When the concrete was subjected to FTCs in a 6.8% composite salt solution 50 times, the loss in the compressive strength increased by 110% for concrete without an initial load and increased by 109% when the concrete was subjected to an initial load of 0.3f compared with the specimens under FTCs in freshwater. The persistent effect of the FTCs also aggravated chloride ion erosion in the concrete, which gradually reduced the concrete’s permeability resistance. Internal pores in the concrete, especially the proportion of above-medium-sized pores, gradually increased along with the increase in the number of FTCs. There is a good linear correlation between the change rule of compressive mechanical properties and the change rules of mass, DEM, and pore characteristics inside the concrete under rapid FTCs in different salt solutions.To determine how the performance of concrete changes after initial load damage and salt freezing, concrete samples were first subjected to loading and unloading, and were then put into salt solutions to carry out rapid freeze–thaw cycle (FTC) experiments. Salt solutions were created based on the saline soil of western Jilin, China, for use in salt freeze–thaw testing. This determined the change law of the compressive strength and the dynamic elastic modulus (DEM). Additionally, low-field nuclear magnetic resonance technology and a scanning electron microscope were applied to investigate the pore characteristics and microstructure of concrete samples after FTCs. This study found that when the concrete specimens were subjected to an initial load of 0.3 Concrete-engineered buildings are frequently subjected to multiple coupling effects. Therefore, concrete durability under those effects has always been a research focus ,2,3. TheThe hydrostatic, osmotic, and expansion pressures generated in concrete during FTCs in freshwater form cracks and reduce concrete strength. In a salt solution, salt crystal pressures are very destructive to concrete subjected to FTCs. Additionally, multiple FTCs in a salt solution will lead to more crystallization, osmotic pressures, and cracking damage in concrete . The actResearchers have conducted a lot of effective studies on the penetration and diffusion behavior of chloride ions in concrete materials, which have mostly concentrated on the effect of load, salt solution soaking, and wet–dry cycles in salt solution as well as studies on the ion diffusion in saturated or unsaturated concrete structures. Experimental studies promote the understanding of chloride diffusion in concrete under loads . The conThe changes in the chloride penetration behavior and mechanical properties of concrete are influenced by many factors. In the previous studies, fewer attempts have been made to study the coupling effect of initial loads and FTCs on the changes in the chloride ion penetration and mechanical properties of cement concrete. Further research is needed to study the relationship between chloride diffusion, mechanical properties, and the microstructure of concrete structures. The research combining macro mechanical properties with pore changes inside the concrete structure to reveal the mechanism of load influence is very meaningful . In thisThis study’s concrete cementitious materials were ordinary Portland cement PO 42.5, fine concrete aggregate with a fineness modulus of 2.2, river sand, and a coarse concrete aggregate of graded gravel with a diameter of 4.75 to 26.5 mm. The concrete mixing proportion and compressive strengths of 7 and 28 d are shown in Rs, where Rs = σ/f, with σ denoting the stress applied on the concrete specimens during the test and f denoting the compressive strength of the concrete specimen at 28 days under standard maintenance. After being maintained under standard conditions for 28 d, the concrete samples were subjected to initial loading and unloading, with respective Rs of 0, 15%, and 30%. Then, the samples were subjected to FTC action. We tested the sample loads and unloaded the stress level loads five times to realistically simulate the effect of those loads on concrete materials [The experiments were focused mainly on the effect of FTCs on the durability of concrete after initial load damage. The 100 mm × 100 mm × 100 mm cubic samples were fabricated for testing compressive strength, and the 100 mm × 100 mm × 400 mm rectangular samples were fabricated for testing the dynamic elastic modulus (DEM). The tested concrete blocks were fabricated following Chinese Standard GB/T 50081-2019, the Standard for Test Methods of Concrete Physical and Mechanical Properties . The cematerials .2SO4), and sodium bicarbonate (NaHCO3) in proportion. The overall experimental scheme is shown in After the initial applied loading and unloading, the samples were immersed in either freshwater, a 3.4% salt solution, or a 6.8% salt solution for rapid FTCs in accordance with Chinese Standard GB/T 50082–2009, the Standard for Test Methods of the Long-Term Performance and Durability of Ordinary Concrete . The mecThe concrete samples were subjected to 0, 15%, and 30% stress levels, then placed in water, 3.4%, or 6.8% concentrations of salt solution for the rapid freeze–thaw experiment. The compressive strength, mass, and DEM were tested after every 25 FTCs. A WAW-600 press  was applied for the compressive strength test. The change law of the compressive strengths of the concrete with various numbers of FTCs is shown in The variation in the compressive strength of the concrete samples was compared with the number of FTCs, and it was found that the compressive strength decreased almost linearly with the increase in the number of salt FTCs. The compressive strength decreased as the number of FTCs, the amount of the initial loads, and the salt solution concentration increased. The initial load affected the concrete mechanism properties and aggravated the damage of the freeze–thaw action on the concrete. The damage of the freeze–thaw action in a salt solution exceeded that in freshwater, and the salt concentration also greatly influenced the freeze–thaw damage.f caused a larger loss in the compressive strength of the concrete specimens than no initial load. Moreover, the loss in the compressive strength increased by 24% after 50 FTCs and by 30% after 100 FTCs when concrete was under FTCs in freshwater, and the loss in the compressive strength increased by 24% after 50 FTCs and by 10% after 100 FTCs when concrete was under FTCs in the 6.8% composite salt solution. The FTCs in the 6.8% composite salt solution caused a larger loss in the compressive strength of the concrete specimens than FTCs in freshwater. The loss in the compressive strength increased by 110% after 50 FTCs and by 29% after 100 FTCs when the concrete did not have an initial load, and the loss in the compressive strength increased by 109% after 50 FTCs and by 10% after 100 FTCs when concrete under FTCs in the 6.8% composite salt solution was subjected to an initial stress action of 0.3f. The coupling action of an initial stress of 0.3f and FTCs in the 6.8% composite salt solution aggravated the damage of FTCs to concrete. When concrete under FTCs in the 6.8% composite solution was subjected to an initial load of 0.3f, the loss in the compressive strength of the concrete was 159% larger after 50 FTCs and 41% larger after 100 FTCs than concrete under FTCs in freshwater without an initial load.The initial stress action of 0.3f, and the difference in compressive strength loss was greater at the beginning of the FTCs. From the compressive strength loss of the concrete samples after 25 FTCs, it can be seen that the compressive strength loss under the combined action of the initial 0.15f load and FTCs in the 3.4% composite salt solution was slightly greater than that under the combined action of an initial 0.3f load and FTCs in freshwater. It was concluded that when the concrete had a load with a low stress level before the FTCs, the salt solution concentration greatly influenced the early stage of FTCs. Additionally, the coupled actions of minor load damage and FTCs in a salt solution had more influence on the compressive strength of the concrete than a large load and FTCs in freshwater.In the FTCs, the initial loads led to an increase in the number and diameter of pores inside the concrete samples. The initial loads led to a higher freezing pressure inside the concrete, and the initial load damage to the concrete reduced the concrete’s compressive strength under the freeze–thaw action. The concrete was also subjected to salt crystallization pressure during the salt solution FTCs. At the same time, the salt solution increased the internal saturation of the concrete structure, which led to more severe damage than in freshwater. Therefore, more FTCs, a greater initial load level, and a higher salt solution concentration resulted in greater internal damage and compressive strength loss. The compressive strength loss in the 6.8% composite salt solution exceeded that under FTCs in freshwater with an initial load of 0.3The dynamic elastic moduli of the 100 mm × 100 mm × 400 mm rectangular concrete samples were tested by a DT-20 DEM instrument. The variation rule of the DEM of the concrete samples subjected to different initial load damage and numbers of FTCs in freshwater, and the 3.4% and 6.8% composite salt solutions is shown in f and then put under FTCs in the 3.4% composite salt solution was more significant than that subjected to an initial stress of 0.3f and then put under FTCs in freshwater.It can be seen that the dynamic elastic moduli decreased with an increasing number of FTCs. The DEM loss of the concrete samples subjected to different initial loads, then put under FTCs in different salt solutions, varied almost linearly with the number of FTCs. Additionally, the loss of the DEM of the concrete under FTCs was proportional to the initial stress level and the concentration of the salt solution. By comparing the change in the DEM of concrete after 25 FTCs in freshwater and two salt solutions, it is apparent that the effect of the FTCs in a salt solution on the concrete’s DEM exceeded the effect of the FTCs in freshwater. The loss of the DEM of the concrete was significant in the early FTCs in the salt solution, and the loss of the DEM of concrete subjected to an initial stress of 0.15f stress action caused a larger loss in the DEM of concrete than no initial load. The loss in the DEM increased by 69% after 50 FTCs and by 71% after 100 FTCs when concrete was put under FTCs in freshwater, and the loss in the DEM increased by 25% after 50 FTCs and by 31% after 100 FTCs when the concrete was put under FTCs in a 6.8% composite salt solution. The FTCs in the 6.8% composite salt solution caused larger loss in the DEM of concrete than FTCs in freshwater. The loss in the DEM increased by 98% after 50 FTCs and by 60% after 100 FTCs when the concrete did not have an initial load, and the loss in the DEM increased by 50% after 50 FTCs and by 25% after 100 FTCs when the concrete under FTCs in the 6.8% composite salt solution was subjected to an initial 0.3f stress action. The coupling action of an initial stress of 0.3f and FTCs in the 6.8% composite salt solution aggravated the damage of FTCs to concrete. When concrete under FTCs in the 6.8% composite solution was subjected to an initial load of 0.3f, the loss in the DEM of concrete was 149% larger after 50 FTCs and 115% larger after 100 FTCs than that under FTCs in freshwater without an initial load. From the change rule of the compressive strength and DEM of concrete, it can be concluded that the change in the DEM of the concrete can be used to characterize the change in the compressive strength of the concrete when the concrete is subjected to different initial loads under FTCs in freshwater or in a salt solution.The initial 0.3The chloride ion concentrations (CICs) at various erosion depths in the concrete samples under the FTCs in the 3.4% and 6.8% salt solutions were tested for two reasons: (1) to study the erosion characteristics of chloride ions on the concrete materials under salt freeze–thaw environments and (2) to analyze the influence of the initial load on the chloride permeability of the concrete. Before the FTCs in a salt solution, one surface of the concrete samples was designated as a chloride ion erosion surface, and the other five surfaces were coated with epoxy resin. After various numbers of FTCs in the two salt solutions, the erosion surfaces of the concrete samples were ground to different depths. Then, the HC-RCTF chloride ion fast measuring meter was applied to test the CICs at those depths. The mass percentages of chloride ions at the various depths under various numbers of FTCs are shown in By comparing the CIC in the samples subjected to the same number of FTCs in the 3.4% and 6.8% composite salt solutions, it can be seen that the concentration of chloride ions in the concrete changed exponentially with the depth. At the same depth, the CIC increased with an increasing number of FTCs. At various numbers of FTCs, the CIC at each depth in the 6.8% composite salt solution exceeded that in the 3.4% salt solution. Samples subjected to an initial load and then FTCs in both salt solution concentrations had a higher CIC than samples without an initial load. This showed that the initial load reduced the impermeability to chloride ions. The change characteristics of the CICs at depths of 1 mm and 15 mm without an initial load under FTCs in both salt solutions are shown in It can be seen that the growth rate of the CIC at the erosion surface of the concrete samples was high for various numbers of FTCs in salt solutions, but that growth rate gradually slowed as the depth under the surface increased. The CIC in concrete specimens under FTCs in the 6.8% composite salt solution was larger than concrete specimens under FTCs in the 3.4% composite salt solution. The CIC at a depth of 1mm from the erosion surface was 40% larger after 50 FTCs and 13% larger after 100 FTCs, and the CIC at a depth of 15 mm from the erosion surface was 5% larger after 75 FTCs and 25% larger after 100 FTCs. The rate of the CIC increasing at a depth of 15 mm under 25 and 50 FTCs in both salt solutions was relatively low but under 75 and 100 FTCs, it was obviously high. This demonstrated that the concrete damage started at the erosion surface and gradually developed at greater depths with the increasing number of FTCs. It was found that the chloride impermeability of the concrete samples was gradually reduced with the sustained action of FTCs. The change law of the CIC ratio in concrete samples under various FTCs in the 6.8% and 3.4% salt solutions is shown in The absolute value of the CIC at the erosion surface increased with the number of FTCs. The difference in the CIC near the erosion surface with the two salt solutions gradually decreased, but deeper under the erosion surface, it gradually increased. When comparing the CIC at the depths of 1 mm, 5 mm, 10 mm, and 15 mm, we found that the ratio of the CIC at depths from 0 to 5 mm after FTCs in the two salt solutions was relatively small, but with the increase in the number of FTCs, the ratio at depths from 10 to 15 mm was larger.The CIC at a depth of 1 mm from the erosion surface increased by 1.4, 1.16, 0.95, and 0.9 times with the one-fold increase in the salt solution of the FTCs when there were 25, 50, 75, and 100 FTCs, respectively. The CIC at a depth of 10–15 mm from the erosion surface increased with the number of FTCs. The CIC at a depth of 15 mm from the erosion surface increased by 1.12, 1.12, 1.21, and 1.25 times with the one-fold increase in the salt solution of FTCs when the number of FTCs was 25, 50, 75, and 100, respectively. This indicated that in the concrete under FTCs in a high-concentration salt solution, the chloride ions continuously penetrated inside the concrete at the erosion surface, and higher numbers of FTCs increased the penetration rate.f, and over various numbers of FTCs in freshwater and a 6.8% composite salt solution.Nuclear magnetic resonance technology has been proven to be an effective, non-destructive testing method for testing pore distribution characteristics and other parameters in cement-based materials ,29. In tThe transverse coordinate in the T2 spectrum represents the relaxation time and is shown by logarithmic coordinates. The relaxation time reflects the diameter of a hole in a material. The longer the relaxation time in the transverse coordinates, the greater the pore diameter. The ordinates in the T2 spectrum represented the signal intensity of the NMR inversion of the pores, and the value of the signal intensity characterized the ratio of the pore diameter in the corresponding transverse coordinate. The larger the ordinate, the larger the proportion of the correspondingly sized pores in the entire material. By comparing the T2 spectra of the concrete samples under various experimental conditions, it could be seen that there were three prominent peaks in the T2 spectra. This indicated that there were three main pore diameters in the structure.f increased by 31% and 56% more than it did under FTCs in freshwater without being subjected to an initial load when the number of FTCs was 50 and 100, respectively.The ordinate values of the T2 spectra of concrete materials increased with an increasing number of FTCs. That is, under FTCs in freshwater and in salt solutions, the total peak area per unit mass gradually increased with an increasing number of FTCs. This shows that the porosity per unit mass of concrete samples increased with the number of FTCs. Comparing the changes in the characteristics of the concrete under FTCs in freshwater and the 6.8% composite salt solution, it was found that the pore volume per unit mass of concrete samples under FTCs in the salt solution was significantly greater than that in freshwater. The T2 spectra area of concrete under FTCs in the 6.8% composite salt solution increased by 31% and 56% more than it did under FTCs in freshwater when the number of FTCs was 50 and 100, respectively. By comparing the influence of the initial load on the value of signal intensity per unit mass of the concrete samples under FTCs in various solutions, it was found that the pore volume per unit mass of concrete samples increased with the increase in initial stress, regardless of whether the FTCs were in freshwater or a salt solution. The T2 spectra area of concrete under FTCs in freshwater subjected to an initial load of 0.3f stress action caused a larger area of the T2 spectra to undergo a second peak than when there was no initial load. The area of the T2 spectra undergoing a second peak increased by 32% after 50 FTCs and by 20% after 100 FTCs when the concrete was under FTCs in freshwater, and the area of the T2 spectra undergoing a second peak increase by 48% after 50 FTCs and by 32% after 100 FTCs when the concrete was under FTCs in the 6.8% composite salt solution. The FTCs in the 6.8% composite salt solution caused a larger area of T2 spectra to undergo a second peak than FTCs in freshwater. The area of the T2 spectra undergoing a second peak increased by 90% after 50 FTCs and by 200% after 100 FTCs when the concrete did not have an initial load, and the area of the T2 spectra undergoing a second peak increased by 185% after 50 FTCs and by 372% after 100 FTCs when concrete specimens under FTCs in the 6.8% composite salt solution were subjected to an initial 0.3f stress action. The coupling action of an initial load of 0.3f and FTCs in the 6.8% composite salt solution aggravated the area of the T2 spectra undergoing a second peak. When concrete under FTCs in the 6.8% composite solution was subjected to an initial load of 0.3f, the area of the T2 spectra undergoing a second peak was 185% larger after 50 FTCs and 372% larger after 100 FTCs than it was under FTCs in freshwater without an initial load.The second and third peaks increased more obviously in the T2 spectra, which shows that the pores in the pore diameter range corresponding to those peaks obviously changed under FTCs. The initial 0.3f and which then underwent FTCs were compared to the spectra of unloaded samples. It was found that the second and third peaks of the spectra increased significantly in the loaded samples, as did the relaxation time of the spectra’s transverse coordinates corresponding to each peak. Similar phenomena were found when concrete specimens under FTCs in composite salt solutions were compared to those in freshwater. These showed that the damage of an initial load and FTCs in a composite salt solution increased the effect of FTCs on the damage inside the concrete and made the pores corresponding to the second and third peaks of the T2 spectrum significantly increase.The T2 spectra of samples subjected to an initial load of 0.3f.The unit mass porosity of the samples was proportional to the number of FTCs, initial load, and salt concentration. This showed that an increase in the number of FTCs, the initial load, and the concentration of the salt solution increased the damage of FTCs on the concrete materials. The damage to concrete samples caused by the FTCs in the 6.8% composite salt solution without an initial load was more severe than it was in freshwater and when subjected to an initial load of 0.3Overall, the FTCs led to the damage inside the concrete; that is, the increase in porosity per unit mass inside the concrete according to the observation from a micro perspective, and the change in the mechanical and physical properties of the concrete samples according to the observation from a macro perspective, showed that the compressive strength and DEM of the concrete samples decreased gradually. Each transverse coordinate of the T2 spectrum corresponded to a special pore diameter, micropores and transition pores (<2.5 ms), mid-sized pores (2.5–100 ms), and large pores and cracks (>100 ms) , which cf, which shows that the damage caused by the salt solution was more severe than that caused by the 0.3f load. This change law of the proportion of pores inside the concrete was consistent with the change characteristics of the compressive strength of the concrete.By comparing the change in each peak area of the T2 spectrum of concrete samples under FTCs in different solutions, it can be seen that the proportion of micropores and transition pores in the concrete samples gradually decreased, whereas the proportion of mid-sized pores and large pores and cracks in the samples gradually increased. The rate of the increase in the proportion of mid-sized pores was larger than that of large pores and cracks. The change of pores inside the concrete subjected to FTCs shows that with the increase in the number of FTCs, the compressive strength and DEM of the concrete were closely related to the increase in the proportion of mid-sized pores and large pores and cracks. It was also concluded that from the changes in the peak ratios in the T2 spectrum, the action of the initial load inflicted a certain amount of damage on the concrete samples. The proportion of mid-sized pores inside the unloaded samples under FTCs in the 6.8% composite salt solution increased more than that in freshwater samples subjected to an initial load of 0.33 Powder X-ray powder diffractometer. An X-ray diffraction analysis of concrete surface erosion after 100 FTCs is shown in 2), gel , calcium hydroxide 2), calcium aluminate hydrate , and hydrated calcium aluminate sulphate (Aft/AFm). There were NaCl crystals in the composite salt. The calcium carbonate (CaCO3) was formed by the reaction of NaHCO3 in the composite salt with Ca (OH)2 in the cement stone. Hydrate calcium sulphate (CaSO4·2H2O) was formed by the reaction of sodium sulphate (Na2SO4) with Ca (OH)2 of the cement hydrate. The ettringite  and hydrated calcium aluminate sulphate  were formed by the reaction of hydrated calcium (CaSO4·2H2O) with tricalcium aluminate  in the cement.The composition of the concrete materials was observed by an X’Pertf and then 100 FTCs in a 6.8% composite salt solution are shown in f and then to 100 FTCs in a 6.8% composite salt solution, more chloride ions, sulphate ions, and carbonate ions eroded into the concrete and formed crystalline salt. At the same time, the laminate crossed-needle-flake ettringite also increased significantly. At that point, the surface of the concrete samples was no longer flat and became looser, and there were even some penetrating cracks inside the structure. The pores inside the concrete structure increased, which corresponded to the macroscopic performance in which the interface bonding was reduced inside the concrete, which led to the damage andstrength reduction of the concrete under FTCs in a salt solution.An SU8010 positron emission scanning electron microscope (SEM) was used to analyze the microstructure of the concrete samples and the micro-composition characteristics of the samples 2 mm under the erosion surface before and after FTCs in salt solutions. The SEM images of the concrete before the FTCs are shown in It can be seen from the previous analysis that FTCs led to concrete damage, and changes in the compressive strength, DEM, and the T2 spectrum of the concrete occurred regularly. To study the relationship between the macroscopic mechanical properties of the concrete and the microscopic pore changes inside it, linear correlations were made between the compressive strength of the concrete and the concrete mass, DEM, the area of the T2 spectrum, the areas of the first, second, and third peaks of the T2 spectrum, and the proportion of the first peak. By comparing the linear correlation coefficients between each index and the compressive strength of concrete, it can be seen that there was a close linear correlation between the change in the compressive strength of the concrete and the concrete mass, DEM, the area of the T2 spectrum, the areas of the first, second, and third peaks of the T2 spectrum, and the proportion of the first peak when the concrete was first subjected to a different initial action with a low load and then to FTCs in different low-concentration salt solutions. The values of most linear correlation coefficients were approximately 0.9, with individual coefficients close to 1. Those results show that the change rules of mass, DEM, and pore characteristics inside the concrete were similar to the change rule of the compressive mechanical properties of concrete samples under the rapid FTCs in different salt solutions. Among the pore characteristics of the T2 spectra of the concrete samples, the change in the proportion of the first peak of the T2 spectrum had a close negative linear correlation with the compressive strength of concrete, and the linear correlation between the two properties of the concrete was relatively stable under the rapid FTCs.(1)When the initially loaded concrete samples underwent FTCs in freshwater or salt solutions, internal damage occurred, and more internal cracks were generated. The combined action of the initial load and the salt freeze–thaws led to more severe damage to the concrete.(2)When concrete samples underwent FTCs in the low-concentration salt solution, the negative effect of the salt produced considerable freezing pressures inside the concrete, which led to more severe damage. The increase in the number of FTCs intensified the concentration of chloride ions, which eroded the concrete samples.(3)It can be seen from the change in the microscopic structure of the concrete materials under FTCs in freshwater and salt solutions that the overall porosity of the concrete increased with an increasing number of FTCs, and the proportion of mid-sized pores and large pores and cracks gradually increased inside the concrete. During the FTCs, the compressive strength and DEM of the concrete gradually decreased, which had a close correlation with the proportion of the increase in the mid-sized pores and large pores and cracks.(4)This paper discusses the mechanical, physical, and microscopic pore change properties of ordinary cement specimens under FTCs in a low-concentration salt solution and concrete specimens subjected to low-stress initial loads. There is still a need for further studies on the mechanical, physical, and internal pore morphology changes of high-strength cement concrete or concrete under FTCs subjected to high-stress initial loads.


Staphyococcus lugudnensis (SL) is a coagulase negative Staphylococcus species with a potential to cause invasive infection. Few studies have evaluated characteristics and outcomes of SL bacteremia (SLB) compared with Staphylococcus aureus (SA) and Staphylococcus epidermidis (SE).We performed a single center retrospective case-control study of patients > =18 years of age with SLB with at least two sets of positive blood cultures at Kyoto University Hospital, Japan from January 2005 to December 2021. Patients who had SA bacteremia (SAB) with at least one set of positive blood culture and those who had SE bacteremia (SEB) with at least two sets of positive blood cultures were randomly selected in a 1:5:5 (SL:SA:SE) ratio during the same period. Characteristics and clinical outcomes of SLB were compared with those of SAB and SEB.A total of 24 patients with SLB, 120 patients with SAB, and 120 patients with SEB were included. Patients’ median age (interquartile range) was 69 , 68  and 65  in order of SL, SA, and SE. The rate of hospital-acquired infection in SL was similar to that of SA , lower than that of SE . Rates of methicillin resistance and intravascular catheterization were higher in SE . Patients with SLB were more likely to be on hemodialysis (25%). Rates of polymicrobial bacteremia and blood cancer was lower in SA . Echocardiography was done for 14 patients in SL, lower than in SA . The rate of infective endocarditis (IE) (primary and secondary) was not significantly different among three groups . There was no significant difference in rate of metastatic lesions between SL and SA , statically lower in SE than in SL . Seven-day mortality was similar between SL and SA , lower in SE than in SL . Thirty-day mortality in SL was not significantly different in other groups .The rates of metastatic lesions and 7-day mortality in SL were similar to that of SA, higher than that of SE. Appropriate evaluation and treatment that are recommended for SAB may be warranted for patients with SLB.All Authors: No reported disclosures.


This study will investigate the effect of non-woven PET plastic tissue on the fresh, physical, mechanical, acoustic, thermal, and microstructural behaviors of concrete. Including reference specimens, non-woven fabrics were considered in two ways: (a) as a layer with four various configurations of 1-layer, 2-sides, 3-sides, and full wrapping (4-sides) to strengthen specimens, and (b) as (10 × 10) mm cut pieces with three different incorporated percentages of 0.25%, 0.50%, and 0.75%. Based on the experimental results, mechanical properties  were remarkably improved by applying non-woven sheets as a layer. For instance, the cylindrical compressive and split tensile strengths were improved by 13.40% and 15.12% for the strengthened specimens compared to the reference specimens, respectively. Moreover, control specimens were damaged to many fragments after mechanical testing, but the samples strengthened by such fabrics or containing cut pieces were maintained and not separated into many small parts. The acoustic behavior and thermal conductivity declined by 9.83% and 19.67% with the attachment of tissue on one side and 2-sides, respectively. Acoustic behaviors decreased by 10.0%, 17.60%, and 26.30% and thermal conductivity decreased by 6.60%, 12.10%, and 15.50%, with the incorporation of 0.25%, 0.50%, and 0.75% of cut pieces, respectively. Finally, it was discovered that non-woven tissue is advised to enhance particular properties of concrete. In recent decades, plastic consumption has been vastly increased because of rapid urbanization and economic growth. The recycled amount is still comparatively lower and results in an increase of plastic wastes. These wastes cause many environmental problems because of the absence of enough space for landfilling and their low biodegradability ,3,4,5,6.In general, plastics are classified into two groups based on their ingredients and mix proportions: (1) Thermoplastics can melt when heated and harden when cooled. Based on their usage, thermoplastics are subdivided into polyethylene terephthalate (PET), high-density polyethylene (HDPE), low-density polyethylene (LDPE), polyvinyl chloride (PVC), polypropylene (PE), and polystyrene (PS). (2) Thermosets are plastics that undergo chemical change and can be remolded or softened by heating ,13.Furthermore, the most used thermoplastic is polyethylene terephthalate (PET), which has a wide range of uses including blown bottles, bottles for soft drinks, containers for packing and food, etc. In 2007, a total of 10 million tons of PET plastic were used globally, which is equal to 250 billion bottles, and this amount increases nearly 15% annually. It is known that PET bottles used just once are discarded and result in plastic wastes that cause many environmental problems. Therefore, researchers have tried to discover ways to reduce or eliminate these environmental issues. The substitution of PET wastes by plastic aggregates or the addition of plastic fibers into cementitious materials ,14 appeaThe properties of concrete with varying percentages of coarser, flakier, and irregularly shaped plastic aggregates substituted by natural aggregates were investigated in an experimental investigation. The authors observed a substantial reduction in slump value for specimens having plastic aggregates compared to the reference samples. Additionally, the concrete matrix with waste plastic aggregates had lower drying shrinkage than normal concrete. This might be because plastic waste is impermeable and has a great capacity to absorb water while the concrete is in a fresh state . ConcretAdditionally, the results of an experiment on the physical and mechanical characteristics of mortars with 3%, 10%, 20%, and 50% replacement of sand with PET waste aggregates show that the compressive strength decreased as the percentage of plastic aggregates increased due to the poor bond between cement paste and plastic aggregates . The resk) significantly decreased for the specimens having PET fibers compared to the reference ones. This might be a result of plastic fibers’ lower thermal conductivity compared to cement and aggregates [In addition, experimental work was conducted to explore the sound velocity of self-compacting mortar containing 0%, 10%, 20%, 30%, and 50% of plastic waste as fine aggregates. The findings underline a remarkable reduction in sound velocity of specimens with plastic aggregates for every substitution. This can be seen in the cement’s hydration products, which fill the material’s existing cavities . In addiOn the other hand, one of the most crucial topics in civil engineering is the strengthening and retrofitting of damaged or new structural elements. Concrete could deteriorate throughout the service life because of errors in design, change in usage, inadequate maintenance, material deficiencies, overloading, fire, earthquake, or other environmental aspects. Thus, researchers have considered different materials and methods for strengthening and retrofitting of structural elements ,32,33. I® is a microfilament textile made from a combination of short and long fibers, and bounded together by chemical, mechanical, heat, or solvent treatment was used in the present study. This product offers many possibilities for tapping into new markets and developing applications. They are used for technical packaging for the automotive and electronics industry, anti-allergy encasings, or as cleaning cloths and sports towels, etc. In addition, the chosen product was made from PET, which is a type of plastic with a wide range of applications, strong mechanical properties (strength and stiffness), long durability, etc., compared to other types [The above bibliographic research indicates that plenty of research was performed on concrete having plastic wastes as substituted aggregates or incorporated fibers. Numerous researchers looked at concrete elements that were repaired with various materials. However, none took PET non-woven tissue into consideration as a layer to reinforce concrete samples or as cut pieces to alter specific properties of concrete. Therefore, a product of the FREUDENBERG Company named Evoloner types . Additioer types . However2/gr and specific gravity of 3.041. In the current study, concrete mixtures were manufactured using locally accessible Ordinary Portland Cement known as Ghori that complied to ASTM C150  with theIn addition, two different sizes of coarse aggregates (10 mm and 25 mm) crushed from mountain rocks and fine aggregates with 6.3 mm maximum size obtained from the natural sand of a river were used in concrete mixtures. Additionally, ADIUM 150, a new generation of polycarboxylate-based water reduction agent that was confirmed by EN 934-2  and obta® microfilaments were sourced from the FREUDENBERG Company  [® microfilaments are very durable fabrics, have very good sound absorption, and thermal insulation properties.Finally, non-woven plastic tissue or Evolon France) . These f3. The mix design with 0.0% of cut pieces was considered for the samples using non-woven sheets as a layer, while for concrete mixtures containing cut pieces of non-woven sheets, the mix proportions were slightly modified with the addition of cut pieces and superplasticizer due to lower consistency. In this case, the content of fabrics for one cubic meter is measured by taking the mass of concrete as 2133 kg. For instance, the amount of 0.50% of non-woven sheets by mass of concrete is taken as 0.50 × 2133/100 = 10.66 kg/m3. The detailed amount of ingredients for samples with a non-woven sheet as a layer or cut pieces are presented in In the present study, non-woven sheets were used in concrete mixtures with two methods: (1) as a layer to strengthen samples, and (2) as (10 × 10) mm cut pieces incorporated with various percentages of 0%, 0.25%, 0.50%, and 0.75%. Based on ACI Standard Practice ACI 291.1   mm. The fresh density was obtained from three samples and their average was 2680.4 kg/m(a)Compressive strengthAs indicated by the fracture pattern, the reference specimens clearly show numerous cracks after the ultimate load, whereas the specimens with the 1-layer, 2-sides, and 4-sides strengthening configurations did not exhibit many cracks. It indicates that samples were maintained by tissue, and particularly the strengthened sides as shown in Even though the research study did not consider plastic non-woven tissue for strengthening purposes, the improvement of the compressive strength was verified by the previous experimental works, whereas concrete specimens were strengthened by fiber reinforced polymer (FRP) sheets using various methods. However, there is a difference between the outcomes of the current study and the previous studies due to great difference between material strengths, adhesive materials, etc. ,51,52.(b)Flexural strengthThe flexural strength was found under a four-point loading setup. The outcomes clearly demonstrate that the flexural strength was enhanced significantly or highly significant for the strengthened beams compared to the reference beams Reference beam: The reference beams failed abruptly and completely divided into two parts after failure and had wider ultimate cracks during failure as shown in 1-layer: After the ultimate loading, beams containing a single layer of non-woven tissue at the bottom were damaged but not divided into two portions and were maintained by the layers of tissue. The width of crack was remarkably decreased as was observed for the reference beams. In addition, the layer of non-woven sheets was locally detached at one or both sides of the crack but not broken as shown in 2-sides: These beams were broken at the bottom of the flexural zone. The cracks were seen at the bottom and top of the beams but were covered completely by non-woven sheets at vertical faces. In addition, the tissue was slightly broken at the bottom of beams but remained unbroken close to the top of beams as shown in 3-sides: The failure occurred at the bottom of the beams under non-woven sheets. In this case, the non-woven tissue was not broken but was detached around the entire cross-section and such detachment was more significant at the bottom of the beams. Moreover, the samples were entirely maintained by the tissue and were not separated into two parts as shown in Additionally, the cracking mechanisms of all reinforced beams were similar to those of the control beams, where flexural cracks started at the middle of the beams between two loading points, spread to the depth of the beams, and were then followed by a single, widened crack until the ultimate failure. However, the final modes of failure for reference and strengthened beams were observed as follow:There is no bibliographic research that considered such fabrics to retrofit concrete samples. However, many researchers conducted similar research but considered different materials such as FRP, cementitious materials, etc., to strengthen concrete beams. However, the current outcomes match the results of previous research, and they also found a remarkable improvement with the use of strengthening materials. In addition, this enhancement was more significant for U-wrapping, and 2-sides compared to the 1-sides. The difference between the current results and previous results is only linked to the properties of strengthening materials ,54,55,56(c)Split tensile strengthThe split tensile strength test uses a cylinder that splits across the vertical diameter to indirectly assess the tensile strength of concrete specimens. The outcomes of cylinders tested under the tensile splitting setup are presented in In addition, the control specimens failed with the brittle fracture and were separated into two entirely parted fragments. Contrarily, cylinders wrapped with the tissue were not separated but were kept together. This indicates that samples could withstand larger splitting loads when plastic tissues are attached, and the ultimate failure will be without separation as seen in (a)Ultrasonic pulse velocity (UPV)This test measures the speed of the ultrasonic pulses’ transit time. The electro-acoustical transducer used in the UPV test produces ultrasonic pulses with a frequency of 50–58 kHz that travel from one surface of the element to the other. The transit time of ultrasonic pulses is influenced by the density, elastic and other properties of the material being tested.(b)Thermal conductivityλ). Building energy consumption is directly impacted by the quantity of heat loss via the walls and roof. The amount of heat transfer depends on the physical and mechanical properties of concrete materials, mix proportion of concrete, moisture content, etc.In order to understand how much heat is transferred through conduction, one of the most important characteristics is the concrete’s thermal conductivity WorkabilityThe slump values of concrete mixtures with various percentages of cut pieces are shown in The reduction of slump value with the incorporation of cut pieces was confirmed by previous research. The workability decreased when plastic fibers were added, and this reduction was more pronounced at higher percentages ,57. This(b)Fresh densityThe fresh density of concrete illustrates its mass per unit volume at the fresh state. The fresh density depends on the mix proportion, characteristic of concrete constituents, etc.3 to 2360.6 kg/m3 as presented in Wet densities vary from 2680.4 kg/mEven though prior experimental studies incorporated other kinds of plastic materials with various properties into concrete mixtures, similar trends were observed as in the present study. The outputs indicate that the fresh density has decreased with the addition of plastic fibers and decreased even more for higher percentages. This might be because plastic fibers have a lower specific gravity (1.12) than concrete components .(a)Dry density3 to 2084.9 kg/m3. The use of non-woven tissue resulted in an insignificant reduction of dry density because non-woven fabrics were lighter than cement and aggregates, and incorporation of such fabrics resulted in porous concrete compared to the control. Distinct changes in the dry density were detected for a higher volume fraction of tissue, as presented in The bulk densities of studied concretes were within the range of 2201 kg/m(b)Porosity and water absorptionThe porosity of concrete specimens with different percentages of non-woven cut pieces is shown in In addition, the water absorption was calculated for concrete specimens containing non-woven plastic tissue from 0% to 0.75%. The outcomes clearly demonstrate that concrete samples with plastic fabrics had significantly or very significantly higher water absorption than the reference samples. This increase was more remarkable for higher volume fractions of plastic fabrics as shown in Although no research was available in the literature that considered cut pieces of non-woven sheets incorporated into concrete mixtures, the effect of non-woven tissue on the physical properties was confirmed by previous investigations. These found that the dry density decreased, and water absorption and porosity increased with the incorporation of plastic fibers and these variations were more remarkable for higher percentages ,58.(a)Compressive strengthThe compressive strength of concrete specimens with different percentages of cut pieces is in The cracking pattern made it obvious that samples without cut pieces were broken into numerous pieces after the maximum force. However, specimens with 0.25%, 0.50%, and 0.75% were not separated into many parts and were maintained by such small pieces, especially for the cubes containing 0.75% of cut pieces. This is attributed to cut pieces that act as fibers inside the concrete samples and prevent the pieces of concrete from separation as shown in (b)Split tensile strengthEven though small pieces of non-woven fabrics were not beneficial for split tensile strength, it was clearly observed from the cracking pattern that samples without cut pieces were divided into two separate parts, while samples with 0.25%, 0.50%, and 0.75% were not parted into two parts and were in such small pieces from splitting. In addition, it can clearly be seen in the pictures that the width of the splitting crack was reduced considerably with the increase of percentage of cut pieces as shown in In addition, the current results do not comply with the literature that present an improvement in the mechanical strengths after the introduction of plastic fibers. This is attributed to the mechanical properties of the materials themselves ,20,30.(a)Ultrasonic pulse velocity (UPV)The UPV value was measured for concrete mixtures without fabrics and with 0.25%, 0.50%, and 0.75% of cut pieces. The results in (b)Thermal conductivityCompared to the control specimens, the thermal conductivity of the specimens containing cut pieces decreased. Furthermore, the reduction was more significant for the samples containing higher percentages of cut pieces as shown in Even though the effect of cut pieces incorporated into concrete mixtures on thermal behaviors of concrete was not previously studied, the data of the current study regarding the transfer properties are in good agreement with previous research that considered other types of plastic wastes. This means that previous authors also found a decrease in transfer properties for plastic fiber-reinforced concrete ,60.2 = 0.99) for the split tensile strength obtained from specimens having various dry densities. However, for compressive strength, a slight variation was observed while density was changed, but the relation between dry density and compressive strength still had the best fit line (0.90), as shown in From the experiments, the relationship between dry density and compressive and split tensile strengths was plotted for concrete mixtures with 0, 0.25%, 0.50%, and 0.75% percentages of cut pieces after 28 days of curing. In the above equations, 2 is equal to 0.96 and 0.97 for the compressive strength and split tensile strengths, respectively. Finally, from the above correlations, the following equations were obtained to estimate the compressive and split tensile strengths in terms of the porosity of concrete:The relationship between the porosity and compressive and split tensile strengths are shown in In the above equations, Furthermore, the splitting tensile strength was plotted versus the compressive strength from the experiment and to those developed by past investigators who worked on the incorporation of waste plastics in concrete mixtures. It is clearly observed from 2 values are 0.96 and 0.92 for UPV and thermal conductivity, respectively. Here, the UPV value and thermal conductivity can be found from dry density with the help of the following formulas:Moreover, the UPV and thermal conductivity are greatly dependent on the dry density of concrete. Therefore, the relationship of dry density with UPV and thermal conductivity was plotted to predict such values while only the dry density of concrete is measured. In the above equations, Additionally, 2 coefficient clearly indicate that UPV and thermal conductivity could correlate with the compressive strength in an accurate manner. Here, the UPV value and thermal conductivity can be found from the compressive strength with the help of the following formulas:Furthermore, In the above equations, 2 correlation coefficient (0.98) that for reference concrete mixtures and mixtures containing 0.25%, 0.50%, and 0.75% of cut pieces, the relationship between UPV and compressive strength is very good. Thereafter, the present data were predicted by models developed by past investigators who worked on the incorporation of waste plastics in concrete mixtures. Even though the present model has a slight safety related to the relationship obtained from [Additionally, ned from ,65 but s2 correlation coefficients clearly indicate that the percentages of cut pieces have an excellent correlation with certain properties of concrete.Finally, Without the use of any adhesives, non-woven tissue adheres well to concrete specimens.The workability and homogeneity of concrete were unaffected when non-woven tissues were applied as a layer on the exterior sides of concrete examples. However, the workability decreased very significantly as a result of the addition of cut pieces into concrete mixtures.The cube compressive strength is little affected by the attachment of non-woven tissue; however, the compressive strength of cylindrical samples strengthened with the tissue increased significantly. For the specimens having cut pieces, the compressive strength decreased significantly or high significantly. Additionally, unlike the reference samples, specimens with non-woven tissue did not break up into numerous pieces at the ultimate compressive force.Concrete beams reinforced with 1-layer, 2-sides, and 3-sides of non-woven tissue had greater flexural strength than the control beams. Additionally, control beams failed brittle and were split into two pieces, whereas non-woven tissue-covered beams displayed relatively ductile behavior, were not split into two parts, and had less widen cracks than control beams.At all curing regimes, the splitting tensile strength greatly improved for the cylinders covered with non-woven tissue compared to the reference cylinders. After the peak load, covered samples were maintained by non-woven tissue, while non-covered samples were separated into two distinct sections.Incorporation of non-woven cut pieces into concrete mixtures resulted in a remarkable decrease of dry density due to the lower density of non-woven fabrics and an increase of water absorption and porosity because of the weak transition zone, macro cracks, and voids present in the interfacial transition zone between plastic tissue and cement paste.The UPV findings fluctuated between 3.42 km/s and 4.64 km/s in the present study. The control specimens had the highest UPV value, whereas samples with non-woven tissue on 2-sides had the lowest UPV value. The addition of cut pieces greatly reduced the UPV value, and this reduction was more pronounced for higher percentages.The specimens containing layer or cut pieces of non-woven sheets had better thermal insulation than control specimens.2 coefficient and line trend clearly show the great accuracy and indicated that certain properties of concrete could be predicted based on previously observed behaviors. Additionally, an earlier developed model was used to validate the new research data, which demonstrates excellent accuracy.Lastly, the relationships between various concrete properties were plotted and the RFinally, this research study demonstrates that non-woven tissue can be employed in concrete since it adheres well to specimens and can enhance several concrete properties. Therefore, more research should be done to understand additional characteristics such as resistance in aggressive environments, microstructural analysis, durability, etc. However, additional research is also necessary to determine the mechanism behind the bond between non-woven tissue and concrete and especially the effect of water content, addition of superplasticizer, and type of surface on their bond properties. In addition, it is suggested to study the mechanical properties of concrete samples with two or more layers of non-woven sheets attached to one another using adhesive materials.This study highlights the possibility of using plastic non-woven tissue in concrete. The key findings are outlined below:


Currently, the costs of building materials, especially cement, are increasing. Waste marble powder (WMP) could be used as a cement replacement material to produce environmentally friendly concrete to help preserve resources and reduce environmental pollution. The study’s goals are (1) to evaluate the effects of using marble powder in place of cement in high-strength concrete (HSC) on the material’s mechanical properties and durability characteristics. (2) The study is expanded to assess the effect of using partial WMP on the shear behavior of HSC beams under static loads. Eight half-scale simply supported reinforced beams with and without WMP have been tested. Each beam’s cross-section was 120 × 200 mm, and each beam had a total length of 1000 mm. The ratios of the used WMP were 0%, 2.5%, 5%, 7.5% by weight, and two different stirrup ratios, 0% and 0.47%, were used. When applied to HSC beams with and without WMP, the shear strength provisions of two of the most used codes, such as the locally used Egyptian Code (ECP 207) and the internationally used American Concrete Institute’s (ACI-2019), were examined. Using the ABAQUS software, the experimental results were compared to the findings of the nonlinear finite element analysis. The results established that partial replacement of cement by WMP led to increases in the concrete’s compressive and tensile strengths of about 15% and 16%, respectively. When tested specimens were exposed to acid attack, there were slight losses in weight and compressive strength (1.25% to 2.47%) for both with and without the addition of WMP. Both the concrete with and without WMP showed the same level of water absorption. Additionally, WMP led to an enhancement in the shear capacities for all beams. Increasing the WMP ratio from 0% to 2.5%, 5%, and 7.5% increased the shear capacity by about 13%, 20%, and 28%, respectively, for beams without stirrups, while for beams with stirrups, the shear capacity improved by 12%, 19%, and 25%, respectively. The enhancement in the beams’ shear capacities could be attributed to the advanced concrete matrix produced by WMP’s extremely small particle size. For centuries, natural decorative stones, such as marble, have been widely used around the world, particularly in developing countries. Subsequently, when these stones are prepared for use by processing, sawing, and shaping them, a huge amount of powder waste is produced, which causes a global environmental problem. Therefore, the recycling of waste marble powder (WMP) in the building sector for the manufacture of sustainable concrete as a replacement for cement has been the subject of several studies in the past decade ,21,22,23Recently, the structural applications of concrete made by replacement of cement with another cement replacement additive to help in solving environmental pollution caused by cement production have been experimentally investigated ,25. MahmThe use of waste materials, especially geopolymers, as environmentally friendly materials has been the subject of experimental study ,27. Red The study’s goals are (1) to evaluate the effects of using marble powder in place of cement in high-strength concrete (HSC) on the material’s mechanical and durability characteristics. (2) The study is expanded to assess the effect of using partial WMP on the shear behavior of HSC beams under static loads. For this aim, eight half-scale HSC beams with varied WMP% ratios were tested under static loading conditions. The percentage ratios of used WMP were 0%, 2.5%, 5%, and 7.5% by weight. In addition, the beams were constructed with and without stirrups to validate the contribution of WMP in concrete shear resistance when stirrups are not present. Two of the most used codes, such as the locally used Egyptian Code (ECP 207)  and the 3 and an average particle size of 20.67 µm. An identical batch of cement was utilized for all the tests. 3, 1.91%, and 2.23, respectively. The coarse aggregate used was 8 mm crushed limestone. The used cement was ordinary Portland cement with the commercial name CEM I 52.50 N, which has a specific gravity of 3.10 g/cmcf′) and the average cube compressive strength (fcu), respectively. The compressive strength of the concrete cylinder or cube is measured as a continuous load applied to the specimen till failure. To determine the average concrete tensile strength (tf), three more concrete cylinders were taken for each ratio of the WMP. The tensile test is an indirect method for assessing the tensile strength of concrete. In this test, the concrete cylinder is set out horizontally, and a force is applied radially on its surface, causing a vertical fracture to develop along the cylinder’s diameter. Forty-five cube specimens for each mixture (100 × 100 × 100 mm) were cast to determine durability characteristics, such as acid resistance and water absorption. Three concrete cylinders (ϕ150 × 300 mm) and three concrete cubes (150 × 150 × 150 mm) were taken for each percentage of the WMP mix to determine the average cylinder compressive strength  and 2% hydrochloric acid (HCl). The specimens were air dried, chilled at ambient temperature, weighed using an electronic balance, and then submerged into an acid bath after the 28-day curing period. Before immersion, the initial weights of each specimen were noted. The weight losses and compressive strengths of conventional and marble powder concrete specimens were measured after immersion for 15 days in acid, and the results are shown in The acid solution was created by combining distilled water with 3% sulfuric acid  were 0% and 0.47%. Vertical stirrups were constructed using 100 mm-spaced, 6 mm diameter bars with 240 MPa yield stress. According to ACI Code provisions (ACI-2019) [Experimental testing was performed on eight simply supported waste marble powder high-strength reinforced concrete beams. To divide the beam into two identical shear spans, all beams were tested with a single concentrated load at the mid-span point. As mentioned above, the concrete strengths were decreased at WMP ratios of 10% in comparison to specimens that have 7.50% WMP. Thus, the percentages ratios of used WMP were 0%, 2.5%, 5%, and 7.5% by weight with the concrete mix are illustrated in CI-2019)  for the Each specimen was examined using a standard universal machine. The loads were measured using a load cell with a 300 kN capacity and 0.1 kN precision. cr) and the ultimate failure load (Pu) for each beam are given in cr with respect to Pu. It should be emphasized that the formation of diagonal cracks inside the beam’s web, which becomes unstable and breaks, is the primary reason for the shear failure of the reinforced concrete beams. Therefore, the compressive and tensile strengths of the concrete utilized have a major impact on the shear failure mechanism of the beam. Consequently, as the WMP ratio increased, the concrete compressive and tensile strengths increased, and the beam’s shear capacity increased. The failure cracking patterns of the tested beams are illustrated in u) corresponding to the ultimate failure load (Pu) is presented in u by about 13%, 20%, and 28%, respectively, for beams without stirrups, while for beams with stirrups, the ultimate load improved by 12%, 19%, and 25%, respectively. It could be confirmed that the use of WMP increased the shear resistance because the WMP is vital to increasing the compressive and tensile strengths of concrete, which enhance shear resistance.The load-deflection relations were recorded for all tested specimens and are displayed in To show the influence of adding WMP on the stirrup strains, the curves of load versus tensile stirrups strain are shown in u) in a concrete beam reinforced with stirrups, which is resisted by both the concrete (Vc) and the stirrups (Vs), is given by the equations below:cf′ is the concrete compressive strength of the cylinder in MPa; b is the beam width in mm; d is the effective beam depth in mm; s is the spacing between vertical stirrups in mm; Av represents the shear reinforcement area (mm2); and ysf is the stirrups’ yield stress in MPa.According to the ACI code , the criu) is computed as per ACI 318-19, except for the concrete shear force (Vc), which has the following calculation:cuf is the concrete compressive strength of the cube in MPa, which is about 1.25 times cf′, and γc is a strength reduction factor for concrete and equal to 1.50.According to ECP Code , the criu exp.) were compared with those determined from the ACI 318-19 (Vu ACI) and ECP 207 (Vu ECP) codes. As depicted in The previous section, “Code Provisions”, can be considered an introduction to the current section. As shown in The ABAQUS program was used to carry out finite element simulations of the tested reinforced concrete beams. Nonlinearity in the materials was considered and described as follows.c) and tension (dt). When the concrete material reaches its maximal stress, they depict the progression of the stresses in concrete. t was calculated according to Eurocode 2 [tε is the tensile strain in the concrete at the peak stress tf, ε is the tensile strain in the concrete, and tf is the concrete tensile strength, which is taken from experimental results. For the steel longitudinal bars in the finite element model, an elastic completely plastic model with equal behavior in tension and compression was adopted. ABAQUS software defined the Young modulus (Es) and Poisson’s ratio (v) as equal to 2 × 105 MPa and 0.30, respectively, with yield stress yf for longitudinal and transverse bars, as illustrated in the experimental program.The concrete damage plasticity (CDP) model is utilized in this study to explain the behavior of the concrete beams. rocode 2  as:σt = The solid elements (C3D8R) from the ABAQUS library are used to model the concrete beam. They are reduced integration, eight-node elements with hourglass control, and each node has three degrees of freedom for translation as well as a truss element (T3D2) to simulate reinforcing bars. It consists of two nodes with three degrees of freedom each . In this study, embedded technology was used to create frictional contact between the steel and concrete in ABAQUS . To choo1 = U2 = 0.0) and hinged support (U1 = U2 = U3), as illustrated in 1, U2, and U3 are translation in X, Y, and Z directions, respectively, to mimic the experimental test setup.The load was applied as a one-point load, and the supports of tested beams are roller support  for both with and without the addition of WMP.Both the concrete with and without WMP showed the same level of water absorption.For stirrup-equipped specimens, raising the WMP ratio from 0% to 2.5%, 5.0%, and 7.5% resulted in a decrease in the stirrup strain of about 16%, 22%, and 27%, respectively.The average values of the ratios between the experimentally measured shear failure force and those derived from ACI 318-19 and ECP 207 were 1.40 and 1.59, respectively, indicating that the ECP Code is more conservative when designing shear than the ACI Code.The average ratio of the experimental to the FE ultimate load was 0.96, while the average ratio of the experimental to the FE mid-span displacement was 1.11. This indicates that the experimental findings and FE simulations were in good agreement.The results of the experimental investigations and analytical analyses of the shear behavior of WMP reinforced concrete beams can be used to draw the following conclusions:


To investigate the mechanical properties of hybrid basalt fiber (BF) and polyvinyl alcohol fiber (PVAF)-reinforced low-heat Portland cement concrete (LHPCC), two groups of concrete were formulated. The BF and PVAF were equal in the first group, and the total fiber contents were 0–0.4%. The second group was the total fiber content of 0.3% and the occupancy of BF in the hybrid fiber of 0, 25%, 50%, 75%, and 100%. Two groups of concrete were tested for compressive, splitting tensile, and flexural strengths to illustrate the enhanced mechanism of the mechanical properties of LHPCC by hybrid fiber. The best mechanical property enhancement was achieved when BF and PVAF were in equal proportions and the fiber content was 0.3%. Meanwhile, the test results for the mechanical properties were also compared with the predicted values of ACI 318 and Eurocode 2. Moreover, the hybrid BF-PVAF-reinforced concrete was regarded as a three-phase composite material consisting of fiber-reinforced mortar, coarse aggregate, and an interfacial transition zone. The axial compressive and splitting tensile strengths, damage processes, and mechanical strengthening mechanisms of concrete were investigated for different total fiber content at equal ratios of BF and PVAF, and the results were compared with the macroscopic mechanical test findings. The results show that the conclusion of the meso-simulation matches well with the test. Finally, the effect of aggregate and hybrid fiber content on the mechanical properties of LHPCC was predicted by a simulation. The results of this study can provide references for future mechanical modeling, performance studies, and practical engineering applications of LHPCC. Concrete is used in many civil engineering fields because it is easy to obtain materials, reasonably priced, and convenient to construct. Ordinary Portland cement (OPC) is one of the typical raw materials for concrete, but it has the following defects: high hydration heat, poor corrosion resistance, and wet and heated curing, so it is not suitable for pouring hydraulic high-volume concrete. Relative to OPC concrete, low-heat Portland cement concrete (LHPCC) has a slower early temperature rise and high late strength, which can effectively reduce the difficulty of temperature control and crack prevention in mass concrete ,2,3,4. HThe study shows that the addition of fibers does not affect the characteristics of the concrete and can bring its material properties for toughening and crack resistance. Common fibers include steel fibers ,7,8, syn3 whiskers of 1%, and steel fibers of 0.25%. El Ouni et al. [The same type of fiber has a limited effect on improving the mechanical properties of concrete. However, the concrete is reasonably hybrid with different kinds of fibers and can fully combine with the cement matrix, which effectively improves the mechanical properties of concrete . Almusali et al.  showed tHigh elastic modulus and ductility of fibers that are hybrid in a particular ratio can generally significantly improve the tensile and ductile properties of concrete, which can enhance the initial cracking, strength, ductility, and toughness of concrete with the property of fibers . AdditioIn recent years, finite element analysis has become an essential tool for studying material properties. Scholars have tried to use this method to simulate and analyze the mechanism of performance enhancement of concrete by fibers ,33,34,35In this paper, the hybrid BF and PVAF-reinforced LHPCC were studied to improve the performance of concrete in multiphase, multi-structure, and multi-level by the complementary combination of two fibers to obtain more significant mechanical properties than those under single fiber conditions. Based on this, this paper presents a comprehensive investigation of the workability, compressive, splitting tensile, and four-point flexural properties of hybrid fiber-reinforced LHPCC. The hybrid BF-PVAF-reinforced LHPCC model at the mesoscale level was also established using Abaqus finite element analysis software. The damage evolution laws of LHPCC with various hybrid fiber contents and the macro-mechanical test results were compared and analyzed. The two fibers in this study are hybridized to improve the deformability and toughness of LHPCC, which alleviates the disadvantages of its low toughness and higher brittleness. At the same time, a practical and relatively simple numerical model is provided for the analysis of hybrid fiber-reinforced LHPCC. The development of this study can provide a new way for the technical application of LHPCC in water conservancy projects.The cement is P·LH42.5 produced by Jiahua Jinping Special Cement Co., Ltd. from Sichuan, China. The test results meet the requirements for “Moderate heat Portland cement, Low heat Portland cement, and Low heat Portland slag cement” (GB200-2003), and the test results for each performance index of the cement are shown in According to the available research results, the design principles of concrete cubic compressive, tensile, and flexural resistance can be used when the fiber content is low. This method is approximately the same as the design method for the plain concrete mix proportion . AccordiDry mix coarse aggregate, fine aggregate, low-heat Portland cement, coal fly ash, and a water-reducing agent in the mixer for 2 min to get the aggregate mixture. Add half of the short-cut BF and dry mix for 1 min, then add the other half of the BF and dry mix for 1 min. As the fiber-reinforced concrete is prepared, PVAF is easy to cluster. So, the dispersion of fibers should be fully considered to ensure that the fibers are not clustered, not in bundles, and evenly dispersed in the concrete. After several trial mixes, PVAF was used to add the technology: mix the dispersant, PVAF, air-entraining agent, and the appropriate amount of water, then stir in the magnetic spectroscopy stirrer for 30 min–1 h. After PVAF was pre-dispersed, it was added to the aggregate mix mentioned above and continued to be stirred for 10 min to obtain the hybrid BF-PVAF-reinforced LHPCC mix, which was then filled into the mold. The preparation steps are shown in Since the setting time of low-heat Portland cement is slower than that of ordinary cement, the specimens were placed indoors for 48 h and then removed, during which the room temperature was ensured to be 20 ± 5 °C. Subsequently, the specimens were moved into the standard curing room for 28 d. The temperature was 20 ± 2 °C, and the relative humidity was above 95%. The specimens in this test are non-standard specimens; the size of the compressive and splitting tensile specimens is 100 × 100 × 100 mm, and the size of the flexural specimens is 100 × 100 × 400 mm.The slump test was carried out according to ASTM C143  to evaluIn this study, the effects of total fiber content and the ratio of two fiber hybrids on slump were investigated separately. The results of the workability tests are illustrated in In this paper, two groups of tests were set up for mechanical property testing. Group 1: BF and PVAF were selected to be hybridized at a ratio of 1:1, and the total fiber content was 0%, 0.1%, 0.2%, 0.3%, and 0.4%, as presented in The 28-d compressive strength of the concrete at various total hybrid fiber contents is presented in The 28-d splitting tensile strengths of LHPCC with different total hybrid fiber contents are shown in The effect of total hybrid fiber contents on the flexural strength of LHPCC is shown in The flexural strength of LHPCC in various fiber hybrid proportions is shown in This paper compares the test values with the expressions recommended in the existing American code ACI 318-11  and EuroComposites theory regards fiber-reinforced concrete as a two-phase system composed of fibers and concrete, and the sketch is shown in Theoretical analysis of the reasons for the toughening of concrete by fibers can suggest theoretical support for the effects of fibers and the development of new materials. The enhanced toughness of hybrid BF and PVAF-reinforced LHPCC compared to plain concrete is due to the synergistic mechanism of BF and PVAF in concrete. BF has a relatively large elastic modulus and can mainly assume the bridging role at the crack. In contrast, PVAF has better deformation performance and ductility, which can consume more energy through its deformation during the process of crack expansion. The explicit division of labor and synergistic work of the two fibers suppress cracking throughout the whole process and ensure an increase of LHPCC toughness. Meanwhile, as PVAF has better dispersion in cement than BF, it can also help BF disperse evenly after hybridization and enhance the bonding effect between BF and cement, which enables the fibers to consume further energy in the pull-out process.The study of the crack resistance mechanism of hybrid fiber-reinforced LHPCC is the theoretical basis for its application to concrete structures. LHPCC in the mixing and pouring process, BF and PVAF in the concrete random distribution and lap, forming a mesh structure to prevent the sinking of coarse and fine aggregates. The hybrid of various diameters of BF and PVAF can enable the compaction of LHPCC and mitigate the development of cracks . MeanwhiThe effect of BF and PVAF on the matrix of LHPCC exists throughout the hardening process of concrete. The lower elastic modulus of PVAF retards the formation and expansion of microcracks in the early stage of LHPCC hardening. The high elastic modulus of BF allows the fibers to form a load-bearing framework in the matrix, which has a more pronounced inhibition of crack expansion in hardened concrete .From the studies mentioned above, it is shown that the appropriate amount of BF and PVAF were hybrid to improve the mechanical performance of LHPCC effectively.Firstly, since the dispersion of PVAF in concrete is better than that of BF, BF tends to cluster in concrete when the fiber contents are larger, thus generating weak structural zones. The excellent dispersion of PVAF can form a force-transmitting fiber micro-rebar mesh with BF, restraining the small cracks in the concrete due to shrinkage or water evaporation. These fiber-meshes exert a hoop-like working effect when the concrete specimen is subjected to axial pressure, increasing the compressive strength of the concrete by providing lateral constraint force, as shown in Secondly, tensile and plastic strength during the early hardening of concrete were increased by the addition of BF, which can reduce the porosity inside concrete by reducing of early shrinkage cracks. The addition of PVAF enhances the bonding between the hybrid fibers and the cement. It also improves the elastic modulus of the concrete matrix at the early stage of hardening. The better bonding between the hybrid fibers and the cement reinforced the above effects. In addition, the combination of the two fibers improves the interface transition zone (ITZ)  and reduFinally, BF assumes the bridging role at the cracks when concrete is subjected to flexure and tension. At the same time, PVAF absorbs a large amount of energy through its deformation, and the synergistic work of the two fibers significantly enhances the flexural performance of LHPCC. The action forms of BF and PVAF in the flexural specimens are shown in From an economic point of view, hybrid fiber also has certain advantages. The high tensile strength and elastic modulus of PVAF are good for toughening and crack resistance in concrete, but the cost is high. BF is economical, but toughening and crack resistance effects are relatively weak compared to PVAF. Therefore, the hybrid of BF and PVAF can increase the strength, toughness, and crack resistance of concrete with less cost, which is good for improving the brittle characteristics of concrete.Based on the macro-mechanical study, the mesoscale level analysis of BF and PVAF-reinforced LHPCC is used to laterally respond to the failure mechanism of specimens at the structural level from the change mechanism in each component performance at the material level. Establishing an accurate link between the macroscale and mesoscale mechanical tests, as shown in There are two types of modeling approaches for fiber-reinforced concrete. One is to model the separated fibers from the cement mortar and assign specific material properties to the fibers, which is common in coarse diameter and large volume steel fiber concrete ,53. The d = 17 mm), medium stone (d = 12 mm), and small stone (d = 7 mm), with a total aggregate content of 50%. The green area indicates ITZ, and the interface thickness is set to 0.2 mm, considering the computation amount and combined with the actual ITZ thickness [In this study, the 3D concrete structure is simplified to a 2D plane for the numerical simulation study, assuming a circular aggregate shape ,57. The hickness ,58. The hickness ,60.d is a stiffness degradation variable with a value between 0 and 1, where 0 means no damage and 1 means complete damage; td and cd are tensile and compression damage factors, respectively. The stress-strain relationships for the material in uniaxial tensile and compressive states are shown in Equations (2)–(5).cσ and tσ are the compressive and tensile stresses; cε and tε are the compressive and tensile strains; E0 is the initial elastic modulus; cd and td are the compressive and tensile damage factors; Test studies ,62 have σ-ε curve. Therefore, the parameters of the CDP model are determined using the concrete constitutive relations provided by GB50010-2010 [tα is the parameter value of the descending stage of the uniaxial stress-strain curve for concrete, take 1.95; −6; td is the uniaxial tensile damage evolution parameter of concrete.The expansion angle, eccentricity, ratio of biaxial compressive strength to uniaxial compressive ultimate strength, invariant stress ratio, and viscosity parameters in the concrete CDP principal model were taken as 30, 0.1, 1.16, 0.6667, and 0.0005, respectively . In the 010-2010  in this cα is the parameter value of the descending stage of the uniaxial compressive stress-strain curve of concrete, which is taken as 1.65; −6; cd is the uniaxial compressive damage evolution parameter of concrete.The stress-strain relationships of concrete in uniaxial compression are shown in (10)–(14).The boundary conditions applied to the compressive and splitting tensile models are shown in The compressive and tensile simulations were performed on the standard cubic specimens of concrete to determine the mechanical parameters of each mesoscale component, as detailed in From the study in Chapter 3, it was found that the total content of hybrid fibers in the concrete affected the mechanical properties to a greater extent than the proportion of the two fibers. This chapter focuses on simulating the effect of hybrid fiber content on the compressive and splitting tensile strengths of LHPCC by the mesoscale finite element method, and the simulation results were compared with the test findings.The compressive strength of LHPCC with different hybrid fiber contents was simulated and compared with the average compressive strength obtained from mechanical tests, as shown in The compressive stress-strain curves are depicted in The stress-strain curves obtained from the tests and simulations were compared, as shown in In summary, the hybrid fiber-reinforced LHPCC compressive mesoscale numerical model established in this section can obtain better simulation results regarding damage characteristics, compressive strength, and stress-strain relationships.Similar to the case of uniaxial compressive damage, when the specimen is subjected to splitting tensile damage, cracks are first produced in the ITZ. With the increase in load, the cracks gradually spread around the ITZ, and the cracks penetrate the model, as illustrated in Comparing the data on splitting tensile strength obtained from simulation and test, as shown in It can be seen that when the stress was relatively small, the specimens were in the linear elastic stage, and the overall stiffness of the models was significant. In this stage, the stress-strain curves at different fiber contents were basically the same. Significant differences appear in the softening phase after the peak stress. The increase in fiber content causes an increase in ITZ strength and a change in the mesoscale heterogeneity, thus causing a difference in the stress-strain curve at the softening stage. With the further increase in external load, the overall stiffness of the model decreases, the damaged area expands, the splitting crack extends and expands, and the concrete material enters the plastic deformation stage. Finally, the ultimate bearing capacity is exceeded, and brittle damage occurs. Based on the stress-strain diagram, the peak stress and strain increase with the addition of fiber content. This proves that in the range of fiber content in this paper, the higher the content, the stronger the toughening and cracking resistance effect exerted by the fiber. The toughening effect makes the peak stress gradually increase, and the cracking resistance effect makes the peak strain also increase.The stress-strain curves obtained from the finite element simulation were compared with the mechanical test curves, as shown in The aforementioned mesoscale simulation combined the actual test, and the aggregate content was set to 50%. The results were obtained with higher accuracy through the simulation. Therefore, this part keeps all other parameters constant and simulates the effect of aggregate content on the compressive and splitting tensile strengths of hybrid BF and PVAF-reinforced LHPCC to provide a reference for the ratio test study.In this section, the LHPCC models with aggregate contents of 30%, 40%, 50%, 60%, and 70% are set, and the actual aggregate content of 50% in this paper was used as an intermediate value to investigate the strength differences of LHPCC with different aggregate contents, as shown in The simulation study predicted the common effect of aggregate and hybrid fiber content on the mechanical properties of LHPCC. Therefore, in this paper, a non-linear surface was fitted to the simulation data conclusions to evaluate the effects of the two variables on the compressive and splitting tensile strengths of the material quantitatively through equations. The fitted surface is shown in cf is the compressive strength of LHPCC and stf is the splitting tensile strength. x denotes the aggregate content (%), and y represents the total hybrid fiber content (%).The formula for splitting tensile strength is shown in Equation (16).The results show that the nonlinear surface fitting models of compressive and splitting tensile strengths of LHPCC can effectively match the simulation results, which is important for the application of hybrid fiber-reinforced LHPCC in hydraulic buildings.Within the research range of this study, the effect of total fiber content on the slump of fresh concrete is greater than that of different fiber hybrid proportions. When the proportions of the two fibers are 1:1 and the total content is 0.4%, the slump decreases the most, up to 54.55%;When BF and PVAF were in equal proportions, the compressive and flexural strengths were greatest when the fiber content was 0.3%, which increased by 29.34% and 35.41% compared to the control group. The splitting tensile strength was greatest when the fiber content was 0.4%, with an increase of 31.59% compared to the control group;When the total fiber content was 0.3%, the concrete compressive, splitting tensile, and flexural strengths presented tendencies of ascending and then decreasing as the occupancy of BF increased in the hybrid fiber. The corresponding optimal occupancy of BF was 50%, 75%, and 50%, and the strengths increased by 13.11%, 32.75%, and 16.24% compared with the control concrete;The errors in the compressive and splitting tensile strengths of the hybrid BF-PVAF-reinforced LHPCC obtained by numerical simulations and tests are within 5%. The mesoscale model can accurately verify the damage mechanism of concrete specimens, which validates the reliability of the mesoscale numerical model of hybrid BF-PVAF-reinforced LHPCC established in this study.In this study, mechanical property tests and mesoscale numerical simulations of hybrid BF and PVAF-reinforced LHPCC were conducted to reveal the effect mechanisms of different hybrid fiber contents and the ratio of the two fibers on LHPCC. The major research findings are presented as follows:The study of hybrid BF and PVAF-reinforced LHPCC in this paper has the following basic assumptions: Firstly, the fibers are uniformly distributed in the concrete and in the same direction as the force under external loading. Secondly, the bonding force between the fibers and the concrete is so large that there is no relative slip between them. Although the feasibility of hybrid BF and PVAF to enhance LHPCC was investigated in this paper, it is desirable to properly adjust the basic mix proportion of concrete to obtain more stable properties of LHPCC. As for the study of mesoscale simulation, 2D is less intuitive than the 3D model to reflect the failure mechanism of concrete, which is necessary to be further explored in future studies. In the future, the following aspects can be investigated in depth to further enhance the feasibility of promoting the application of hybrid BF and PVAF-reinforced LHPCC.The data on the toughness and ductility of fiber-reinforced concrete are equally necessary, which is crucial to know in hybrid fiber-reinforced LHPCC;Concrete materials are brittle and prone to potential safety hazards in hydraulic buildings. Therefore, the fracture properties of hybrid BF and PVAF-reinforced LHPCC should be investigated to overcome the limitations of quasi-brittle fracture of the material;The durability study of hybrid BF and PVAF-reinforced LHPCC can be used for life prediction, such as antifreeze, sulfate corrosion resistance, chloride penetration resistance, anti-carbonation, and impermeability properties of concrete materials, for early application in the field of engineering practice.


Antibiotics are among the essential veterinary medicine compounds associated with animal feed and food animal production. The use of antibiotics for the treatment of bacterial infections is almost unavoidable, with less need to demonstrate their importance. Although banned as a growth factor for a few years, their use in animals can add residues in foodstuffs, presenting several environmental, technological, animal health, and consumer health risks. With regard to human health risks, antibiotic residues induce and accelerate antibiotic resistance development, promote the transfer of antibiotic-resistant bacteria to humans, cause allergies (penicillin), and induce other severe pathologies, such as cancers , anaphylactic shock, nephropathy (gentamicin), bone marrow toxicity, mutagenic effects, and reproductive disorders (chloramphenicol). Antibiotic resistance, which has excessively increased over the years, is one of the adverse consequences of this phenomenon, constituting a severe public health issue, thus requiring the regulation of antibiotics in all areas, including animal breeding. This review discusses the common use of antibiotics in agriculture and antibiotic residues in food/feed. In-depth, we discussed the detection techniques of antibiotic residues, potential consequences on the environment and animal health, the technological transformation processes and impacts on consumer health, and recommendations to mitigate this situation. Antibiotics are among the essential veterinary medicine compounds related to food animal production, defined as substances that can kill or inhibit the growth of bacteria . Its appAntibiotics help treat and prevent various infections in animals, such as mastitis, arthritis, respiratory diseases, and gastrointestinal and other bacterial infections , and areTherefore, the World Health Organization (WHO), the American Medical Association, and the American Public Health Association have urged a ban on growth-promoting antibiotics  and estaWith regard to the issue of residues as a topical public health concern and the excessive growth of antibiotic resistance over the years . This reThis review article was conducted by exploiting numerous review articles, original articles, and related books from reputable databases, such as Web of Science, PubMed, and Scopus. The papers published with toll access have been made available using the facilities provided by the Peoples’ Friendship University of Russia, Moscow, Russia. The literature investigation process was conducted in English and French between October 2020 and April 2021. The keywords explored during the literature search consisted of combinations of the following words: “antibiotic,” “animals,’’ “residue,” “food,” “antimicrobial drugs,” “detection,” “meat,” “milk,” “eggs,” “antibiotique,” “animaux,” “résidus,” “aliments,” and “médicaments antimicrobiens.”Antibiotics are used for food production for several reasons, including their primary use as preventive or curative measures against animal infection. Others are used as growth promoters for improved feed conversion efficiency, carcass quality, and economic production . Howeveret al. [Several factors occur before antibiotic residues are found in food. We adapted the conceptual representation proposed by Sharma et al.   and confirmatory method (2). These two methods differ because the first one is globally qualitative or semiquantitative. In contrast, the second one ensures its determination with high precision of the type and concentration of the investigated residue.Micrococcus luteus and Bacillus subtilis. Inhibitory zones lacking bacterial colonies around the sample deposit sites indicate the potential presence of antibiotics [Bacillus stearothermophilus var. calidolactis C953  [All screening methods are essentially microbiological or immunological. The most well-known and earliest microbiological technique is the so-called “four plates” technique. This method inhibits the growth of ibiotics . This meibiotics -60. SimiIP 5281) .Furthermore, if the milk analyzed contains antibiotics, the bacteria will not degrade the lactose, and the color of the medium will remain unchanged. On the other hand, the absence of antibiotics results in a color change from blue to yellow, indicating acidification. However, despite these techniques being accessible, inexpensive, and performed by a nonprofessional, there is a lack of specificity and long incubation time. Thus, to overcome these disadvantages, several companies have manufactured different commercial kits under different trade names . Such tests detect numerous antibiotics at thresholds generally close to the MRL .Compared with microbiological methods, immunological methods such as enzyme-linked immunosorbent assay, fluoroimmunoassay, and time-resolved fluoroimmunoassay are highly specific, highly sensitive, simple, and cost effective. In addition, rapid-detection immunochromatographic kits (on strips) have been developed (TwinSensor), allowing within one assay the simultaneous screening of penicillins and cephalosporins (TwinSensor KIT034); beta-lactam and tetracycline (TwinSensor KIT020); beta-lactam antibiotics tetracyclines, streptomycin, and chloramphenicol (4Sensor BSCT-KIT060); beta-lactam antibiotics, sulfonamides, tetracyclines, and (Fluoro) quinolones (4Sensor BSTQ-KIT072) -64.The main advantage of confirmatory methods is their high specificity, but they are expensive, time-consuming, and require personnel and an adequate laboratory . Confirmet al. [Fully automatic biosensors are becoming increasingly important in detecting antibiotics in food . The bioet al. , in theiet al. . They alIt is challenging to control the use of antibiotics in agriculture in a uniform way because their use varies significantly from one country to another . For example, it was reported that China is the first country to use antibiotics in food animals (23%), followed by the United States (13%), Brazil (9%), India (3%), and Germany (3%) . This stAdverse consequences of antibiotic residues can be seen on four levels Figures- and 3 7: (1) On We will not discuss the consequences of antibiotics on animals, only those of their residues. It is well established that antibiotics administered to animals can be found in their feces -56. The The indiscriminate and improper use of antibiotics can result in higher concentrations of antibiotics in the environment, which is referred to as antibiotic pollution . Most deThe main technological risks presented by antibiotic residues in foodstuffs are applied to products processed by microbial fermentation, such as milk (fermented milk products and cheese), meat , and fish . Indeed, antibiotic residues in these raw materials can interfere with the fermentation process by inhibiting the starter cultures, leading to manufacturing accidents and poor-quality foods.Antibiotic residues are a severe public health issue , with thRecently, several studies have reported that antibiotic residues can elicit allergic reactions. Most of the reported allergies are related to beta-lactam antibiotic residues, especially penicillin and cephalosporins. They include skin rashes, serum sickness, thrombocytopenia, erythema multiforme, hemolytic anemia, vasculitis, acute interstitial nephritis, Stevens–Johnson syndrome, and toxic epidermal necrolysis . For exaet al. [Limited data exist on the consequences of antibiotic residues on the liver, possibly due to a lack of investigations pointing toward this direction. However, the hepatotoxic effects of some antibiotics are well known. For example, Hautekeete  reportedet al.  and Hautet al.  reportedet al. . ConsequThe intestinal flora contains several microorganisms (with nearly 1000 species) that play an important role in human physiology and health . Despiteet al. [In a recent study summarizing data from 73 scientific studies reporting antimicrobial residues in animal products readily available for sale, Treiber and Beranek-Knauer  highlighet al.  mentioneSome antibiotic residues, such as sulfamethazine, oxytetracycline, and furazolidone, have carcinogenic effects ,48,87. AEscherichia coli, and macrolide or fluoroquinolone-resistant campylobacters [The current transmission mechanisms of antibiotic resistance are better understood than those in the past. It has been established that the exposure of bacteria to low doses of antibiotics is likely to lead to bacterial adaptation, making them more resistant and more virulent -94. Sincobacters . Since cobacters . This reSolutions to the problems of antibiotic residues in foods require the implication of both producers and legal organizations. With regard to the responsibilities of legal organizations, we suggest (1) that more rigorous control over the types and concentrations of antibiotics used should be established, (2) antibiotics should be marketed only by professionals who should sell them only with a prescription from a veterinarian, (3) prohibition of antibiotics whose toxicity is established  and those more likely to induce direct or cross-resistance to antibiotics, (4) mandatory quality controls of food before marketing and the fight against black market products, and (5) permanent awareness of the dangers posed by antibiotic residues in food and resistance to antibiotics. Similarly, producers must (1) use antibiotics only when necessary and under the prescription of a veterinarian, (2) respect withdrawal times and other good practices related to antibiotics, (3) systematically test the presence of residues of the antibiotics used in their production, and (4) educate themselves on the regulations in force and respect them. In a similar manner, economic and straightforward field tests should be developed to identify antibiotic residues in animal products quickly. Meanwhile, methods such as heat treatment, activated charcoal, resin, and UV irradiation, may help inactivate antibiotics. Finally, probiotics and active phytochemical compounds should be further investigated and used as alternatives to antibiotics.The residues of antibiotics in food are of severe public health concern. Although necessary, even essential in agriculture, they should nevertheless be used more sparingly to avoid the consequences (direct toxicity and resistance to antibiotics) they can cause. Comprehensive antimicrobial use databases should be set up to identify global hotspots where antimicrobials are disproportionately used. Furthermore, risk assessment approaches for preventing diseases, including developing and spreading of antimicrobial resistant bacteria, need to be established. In a similar manner, inexpensive and easy-to-use tests should be developed to detect antibiotic residues in foods rapidly. Finally, healthier approaches such as probiotics and herbal remedies should be used.MMJA, AKLD, and PIV: Conceptualized and designed review, literature search, and wrote the first manuscript draft. MMJA, SLA, SS, IK, DMS: Edited and revised the draft of the manuscript. All authors critically reviewed the manuscript and approved the final manuscript.