydrophobic surfaces after modification with low surface energy materials. This process involves the hydration of IOTS to form silanols (Si-OH), followed by the reaction of silanol with C-S-H, Ca(OH)hobicity . SimilarPUA is a block polymer material, as given in The strength of PUA primarily relies on its hard segments, while the elongation is determined by the soft segments. Due to its unique properties, PUA forms a seamless, leak-free membrane, making it highly suitable for enduring continuous ponding water conditions. Moreover, PUA coatings are renowned for their exceptional durability, offering remarkable elongation and tensile strength, making them an excellent choice for various surface coating applications ,49. SevePrior to salt spray exposure, RCC-SS, RCC-IOTS, and RCC-PUA exhibited 24 h water absorption rates 22.8%, 77.2%, and 89.8% lower than those of the control RCC, respectively.After 300 cycles of salt spray, the abrasion loss per unit area of RCC-SS, RCC-IOTS, and RCC-PUA is reduced by 0.3%, 4.4%, and 34.3%, respectively, compared to the control RCC.The compressive strength of RCC-SS, RCC-IOTS, and RCC-PUA is higher by 3.8%, 0.89%, and 0.22%, and the total absorbed energy at fracture is 64.8%, 53.2%, and 50.1% higher than that of control RCC, respectively.Crystalline fillers are found in the pores of control RCC, RCC-SS, and RCC-IOTS, excluding RCC-PUA. However, the volume percentage of small pores in all RCCs decreases, while the volume percentage of large pores increases.This study presented the deterioration of RCC both with and without surface coatings during salt spray cycles. The following conclusions can be drawn from the test results: