Machine-made sand is gradually replacing natural sand to achieve sustainable development. Experimental studies and gray-correlation analysis were used to study the properties of tunnel slag machine-made mortar and concrete. The properties of machine-made mortar with different stone powder content were analyzed through experiments. By analyzing the performance of machine-made sand concrete with equal amounts of cement replaced by stone powder, the optimum replacement ratio is obtained. Gray-correlation analysis was used to compare the degree of influence of fineness modulus and stone powder content on the performance of concrete. Scanning electron microscopy (SEM) and X-ray diffractometry (XRD) were used to analyze the microstructure of tunnel slag sand concrete. The test results showed that the flexural and compressive strengths of the machine-made sand concrete were greater than the standard sand with the same stone powder content. The 28-day flexural and compressive strengths had a maximum difference of more than 30%. The best stone powder content of the machine-made mortar is in the range of 5% to 8%. When the replacement cement content of stone powder is about 6%, the mechanical and working properties of machine-made sand concrete achieve the optimal state. The lower the stone powder content, the closer the mechanical and working properties of machine-made sand concrete and river sand concrete. The correlation between the performance of machine-made sand concrete and fineness modulus is the largest. When the stone powder content is low, it has almost no effect on the compressive strength of concrete. The results point out the direction for the quality control of tunnel slag machine-made sand concrete. Concrete is the most widely used building structure material today . With thThe most obvious difference between the machine-made sand and natural sand is that the machine-made sand will produce stone powder with particle size less than 0.075 mm. The limit value of stone powder is 10% according to the national standard in China, but the content of artificial sand in actual production is usually as high as 10–20% . The stoUnlike natural sand, the mineral and chemical composition of stone powder is the same as that of the parent rock of machine-made sand. The effect of stone powder content on mortar properties has been extensively studied ,24. ChonThis study focuses on the following aspects of tunnel slag sand concrete. Experimental studies and gray-correlation analysis were used to study the properties of tunnel slag mortar and concrete. The flexural strengths of standard sand and machine-made sand concrete with different stone powder contents were analyzed through experimental studies. The workability and mechanical properties of the concrete with the same amount of cement replaced by stone powder were analyzed to find out the best stone powder replacement ratio. The correlation between fineness modulus and stone powder content on the slump and strength of the machine-made sand concrete was calculated. The degree and law of influence of different factors on the performance of machine-made sand concrete were analyzed. Scanning electron microscopy (SEM) and X-ray diffractometer (XRD) were used to analyze the microstructure of tunnel slag sand concrete.3, and the crushing value was 10.2%. The aggregates were washed manually to clean the powder on the surface. The fine aggregate for the test is the machine-made sand obtained by artificial crushing of the parent rock. The content of particles less than 75 μm in the machine-made sand was fixed at 2.4%. The fineness modulus is 2.9. The fly ash is grade II fly ash. The external additive is polycarboxylic acid high performance water reducing agent. In this study, the raw material cement was P.O 42.5 grade ordinary silicate cement of Changshan South brand. Two grades of 5–10 mm and 10–20 mm were used as coarse aggregates for the test. The chert gravel was mixed into 5–20 mm continuous graded gravel in the ratio of 4:6. The surface bulk density of mixed coarse aggregate was 1456 kg/mThe source of the base material is the tunnel slag produced from the inspected and qualified tunnel working face. Tunnel slag and machine-made sand produced are shown in The biggest problem in the practical application of tunnel slag sand concrete is the poor working performance. Therefore, it is of utmost importance to study the compatibility of the machine-made sand concrete. Compared with natural river sand, the appearance morphology, angularity and fineness modulus of the machine-made sand have large differences. The effect of stone powder content in the machine-made sand on the workability of mortar and concrete is very significant. For now, the research on the machine-made sand concrete properties is still controversial. In addition, most studies are limited to limestone  and granThe mechanical properties of mortar are related to whether the structure of mortar can meet the requirements of engineering use. The flexural and compressive strengths of the mortar of standard sand and machine-made sand with different stone powder contents were studied. In the preliminary preparation of the experiment, the standard sieve with minimum size of 0.075 mm was used to obtain the pulverized sand rock powder by sieving the machine-made sand step by step. Then the amount of cement was replaced by the equal mass of stone powder to prepare standard sand mortar. The test design of standard sand mortar is shown in Machine-made sand concrete mixes with equal amount of cement replaced by stone powder were used to study the effect of stone powder replacement of cement on the properties of concrete. After several mixing sessions, the slump, slump expansion and compressive strength of the machine-made sand concrete were recorded. The performance of the machine-made sand concrete with equal amount of cement replaced by stone powder was analyzed to arrive at the optimum stone powder replacement ratio. To investigate the degree of influence of fineness modulus and stone powder content on the properties of concrete, we prepared river sand concrete with different fineness modulus. Machine-made sand concrete with different fineness modulus and stone powder content was prepared. The fineness modulus of river sand and machine-made sand was taken from 2.4 to 3.0, adjusted by 0.1 for each level. In addition, the stone powder content was taken from 0 to 10%, adjusted by 2% for each level. The test performance is based on workability and mechanical properties. The workability test indexes are slump and slump expansion, and the mechanical property indexes are 3-day, 7-day, 28-day and 56-day compressive strengths. The degree of influence of the index such as fineness modulus of tunnel slag machine-made sand on the concrete properties is different. The properties of concrete with different stone powder content and fineness modulus were tested. Gray-correlation analysis was used to calculate the correlation between the stone powder content, fineness modulus and the slump, strength of concrete . Determine the data column.Gray-correlation analysis is commonly used in concrete performance studies. In the analysis to investigate the effect of machine-made sandstone powder content, fineness modulus and concrete workability and mechanical properties. Two subfactors are tunnel cavity slag stone powder content and fineness modulus. Three parent factors are concrete slump, 7-day and 28-day compressive strengths. Each parent factor has two correlation degrees corresponding to the two subfactors. The calculation steps are as follows.kth case.2.Dimensionless processing.Determine the reference data column, denoted as 3.Calculate the correlation coefficient and correlation degree.The dimensionless processing can be used to divide each number in the series by the maximum value in the series in turn.k comparison subsequencesThere are 4.Construct the matrix.The degree of correlation is calculated as follows.m parent factors with the corresponding n subfactors are obtained. The correlation matrix R allows for the dominance analysis of the parent and child sequences.The correlations of The strength grade of concrete is C35, and the concrete mix ratio design of concrete is shown in The flexural and compressive strengths of standard sand and machine-made sand mortar with different stone powder contents were studied experimentally. The average value of the three test results was taken as the strength value, and its variation law was summarized. The test results of standard sand and machine-made sand mortar with different stone powder content are shown in From In addition, it should be noted that the 7-day, 14-day and 28-day flexural strength maxima of the cement sands do not correspond to the same stone powder content. This is due to the fact that the stone powder particles provide a favorable surface for the hydrated silicate gel to nucleate and grow during the early hydration of the cement. It accelerates the hydration of silicate cement and plays a microcrystalline nucleation acceleration effect. However, this accelerating effect is only useful for the early strength formation of concrete. It does not help much for the later hydration of cement, so it is beneficial to increase the stone powder content appropriately for the early strength formation of the cement.It can be seen from To investigate the effect of stone powder replacing equal amounts of cement on the properties of concrete, we tested the concrete mixes of machine-made sand with different amounts of stone powder blended to replace cement. The results of slump, slump expansion and compressive strength tests the concrete are shown in As can be seen from As can be seen from To investigate the degree of influence of fineness modulus and stone powder content on the properties of concrete, we tested river sand and machine-made sand concrete mixes with different fineness modulus and stone powder content. The results of the tests for river sand concrete with different fineness modulus are shown in The slump and slump expansion of the concrete have the same trend. The slump gradually decreases with the increase of stone powder content, which is consistent with the findings of the The compressive strengths of the machine-made sand concrete at different ages have a similar trend. The compressive strength of concrete tends to decrease roughly with the increase of stone powder content. The compressive strength of the machine-made sand concrete does not change significantly with the increase of fineness modulus. When the fineness modulus was around 2.7, the compressive strength of the concrete was the maximum, and the mechanical properties were the best at this time. The compressive strength of machine-made sand concrete decreases significantly with the increase of stone powder content when the fineness modulus is 3.0. With the increase of fineness modulus, the change in compressive strength of river sand concrete is very small. When the fineness modulus is 2.5, the maximum 56-day compressive strength of river sand concrete is 48.2 MPa, while the maximum 56-day compressive strength of machine-made sand concrete reaches 50.7 MPa. When the fineness modulus of machine-made sand concrete is greater than 2.7 and the stone powder content is less than 4%, the mechanical properties of machine-made sand concrete are better than those of river sand concrete. Compared with river sand, the machine-made sand particles are irregular in shape, angularity and rough surface, and the bite between the machine-made sand aggregates and the bond strength between cement and fine aggregates are greater. Thus, when the right amount of stone powder, the machine-made of sand concrete compressive strength is greater. The test results show that under the premise of controlling the amount of stone powder, the concrete prepared by tunnel slag machine-made sand has higher strength and better structure than river sand concrete.R was obtained.Based on the results of the tests of the machine-made sand concrete with different fineness modulus and stone powder content in R of the properties of the machine-made sand concrete, i = 1,2,3) indicate that there is no obvious correlation between concrete performance and stone powder content. When the content of stone powder is less than about 10%, stone powder has little effect on the compressive strength and slump of concrete. As for the failure characteristics of concrete, the most frequent parts of failure are the interface between aggregate and cement slurry, and most of them are the failure mode of bond surface. Stone powder concrete has little influence on bonding effect. Therefore, the improvement effect of stone powder on the compressive strength of concrete is limited. Comparing the correlation matrix The microstructure of the material determines the macroscopic properties. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffractometer (XRD) ,39,40 ph2, with small amounts of feldspar, calcium silicate, calcium feldspar and calcium cross-zeolite-potassium [2 and Al2O3.On the one hand, under alkaline excitation, zeolite can react with Ca(OH)2 precipitated by cement hydration to produce hydrated calcium silicate colloid, which promotes the hydration reaction of cement. On the other hand, zeolite has a lattice-like structure, and its interior is filled with uniformly sized pores and channels. Artificial sand has a large specific surface area after being finely ground by machine, and it can absorb a large amount of water and gas in its natural state and balance with the relative humidity of the atmosphere. When it is mixed into concrete, it can absorb the excess mixing water in concrete and overcome the water retention of concrete. It can make the concrete viscosity increase and increase the amount of aggregate coating. Therefore, it can improve the work performance of concrete.From the concrete energy spectrogram and quantitative structural analysis, it can be seen that the elemental compositions of the tunnel slag concrete are mainly O, Si, Ca, Al, C, and Fe. The tunnel slag concrete specimens were tested by XRD. The diffraction pattern was analyzed and the molecular formula and percentage content of the chemical composition of the material constituents were obtained. It was found that the main composition of the tunnel slag concrete samples was SiOotassium . CalciumMachine-made sand mortar flexural and compressive strengths are greater than the same stone powder content of standard sand. The maximum differences of 28-day flexural and compressive strengths are more than 30%. The best stone powder content of the machine-made mortar is in the range of 5% to 8%.By analyzing the performance of the machine-made sand concrete with equal amounts of cement replaced by stone powder, we conclude that the mechanical and working properties of the concrete reach the optimal state when the amount of cement replaced by stone powder is about 6%.The slump of river sand concrete is slightly greater than that of machine-made sand. The compressive strength of machine-made sand concrete is greater with the right amount of stone powder. Under the premise of controlling the amount of stone powder, the tunnel slag machine-made sand concrete has higher strength than river sand concrete.Gray-correlation analysis was used to compare the influencing factors of mechanical properties of concrete. The correlation between the concrete properties and the fineness modulus is the greatest. This points to the direction for the quality control of tunnel slag sand concrete.With a shortage of natural sand resources, the use of tunnel waste rock as a raw material for sand has become an option for sustainable development. In this paper, a study of the performance of tunnel slag machine-made sand mortar and concrete was carried out through experimental research and gray-correlation analysis. From the experimental results, the following conclusions can be drawn.This study mainly considered the properties of machine-made sand concrete. Future studies may analyze the effect of stone powder content on the durability performance of machine-made sand concrete.


GPC has proven effective for structural applications due to its workability and analogical strength compared to standard cement concrete. This review article discusses the engineering properties and microstructure of GPC and shows its merits in construction applications with some guidelines and suggestions recommended for both the academic community and the industrial sector. This literature review also demonstrates that the mechanical properties of GPC are comparable and even sometimes better than those of PC concrete. Moreover, the microstructure of GPC is significantly different from that of PC concrete microstructure and can be affected by many factors.Portland cement (PC) is considered the most energy-intensive building material and contributes to around 10% of global warming. It exacerbates global warming and climate change, which have a harmful environmental impact. Efforts are being made to produce sustainable and green concrete as an alternative to PC concrete. As a result, developing a more sustainable strategy and eco-friendly materials to replace ordinary concrete has become critical. Many studies on geopolymer concrete, which has equal or even superior durability and strength compared to traditional concrete, have been conducted for this purpose by many researchers. Geopolymer concrete (GPC) has been developed as a possible new construction material for replacing conventional concrete, offering a clean technological choice for long-term growth. Over the last few decades, geopolymer concrete has been investigated as a feasible green construction material that can reduce CO Extremely high carbon dioxide levels are released into the air during the cement manufacturing process (roughly one tonne of cement production releases one tonne of CO2). This causes it to account for about 7% of all manufactured CO2 emissions. Concrete is a widely utilised material in the building industry worldwide ; because2 emissions; this is a significant concern when utilising the PC. One of the most promising options is using geopolymers as a partial or complete substitute for cement [Additionally, r cement ,6.2O(n)SiO2 type in the synthesis of geopolymers. Sodium hydroxide (NaOH), sodium carbonate (NaCO3), potassium hydroxide (KOH), or sodium sulphate (Na2SO4) are common activators that contain the alkali metal (M) indicated by MOH [In 1979, Davidovits introduced the term geopolymer to refer to a group of mineral binders similar to zeolites within amorphous microstructure and chemical composition . This mad by MOH . In addid by MOH .2 emissions in the construction industry by abolishing PC as a binder in concrete production [2 emissions by about 22–72% compared to that of PC concrete at a similar cost [The environmental benefits of geopolymer concrete have led many to call it the “next generation” of concrete. It provides a novel approach to reducing COoduction ,17,18. Uoduction . In addilar cost . In addilar cost ,22,23,24It was observed in the literature that there are many existing review studies to analysing the behaviour of geopolymer concrete ,32,33,34The published literature papers were evaluated regarding the production of GPC and its mechanical behaviour. This paper discusses the mixed design, mechanical characteristics, and durability of GPC. Using the GPC as an alternative construction material is essential for environmental purposes. Before it can be used in construction, much research needs to be conducted on how structures behave with huge structural elements.Therefore, this review article aims to provide inclusive information on GPC production, its economic benefits, durability, and environmental influences; the basic process for GPC production; and the factors affecting its mechanical properties.2SiO3 ratio, NaOH dosage, water to ash ratio, and superplasticiser on the behaviour in terms of workability and compressive strength of GPM [3 solution as a liquid for the mix, they found that the maximum strength of GPM is acquired by employing a Na2SiO3-to-NaOH mass ratio of four. Moreover, more discussion about geopolymer mortar properties is reported in the following sections.Classic cement mortar is often utilised as a standard binding and repairing material in various engineering structures. Many scholars have addressed GPM’s viability and potential applications as a suitable replacement for regular cement mortar . Sathonsh of GPM . Geopolyh of GPM , who pre2SiO3 to NaOH. The flowability of modern mortars is typically controlled with the addition of water, which does not compromise the mortar’s strength [The workability of fresh GPM is crucial in determining the hardened GPM quality. The concentration ratio of NaOH determines the geopolymer mortar’s workability and the Nastrength . Flow, wstrength . Some testrength  studied 2/Na2O ratio inactivators on GPM workability. They found that the flow value percentage increases with the fly ash/sand ratio, and the fresh geopolymer mortar’s flowability increases as the SiO2/Na2O ratio in the activator increases, as shown in Bhowmick and Ghosh  determinFresh mortar setting time is critical for transporting, casting, and compacting the mortar within the time restriction. The Vicat needle device can be utilised to test the setting times per the BS EN 480-2 and ASTM C 807-13 standards ,41. The The setting time reduction in GPM has been attributed to the increased use of PCs. As seen in Numerous types of source materials are employed as base materials for producing geopolymers. The raw materials used and the proportioning factors impact the strength of GPM. A. Erfanimanesh et al.  tried to2SiO3 medium replacement. Ismail et al. [Yusuf et al.  studied l et al.  studied 3), found that high calcium FA GPM comprised of PC type I showed increasing PC replacement levels and NaOH concentrations as well as increasing mortar compressive strengths.Phoo et al. , who stuA. De Rossi  discoverIn cement mortars, compressive and flexural strength are tightly linked. However, due to the incredible fragility of the geopolymer and its firm adherence to the aggregate particles, geopolymer mortars have high flexural strength but poor compressive strength . With th2CO3 concentration was about 10% by weight of powder mixes (zeolite and slag), and 100% Fine Aggregate). GPM’s flexural strength was tested using two distinct mix designs that used slag and zeolite as base ingredients. As shown in According to Erfanimanesh et al. , flexuraWongsa et al.  examined2 emissions dramatically [2 than PC when (5–15%) Portland cement is substituted. This is because geopolymer concrete may attain an early compressive strength of 66 without needing external heat [2SiO3. Despite minimising the cost of GPC, no research on the availability and cost of GPC raw materials has been conducted globally. A global review of raw materials availability has been conducted, focusing on China and the U.S. The demand and cost of each raw material, including FA, SC, MK, NaOH, Na2SiO3, and silica fume, were analysed for China, the United States, and other major markets for which data are available. This study is essential to see if GPC can be a viable commercial alternative to PC concrete. Raw material supply is a pivotal impediment to widespread GPC adoption [GPC is a cost-effective alternative that can be applied in place of standard cement. Thus, using GPC instead of PC cuts COatically . FA, MK,atically . GPC conatically . GGBS, Fatically . FA is tatically . Geopolynal heat . In ordeadoption , so whil2/Na2O ratio rises [2/Al2O3 ratios by mass. Because the particles on the alkaline activator mixture grow as the dosage of NaOH increases, it is also noted that the dosage of NaOH considerably impacts the workability of GPC.Umniati et al.  highlighio rises . Saranyaio rises  also useio rises  studied Hassan et al.  evaluateSarker et al.  examinedThe steel and iron industries produce ground granulated blast furnace slag (GGBS). According to Patilet et al. , using GFumed silica is a byproduct of the silicon and ferrosilicon alloy industries. Khater  states tSetting time refers to the time that concrete can be cast, compacted, and transported . As per Brew et al.  produced2/Na2O ratio, and water/FA ratio on compressive strength, and according to the findings, the Na2SiO3/NaOH ratio has an entirely different impact on GPC compressive strength than the SiO2/Na2O ratio. When the Na2SiO3/NaOH molar ratio is set at 2.5, there is no significant increase in the compressive strength of GPC. The compressive strength of a structure significantly impacts its stability and safety. The curing conditions and the raw materials impact the compressive strength of FA/GGBS-based geopolymer concrete [Compressive strength has usually expressed the behaviour of concrete in compression, and the initial elastic modulus represents the strength development with the shape and age of the stress–strain relationship. Lakshmi and Nagan  reportedconcrete . Erfanimconcrete  reportedThe splitting tensile strength (fsp) and the flexural strength (fr) of GPC increase in tandem with the compressive strength , and theX-ray diffraction is a microstructural scanning test performed to investigate and identify a material’s atomic and crystallographic nature. The XRD analysis test involves the irradiation of materials with entrant X-rays and then counting the intensities and scattering angles at which X-rays are emitted; the dispersed rays are expressed in terms of scattering angles, which examines the position of the substance to identify its composition, and identifies scattered intensity peaks. XRD is used in conjunction with other microstructural analyses such as optical light microscopy, electron microprobe microscopy, and scanning electron microscopy in geologic research, mainly if the sample to be analysed is a mixture; XRD data can identify each mineral in a sample and its concentration.Different researchers have studied the XRD pattern of geopolymer concrete ,93,94,95SEM involves examining and scanning the material’s surface with a focused beam of electrons through image analysis to measure and assess fine details. When electrons contact sample atoms, they provide multiple surface topography and composition signals, highlighting component failures, detecting particles, and analysing the interactions between substances and substrates.Some studies have investigated the SEM and EDX test of GPC ,97,98,99Jittabut et al.  showed t−1. Rajini et al. [−1 are caused by the tensile vibrations of H-O-H bonds, whereas the broad bands at 1640–1646 cm−1 are caused by the bending vibration of the water-associated-OH group.FTIR techniques are used to measure the infrared absorption, emission, and photoconductivity of a solid, liquid, or gas and identify PHB functional categories. Very limited studies have investigated the FTIR test of GPC ,101,102.−1, 900–1200 cm−1, 1200–1300 cm−1, 1300–1600 cm−1, 1600–1700 cm−1, and 2850–3700 cm−1 .Different researchers have studied the DSC analysis of geopolymer concrete ,106,107.TGA aids in the identification of several concrete phases, including calcite, portlandite, C-A-H, C-A-S-H, etc. The hydration reaction is often checked by measuring the CH content; if the CH level decreases, it indicates that CH has been consumed in the hydration reaction. Researchers from several fields have examined the geopolymer concrete TGA ,110,111.Geopolymer concrete offers much potential in the construction industry. Even though geopolymer concrete has been researched very well in the last few years, several aspects should be covered, and extended data should be collected to understand the behaviour of geopolymer concrete before introducing it to the construction sector. The large-scale structural elements of GPC and the performance of reinforced geopolymer concrete should be investigated. Moreover, the behaviour of geopolymer materials in an aggressive environment, such as a marine environment, must be studied.Research studies available on structural members of GPC are still lacking. Thus, more investigations need to be carried out on the structural behaviour under the different loading states, and proper modelling is essential, such as developing a proper relationship between the flexural strength, compressive strength, shear strength, and modulus of elasticity of GPC. Moreover, the elasticity and plasticity of geopolymer materials should be well studied to help structural engineers when they are designing buildings. Based on fundamental research, embarking on solid wastes to explore the preparation of varied characteristics of geopolymers in order to produce high-value-added application domains should be one of the primary paths of future geopolymer research development ,131,132.Construction with geopolymer concrete is more durable and stronger than with PC concrete;Many factors, including curing conditions, the ratio of alkaline to the binder, and the type of activator, have an important impact on the mechanical properties of geopolymer concrete. Consequently, a proper mix design is required to achieve the target strength;Geopolymer concrete possesses all the potential characteristics for future applications in civil engineering because it is a green material and requires strength and durability properties for all types of projects in the construction industry;Even though it is known that GPC could be used as a replacement material and is a cleaner and more sustainable form of concrete, it is still not widely used in construction;Geopolymer concrete needs a standard code to be used more often in building structures;In terms of mechanical and microstructural performance, geopolymer concrete was better than PC concrete, especially after exposure to high temperatures;The effect of using geopolymer as a partial replacement for PC on the microstructure can be easily noticed; the microstructure has become significantly denser and more homogenous compared with the control specimen, while the number of voids has decreased;C-S-H gel and geopolymer gel enhance the mechanical and microstructural properties of precursors that are either high in Ca or contain a combination of Ca components.The mechanical properties and microstructural characteristics of geopolymer concrete were reviewed. From the above literature, the following are the final thoughts, along with suggestions for more research:


Early-life antibiotic exposure is associated with the development of later obesity through the disruption of gut microbiota in the animal models. However, the related epidemiological evidence is still conflicting.A birth cohort was consisted of 2140 mother-infant pairs in Chaoyang District Maternal and Child Health Care Hospital in this study. Here, their available antibiotic exposure during the first one year of life was ascertained using a open-ended questionnaire and related anthropometric parameters from the health screening program. The compositions of gut microbiota were comprehensively analyzed by16S rRNA high throughput sequencing. Then the spearman correlations were performed by the multiple covariance-adjusted regressions between the antibiotic exposure with anthropometric parameters and compositions of gut microbiota.Faecalibacterium, Agathobacter and Klebsiella, and lower percentage of Bifidobacterium. Moreover, there were positively potential associations between early-life antibiotic exposure with the accelerated anthropometric parameters and disruption of Faecalibacterium, Agathobacter, Klebsiella and Bifidobacterium at two and a half years.Among the 2140 subjects, the antibiotic exposure during the first one year of life was 53.04%, mainly by Cephalosporins (53.39%) and Erythromycins(27.67%) for the treatment of respiratory tract infection (79.56%), which were not significantly different among the subgroups. Compared to the control group, both childhood overweight and obesity at two and a half years were higher in the antibiotic exposed group, with higher percents of Faecalibacterium, Agathobacter, Klebsiella and Bifidobacterium, which would propose the theoretical basis for rationalizing the personalized antibiotic exposure among the infants to truly reflect the fairness of public health.These above results proved that early-life antibiotic exposure was positively associated with the accelerated childhood overweight and obesity from one year to two and a half years by impacting the disorders of The online version contains supplementary material available at 10.1186/s12941-022-00535-1. Obesity is a major challenge of worldwide public health nowadays , 2. CurrRecently, there are many increasing epidemiological evidence that could disrupt the early-life microbiome on the progression of obesity , 16. In Considering that antibiotic exposure is frequently prescribed among the Chinese infants, a precise assessment of the relationship between antibiotic exposure and childhood overweight and obesity is still important . So a biWe conducted a longitudinal prospective birth cohort, with recruiting 2140 mother-infant pairs in Chaoyang District Maternal and Child Health Care Hospital from May 2017 to October 2018 according to the following strict inclusion and exclusion criteria. Specifically, all subjects were healthy at 20–45 years old without smoking and drinking history at the 6–12 gestational weeks among the Chinese Han population and intended to deliver in this hospital. Meanwhile, the infants should be full-term healthy newborns, exclusive breast-feeding to six months and routinely examined their anthropometric parameters by flowing up to two and a half years old. Conversely, the subjects were excluded if they had the following medical diseases , long-term history of medicines and chemical reagents  during the whole pregnancy. Moreover, the subjects with maternal antibiotic exposure during the whole breastfeeding and their infants with birth defects, genetic and metabolic diseases, ischemia, hypoxia, premature and low body weight at birth were also excluded. Furthermore, the subjects could be actively withdrew from this study if they were loss of interests and follow-up records, and the other unknown reasons.http://www.chictr.org.cn/showproj.aspx?proj=4673 . And all subjects were granted both the written consents and health insurance portability and accountability act authorization after they were clearly informed the significance of this survey by the trained investigators.This clinical research was approved by the Ethics Committee of Beijing Children’s Hospital, Capital Medical University (No: 2016-20), which was also recorded at the website of The basic maternal characteristics, including the age, height, pre-pregnancy weight, pre-pregnancy overweight and obesity, prenatal weight, education, and medical history and antibiotic exposure during the pregnancy were obtained by the trained investigators through face to face method when the participants were involved in this study. Meanwhile, the infant basic questionnaire such as sex, gestational age, mode of delivery, breast-feeding duration and introduction to solid foods was obtained to get the information when they had their physical examination.All biological samples were executed in the morning by the trained professional researchers under the strict aseptic conditions and uniform protocols. Exactly, 5mL breast milk was collected at the 3 months physical examination of their infants. Then approximately 1 g fecal samples were obtained using the sterile plastic spoons at two and a half years old. All biological samples were immediately transported to the laboratory and preserved at − 80 °C until use.The antibiotic exposure in the first year of life was drawn by a open-ended questionnaire and patient-recorded medications from the primary care visits at their physical examination of 3 months, 6 months and one year old, in which both the antibiotic exposure and related diseases were recorded as the categorical medication rather than as specific dose (documented as “yes” or “no”) because the specific doses were not always presented. Then all subjects were divided into two groups as the control and antibiotic exposed groups according to the recurrent antibiotic exposure in the first year of life, in which the subgroups  were respectively obtained as the age of firstly antibiotic exposure.2), length for age Z score (LAZ), weight for age Z score (WAZ) and BMI for Z score (BMI Z) were calculated according to the growth curves under 5 years of age using the ANTHRO 2005 software and downloaded from WHO website (http://www.who.int/childgrowth/software/en/).The anthropometric parameters (length and weight) at birth and each subsequent follow-up visits were obtained by the pediatricians using the nearest millimeter  on a digital measuring board with three repeated measurements to calculate the means, which were then recorded and gotten from the Child Welfare Clinic and School Health-care in detail. The related BMI (kg/m60 subjects were randomly enrolled in the control (n = 1005) and antibiotic exposed groups (n = 1135) to determine the colonization of gut microbiota, whose milk microbiota was also evaluated as the gut microbiota.Within the strictly controlled workplace, total DNA samples in the faeces (approximately 200 mg) and milk among the above enrolling subjects (n = 60/group) were extracted using the QIAamp DNA Mini Kits . The isolated DNA samples were eluded in 50µL distilled water with their well controlled quality and quantity.https://magic.novogene.com/customer/main#/login). Exactly, α indicators evaluating the richness (Ace and Chao) and diversity of microbial community (Shannon and Simpson) were calculated using the Faith phylo-genetic diversity. Principal coordinate analysis (PCA) and Non-Metric Multi-Dimensional Scaling (NMDS) analysis based on Bray-Curtis distance as the β diversity indicators were performed to compare the compositions of gut and milk microbiota at the control and antibiotic exposed groups. Through the Lefse, network, ternary plot and evolutionary_tree analysis, the biomarkers with statistical differences were found between all groups, then t test and ANOVA (q test) was analyzed the significant differences at the phylum and genus levels. Meanwhile, the contribution differences were quantified by the simper analysis. The Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) was chosen to predict the meta-genome function. The spearman rank correlations and CCA/RDA analysis were used to measure the associations between the antibiotic exposure with anthropometric parameters and compositions of gut and milk microbiota.The variable regions 3 and 4 (V3-V4) in the 16 S rRNA gene were sequenced on the IlluminaHiSeq Platform 2500 using the modified 515 F (5′-GTGCCAGCMG CCGCGGTAA-3′) and 806R (5′-GGACTAC NNGGGTATCTAAT-3′) primers at Novogene . Then the colonization of gut and milk microbiota was evaluated and analyzed using the NovoMagic platform in Beijing SinoGenoMax Center Co., Ltd . Then the spearman correlations between the antibiotic exposure with anthropometric parameters and compositions of gut microbiota were determined by the multiple covariate-adjusted regressions by controlling the maternal age, BMI before delivery, gestational age, mode of delivery, sex, antibiotic types, usage and related disease treatment.The normal distribution of outcome variables was evaluated by the Kolmogorov-Smirnov test. All data was presented as mean ± standard deviation (SD) or standard error (SE). The differences among all the groups were tested by analyzing the variances for the repeated measurement data based on whether the data was normally distributed .The characteristics of mother-infant pairs was presented as Table 53.04% infants (n = 1135) were dispensed at least one course of antibiotic exposure within the first one year of life .As shown in Table ife Fig.  A, in whife Fig. B and D, ife Fig.  F. MoreoP < 0.05). Among the subgroups from less than 3 months, 3 months to 6 months and 6 months to one year, there were no significant differences of height, weight, BMI, LAZ, WAZ, BMI Z and prevalences of childhood overweight and obesity from birth to two and a half years  and antibiotic exposed groups (n = 1135). Comparing with the control group, the α-diversity indicators were not significantly suppressed among the individuals by the antibiotic administration . However, the percents of Faecalibacterium , while the positive correlations were significantly obtained between the percents of Agathobacter and Klebsiella with weight and WAZ, which were also demonstrated between the percentage of unidentified_ Lachnospiraceae with BMI and BMI Z (P < 0.05).The associations between antibiotic exposure with significant compositions of gut microbiota at two and a half years were presented in Fig. With the increasing abuse of antibiotic exposure in the infancy, we are not only faced with the threat of antibiotic resistance, but also a rising concern about the potential long-lasting effects on the health, in which the occurrence and progression of obesity is a condition resulting from the complex interactions of genetic, dietary and lifestyle factors. So far, there are numerous elements that have been convincingly found to be associated with the implications of childhood overweight and obesity as reported in the previously systematic reviews, especially the higher rates of antibiotic prescriptions, and accelerated infant weight gain , 34. MorBifidobacteria), and increasing percentages of Bacteroidetes and Proteobacteria  to cause the proliferation of potentially pathogenic bacteria [Clostridiales and decreased Bacteroidacea [Faecalibacterium, Agathobacter and Klebsiella, and decreasing percentages of Bifidobacterium at the genus level, which were consistent with the past studies [Bifidobacteriaceae, Bacilli, and Lactobacillales in ways that were predisposed the children to increase the weight gain by reducing the bacterial diversity, increasing the abundance of endotoxin producing organisms, and depleting the beneficial bacteria and organisms to play a key role on the metabolism [Bacteroidales and the marked enrichment of Lactobacillus [Bacteroides to Firmicutes [The mechanisms by which early-life antibiotic exposure indirectly modulates the later childhood overweight and obesity are still unclear. However, there are a number of hypotheses that antibiotic exposure during the first year of life-a critical exposure period in the development of gut microbiota-may have the great impacts on the excessive growth of childhood BMI from the indigestible polysaccharides, and a reduction in the intestinal defense , 39. Meabacteria . Given troidacea , 35–37. roidacea . Meanwhiroidacea , so it i studies , 37. Thetabolism . There wbacillus . And thermicutes .There were still many limitations in this birth cohort. Firstly, the major limitation was that the early-life antibiotic exposure in the first one year of life was obtained by the retrospective non-randomized data collection using the questionnaires, so it was unable to determine the causative correlations between early-life antibiotic exposure and childhood obesity by the prospective randomized clinical studies. The other limitation was included a lack of determined information on the dietary structure to avoid the excessive energy intake to cause the childhood overweight and obesity. Furthermore, the sample size was small, so we were able to conduct further analyses on the correlations between early-life antibiotic exposure and childhood overweight/obesity to better account for the confounding factors with much larger cohort studies.Faecalibacterium, Agathobacter, Klebsiella and Bifidobacterium at the genus level. Therefore, the implementation of this project could propose the theoretical basis for rationalizing the personalized antibiotic exposure among the infants to truly reflect the fairness of public health. It will not only ensure the reasonable utilization of early-life antibiotic exposure in the first one year of life, but also provide a new idea for the prevention of later childhood overweight and obesity.In summary, our results from this birth cohort proved that the antibiotic exposure during the first one year of life was 53.04% among the infants. They were mainly Cephalosporins and Erythromycins for the treatment of respiratory tract infection, without significant differences among the different age subgroups. What is more, there were positively potential associations between early-life antibiotic exposure with the accelerated childhood overweight and obesity from one year to two and a half years, which might be regulated by the abnormal development of gut microbiota, with the disorders of Below is the link to the electronic supplementary material.Supplementary Material 1


At present, there are many problems in various tests when judging the alkali activity of aggregates. The most practical engineering concrete prism test (CPT) takes one year, and the concrete suppression method needs two years. The aim of this paper is to discuss inhibiting effectiveness of supplementary cementitious materials (SCMs) on alkali–silica reaction (ASR) expansion of concrete and evaluate this rapid test method. Three kinds of aggregates were selected by chemical analysis, XRD and petrographic analysis. The high alkali–silicic acid activity of three aggregates was determined by accelerated mortar bars, concrete microbars and CPT. The expansion of concrete specimens made of three kinds of aggregates was measured and analyzed by using the method of length measurement. By changing the curing temperature to 40 °C, 60 °C and 80 °C, the test period of CPT is accelerated. It proved that the expansion of CPT is larger at 60 °C and smaller at 40 °C. The inhibition test was also accelerated by adding different proportion of SCMs (fly ash or blast furnace slag) and adjusting the curing temperature to 60 °C and 80 °C. On this basis, the inhibition test was accelerated by changing NaOH solution instead of moist air curing. The test period of the accelerated inhibition test can be effectively shortened from two years to 4 months, The expansion trend of each parameter and specimen is evaluated, the evaluation cycle can be adjusted to 5–6 months. The microscopic reaction characteristics of concrete specimens were investigated by means of SEM. According to each parameter and criterion, the judging standard of concrete rapid test and rapid restraint test is given in this paper. AAR is generally divided into alkali–silica reaction (ASR) ,2 and alASR is a process that the alkali in concrete reacts with the active silica in aggregate to form alkali–silica gel. The gel expands after absorbing water, which leads to the cracking and destruction of concrete . It is gAt present, adding SCMs into concrete had become the most common measure to restrain ASR expansion . It can The presence of reactive aggregate is a necessary condition for ASR to occur. The scientific communities avoid using reactive aggregate, but due to the shortage of resources and regional restrictions, some reactive aggregates have to be used. At this time, to strengthen the detection of aggregate alkali activity has become the key to prevent ASR expansion. The research of aggregate alkali activity evaluation method is an important aspect in the ASR research field . Many stIn this paper, three kinds of rocks are used, the metamorphic rocks are Jiuli slate (recorded as JL), the sedimentary rocks are Lianghekou sandstone (recorded as LHK) and the magmatic rocks are Ningbo Tuff (recorded as NHY). To explore the composition and internal structure of the three types of rocks . ChemicaThe cement was selected as P·II 52.5 Portland cement produced by Jiangnan Onoda Cement Co., Ltd. . Its equivalent alkali content is 0.56%. All the aggregates used in the test are applied in practical engineering field. The appearance of the aggregates is shown in The chemical composition of aggregates was determined according to GB/T 176-2017 . The results of chemical composition analysis are shown in XRD was performed on the D8 Advance diffractometer . The mineral composition of sandstone was qualitatively analyzed by X-ray diffractometer. The experimental conditions were as follows: Cu Target, 40 kV, 40 Ma, scanning speed 5°/min, step length 0.005°. The mineral compositions are shown in Microstructure characteristics of samples were performed by means of optical microscopy . The lithofacies of the thin plane prepared from three aggregate samples have been observed by Polarized light microscopy method . As showThe microstructure of the LHK sandstone is shown in The microstructure of NHY tuff is shown in 3 and the equivalent alkali content is 1.68%. The BFS is produced by Shanghai Baosteel New Building Materials Technology Co., Ltd. , and the chemical composition is shown in The fly ash used in the concrete sample is Fuxi grade I FA. The density is 2.4 g/cmt is the expansion after t days of curing, in %; Lt is the test piece length after t days of curing, in mm; L0 is the initial test piece length, in mm; and b is the length of the nail embedded in the concrete, in mm.It is necessary to measure the expansion of concrete specimen, and the formula is shown as (1):The alkali–silicic acid reactivity of three test aggregates was determined by the ASTM C1260, ASTM C1293 and RILEM AAR-2. The expansions of alkali–silicic acid reaction were determined, as shown in As shown in 3 by adding NaOH and mixing water. The concrete specimens were cured at 40 °C, 60 °C and 80 °C in moist air 24 h after forming [On the basis of concrete prism method, the concrete specimens of 75 mm × 75 mm × 285 mm are formed by five-gradation of the aggregates. The alkali content of concrete is 5.25 kg/m forming . The inf forming . The cha forming .When the concrete sample is formed, the supplementary cementitious materials are added to replace the cement, which can restrain the ASR expansion of the concrete samples . They alWhether different curing temperature can change the expansion rate of ASR or not, and whether it has an effect rule on ASR expansion . In thisIn order to solve the above problems, the concrete samples were molded with coarse and fine aggregates of three kinds of rocks, respectively, and the parameters were adjusted to reach the same. The influence of curing temperature on the ASR expansion of concrete was investigated by measuring the expansion value of the specimens.With the increase in temperature, the expansion of prismatic concrete specimens with three kinds of aggregates will be larger, but it does not conform to the rule that the higher curing temperature is, the bigger the ASR expansion is. The concrete prism specimens of three kinds of aggregates all showed the maximum expansion at 60 °C and the minimum expansion at 40 °C. The deformation of concrete sample is due to ASR expansion and hydration shrinkage of cement paste. In the early period of curing, the self-shrinkage of concrete samples is more serious than ASR expansion because of hydration of cement paste, it is practical to measure the negative value of expansion when the concrete specimen shrinks. As time goes on, the ASR reaction intensifies, and the mid-term concrete specimens also show considerable expansion. At the later stage of curing, the expansion of three kinds of aggregate concrete prisms tends to be smooth and reach a relatively stable value under three kinds of temperature.Studies have shown that adding 25% FA, 60% BFS or composite doping can effectively inhibit the occurrence of ASR expansion. Therefore, the ratio used in this test can have a better inhibition effect on ASR. This paper only discusses the change in curing temperature and curing medium to accelerate the process of inhibiting ASR effectively. Comprehensive analysis of the above test results, the addition of 20%, 40% fly ash, 40%, 60% blast furnace slag, and 40%, 60% compound doping SCMs all had good inhibition effects on ASR expansion. The expansion of concrete specimen is mostly in the range of 0.002%~0.015% in one year. Because of the time of the experiment, the following 1–2-year provisional period was not measured, but the curve of the expansion showed that the expansion did not increase significantly in the following 1-year provisional period, the expansion curve has become smooth; therefore, the expansion of the concrete sample will not reach 0.04% in 2 years. The change in curing temperature affects the reaction of alkali–silica reaction to a certain extent, but it does not affect the inhibition effect of SCMS on ASR.It takes two years for the concrete inhibition test, and the interim period is much longer than people expected. Therefore, we hope that the interim period can be shortened by changing the temperature or curing condition to accelerate the inhibition test. The curing temperature is 60 °C or 80 °C in 1.5 mol/L NaOH alkali solution. The concrete specimens prepared with three kinds of aggregates had larger expansion than that cured by moist air, which were mixed with different proportion of SCMs. By increasing the reaction temperature and pressure, the reaction speed is accelerated, and the evaluation time is shortened. It is not difficult to see that there is a certain correlation between the rapid inhibition test data and the moist air curing data. For the JL slate aggregate, when curing at 60 °C, the expansion of alkaline solution curing at 8 to 16 weeks is similar to that of moist air curing at half a year to one year, the expansion of alkali solution curing at the beginning of the sixth week was similar to that of moist air curing at the 16th week, and the trend of expansion was similar too. The same is true for the LHK sandstone and NHY tuff aggregates. It can be concluded that the test cycle of accelerated inhibition test for alkali solution can be effectively shortened from the standard two-year inhibition period to four months. The judging period can be extended to five to six months caused that the samples may still grow at the later stage of the accelerated inhibition test, but the increasing trend is slow and steady.- in the NaOH solution  was continuously consumed with the ASR, and the alkalinity of the reaction system decreased at each temperature as shown in During the inhibition test, the OHAccording to the changing trend in NaOH solution basicity reduction value at 40 °C, 60 °C and 80 °C, it can be concluded that there was a positive correlation between basicity hydroxide radical reduction value and ASR gel formation degree at each temperature at the beginning of reaction. As the reaction continues, the ASR gel content inside the particles increases continuously. Under the expansion pressure of ASR gel, the gel will accelerate the diffusion and dissolution to the alkali solution outside, and the higher the temperature, the greater the diffusion coefficient. In the late reaction period, the system remained relatively balanced, the ASR gel content increased slowly, and the reaction rate decreased significantly.2 106 detector and INCA 4.14 5 X-ray microanalysis software). The selected specimens were LHK specimens cured at 60 °C for 1 year by moist air, LHK specimens mixed with 60% SCMs and cured at 60 °C for 40 weeks by wet air, LHK specimens mixed with 60% SCMs and cured at 60 °C for 12 weeks by 1.5 mol/L NaOH . The aggregates were taken from the three samples and their reaction surfaces were tested by SEM. The micrograph of the concrete specimen is shown in In this section, the microscopic reaction characteristics of concrete specimens are studied by means of scanning electron microscopy , alkali activity level (L), ambient temperature (T), relative humidity (H), mix ratio (M), restraint stress (σ) and time (t), etc. Its expansion can be expressed as a general formula as shown in (2):For a particular concrete, the alkali content (A), the alkali activity level (L) and the mix ratio (M) can be regarded as a constant value. If the relative humidity (H) of concrete can be maintained above 85%, the effect of humidity on ASR expansion of concrete can be ignored; For a particular concrete, the confining stress (σ) of concrete generally does not change significantly. As a result, ASR expansion of concrete is more subject to ambient temperature (T) and time (t).The selection of specimen parameters should be as close as possible to the actual concrete. The selection of specimen size should take into account both the accuracy of measurement and the representativeness of sampling. If the specimen size is too small, it will be too different from the actual concrete and does not have the engineering application ability. If the specimen size is too large, the measurement will be difficult, and the measurement error will be large. The water–cement ratio and cement–sand ratio are as close as possible to the actual concrete project. At the same time, due consideration should be given to the laboratory operability, and the aggregate size and gradation are as close as possible to the actual concrete project. It should match with the size of the specimen. Therefore, the size of the specimen is 75 mm × 75 mm × 285 mm, water–cement ratio is 0.47, sand–cement ratio is 0.25.By comparing the experimental results under the condition of high temperature and high alkali with the experimental results under the condition of no alkali, under the condition of curing at 60 °C or 80 °C in 1.5 mol/L NaOH solution, there is a good correlation between the expansion of 0.04% in 4 months (extended to 6 months) as a criterion under the condition of rapid growth, and the expansion of 0.04% in one year under the condition of wet moist curing. Whether this criterion can be used as the final SCMs to evaluate the ASR suppression effect of the mixture needs to be verified and improved by a large number of high, medium and low activity aggregates.Based on the test results of concrete specimens prepared with three different alkali–silica reactive aggregates mixed with different SCMs and different curing conditions, we can get the following conclusions.(1).The accelerated concrete inhibition test shows that the test can be effectively shortened from the standard 2-year inhibition period to 4 months. Considering that the sample may still grow in the later period of accelerated concrete inhibition test, but the growth trend is slow and stable, the judgment period can be extended to 5 to 6 months and the expansion limit can be set at 0.04%. For the change in aggregate type, SCMs type and low content of SCMs, whether the criterion of accelerated inhibition test can be used as a reference standard is worth further study.(2).The influence of temperature on the inhibition effect of mixed SCMs is not obvious, and the change in temperature will not accelerate or slow down the inhibition degree to a great extent. However, the effect of temperature on concrete prism test is obvious. The concrete specimens show larger expansion at curing temperature of 60 °C and smaller expansion at 40 °C.(3).There was a positive correlation between basicity hydroxide radical reduction value and ASR gel formation degree. The change in temperature directly affects the formation of ASR gel and the expansion of concrete. Whether the change in curing temperature directly affects the internal structure and product characteristics of concrete still needs a lot of research.


In this study, our objective was to assess the association of body mass in preschool children with the use of antibiotics within 6 months after birth. National administrative databases were used to examine all children born between 2008 and 2009 in Korea. Exposure was defined as the use of systemic antibiotics during the first 6 months of age. The observed outcomes were stunting (height for age [HFA] z score < −2.0), short stature (HFA z score < −1.64), overweight (body mass index [BMI] for age z score ≥ 1.04), and obesity (BMI for age z score ≥ 1.64), and the children’s height and body weight were measured from three to six years of age. To balance characteristics between the antibiotic user and non-user groups, propensity score matching was performed. The outcomes were evaluated using a generalized estimation equation with the logit link function. Analysis of antibiotic use by children during the first 6 months of life indicated there were 203,073 users (54.9%) and 166,505 non-users (45.1%). After PS matching, there were 72,983 antibiotic users and 72,983 non-users. Antibiotic use was significantly associated with stunting  and short stature , and had significant negative association with HFA z score (weighted β = −0.023). The use of an antibiotic for 14 days or more had a marked association with stunting. Antibiotic use was also associated with overweight, obesity, and increased BMI for age z score. Antibiotic use during the first 6 months of life increased the risk of stunting, short stature, overweight, and obesity in preschool children. Antibiotics have revolutionized the treatment of infectious diseases , but theStunting and short stature are a serious public health problem and a major topic in children in developing and developed countries, respectively. Stunting is associated with dysfunction of the small intestine, a condition called pediatric environmental enteropathy. This condition is characterized by mucosal inflammation, villi flattening, and increased intestinal permeability . An alteOur purpose is to evaluate the effect of antibiotic use within 6 months after birth with linear and ponderal growth in preschool children by analyzing an administrative nationwide cohort database for South Korea.This study was conducted using the data from the National Health Insurance Service (NHIS) of the Republic of Korea, a single-payer program that is mandatory for all residents. This retrospective population-based cohort used data from the 2008 National Investigation of Birth Cohort in Korea study (NICKs-2008), which consists of all 917,707 children who were born in Korea during 2008 and 2009 [International Classification of Diseases 10th revision [ICD-10]), and outcome data (height and weight) were from the database of the NICKs-2008 cohort. Body mass index (BMI) was calculated as weight in kilograms divided by height in meters squared. Health care utilization data were collected during the process of filing claims for healthcare services. Economic status was estimated by the amount of insurance co-payment and classified by quintiles. Residential status was classified as Seoul, metropolitan , urban, or rural. The first round of the NHSPIC was implemented when subjects were 4 to 6 months old, the fourth round when they were 30 to 36 months old, the fifth round when they were 42 to 48 months old, the sixth round when they were 54 to 60 months old, and the seventh round when they were 66 to 71 months old. Physicians measured the height and weight of all children at each round. Patient demographic characteristics, health care utilization  matching, 72,983 children were assigned to each group .To assess the robustness of the results, an additional cohort consisting of users and non-users of antibiotics within 3 months after birth was also analyzed .Systemic use  of an antibiotic during the first 6 months of age was examined, as this is considered the period when microbial colonization is susceptible to environmental factors ,22. AntiAnthropometric data, including height and weight, were measured at the fourth to seventh rounds of the NHSPIC (from 30 to 72 months old). This age was an appropriate period for follow-up, as most childhood obesity develops by the age of 5 years .The primary outcome was stunting and short stature. Stunting was defined as the height for age [HFA] z score less than −2.0, and short stature was defined as the HFA z score less than −1.64 .The secondary outcome was overweight and obesity. Overweight was defined as BMI for age z score of 1.04 or over, and obesity was defined as BMI for age z score of 1.64 or over .PS matching used the covariates in The additional cohort (antibiotic user vs. non-user within 3 months after birth) was assessed using the same demographic characteristics, nutrition, and perinatal and congenital/chromosomal conditions. Clinical conditions were evaluated by prevalent disease history (ICD-10 codes), drug use (drug classification codes), and the number of hospitalizations and emergency room visits within 3 months after birth.a priori covariates  with 95% confidence intervals (CIs) were estimated using generalized estimated equations (GEE) with the logit link function. Adjusted β values and 95% CIs were estimated using mixed-model analysis to analyze the association of antibiotic use with HFA z score and BMI for age z score . These aTwo pre-specified subgroup analyses examined types of feeding (breast feeding vs. no breast feeding) and birth weight . In addition, we examined the effect of antibiotic use on HFA z score and BMI for age z score by route of antibiotic administration .A two-tailed P value less than 0.05 was considered significant. All statistical analyses were performed using SAS version 9.4 .We initially analyzed the basic sociodemographic characteristics of children who were users and non-users of antibiotics during the first 6 months of life . Before We also analyzed the basic clinical characteristics of children who were users and non-users of antibiotics . Before Our analysis of the basic sociodemographic and clinical characteristics of children in the additional cohort (antibiotic use vs. non-use within 3 months after birth) were also balanced after PS matching .We initially examined the effect of antibiotic use on HFA z score . In the In contrast, analysis of the additional cohort indicated that antibiotic use was not significantly associated with stunting  or short stature  . As in tWe then analyzed the effect of duration of antibiotic use on stunting and short stature at preschool age . The matFurther analysis indicated that the mean HFA z score decreased as the duration of antibiotic use increased in the main cohort and in the additional cohort A,B.We next examined the effect of antibiotic use within 6 months after birth on ponderal growth . Among aIn agreement, analysis of the additional cohort  indicateExamination of the effect of duration of antibiotic use on ponderal growth indicated that use for 8 days or more and 14 days or more significantly increased the risk for overweight and obesity . FurtherOur prespecified sensitivity and subgroup analysis showed that the relationship between antibiotic use and HFA z score was similar in children who were and were not breastfed during the first 4 to 6 months of age . AntibioWe performed a subgroup analysis by dividing children into upper-half and lower-half groups based on the median birth weight of 3.24 kg . In thisWe analyzed the effects of antibiotic use on HFA z score and BMI for age z score according to the route of administration . ParenteOur analysis of a large national administrative cohort showed that antibiotic use within the first 6 months after birth increased the risk for stunting and short stature in preschool children. The effect of antibiotic use on growth was especially evident in those who used antibiotics for longer durations. The significantly adverse effect of antibiotic use on linear growth faltering remained significant regardless of breastfeeding status within 4 to 6 months after birth and regardless of birth weight. In addition, antibiotic use during early infancy had a positive association with ponderal growth of preschool children.Lactobacillus species and increased the abundance of some Streptococcus species [Staphylococcus species in the microbiota of the meconium was negatively associated with height at ages 1 and 2 years [Stunting is associated with changes in the microbiota of the small intestine, whose function is essential for digestion and absorption of nutrients . Certain species ,33. Howe 2 years . To the We assessed the robustness of our results by using two subgroup analyses, one based on breastfeeding status and the other based on birth weight. There is evidence that breastfeeding may prevent infections , overweiThere is conflicting evidence regarding the effect of the route of antibiotic administration on the intestinal microbiota . Study oTwo previous meta-analyses reported associations between early antibiotic use and overweight and obesity during childhood ,42. OthePrevious research indicated that long-term use of an antibiotic had a more evident effect on ponderal growth ,45. In pThis study included a large set of data from many children, allowing the assessment of anthropometric indices measured by physicians in hospitals. Because all children born during 2008 and 2009 in Korea were enrolled and most of them participated in the NHSPIC, the data in this study have representative characteristics, and the results can be generalized. By using PS score matching, we tried to quantitatively assess the association between antibiotic use and childhood growth with adjustment for potential confounders, especially economic status and co-morbidities. In addition, in Korea, the rates of exposure to antibiotics in infants aged <3 months and <2 years old were high, approximately 25% and 99%, respectively ; by contHowever, the present study had some limitations. Firstly, though we used PS matching, the retrospective study design prevents us from inferring causal relationships. In particular, there is a possibility that children who used antibiotics, especially for long durations, had serious clinical conditions that contributed to growth faltering. Secondly, participants in this study were born in 2008 and 2009 and were followed up to their age of 6 years. Since time has passed, it is necessary to confirm the consistency of results with the latest data. Thirdly, we used antibiotic prescriptions to define antibiotic use, although we cannot be certain that prescribed antibiotics were actually administered. Fourthly, we did not have data regarding the different types of antibiotics. Fifthly, we were unable to assess some factors that might have affected the gut microbiota and child growth, including birth height, mode of birth delivery, maternal health status, parental height and weight, and secondary smoking status. Finally, multiple genetic and environmental factors that we could not assess could have affected growth. Therefore, a longitudinal prospective study is needed to confirm our results.Our results suggest that antibiotic use during early infancy is a potential risk factor for stunting, short stature, overweight, and obesity during childhood. We suggest that clinicians more carefully consider the administration of antibiotics during early infancy because of these risks.


Four replacement levels of MK, i.e., 5%, 10%, 15%, and 20% by weight of cement, in addition to control samples, at a constant water-to-cement (w/c) ratio of 0.55 were used. For evaluating the mechanical and durability performance, 27 cubes (6 in. × 6 in. × 6 in.) and 6 cylinders  were cast for each mix. These samples were tested for compressive strength under standard conditions and in an acidic environment, in addition to being subjected to water permeability, sorptivity, and water absorption tests. Chemical analysis revealed that MK could be used as pozzolana as per the American Society for Testing and Materials (ASTM C 618:2003). The results demonstrated an increased compressive strength of concrete owing to an increased percentage of MK in the mix with aging. In particular, the concrete having 20% MK after curing under standard conditions exhibited 33.43% higher compressive strength at 90 days as compared to similarly aged control concrete. However, with increasing MK, the workability of concrete decreased drastically. After being subjected to an acid attack (immersing concrete cubes in 2% sulfuric acid solution), the samples exhibited a significant decrease in compressive strength at 90 days in comparison to those without acid attack at the same age. The density of acid attack increased with increasing MK with a maximum corresponding to 5% MK concrete. The current findings suggest that the local MK has the potential to produce good-quality concrete in a normal environment.Due to the increasing prices of cement and its harmful effect on the environment, the use of cement has become highly unsustainable in concrete. There is a considerable need for promoting the use of cement replacement materials. This study investigates the effect of variable percentages of metakaolin (MK) on the mechanical and durability performance of concrete. Kaolin clay (KC) was used in the current research to prepare the MK by the calcination process; it was ground in a ball mill to its maximum achievable fineness value of 2550 m In recent years, many engineers from all over the world have devoted themselves to research activities aiming to produce economy in the cement and construction industry. In this context, they emphasized the use of cement replacement materials in construction projects. There is a substantial need to encourage the use of cementation ingredients more economical than ordinary Portland cement (OPC) bearing in mind the expensive costs of Portland cement. The usage of additional cementitious materials is the first phase in developing low-cost construction constituents to be used in emerging states. Concrete is the building material usually made use of to counter forces in compression. By adding pozzolanic materials, one can improve concrete workability, strength, durability, and resistance to permeability and cracks . Rojas sSharif et al. expressed that pozzolans are utilized as a part of a solid constituent with an ordinary bond as substitution materials. Initially, the term pozzolan was related to volcanic cinders and calcined earth which would ordinarily respond, within the sight of water, with lime at encompassing temperatures. These days, this term covers all aluminous/siliceous materials which are in fine powder frames and respond with calcium hydroxide within the sight of water to shape mixes that have cementitious properties . Bentz f2Si2O7) has been used as a pozzolan in high-performance concrete applications and has been commercially available since the mid-1990s. Poon et al. found that it typically contains 40–45% Al2O3 and 50–55% SiO2 and is considered a natural pozzolan with high reactivity [For Pakistan, the development of cement replacement materials is of great importance, as the country has started large irrigation projects, highway networks, and building programs as well as plans for their expansion in the near future. Most of the cement replacement materials mentioned earlier are not locally available. Thus, due to expenditure on their import and cost increases, these ultimately become costlier than cement. However, it has been seen that metakaolin (MK) conforming to ASTM C618:2003 is found locally at negligible cost. Sabir et al. explained that MK Al2Si2O has beenSiddique et al.  hypothesThe previous research also concluded that optimal performance was achieved by replacing 7% to 15% of the cement with MK. Compressive strength values for concrete containing MK after 28 days can be 20% higher. A dose of 15% MK caused a decrease in workability. Increasing the proportion of MK in the concrete mix required increasing the superplasticizer dosage to ensure longer workability . JusticeIn this study, special attention was paid to studying the effects of the partial replacement of cement with MK so that we may use it efficiently and obtain the maximum benefit from it according to the local environment. A typical concrete mix ratio, 1:2:4, one part cement, two parts fine aggregate, and four parts of coarse aggregate, was used with MK for different cement substitution levels. Investigations regarding the properties of the ready-mixed and hardened concrete cast from pure (control without MK) and blended cements using MK were performed at 5%, 10%, 15%, and 20% substitutions. The results obtained give a clear picture regarding the effects of partial replacement of cement by locally available MK on the fresh and hardened properties of concrete.OPC manufactured by one of the leading brands in Pakistan “FECTO cement” was used. The physical properties of the cement used are given in Lawrencepur sand was used as fine aggregate for the experimentation. As per ASTM C136-06, sieve analysis of the fine aggregate was carried out, and the results are summarized in Coarse aggregate that was used for experimentation was best-quality Margalla crush. As per ASTM C136-06 guidelines, sieve analysis of coarse aggregate was performed to confirm its standard grading . Using ARegular tap water from the concrete laboratory was used for research purposes. Best-quality kaolin clay (KC) collected from Nagar Parkar, situated in the province Sindh of Pakistan, was purchased from the local pottery/ceramics industry of Gujrat, Punjab. It was in the form of large lumps having off-white color as shown in KC was transported to Glass & Ceramics Research Centre (GCRC) in the PCSIR Laboratories Complex Lahore, Pakistan, for its calcinations to obtain MK. KC was placed in the kiln for 1 h at a temperature of 800 °C. At this temperature duration, most of the absorbed water of KC was removed by the breaking of the water bond structure of KC. This disorder in the structure of KC is called dehydroxilization. This process of thermal activation of clay is termed calcination. The material obtained after heating of KC in the kiln was in the form of small lumps compared to its larger size before calcinations.Then MK, thus produced, was transported to the physical laboratory for grinding in the ball mill to the maximum fineness, and the final ground MK produced is shown in 2, Al2O3, and Fe2O3 in the total content and thus fulfills the requirement as per ASTM C 618:2003 to be used as pozzolana. Ground MK’s XRD graph is shown in XRF was used to conduct the chemical analysis of MK in its final form. Chemical analysis results presented in 3 per batch. All five concrete mixes without and with MK as cement replacement material are detailed in For determining several properties of concrete, the mix ratio selected was one of the most used mix ratios for normal strength concrete, i.e., 1:2:4. A total of four replacement levels of MK by weight of cement, i.e., 5%, 10%, 15%, and 20%, having a constant w/c ratio of 0.55 were used. The motor-operated drum mixer was used to obtain a uniform mixing of concrete. The maximum capacity of the mixer was 2.5 ftUnder normal curing, a total of fifteen identical cubes (6 in. × 6 in. × 6 in.) were cast for each mix to investigate the compressive strength of three identical specimens at each testing age . In addition to normal curing, an additional six cube specimens were cast to investigate the effect of acid attack on compressive strength at the ages of 56 and 90 days. For each mix, sorptivity was investigated at 90 days of curing for three identical cylindrical samples . Three identical specimens were tested to obtain average sorptivity results. Similarly, the water permeability of each mix was examined by averaging the results of three identical cube specimens (5.875 in. × 5.875 in. × 6 in.) at the ages of 28 and 56 days.A detailed discussion of the test results related to workability, compressive strength without and with acid attack, water permeability, sorptivity, water absorption, resistance to acid attack, and density of acid-attacked concrete is given in this section.The workability of various alternative grades of concrete incorporating different percentages of MK  was recorded at constant w/c ratio and weights of cement in the mix. 2 and formed more calcium silicate hydrate (C–S–H), consequently resulting in higher compressive strength. In addition, the miniaturization of MK particles also contributes to increased strength. The optimal alternative MK content was found to be 20% by weight of cement.For each concrete mixture, 15 out of 21 concrete cubes (6 in. × 6 in. × 6 in.) were used for normal compressive strength. After curing under standard conditions, three identical cubes were tested for each testing age, i.e., 3, 7, 28, 56, and 90 days. Thus, in total, 75 cubes were tested for normal compressive strength for all replacement levels of MK. Testing was conducted in accordance with BS 1881:1970. ASTM C 311-07 supports the estimation of the strength activity index (SAI) to assess the pozzolanic behavior of concrete. This is done by replacing predetermined bonds with pozzolans to ensure mortar quality. Test results are affected by the conditions of the concrete used, especially its fineness and soluble base cement. There is also a lime-based pozzolanic activity index that determines the total pozzolanic activity. In the present case, the SAI for MK blended concrete mixes has been calculated by the following equation:A = Normal compressive strength of MK blended concrete;B = Normal compressive strength of OPC concrete (control concrete).Permeability is a measurement of the flow of water under pressure in a saturated porous medium. For the water permeability test, six cubes (5.875 in. × 5.875 in. × 6 in.) were cast for each level of replacement. Samples were cast and cured in the same manner as for compressive strength testing. Three identical cubes were tested at 28 and 56 days of age in an automatic concrete permeabilizer (CN790). The results shown in Sorptiveness (S) is a material property that characterizes the tendency of porous materials to absorb and transport water by capillary action. For the sorptivity test, three identical cylinders  were cast for each concrete mixture to calculate the average results. For test fluid, water was used, and the sorptivity of concrete was measured at age of 90 days. For the water absorption test, three cylinders  were cast for each level of replacement. After casting, the samples were cured by soaking in water for 90 days. The water absorption rate of concrete was confirmed at the age of 90 days. The results are shown in Acid-attacked strength of concrete was checked at the ages of 56 and 90 days by performing a compressive strength test on MK blended concrete samples which were immersed in a 2% sulfuric acid solution after 28 days of normal curing. The compressive strength of acid-attacked concrete is demonstrated in Figures show that 56-day testing of concrete samples immersed in 2% sulfuric acid solution reflected a slight increase in compressive strength as compared to concrete cubes without acid attack at all replacement levels of MK except at 20%. However, an increase in compressive strength of the acid-attacked concrete is observed with increasing substitution levels of MK in the concrete, increasing by 25.02% over the control mixture.However, the compressive strength of concrete cubes after 90 days of acid attack showed a similar decline at all MK levels compared to the strength of concrete cubes without acid attack. As the substitution level of MK in the concrete increases, the compressive strength of the acid-attacked concrete is observed to further increase, reaching a level 34.13% greater than that of the control mix.The density of acid-attacked concrete was checked at the age of 90 days. The density results of acid-attacked concrete were noted for the samples which were immersed in a 2% sulfuric acid solution after 28 days of normal curing. The density results of acid attack concrete with different percentages of cement replacement by MK are given in The density of acid-attacked concrete cubes increases with the increase in the replacement level of MK in concrete. Maximum density of acid-attacked concrete was achieved with a 5% replacement level of MK at the age of 90 days and is 2.94% greater than that of the control mix. On the other hand, at a 20% replacement level of MK for the same age, there is a 0.02% increase in density compared to the control mix.Acid-attacked concrete also showed an increase in density with elapsed time. An increase in density with elapsed time for a 5% replacement level of MK by weight of cement after the ninth week was observed, reaching a level 12.70% greater than the density of acid-attacked concrete after first week. The initial decline after the first week was due to a lack of binding in concrete owing to the presence of extra absorbed water during curing which improved afterward over time. In this way, an increase in density with elapsed time for the 20% replacement level of MK by weight of cement after the ninth week was observed, as it was 1.78% greater than the density of acid-attacked concrete after the first week.Results revealed that the workability of concrete decreased gradually with the increase in the level of replacement of OPC with MK. The highest decrease in workability is up to 60% compared to that of control concrete and was observed for concrete containing 20% MK.Contrary to the workability performance, the compressive strength of concrete increased with increasing cement substitution with MK. A maximum increase of 33.43% in compressive strength was observed for concrete having 20% MK content at the age of 90 days when compared to control concrete at the same age.The water absorption percentage of hardened concrete increased with the increase in MK, although it remained within the permissible limits defined for good-quality concrete in the literature.Concrete samples immersed in 2% sulfuric acid solution did not show a significant decrease in compressive strength at 56 days as compared to the corresponding concrete without acid attack. On the other hand, the compressive strength of concrete at the age of 90 days after being subjected to acid attack showed a considerable decrease in comparison to the compressive strength of concrete not exposed to acid attack at the same age.In order to avoid laborious and costly testing of cement-replaced concrete related to mechanical and durability performance, data shall be collected from the available literature to develop advanced regression and machine learning models in accordance with the previous studies ,22,23,24This study investigated the mechanical and durability performance of concrete incorporating different percentages of MK as a partial substitute for OPC. The following main conclusions were drawn from this study:


Antibiotic-loaded bone cement beads and spacers have been widely used for orthopaedic infection. Poor antibiotic elution is not capable of eradicating microbial pathogens and could lead to treatment failure. The elution profiles differ among different cement formulations. Although Simplex P cement has the least release amount, it is widely used due to its ready availability. Previous methods aiming to improve the elution profiles were not translated well to clinical practice. We sought to address this by using easily available materials to improve the elution profile of antibiotics from PMMA, which allows clinicians to implement the method intraoperatively.Vancomycin was mixed with Simplex P cement. We used Vicryl Rapide sutures to fabricate sustained-release cement beads by repetitively passing the sutures through the beads and/or mixing suture segments into the cement formulation. Vancomycin elution was measured for 49 days. The mechanism of antibiotic release was observed with gross appearance and scanning electron microscopic images. The antimicrobial activities against MRSA were tested using an agar disk diffusion bioassay.Passing Vicryl Rapide sutures through cement beads significantly improved the elution profiles in the 7-week period. The increased ratios were 9.0% on the first day and 118.0% from the 2nd day to the 49th day. Addition of suture segments did not increase release amount. The Vicryl Rapide sutures completely degraded at the periphery and partially degraded at the center. The antibiotic particles were released around the suture, while antibiotic particles kept densely entrapped in the control group. The antimicrobial activities were stronger in passing suture groups.Passing fast absorbable sutures through PMMA cement is a feasible method to fabricate sustained-release antibiotic bone cement. Intra-cement tunnels can be formed, and the effect can last for at least 7 weeks. It is suitable for a temporary spacer between two stages of a revision surgery. Antibiotic-loaded bone cement spacers and beads have been widely used for the treatment of orthopaedic infections, including prosthetic joint infection –3, infecFactors affecting antibiotic elution include antibiotic loading dose, physicochemical properties of antibiotics, mixing methods of antibiotics, cement porosity, and cement composition . VariousThis study aimed to use easily available materials to improve the elution profile of antibiotics from PMMA, which allows clinicians to implement the method intraoperatively. We hypothesized that biodegradable sutures passing through PMMA could leave tunnels to facilitate antibiotic release after the sutures are hydrolyzed.Having the less favorable antibiotic elution data, Stryker Surgical Simplex P  was the target PMMA product in this research. It is a commercial bone cement widely used worldwide. The chemical composition of Simplex P bone cement is shown in Table We speculated that passing sutures through the bone cement and adding suture segments to the bone cement might improve antibiotic elution. Passing biodegradable sutures through PMMA ensures the exposure on PMMA surface at both ends of the suture. It may leave tunnels to facilitate antibiotic release after hydrolysis. Suture segments might act as poragens to create high porosity after hydrolysis of the segments. In previous studies, the addition of biodegradable particles as poragens effectively created a high porosity , 22, 23.There was one control group (no suture) and three experimental groups: 1) passing suture group, (2) passing suture + segment group, and (3) segment group -2,5- diphenyltetrazolium bromide  and incubated at 37 ◦C for 3 h. The absorbance was measured at 570 nm with UV–vis spectroscopy using a SpectraMax Plus-384 spectrophotometer . The cell viability in each group was calculated and expressed as a percentage relative to that of the control group.We used a human osteosarcoma cell line, MG-63 , to test the cell viability. Briefly, MG-63 cells were seeded to 96-well plates at a density of 1 × 10The antimicrobial activity of bead-immersed PBS collected on the 1st, 10th, 19th, 32nd and 49th days was estimated using an agar disk diffusion bioassay. Briefly, 10-mm antibiotic discs were loaded with 30µL of the PBS samples. The discs were subsequently placed on Mueller-Hinton agar plates  inoculated with methicillin-resistant Staphylococcus aureus at 37°C. The zone of inhibition (ZOI) was measured after 24 h to compare the antimicrobial activity between each group . An energy dispersive X-ray spectroscopy (EDS) was also used to visualize and analyze the surface features. The energy of the electron beam was 10 kV. To ensure high quality images, the samples were sputter-coated with platinum using a JFC 1600 auto-fine coater .All statistical analyses were performed using Real Statistics Resource Pack software (release 8.0) on a Microsoft Windows-based computer. The antibiotic release amounts in the four groups at each time point were compared using the Friedman test. Post-hoc analysis with the Nemenyi test was conducted to identify which pairwise groups had a significant difference. Statistical significance was set at a p < 0.05.P = 0.77). The curing time of the control group was 8 min 52 s ± 15 s. Compared with the control group, the mean curing time was 22 s shorter in the “passing suture group” (P = 0.007) and 20 s shorter in the “passing suture + segment group” (P = 0.006). The mean value of the cumulative antibiotic release from the three experimental groups and the control group is shown in Fig. P < 0.001 in the Friedman Test). The post-hoc analysis showed that the “passing suture group” and the “passing suture + segment group” released more antibiotics than the “segment group” and the control group (P < 0.001). The addition of suture segments did not increase the antibiotic release amount . A burst release was observed in each group on the first day. Compared with the control group, the total release amount from the “passing suture group” increased by 39.9%. The increased ratios were 9.0% on the first day and 118.0% from the 2nd day to the 49th day.The polymerization temperature is shown in Fig. P > 0.05 in the Friedman Test). The antimicrobial activities of the bead-immersed PBS were shown in Fig. The cell viability of each group was shown in Fig. Regarding gross appearance, the sutures in the most peripheral area were completely hydrolyzed Fig.  A, whereThe most important contribution of this study is that we successfully improved the vancomycin elution profile by simply passing fast absorbable sutures through antibiotic-loaded PMMA. Because the Vicryl Rapide suture is a commonly used commercialized product , 35, itsAntibiotic release from PMMA cement has been previously reported. The Simplex P cement has the lowest release amount among various formulations. However, it is widely used to fabricate cement spacers owing to its availability , 36. In 2 nanotubes functionalized Simplex-P bone cements could be more than 50% of the total amount. The extended release of vancomycin could last for at least 80 days. Besides, the mechanical properties were well preserved after incorporation of the TiO2 nanotubes [Regarding the sustained release of antibiotics from PMMA, promising results have been reported in previous studies , 40, 41.anotubes . Similaranotubes . In addianotubes , 55. Thianotubes , which aApart from the incorporation of the above materials, another strategy is to change the composition of the PMMA cement . A reducBecause the addition of other materials may disturb the polymerization reaction and increase the release of the toxic MMA monomer, cytocompatibility test is essential to determine the safety. There are various methods, such as MTT assay, lactate dehydrogenase assay and cell counting kit-8 assay, to test the cytotoxicity. In previous studies, MTT cellular viability assay has been the most common method to test the cytotoxicity of bone cements , 48, 52.This study has several limitations. First, we could only confirm the elution profile of vancomycin. Clinicians can use different antibiotics. Vancomycin is one of the most common antibiotics used in cement spacers. Further studies are necessary to determine the effects of other antibiotics. Second, to simulate the general condition, we used an intermediate size of spherical cement beads between the larger cement spacers and smaller beads. It remains unclear whether different sizes or shapes would have different effects. Nevertheless, the rapid absorbable sutures are supposed to degrade in a similar way, which could facilitate antibiotic release as well. Finally, we did not test the mechanical properties of the PMMA cement. Bone cement with mechanical properties close to those of the surrounding cancellous bone may improve prosthesis longevity . BecauseIn conclusion, passing fast absorbable sutures repetitively through PMMA cement is a feasible method to fabricate sustained-release antibiotic-loaded bone cement. Intra-cement tunnels can be formed after suture degradation. The effect can last for at least 7 weeks, which is suitable for a temporary spacer between the two stages of a revision surgery.