Complex concrete elements are typically produced with lost formwork made out of timber or plastic. After usage, these timber or plastic panels are disposed of. This makes complex lost formwork a polluting and high-cost-inducing aspect of concrete construction. A possible solution for this problem could be 3D printing of concrete. This high degree of freedom construction process could easily be used to produce complex formwork. As the formwork stays in place, it has a function during and after the hardening of the inner concrete. Before hardening, the formwork keeps the fresh concrete in place. After hardening, the printed formwork takes the function of a concrete cover. The concrete cover protects the steel reinforcement against aggressive environmental substances such as chlorides and carbon dioxide. To properly execute this function, the printed material and the transition between printed material and inner concrete need to perform at least as well as the inner material. This experimental research investigates the usability of a 3D printed concrete mixture as a concrete cover in a combined concrete structure. The effect of the curing condition as well as two different surface finishing techniques of the printed formwork are taken into account. The effect of the different parameters is compared based on existing service life models. Results indicate that proper curing of the printed formwork is of key importance in order to obtain significant resistance against carbonation- and chloride-induced corrosion. Adjusting the nozzle with side trowels improves the resistance of the printed material against chloride intrusion and carbonation but has only a limited effect on the service life extension. Three-dimensional printed formwork is intended to remain in its place when the infill concrete is hardened. A that point, its function as a formwork has been fulfilled. However, instead of becoming death weight, the 3D printed formwork could take a new function: concrete cover. Within this paper, the possibility of 3D printed formwork to act as a protective layer for concrete reinforcement is investigated. The paper consists of an experimental and numerical part. In the experimental part, the effect of the curing conditions of the printed formwork and possible improvement techniques are investigated. The experimental results are used to calculate the service life of the intended formwork to obtain a better understanding of the possibility of its new function.The number of applications where 3D printed concrete is used has significantly increased in the last couple of years. Walls, columns, and stairs are only a couple of elements that are currently being printed ,2. HowevThe concrete cover protects the reinforcement of the concrete against aggressive substances such as carbon dioxide and chlorides. The concrete cover is a porous material resulting in the fact that after a certain period, aggressive substances can reach the reinforcement and depassivation can start. The period for the substances to reach the rebars is called the initiation period . When thTo predict the service life of reinforced concrete, the International Federation of Structural Concrete (Fib) provided model code 34, the code for service life design . The codOne of the main advantages of 3D concrete printing is that no formwork is needed. However, a concrete formwork does not only support the freshly cast concrete, but it also protects the concrete from drying out at an early age. It is highly warned that an early removal will lead to (plastic) cracking of the concrete . Neverth2) present. This means that the alkalinity of the concrete remains high, which benefits the carbonation resistance. However, in the case of GGBS blended types of cement, this alkalinity is reduced compared to a pure PC mix , 2], and The difference in the evaporation rate between the two curing conditions  and  was investigated with mixture REF. Nine specimens were made of one layer (30 mm × 30 mm × 160 mm). Three specimens were exposed to both curing conditions and three control specimens were made, which were fully covered with foil. At different periods, the mass of the samples was measured. The test was performed up to 96 h (4 days). The mass loss is assumed to be related to the evaporated water. The results are reported as the evaporation rate (1):® DesignTop SF, Koramic Chemicals, Wommelgem, Belgium). This can be seen in The vacuum saturation was performed according to NBN EN 1936 , but onl3].The specimens were placed in a vacuum chamber on line supports. The air pressure was decreased to 2 ± 0.7 kPa. After 2 h, water was gradually inserted into the chamber without increasing the pressure, until the specimens were fully submerged. After another hour, the pressure was slowly increased up to atmospheric pressure. The mass increase was measured for the first time 24 h after submersion had started. The specimens were deemed fully saturated when the mass did not significantly increase (<0.1 m%) after 24 h. At this point, the hydrostatic weight and the saturated mass were obtained. Based on the results, the open porosity t [g/mm2], t [g], 2]. The test was performed for the specimens in test sequences 1. The samples were coated after drying with one layer of epoxy at the top and the bottom side. The nominal dimensions of the exposed surface were measured before testing. Additionally, the mass of the coating and the dry sample was determined by measuring the specimen before and after coating in dry condition. Before testing, the specimens were assumed to be dry as no mass loss was measured after 24 h of drying in an oven at a temperature of 40 °C. The test was performed by placing the specimens in a box on line supports, exposing the side to the water. Water (20 °C) was added until the water level was 5 ± 2 mm above the top of the line supports. On top of the container, a lid was placed to prevent evaporation. The mass of the samples was measured after excess water was removed from the exposed surface by a wet cloth. The mass was obtained at 1, 3, 7, 15, 30, and 60 min and every hour up to 6 h, 24 h, and 144 h after water contact. The results of the test are calculated based on Equation (4).Sequence 1: The effect of the formwork curing conditions2: 1%). Due to a high carbonation rate observed after one week of exposure, the measuring periods were chosen as: 7, 14, 21, and 28 days. On these predefined periods, the carbonation front was obtained by splitting the samples and spraying phenolphthalein on the surface. A picture was taken of every tested surface. The carbonation front of all the samples was analyzed with ImageJ® v.1.54f. For each surface, the carbonation depth was measured every 2 mm. The average of all these depths is the carbonation depth of one sample. For each exposure time, six samples were tested. Before starting, three samples were split to obtain the initial and natural carbonation of the preparation period. The other samples were placed in a carbonation chamber  without drying in the oven. Before testing, a reference measurement was taken to determine the natural carbonation that occurred during curing. Only the printed side or one side of the cast prisms (a molded side) is exposed during testing as the other sides were sealed by aluminum foil, as indicated in After 64 days of curing of the combined samples, the specimens were placed in the COSequence 1: The effect of the formwork curing conditionsAfter 25 days of curing of the printed specimens, 3 concrete cores (Ø100 mm × height 50 mm) were drilled. For all specimens, the bulk material was tested, which means that the curved surfaces were removed until no bulges were visible anymore. Afterwards, the specimens were flattened. Three specimens were tested for each test series (n = 3).Sequence 2: The performance of a combined elementFor all tested specimens, 3 cylinders (Ø100 mm × height 50 mm) are drilled after 63 days of curing. For the cast samples, cores are drilled out of cubes while for the printed specimens the cores are drilled out of the printed wall elements. The bulk material of printed elements is tested by removing the curved outer part up to the point that no bulges are visible anymore. When investigating the effect of the surface finishing, the curved outer layer is kept and exposed to the chloride solution. Three samples were tested for each series (n = 3). Testing procedure of RCM2 solution is added to submerge the specimens. Twenty-four hours after the vacuum exposure started, the specimens are placed in the setup to test the chloride ingress, as shown in nssmD is the non-steady state migration coefficient [×10−12 m2/s], U is the applied voltage [V], T is the average value of the initial and final temperatures in the anolyte solution [°C], L is the thickness of the specimen [mm], dx is the average value of the penetration depths [mm], and t is the test duration [hour]. The test was performed according to NT Build 492 . SpecimeTo properly investigate the influences of the different variables on the durability of concrete structures, the effects are compared with each other based on the corrosion initiation period. Within this paper, the ending of this period (the depassivation point) is indicated as the service life. This makes it also possible to assess the effect of the performed enhancement technique, independent of the testing method. ® v.2023.1 based on the First Order Reliability Method.The service life indicates in this case the period needed for aggressive substances to reach the reinforcement. The length of this initiation period can be estimated based on both chloride ingress and carbonation tests. These experimental values can be combined with benchmark values in a limit state function. By solving these limit state functions, the failure probability for a specified concrete cover thickness after a certain period can be found. Once the failure probability exceeds a certain threshold value, the service life is deemed to end. For the service limit state described in Fib 34 , a maximTo predict the service life of the tested 3D printed formwork, some assumptions have to be made to design the concrete structure. The designed structure is located in the exposure class XS1. The metrological data is taken from the Belgian coastal area;The structure is designed for a service life of 50 years. This is the default design service life for buildings and common structures;The used experimental values are the bulk properties of the printed concrete.Taking into account these parameters, the required concrete cover could be estimated for carbonation and chloride-induced corrosion. Moreover, a possibility exists that the service life of a predetermined printed layer thickness can be estimated. For example, the prescribed concrete cover according to Eurocode 2 for the given assumptions is 45 mm. However, it should be noted that current models are only validated for cast concrete and have never been evaluated for printed concrete. d to the carbonation depth c(t)x at a certain point of time t.d is the concrete cover [mm] and t [years]. The calculation of the carbonation depth 2 concentration [kg/m2], t time [years] and the weather function [-]. The environmental function 2/year)/(kg/m2)] and 2/year)/(kg/m2)]. The inverse carbonation resistance of the accelerated test can be calculated based on Equation (11).2/year)/(kg/m2)]0.5. In the Fib 34 model code , the ful2-concentration, as shown in Equation (12).2 concentration and 2. Similar conversions have been performed by Van den Heede et al. , x is the carbonation ingress.The ingress of the carbonation front after 28 days  to estimate the service life can be found in t of the concrete elements ends at the moment a critical chloride content d [m]. This leads to the limit state function of Equation (15).The durability of reinforced concrete structures exposed to chlorides is explained in Fib bulletin 76 . The serd after a certain service time tt time [years], 2/s] and The quantity of chlorides at depth 2/years], The apparent chloride diffusion coefficient The environmental variable takes into account the ambient temperature. As chloride transport is a thermodynamic process, this cannot be overseen. The effect of the temperature on the diffusion process can be written based on the Arrhenius equation.The data used to estimate the service life by chloride-induced corrosion is given in 2·h) was observed, which is significantly lower than the threshold value of ACI (1 kg/m2·h) [kg/m2·h) . ExceediAccording to Bakshi et al. , two difOne must keep in mind that the decrease in RH is not uniform within the printed concrete, but will change gradually throughout the depth of the specimens. As a result, a drying front will be formed within the printed material. This can be observed in The immediate exposure to air leads to a large reduction in water content within the first hours. Additionally, over the first days a significant amount of water evaporates, which can be seen in p-value: 0.02). The porosity of the M2 and REF mix is not significantly different under this curing condition . However, when curing at a lower RH, there is a significant difference between the open porosity of all mixtures .First of all, the porosity of the M1 mixture is not significantly affected by the curing condition, which is not the case for the GGBS-incorporated mixtures. The porosity of M2 and REF increased respectively by 44% and 120% when immediately exposing the concrete to drying (RH = 60%). The increase in porosity is mainly the result of the evaporation of mixing water. As the hydration is also slower, more water can evaporate. When the evaporation rate of the water is faster than the hydration rate to fill the pores, a higher porosity will be obtained. Additionally, the reduction in available water will slow down the hydration of the GGBS, potentially leading to hindrances. When the hydration stops, the filling effect is not possible anymore. These two factors could result in a higher porosity. M2 contains a lower quantity of GGBS than REF, which explains the difference in the effect of the curing condition. In the case of pure PC binder, the hydration kinetics are faster and will be less affected by the evaporation after the first few hours. Therefore, the same porosity under different curing conditions is observed. Similar observations have been seen by Ortega et al.  and YounThe water absorption of concrete can be divided into two stages: a rapid and a slow absorption stage . The driThe ingress of water into the printed concrete can be divided into an initial and secondary sorptivity. The initial sorptivity of the rapid stage  of at least 0.81. 2 content makes these types of concrete more prone to carbonation. Secondly, in 2. As a result, the carbonation coefficient would be significantly higher than for the M1 mixture. The curing conditions have a significant effect on the carbonation resistance of the printed concrete. The magnitude of the influence is dependent on the mixture composition. While for M1 (pure PC as binder) the carbonation coefficient is 2.05 times higher due to improper curing (RH = 60%), this becomes 7.42 and 14.60 times higher for M2 and REF. There are two possible reasons for this effect. First of all, by incorporating GGBS into the concrete mixture, the alkalinity will decrease. The reduction in Ca(OH)In the case of proper curing conditions (RH > 95%), the carbonation resistance of M1 is lower than for M2 and REF. This was unexpected, as a pure PC mixture has a better resistance against carbonations than slag-blended cementitious mixtures. Additionally, the results of 2 is shown. First of all, a significant difference between the results of In Not only the environment, but also the production method plays a significant role. A visible difference can be observed between the casting and printing processes. An explanation can be found in the difference in pore structure and porosity of the printed specimens compared to cast specimens. Printed concrete contains larger pores compared to cast concrete. These larger pores are more interconnected, while in cast concrete this is less common . As a reTo obtain a construction method closer to casting, side trowels can be mounted on the nozzle. In this case, printed layers could obtain a higher degree of compaction in comparison to layers for which the outflow is free. As the material is better compacted, the pore structure could change, improving the durability aspects. Based on the results shown in The specimens used to define the chloride migration coefficient cured at an RH = 60% showed an increase in chloride migration coefficient for mixture M1, M2, and REF, respectively, with 23.3, 98.9, and 48.9% compared to specimens cured at an RH > 95%. This indicates that the curing conditions have a significant influence on the chloride migration coefficient of the concrete. However, the chloride migration is less affected by the tested mixture, while this was the case for the carbonation resistance and the water absorption. Literature indicates that these latter tests are highly influenced by the quantity of capillary pores present in the mixture. However, in the case of the chloride migration resistance, the pore distribution and size are more important. Moreover, incorporation of GGBS in concrete can improve the chloride binding potential, reducing chloride ingress. Although the chloride binding is expected to be very low during the forced migration test setup, previous research showed that GGBS still reduces the chloride migration coefficient. In Within this section, the service life of concrete structures with 3D printed formwork is studied in relation to the considered concrete cover thickness and curing conditions. Mind that these reported values are subjected to the limitations of the used model and its parameters. Any changes to the input will alter the outcome. Therefore, the reported results should be seen as indicative values.A significant difference in performance can be observed between the different situations. First of all, all printed concrete that was cured in RH > 95% conditions have a significantly higher reliability index than 1.3 after 50 years of exposure. However, this is not the case for the concrete with the same mix composition cured in RH = 60% conditions. In the latter condition, two out of three tested mixtures (M2 and REF) indicate an earlier depassivation than the anticipated 50 years. According to the results, the service life of REF and M2 designed according to Eurocode 2 is reduced to respectively 5 and 23 years. Therefore, the concrete cover described as 45 mm is not sufficient. Additionally, the reliability index of M1 after 50 years increases from 1.69 to 3.41 when changing the curing condition from RH = 60% to RH > 95%. In the case of REF and M2, the reliability index increases respectively from −0.04 to 6.48 and from 0.80 to 5.86. This indicates that the effect of different curing conditions is highly mixture-dependent. Nevertheless, all of the tested mixtures indicate an increased reliability index, indicating a prolonged service life when properly cured (RH > 95). To meet the requirement of a service life of 50 years, the cover thickness could be adapted. The results for the tested concrete mixtures can be seen in 50 years = 7.09). Printing the concrete and curing it properly results in a reliability index after 50 years of 5.44. However, by adding side trowels to the nozzle, an improvement can be made, which increases the reliability index to a value closer to the one of cast concrete (β50 years = 6.53). As the resulting reliability index values are high, a reduction of the formwork thickness can be made see . In the Nevertheless, the increase in reliability index by curing the concrete properly is lower for chloride-induced corrosion than for carbonation-induced corrosion. This can be seen in 50 years = 3.06), as shown in 50 years = 2.87). Nevertheless, taking the thickness of the printed layer equal to the concrete cover described in Eurocode 2, a service life of 50 years could be obtained for the structure regardless of the fabrication method. Similar to the carbonation resistance, casting can be seen as the best production method for the formwork  printed formwork was suitable when designed according to Eurocode 2, whereas improperly cured (RH = 60%) printed formwork was rarely applicable. Therefore, special measurements have to be taken during construction to ensure proper curing in a way that the required service life is obtained.In this paper, the applicability of 3D printed concrete as formwork material was evaluated. Based on experimental and numerical evaluation, the following conclusions can be drawn:


In order to achieve effective monitoring of concrete structures for sound structural health, the addition of carbon nanotubes (CNTs) into cementitious materials offers a promising solution for fabricating CNT-modified smart concrete with self-sensing ability. This study investigated the influences of CNT dispersion method, water/cement (W/C) ratio, and concrete constituents on the piezoelectric properties of CNT-modified cementitious materials. Three CNT dispersion methods  and carboxymethyl cellulose (CMC) surface treatment), three W/C ratios , and three concrete constituent compositions  were considered. The experimental results showed that CNT-modified cementitious materials with CMC surface treatment had valid and consistent piezoelectric responses to external loading. The piezoelectric sensitivity improved significantly with increased W/C ratio and reduced progressively with the addition of sand and coarse aggregates. As the most widely used construction material, concrete has taken our civilization forwards for centuries. However, concrete structures may be subjected to various environmental threats including erosion, impact forces, and harsh weather conditions. Excessive exposure to such adverse environmental conditions could induce cracking and delamination of concrete, leading to potential long-term safety concerns. Thus, close monitoring of concrete structures in these environments is needed to prevent catastrophic failure ,2.The most popular methods to inspect of concrete damage and deformations include visual inspection and the usage of attached or embedded sensors ,4,5. AltSmart materials  are intelligent systems with advanced properties such as shape memory or self-sensing ,10. SmarAmong the various different types of functional fillers, carbon nanotubes (CNT) are recognized as one of the promising functional fillers that enable cementitious materials to achieve self-sensing properties ,18,19. TPrevious studies showed that achieving satisfactory sensing properties in CNT-modified smart concrete is highly dependent on the proper dispersion of CNTs in the cementitious matrix. In other words, CNTs need to be well-dispersed in a cement matrix to form an extensive conductive network inside the concrete to achieve consistent sensing properties . HoweverIn addition to the effectiveness of dispersion, a good self-sensing property of smart concrete is also influenced by a variety of other factors such as the water/cement ratio and concrete constituents. The water/cement (W/C) ratio, a universally influential factor for most of the properties of cementitious materials, can change the deformation capacity of CNT-modified cementitious materials and CNT dispersion in the cement-based matrix ,33. HighIn this paper, the influences of the dispersion method, W/C ratio, and concrete constituents on the piezoelectric response of CNT-modified smart concrete are systematically investigated. Three different dispersion methods , three W/C ratios , and three concrete constituent compositions  were considered and experimentally tested. This paper will add to the fundamental understanding of CNT-modified smart cementitious materials with piezoelectric behavior for the purpose of self-sensing applications.3(CH2)11OSO3Na. The molecular weight of the CMC used was around 90,000 g/mol and its chemical formula was CH3(CH2)11C6H4SO3Na. The matrix material and aggregates were purchased from The Quikrete Companies, Atlanta, GA, USA. The matrix material was Type 1 Portland cement which met ASTM C387 for compressive strength requirements. In accordance with the ASTM C33 standard, all-purpose sand with a diameter range from 0.3 mm to 2.36 mm was used as the fine aggregate, and gravels with an approximate diameter of 9 mm were applied as the coarse aggregate. Due to the fact that this study focuses on the investigation of piezoelectric properties of cementitious materials, no superplasticizer additives were applied in this study to avoid additional influencing factors and potential interaction among the plasticizers, surfactants and CNTs.Since previous research showed that the multi-walled CNTs (MWCNTs) have superior electrical conductivity compared with the single-walled CNTs, the multi-walled CNTs  were adopted as the functional fillers in cement. The detailed specifications of the CNTs are listed in CNT-modified smart cementitious materials were prepared using three different dispersing methods, including mechanical stirring, and surface treatments using NaDDBS and CMC. Regarding the mechanical stirring, the direct mixing method was adopted in this study due to its low cost and ease of application ,40. The −2 mol/L  was set as the input surfactant concentration [For the NaDDBS surface treatment, a critical micelle concentration of NaDDBS in water of 1.4 × 10ntration . First, ntration  with NaDRegarding the CMC surface treatment method, a previous investigation by the authors determined that 0.5% CMC was the optimal percentage to ensure piezoelectric sensitivity of cement paste. Thus, 1.2 g of dry CMC was gently added into 120 mL of water, since CMC tends to clump in water owing to its high-water absorption and retention. The CMC solution was mixed on a magnetism stirrer for up to 30 min until the CMC was free of clumps and completely dissolved into the water. After mixing with 0.2 g of CNTs, the CMC/CNT solution was transferred to a 50 mL test tube and placed on a tube rotator for at least 72 h to ensure a proper coating of CMC on the CNTs. Then, 400 g of cement was added into the solution. The key dispersion procedures of NaDDBS and CMC surface treatments are shown in In addition, to investigate the influence of concrete constituents, three cementitious composites were studied including pure cement paste, cement mortar, and concrete with cement, sand, and coarse aggregate. To prepare the cement mortar, 400 g of sand was added into 200 g of the cement pastes which were prepared in the last section, yielding a 1:2 design mix ratio of cement and sand. To prepare the concrete with cement, sand, and coarse aggregate, the well-prepared cement paste was mixed with 400 g of sand plus 600 g of coarse aggregate by hand using a trowel, resulting in a 1:2:3 design mix ratio of cement, sand, and coarse aggregates. After all the materials were thoroughly mixed, the pastes were placed into molds to make concrete cubes. The edge length of a concrete cube was 50.8 mm, as shown in 6) corresponding to the applied loading. The frequency of the loading was set to 0.1 Hz. All the samples were tested at room temperature.The prepared samples were assessed under dynamic loads to assess their piezoelectric sensing capacity. Many previous studies investigating piezoelectric properties of CNT-modified smart cementitious materials used pure cement as the matrix material ,41,42. FThe NaDDBS surface treatment method has been proved effective in modifying CNT dispersion in cement to achieve a piezoelectric effect ,43. FiguThe results above are a preliminary indication of the effectiveness of different dispersion methods. In order to further illustrate the influence of dispersion methods on the piezoelectric properties of CNT-modified cementitious materials, comparisons were made among CNT-modified cementitious materials with same testing conditions except the dispersion method. According to the previous discussion, CNT-modified smart cementitious materials with dispersion methods using direct mixing or NaDDBS surface treatment failed to exhibit significant piezoelectricity. Therefore, the discussions regarding W/C ratios and concrete constituents were based on CNT-modified smart cementitious materials with the CMC surface treatment method only. A similar tendency was also found for the cement mortar samples. The comparison between three different dispersion methods showed that the CNT-modified cementitious materials with CMC surface treatment showed functional and significant piezoelectric responses with better consistency, whereas direct mixing and NaDDBS surface treatment failed to exhibit an obvious piezoelectricity in CNT-modified cementitious materials.With the increase in the W/C cement ratio, the piezoelectric sensitivities of both CNT-modified cementitious materials with and without sand addition were improved significantly, which was consistent with previous research findings. Specifically, this study found that by increasing the W/C ratio from 0.4 to 0.6, the piezoelectric responses can potentially increase by more than eight times.Adding aggregates significantly reduced the piezoelectric sensitivities of CNT-modified cementitious materials. Especially, for CNT-modified smart concrete with both fine and coarse aggregates, the sensing ability could decline to 78% of that of pure cement. When fabricating CNT-modified smart concrete, the influences of aggregates should be considered.This study investigated the influences of CNT dispersion methods, the W/C ratio, and concrete constituents on the piezoelectric sensing ability of CNT-modified smart cementitious materials. The following conclusions can be drawn based on the findings from this study:The conclusions of this paper confirm the importance of aggregates on the piezoelectric properties and self-sensing performance of CNT-modified cementitious materials. Even with optimized dispersion method and W/C ratios, CNT-modified concrete with sand and coarse aggregates ended up with a rather weak piezoelectric sensitivity. Thus, improving the piezoelectric sensitivity of CNT-modified concrete still needs further investigation.


TLR4 gene and the immunological profile of household contacts (HHC) of leprosy patients. Leprosy classification is usually complex and requires the assessment of several clinical and laboratorial features.The aim of the present study was to investigate the association between the single nucleotide polymorphism (SNP) rs1927914 A/G in TLR4SNP.Herein, we have applied distinct models of descriptive analysis to explore qualitative/quantitative changes in chemokine and cytokine production in HHC further categorized according to operational classification [HHC(PB) and HHC(MB)] and according to M. leprae stimuli induced an outstanding production of chemokines  by HHC(PB), while increase levels of pro-inflammatory cytokines  were observed for HHC(MB). Moreover, the analysis of chemokine and cytokine signatures demonstrated that A allele was associated with a prominent soluble mediator secretion . Data analysis according to TLR4 SNP genotypes further demonstrated that AA and AG were associated with a more prominent secretion of soluble mediators as compared to GG, supporting the clustering of AA and AG genotypes into dominant genetic model. CXCL8, IL-6, TNF and IL-17 displayed distinct profiles in HHC(PB) vs HHC(MB) or AA+AG vs GG genotype. In general, chemokine/cytokine networks analysis showed an overall profile of AA+GA-selective (CXCL9–CXCL10) and GG-selective (CXCL10–IL-6) axis regardless of the operational classification. However, mirrored inverted CCL2–IL-10 axis and a (IFN-γ–IL-2)-selective axis were identified in HHC(MB). CXCL8 presented outstanding performance to classify AA+AG from GG genotypes and HHC(PB) from HHC(MB). TNF and IL-17 presented elevated accuracy to classify AA+AG from GG genotypes and HHC(PB) (low levels) from HHC(MB) (high levels), respectively. Our results highlighted that both factors: i) differential exposure to M. leprae and ii) TLR4 rs1927914 genetic background impact the immune response of HHC. Our main results reinforce the relevance of integrated studies of immunological and genetic biomarkers that may have implications to improve the classification and monitoring of HHC in future studies.Our results showed that  Mycobacterium leprae infection that affects the skin, peripheral nerves and nasal mucosa presenting a wide range of clinical manifestations  from HHC categorized based on operational classification (PB and MB) and the qualitative and/or quantitative changes in their levels evaluated according to TLR4 rs1927914 polymorphism.The present study intended to investigate the association between TLR4 SNP and the immunological profile of household contacts (HHC) of leprosy patients. For this purpose, chemokines and cytokines were measured in the supernatant of This is a cross-sectional investigation carried out in Governador Valadares, Minas Gerais State, Brazil, a hyperendemic area for leprosy  . A totalThe inclusion of participants was based on convenience sampling using a non-probabilistic approach. There was no pattern in selecting the participants. The household contacts invited to participate in the present investigation, comprised leprosy patient companions contacted at the outpatient unit Reference Center for Endemic Diseases and Special Programs (CREDEN-PES) at the Department of Public Health of Governador Valadares municipality, MG, Brazil.The study was submitted and approved by the Ethics Committee from Universidade Federal de Juiz de Fora – UFJF (Research Protocol CAAE #56863016.6.1001.5147). All participants have read and signed the informed consent form before the inclusion in the study.in vitro cultures. PBMC were isolated by Ficoll Hypaque cushion gradient, washed twice and resuspended in RPMI-1640, supplemented with 10% fetal bovine serum, 2mM L-glutamine, penicillin (100U/mL) and streptomycin (100μg/mL). Cells (2x105/well) were cultured in duplicates on flat-bottom 96-well plates, at 37°C, 5% of CO2 in humidified incubator. Parallel batches of cultures were carried out in the absence of exogenous stimuli (unstimulated culture) and in the presence of 10 irradiation-killed M. leprae bacilli/cell (M. leprae-stimulated culture). The M. leprae bacilli were kindly provided by the Leprosy Laboratory at FIOCRUZ-RJ and Instituto Lauro de Souza Lima - ILSL/SP, obtained as previously described by Heparinized whole blood samples (10mL) were collected from each participant and used to obtain peripheral blood mononuclear cells (PBMC) for chemokine and cytokine quantification in supernatant from rmTM Bioanalyzer . Data analysis was performed using the FCAP Array multiplex assay analysis software .Quantitative analysis of chemokines and cytokines was performed by Cytometric Bead Array  purchased from BD Bioscience, Pharmingen,  as recommended by the manufacturer. A total of 400 events/chemokine or cytokine-specific beads were acquired on a FACSVerse® blood genomic Prep Mini Spin Kit  was used to extract DNA from the 250µL of whole blood samples from a subgroup of household contacts of leprosy patients  and genotyping of SNP rs1927914 A/G in TLR4 gene by the allelic discrimination using a validated predesigned Taqman® quantitative Polymerase Chain Reaction (qPCR) from Life Technologies® . The assays were performed according to the manufacturer’s instructions and employed the 7500 Fast Real-Time PCR (Applied Biosystems®) system platform and the ABI software v 2.0.6 for data analysis.The Illustrat or Mann-Whitney tests were employed for pairwise comparisons between HHC(PB) vs HHC(MB).Conventional statistical analysis of chemokines and cytokines were carried out using the Prism GraphPad software . Student M. leprae-stimulated culture . Following, the proportion of subjects (%) with chemokine and cytokine levels above the intrinsic cut-off were calculated for each study subgroups. The chemokines and cytokines with proportion of subjects above the 50th percentile were underscored and considered with increased levels.Additional descriptive analysis of biomarker signatures was carried out as previously reported by Marçal et al. , modifieTLR4 rs1927914 was carried out to check for deviation from Hardy–Weinberg equilibrium (HWE) using the online calculator, available at https://gene-calc.pl/. Comparative analysis between A vs G alleles was performed by Student t or Mann-Whitney tests. ANOVA variance analysis followed by Tukey or Kruskal-Wallis with Dunn’s post-test was used for multiple comparisons amongst HHC(PB) and HHC(MB) subgroups according to TLR4 rs1927914 genotypes as well for dominant genetic model (AA+AG vs GG). In all cases, significant differences were considered at p< 0.05.The analysis of genotype data for the SNP https://cytoscape.org) was employed to construct the circular layout networks, with nodes representing the chemokines and cytokines. Connecting edges illustrate positive (continuous lines) and negative (dashed lines) strong correlations (“r” scores ≥ |0.67|) between pairs of attributes.Assessment of integrative chemokine and cytokine networks were assembled using only significant “r” scores at p<0.05 obtained from Pearson and Spearman correlation analysis. The Cytoscape software platform  was used for performance analysis. The Area Under the ROC Curve (AUC) was used as an indicator of global accuracy. Significance was considered at p<0.05. The cut-offs provided by the ROC curve analysis were used to assess the performance indices, including sensitivity (Se), specificity (Sp), and likelihood ratio (LR).The analysis of Receiver-operating Characteristic Curves (ROC) was carried out for evaluating the accuracy of chemokines and cytokine measurements to classify HHC into categories, according to operational classification and SNP th, 50th and 75th) was used to identify clusters of subjects with distinct (low or high) levels of chemokines and cytokines in each subgroup of household contacts of leprosy patients.Exploratory heatmap constructs were assembled using conditional formatting in Microsoft Excel Office version 2016. The analysis was performed using customized functions, considering the column Row Z-score, scaled from -2.5 to +5.0. A color key (25in vitro culture of PBMC from HHC(PB) and HHC(MB) and the results shown in the M. leprae-stimulated culture, higher levels of CXCL8, CCL2, CXCL9 and CXCL10 were observed in HHC(PB) as compared to HHC(MB). Conversely, higher levels of pro-inflammatory cytokines  were detected in the supernatant of PBMC cultures from HHC(MB) as compared to HHC(PB)  and cytokines  were measured in the supernatant collected upon in vitro culture of PBMC from HHC(PB) and HHC(MB) were further reported as biomarker signatures. The results are shown in M. leprae-stimulated cultures  along with increased levels of IL-10 were observed for HHC(PB), increased levels of pro-inflammatory cytokines  besides higher levels of CCL5 were detected for HHC(MB)  and HHC(MB) populations displayed HWE. The distribution of allelic  and genotypic frequency  did not show significant differences between HHC(PB) and HHC(MB). Moreover, the distribution of frequency of carriers of A allele  or the GG major homozygous genotypes  did not differ between HHC(PB) and HHC(MB) Figure 3TLR4 rs1927914 and the pattern of immune response, the levels of chemokines and cytokines were measured in the supernatant collected upon in vitro culture of PBMC from HHC(PB) and HHC(MB). The groups were then categorized as: carriers of A and G alleles as well as AA, AG and GG genotypes. The results are presented in M. leprae-stimulated cultures (Aiming at verifying the association between the SNP in vitro culture of PBMC from HHC(PB) and HHC(MB) were further reported as biomarker signatures according to the TLR4 rs1927914 alleles/genotype. The results are shown in M. leprae-stimulated cultures.The levels of chemokines and cytokines measured in the supernatant collected upon M. leprae antigen recall in vitro, it is evident that while the A allele exhibited a more prominent secretion of CXCL8, CXCL9, IL-6, TNF and IFN-γ, the G allele presented only increased levels of IL-6  and AG  genotypes were associated with a more prominent secretion of chemokines and cytokines in both culture conditions  and HHC(MB) were compared considering the dominant genetic model (AA+AG vs GG). The results are presented in M. leprae-stimulated cultures, lower CXCL8 and higher IL-6 and IL-17 were observed in HHC(MB) with AA+AG genotypes as compared to HHC(PB) with the same genotype. Additionally, higher TNF and lower IL-17 were observed in HHC(PB) with GG genotype as compared with HHC(MB) with the same genotype  with GG genotype as compared to HHC(MB) with AA+AG genotypes, demonstrating that TLR4 rs1927914 and the operational classification of household contacts, integrative biomarker networks were assembled considering the “r” scores of significant correlations between chemokines and cytokines. The data are shown in M. leprae exposure and TLR4 rs1927914 genotypes. In this sense, TLR4 rs1927914-associated patterns, referred as AA+GA-selective (CXCL9 – CXCL10) and GG-selective (CXCL10 – IL-6) axis were identified. Conversely, connectivity patterns associated with distinct M. leprae exposure profiles were also observed, as demonstrated by the mirrored inverted CCL2 – IL-10 axis displaying positive correlation (↗) in HHC(PB) and negative correlation (↘) in HHC(MB). Besides, an HHC(MB)-selected axis (IFN-γ – IL-2) was also detected  and HHC(MB) categorized according to the TLR4 rs1927914 dominant genetic model. For this purpose, Receiver-operating Characteristic Curves (ROC) were assembled and the Area Under the Curve (AUC) was used as an indicator of global accuracy  and HHC(MB) with elevated global accuracy . Moreover, IL-17 was able to classify household contact with GG genotypes according to the M. leprae exposure into HHC(PB) and HHC(MB) with excellent global accuracy (AUC=1.00)  and HHC(MB)] and the SNP M. leprae-stimuli induced higher levels of chemokines  in HHC(PB) as compared to HHC(MB). Conversely, higher levels of pro-inflammatory cytokines  were detected in HHC(MB). The analysis of chemokine and cytokine signatures further corroborate these findings, showing that M. leprae-stimuli triggered higher levels of chemokines  in HHC(PB), while increased levels of pro-inflammatory cytokines  were detected for HHC(MB). The enhancement of pro-inflammatory cytokines in HHC(MB) has been already reported in previous studies from our group . Data analysis according to TLR4 SNP genotypes further demonstrated AA  and AG  genotypes were associated with a more prominent secretion of soluble mediators as compared to GG that was associated with lower levels CXCL8, CXCL9, TNF and IFN-γ. These data supported the clustering of AA and AG genotypes into dominant genetic model. Using this dominant genetic model, we have assessed the simultaneous impact of TLR4 rs1927914 polymorphism and the HHC operational classification on the overall chemokine and cytokine profiles. Data from M. leprae-stimulated cultures demonstrated that both: i) differential M. leprae exposure and ii) TLR4 rs1927914 genotypic background have an impact on the immune response of HHC. Lower levels CXCL8 and higher levels of IL-6 and IL-17 were observed in HHC(MB) with AA+AG genotypes. Conversely, higher TNF and lower IL-17 were observed in HHC(PB) with GG genotype.The analysis of chemokine and cytokine signatures further demonstrated that HHC bearing the A allele of TLR4 rs1927914. Overall, our findings showed that the resistance-associated genotype (GG) presented an inflammatory axis CXCL10 – IL-6 while the susceptibility-associated dominant genetic model (AA+AG) presented an inflammatory axis CXCL9 – CXCL10. According to Geluk et al.  was associated with an IL-10 modulated axis (↗CCL2 – IL-10), while higher exposure to M. leprae exemplified by HHC(MB) did not exhibit a modulatory axis (↘CCL2 – IL-10) and also presented a (IFN-γ –IL-2)-selective axis. It has been shown that CCL2 in association with IFN-γ is a relevant biomarker of subclinical infection of HHC, as also a parameter for early infection monitoring (Our data demonstrated that lower exposure to nitoring .TLR4 rs1927914 genotypic background. Our results demonstrated that CXCL8 presented an outstanding performance to classify AA+AG (high levels) from GG (low levels) genotypes in both HHC subgroups. Moreover, amongst AA+AG, CXCL8 was able to cluster HHC(PB) (high levels) from HHC(MB) (low levels). CXCL8 has been pointed out as a potent pro-inflammatory chemokine playing a role in M. leprae infection (M. leprae HHC(PB) presented higher levels of CXCL8. These apparently controversial results, in fact, demonstrated the relevance of carrying out integrated studies of immunological and genetic biomarkers to classify and monitor HHC. Indeed, our results demonstrated that HHC(MB) further classified according to the dominant genetic model (AA+AG) presented lower levels of CXCL8. Ultimately, this finding illustrates the impact of differential M. leprae exposure over the TLR4 rs1927914 genotypic background.Intending to transpose the laboratorial findings into clinical applied biomarkers, translational analysis was carried out to determine the performance of chemokines and cytokines to classify HHC according to SNP nfection . Our finThe results showed that TNF has elevated accuracy to classify HHC(MB) into AA+AG (high levels) from GG (low levels) genotype. Previous studies of our group demonstrated that TNF was able to classify HHC according to the operational classification with HHC(MB) presenting low levels as compared to HHC(PB) . This apTLR4 rs1927914 genotypic background. It is notably the presence of an important IL-17-mediated inflammatory response in the HHC(MB) group regardless of the TLR4 rs1927914 genotype. The role of IL-17 in leprosy is still controversial. While some studies demonstrate low levels of IL-17 in serum and in situ, other reports showed increased levels of IL-17 in leprosy lesions  (high levels) from HHC(PB) (low levels) regardless of the SNP  lesions , 46. Stu lesions , the levOverall, our data support the relevance of investigating the immune response together with genetic profile as potential biomarkers to monitor household contacts. It is important to mention that the present study has some limitations. The small sample size that could reduce the statistical power of our findings requires further investigations with a higher number of subjects. Moreover, the use of multiple comparisons without corrections for confounding variables such as the bacilloscopic index may also impact the conclusions. The study may present a degree of bias, since the participants were selected as a non-probabilistic sampling and therefore, further studies are required to validate these findings prior transposing them as a general statement to a populational basis. Moreover, the observational design must be further validated by longitudinal follow-up of HHC subjects to monitor the development of leprosy disease. Furthermore, simultaneous investigations of household contacts and matching index cases should be considered.M. leprae exposure. The observation that the degree of M. leprae exposure over impacts the TLR genotypic background and vice versa, reinforces that an interplay between these biomarkers should be considered while monitoring HHC. Thus, the integration of immunological and molecular methods to follow-up the development of subclinical infection in HHC is strongly recommended.In conclusion, the present study demonstrated that CXCL8 and IL-17 are relevant biomarkers to monitor HHC. While CXCL8 presented a profile closely related to the genetic background, IL-17 appears as an important hallmark of high The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.The studies involving human participants were reviewed and approved by Ethics Committee from Universidade Federal de Juiz de Fora – UFJF (Research Protocol CAAE #56863016.6.1001.5147). Written informed consent to participate in this study was provided by the participants’ legal guardian/next of kin.Study Design: PHFM, JKF and LAOF Funding Acquisition: JKF, ROP, ENS and LAOF. Sample collection, experimental procedures and data acquisition: EHMC, RSG, LBOP, MLS, TNSV and CVR Data Analysis: EHMC, PHFM, JPBS, MLS, CVR, OAMF and LAOF. Writing and reviewing the manuscript: EHMC, PHFM, CVR, OAMF and LAOF. All of the authors read and approved the manuscript.


Modern infrastructure heavily relies on robust concrete structures, underscoring the critical need for effective monitoring to ensure their safety and durability. This paper addresses this imperative issue by introducing an innovative automated and wireless system for continuous structural monitoring. By employing embedded electrical resistivity sensors coupled with a wireless-based data transmission mechanism, real-time data collection becomes feasible. We provide a general description of the system’s architecture and its application in a pilot study covering the effects of the devices on concrete properties and data transmission. The dielectric properties of concrete specimens were investigated under natural and accelerated curing/degradation and the results were used in the final design of the antenna device. Furthermore, a pilot test comprising four reinforced concrete columns was used to investigate the range of data transmission from inside to outside of the concrete, the effects of the hardware device on the compressive strength and concrete distribution in the columns, and the data transmission quality in real time under realistic exposure conditions. Concrete structures form an essential foundation for modern society, serving as the backbone of various infrastructural developments, including buildings, bridges, highways, and dams. As these structures are subjected to numerous environmental and operational factors, their durability and safety become critical concerns. The early detection of structural degradation and performance issues is imperative to prevent catastrophic failures, ensure public safety, and optimize maintenance efforts. In this context, structural health monitoring (SHM) has emerged as an indispensable tool to assess the integrity and performance of concrete structures ,2,3. To Another very important aspect in monitoring concrete structures is strength development, especially at early ages. Depending on the concrete type, strength development after 3 days can already amount to 40 to 70% of the 28-day strength, which could enable, for example, a faster removal of formworks or advancements in the construction stage. However, real-time monitoring of concrete strength using non-destructive methods is still a big challenge and a major source of uncertainty. In this context, maturity methods for in situ estimation of concrete strength, based solely on temperature, have been widely used ,13,14,15In terms of data collection and transmission during the monitoring of concrete structures, traditional wired monitoring systems have been in use for decades and rely on physical cables to connect sensors to data acquisition units. These wired systems often involve significant installation efforts, especially in existing structures, which can be both time-consuming and expensive . MoreoveWireless communication of antennas within concrete structures poses a unique set of challenges due to the high attenuation and signal loss caused by the dense and absorbent nature of concrete . The proRegarding monitoring techniques, the utilization of electrical resistivity (ER) measurements within concrete emerged in several studies as an indicative measure of moisture content and durability ,24. FurtER measurement with embedded sensors in fresh concrete serves as a gauge for the efficiency of the curing process and serves as an indicator for the long-term durability of concrete. However, existing ER-based sensors in the literature or commercially available ones tend to be costly or limited to single-point measurements in the concrete cover depth . To ensuConsidering all the points mentioned above regarding the needs and challenges for new and more efficient monitoring devices and systems for concrete structure, in this study, we describe a novel, automated, and wireless system for monitoring concrete structures based on embedded electrical resistivity sensors. This solution could be applied to monitor strength development in real time at early ages, and durability aspects such as the progress of carbonation at later ages, overcoming the drawbacks of traditional solutions that in most cases depend on wired connections for data collection and/or transmission , limiting the wireless readout range to only “a couple of meters”), and rely solely on temperature data for maturity and strength prediction. This paper covers a general description of the system’s architecture and its application in a pilot study investigating the effects of the devices on concrete properties and data transmission. The experimental setup consisted of laboratory-scale testing for the determination of dielectric properties of concrete mixtures, which were afterwards used for the construction of a pilot case composed of reinforced concrete columns. The reinforced concrete columns were used to test (1) the effects of the embedded devices on the strength and microstructure of the concrete, (2) the data collection and transmission in the presence of steel reinforcement, and (3) the antenna range under more realistic conditions. In the following subsections, details are given for the concrete mixtures used in the study, as well as the production and testing of specimens. Before detailing the test methods, an overview of the system, from now on named “the COMMODORE solution”, is presented.The concrete resistivity sensor is shown in The sensor was constructed with hard-plated gold electrodes on a PCB substrate. The fabrication technique is in line with standard PCB board manufacturing. Hence, there is potential for cost reduction with mass fabrication. The spacing between the electrode pairs over the concrete cover depth and their respective cell constants are given in The sensor operates at an excitation amplitude of 17 mV and frequency of 3 kHz. At this frequency, the phase angle is 0 degree, and therefore the impedance measurement of the ER can be used as a measure of the resistivity of the concrete. The sensor along with the readout and wireless communication module are enclosed in a compact housing. Initially, the value of 17 mV excitation voltage was chosen to design and calibrate the sensors. This value was carefully chosen for this electrode design so that the resulting current in concrete stayed within the instrumentation limits. The range of current measurement is from 2 nA to 90 µA. Instrumentation details of the measuring electronics are provided in . The desAll the hardware components are protected from the surrounding harsh environment (inside concrete) by a 3D-printed housing. The housing material is polyamide 11 (PA11) and is printed using the SAF (Selective Absorption Fusion) 3D-printing technology. In addition, three lithium AA batteries are placed inside the housing to provide the required power for operation of all the units. The electronics PCB acts as the hub for impedance measurements through the designed sensor board. This function is orchestrated by a Cortex-Arm processor, the central processing unit of this module. By seamlessly integrating with the connectivity module (Quectel BG95-M6), wireless communication capabilities are enabled. This module is based on Low-Power Wide-Area (LPWA) technology, ensuring energy-efficient, long-range wireless connectivity. The PCB includes a SIM card slot that connects to the connectivity module. This combination of the SIM card and connectivity module harnesses the potential of Narrowband Internet of Things (NB-IoT) and LTE Machine-Type (LTE-M) communications, as standardized by 3GPP. NB-IoT emphasizes extended battery life, cost-effectiveness, and high connection density. In contrast, LTE-M offers greater speed, optimizing communication duration.During communication sessions, the Quectel module assesses both NB-IoT and LTE-M networks, automatically selecting the one with superior connectivity. In scenarios where network access is unavailable, measurements are temporarily stored for subsequent transmission. Following each data exchange, the information is securely stored within the Unitron cloud (uCloud), allowing for comprehensive data analysis.As highlighted earlier, the existing literature presents several approaches for transmitting data from nodes to a database. These methods include wired solutions , short-rAs mentioned in the previous section the captured data are transmitted to Unitron cloud (uCloud). Data being sent via either NB-IoT or LTE-M are transferred to the uCloud via the MQTT-SN (Message Queuing Telemetry Transport for Sensor Networks) messaging protocol. The selection of MQTT-SN stems from its adeptness in catering to the intricacies of IoT communications, manifesting in robustness, reliability, data integrity, and the perpetuation of sensor longevity via enhanced battery utilization. Within the framework of MQTT-SN, the devices, referred to as clients, dispatch messages to a central broker. This broker, in turn, receives these messages and disseminates them to designated subscribers. The classification of each message is contingent on its associated topic—an addressing mechanism assigned to each published message. By subscribing to one or more specific topics, the recipients gain access to messages allocated to those topics.Upon arrival at uCloud, the transmitted measurements are meticulously stored and systematically organized within a dedicated database. To interact with this database, a web application serves as the interface. Furthermore, accessibility to the database extends to authorized personnel, who can engage in the processing and analysis of the archived measurements. This analytical exploration lends itself to the refinement and visualization of the stored data, enabling a comprehensive understanding of the information at hand.Two concrete mixtures were used in this study, chosen to be representative of common applications for structural concrete. The mixtures will be here defined as M1 and M2. Details of the mix designs are presented in 2 concentration of 1%) where they remained during the whole monitoring period. Cubes were used to facilitate the measurements and to be able to assess the connectivity given the permittivity of the used concrete. This was to make sure that we achieved the desired range given the design and the used RF technology. The measurement protocol entailed selecting two smooth surfaces on each cube to ensure consistent and stable readings. Three distinct locations were chosen on each surface to account for the inherent heterogeneity of concrete composition. These designated locations were consistently measured at each time point to ensure accurate tracking of permittivity evolution. This procedure was iterated for every concrete type and aging condition under investigation. For each distinct concrete type used in the columns, specimens in the form of cubes with side length of 150 mm were cast and exposed to two different conditions: (1) cubes were molded and placed in a room with controlled atmosphere (temperature of 20 ± 2 °C and relative humidity of 60 ± 5%), demolded after 24 h, and then stored again in the same room during the whole monitoring period of three months; (2) cubes were molded and placed under curing conditions for 28 days  and then transported to a carbonation chamber  of SPEAG  in conjunction with the Rohde & Schwarz ZNB20 vector network analyzer (VNA), see For testing with the embedded wireless sensors, four reinforced concrete columns were built. The columns had dimensions of 320 mm × 320 mm × 820 mm and a concrete covering of 30 mm. Three of them were fabricated with concrete M1 and the fourth column with concrete M2. In each column, two devices were embedded , one forAfter the data collection, the concrete columns produced with concrete M1 were used to further investigate the effects of the sensor device on the concrete properties. Two of them were used to verify the effects of the embedded devices on the compressive strength of the concrete and the third one to verify the influence of the device on the distribution of concrete around the sensor.To test the compressive strength, two cubes with dimensions 320 mm × 320 mm × 320 mm were cut from two of the reinforced concrete columns . The cubTo investigate possible influences of the presence of the housing device on the distribution of concrete inside the column and possible increase in the air content/voids near the devices, a non-destructive and three-dimensional technique such as micro-computed tomography (micro-CT) was required . A cylinThe quantification of the air voids was carried out by separating the reconstructed volume into two regions: region 1, containing the housing device; and region 2, formed by the bulk of the reinforced concrete core. A total of 1520 slices were used for the analysis of region 1, and 1204 for region 2. Firstly, a segmentation of the voids was performed to isolate them from the rest of the core. Afterwards, each void was assigned geometric properties to quantify the total volume per region. Lastly, a distribution of the different sizes of air voids was obtained. This investigation was justified based on preliminary tests that showed a significant influence of the hardware on the distribution of concrete and air voids in the areas surrounding the device when it was embedded in a concrete cube with side length of 150 mm .To verify the quality and robustness of the wireless connection of the presented solution, we monitored the Received Signal Strength Indicator (RSSI) metric of the uplink channel, i.e., of the packages from the sensor nodes to the cell tower, over the course of a month while the nodes were embedded on the rebar in the concrete columns. During this time, the concrete was poured, the concrete dried, and the structure was demolded and moved. This highly variable environment for the node displays the robustness of the communication link. The chip for the communication used is Quectel BG95-M6, using the Proximus network in Ghent, Belgium. The observation that the parameters of concrete are constant over time has the consequence that the communication link will not be influenced by the concrete life cycle, by which we mean that the variation in the communication link will not originate from the variation in the concrete parameters, as these are constant. This will ease the robustness requirement during the antenna design. The dielectric parameters will have a large impact due to the dielectric loading of the environment on the antenna. These being constant over time facilitates the design, which is used during the evaluation of The designed antenna will be discussed in detail in a follow-up paper. Ma model ). The robustness of the communication link is measured as follows. The node tries to send a package every hour. When a package is not received, the node will try to resend the package. Due to the time it takes to resend the package, the time between each package will determine the number of retransmissions (ignoring the drift in the RTS clock of the device). In the case of mixture M1, an initial impedance of 372 Ohms was observed upon concrete pouring. Over a span of 30 h, this value gradually escalated to 639 Ohms. Subsequently, within one day, a peak value of 120 kOhms manifested—a peak intricately linked to sudden shifts in the internal concrete temperature following cement hydration. These temperature fluctuations saw a rise from 21.7 °C to 39.9 °C. A few hours later, the temperature decreased to 24.6 °C and consequently so did the impedance. Following this thermal upheaval, there was a swift decline in temperature to 24.6 °C, mirrored by a corresponding dip in impedance. Nonetheless, the impedance continued increasing due to the ongoing concrete-hardening process. Notably, the undulations in the impedance curve concurred with the oscillations in temperature. After the passage of 28 days, M1 exhibited an impedance of 126 kOhms.As for column M2, the initial impedance measured during concrete pouring stood at 570 Ohms. In a manner akin to M1, a temperature surge from 23 °C to 31.1 °C prompted a corresponding 2853 Ohms rise in impedance. Despite subsequent temperature diminution to 25.7 °C, the measured impedance reached 17 kOhms 46 h after the mixture was poured. Evidently, the fluctuations in the resistivity curve mirrored the temperature variations with remarkable fidelity. Upon the culmination of 28 days, the impedance reached 221 kOhms. Comparatively, M2 displayed a more rapid rate of impedance increase than M1. Impressively, after a span of 83 days, M2′s impedance surpassed that of M1 by a factor of 6, which can be linked to the different dynamics of the cement hydration reaction given that M2 was produced with a blended cement type, in which a secondary chemical reaction (the pozzolanic reaction) is expected to take place at later ages, contributing to a densification of the matrix and further strength development. After a duration of 83 days, both devices remained operational without any reported issues for the batteries or in data transmission. This serves as a testament to the robustness and dependability of the wireless communication system in use, regardless of the presence of steel reinforcement and cement types. In addition, after 83 days, the batteries were still at their highest capacity, meaning that the current consumption of the nodes in the long term has been stable.2 .In terms of compressive strength, the cubes extracted from the concrete column in the region without the devices presented an average value of 49 MPa at the age of 99 days. In contrast, the average strength of the cubes containing the two devices was 43 MPa. This represents a reduction of 12% in the compressive strength value due to the presence of the device. However, regarding ordinary applications, this reduction could be considered acceptable. In addition, the configuration of the columns with the devices as presented here also amplifies the negative effects of the devices on the strength, given that in a cross-sectional area of 320 mm × 320 mm (referring to the tested cube), the devices occupy together an area of 12,480 mmAs for the distribution/content of air/voids, it is possible to observe that there is no change in the concrete matrix nor accumulation of air voids in the surrounding areas of the housing device. In The total volume of air voids was quantified to compare both regions. The image analysis workflow see  using AvIn 7 µm3 on R2 and, therefore, it is not considered that a significant difference exists between both regions due to the presence of the housing device. Finally, a histogram per region is displayed on The permittivity of concrete does not change during its lifetime after it has dried out, not even under accelerated degradation conditions (accelerated carbonation). Thus, the communication link will not be influenced by the concrete life cycle, which will reduce the robustness requirement during the antenna design stage.There was no interference of the reinforcement steel bars on the in-to-out transmission of concrete antenna communication and a long-range communication link from in-to-out concrete to an LTE cell tower was achieved. Thus, wireless communication will not limit the use of this system for any concrete application. The sensors and whole hardware device performed in a stable and reliable way during data collection and transmission in the pilot study for the two cement types used under realistic conditions, which means that the system could be used for many applications within the concrete industry .The presence of the hardware device did not promote a poor distribution of the concrete in the areas close to the sensor, and no increased air void or poor adherence between the concrete and the device were found. This proves that the use of the system will not significantly interfere with the properties of the concrete structure.In this paper, we investigate the feasibility and working mechanisms of a novel solution for monitoring concrete structures based on a wireless electrical resistivity sensor. As an alternative to current commercial solutions, this system has the added features of large-range wireless data transmission and simultaneous recording of electrical resistivity on different depths of the concrete cover. The research covered the determination of the dielectric properties of concrete under semi-realistic curing conditions as well as accelerated degradation conditions, the data transmission and antenna range in the wireless communication of the sensor device embedded in real structures, and the effects of the hardware on properties of the concrete such as compressive strength and distribution of concrete/presence of air voids in the proximity of the devices. In summary, the following conclusions could be drawn from the study:


The use of WGP enhanced the CS of cement mortar, as noted from the experimental results. Maximum CS was attained by substituting 10% WGP for cement and 15% WGP for sand. The findings of the modeling techniques demonstrated that the decision tree had a reasonable level of accuracy, while the AdaBoost predicted the CS of WGP-based cement mortar with a higher level of accuracy. Utilizing ML approaches will benefit the construction industry by providing efficient and economic approaches for assessing the properties of materials.This study utilized both experimental testing and machine learning (ML) strategies to assess the effectiveness of waste glass powder (WGP) on the compressive strength (CS) of cement mortar. The cement-to-sand ratio was kept 1:1 with a water-to-cement ratio of 0.25. The superplasticizer content was 4% by cement mass, and the proportion of silica fume was 15%, 20%, and 25% by cement mass in three different mixes. WGP was added to cement mortar at replacement contents from 0 to 15% for sand and cement with a 2.5% increment. Initially, using an experimental method, the CS of WGP-based cement mortar at the age of 28 days was calculated. The obtained data were then used to forecast the CS using ML techniques. For CS estimation, two ML approaches, namely decision tree and AdaBoost, were applied. The ML model's performance was assessed by calculating the coefficient of determination (R


Routine usage of antibiotics for animal health is a key driver of antimicrobial resistance (AMR) in food-producing animals. Taxation is a possible approach to incentivise appropriate antibiotic usage in food-producing animals. Taxation can be applied flatly across all antibiotic classes, targeted to single antibiotic classes, or scaled based on resistance in each class, so called “differential” taxation. However, quantifying the potential impact of taxation is challenging, due to the nonlinear and unintuitive response of AMR dynamics to interventions and changes in antibiotic usage caused by alterations in price. We combine epidemiological models with price elasticities of demand for veterinary antibiotics, to compare the potential benefits of taxation schemes with currently implemented bans on antibiotic usage.Taxation strategies had effects comparable to bans on antibiotic usage in food-producing animals to reduce average resistance prevalence and prevent increases in overall infection. Taxation could also maximise the average number of antibiotics with a resistance prevalence of under 25% and potentially generate annual global revenues of ∼1 billion US$ under a 50% taxation to current prices of food-producing animal antibiotics. Differential taxation was also able to maintain a high availability of antibiotics over time compared to single and flat taxation strategies, while also having the lowest rates of intervention failure and highest potential revenue across all taxation strategies. These findings suggest that taxation should be further explored as a tool to combat the ongoing AMR crisis. •Taxation can be as effective as bans on antibiotic usage in food-producing animals to reduce antimicrobial resistance.•Taxation can generate ∼1 billion USD under a 50% increase in antibiotic price for food-producing animals.•Economic interventions should be explored as a viable alternative to current bans on antibiotic usage in food-producing animals. In partEnterococcus spp. in broiler chickens and cattle. [Interventions to target antimicrobial usage include bans or regulations on the prophylactic usage of antibiotics in agriculture. Such interventions were initiated in the EU in the 1990s, and with current WHO guidelines recommending the restriction of antimicrobials in growth promotion roles . Bans on cattle. ,11,12.Market based instruments (MBIs) are an alternative to bans on antibiotic usage and include interventions such as taxation. MBIs have the benefit of allowing flexible compliance compared to bans, reducing the selective pressure for AMR by disincentivising usage, and generating income . To dateUnderstanding and quantifying the impact of interventions, such as taxation, is complex due to the unintuitive nature of AMR dynamics . HoweverIn this work, synthetic price elasticities of demand are combined with an epidemiological model. We compare the effectiveness of different taxation strategies on the altering the price and usage of antibiotics, and subsequently on the prevalence of AMR, the number of overall infections caused by both drug-sensitive and resistant pathogens, and the maintenance of a portfolio of available antibiotics under a 25% resistance threshold. We explore multiple taxation strategies: flat taxation applied uniformly across all antibiotic classes, targeting single antibiotic classes and scaling taxation for each antibiotic class proportional to their relative level of resistance in food-producing animals . The effectiveness of taxation is compared with bans on usage of specific classes of antibiotics.22.11, R2, R3), two drugs  or three drugs (R123) was modelled using a deterministic model . Fitness costs had the impact of driving heterogeneity in transmission across the three modelled drug resistance classes. Recovery from WT, singly resistant, doubly resistant and triply resistant infections were modelled as rates rWT, rr, rrr, rrrr respectively and were dependent on the extent of antibiotic usage of the three modelled antibiotic classes.The proportion of food-producing animals uninfected (U), infectious with wild-type bacteria (WT), bacteria resistant to one drug . The impact of antibiotic exposure is two-fold: 1) a therapeutic effect resulting in an increased rate of recovery (rt), with probability 1-ρ [wt, ηrr and ηrrr for individuals colonised with singly, doubly or triply resistant strains.Antibiotic usage was described as the proportion of food-producing animals exposed to one of three antibiotic classes (σlity 1-ρ  and 2) a1 + σ2 + σ3), with a lack of antibiotic pressure allowing for fitter WT bacteria to outcompete resistant strains [Treatment failure and generation of resistance was assumed to occur in a stepwise fashion and can be considered analogous to antibiotic usage acting as a selection pressure, allowing for the proliferation of an implicitly assumed, small, non-infectious quantity of resistant bacteria. Reversion from resistance back to WT infection was assumed to only occur in infected food-producing animals not exposed to antibiotics  [1, R2 and R3, and defined as the sum of the population resistant to each antibiotic class (i.e. R1 = R1 + R12 + R13 + R123).The three antibiotic classes were fitted as a baseline scenario using an approximate Bayesian computation sequential Monte-Carlo (ABC-SMC) to ensure high (40%), medium 25%) and low (10%) levels of resistance respectively for the three antibiotics modelled .Taxation was described as % alterations in the price of each antibiotic class, adapting the price elasticity of demand (PED) formula A synthetic demand matrix described the effect of PEDs, with the diagonal and non-diagonal elements representing the own-PED for each antibiotic and cross-PED respectively. The cross-PED can be interpreted as the impact of taxation of antibiotic classes on the usage of other antibiotics. We use a case study assigning first (class 1), second (class 2) and last-line antibiotic (class 3) identities to the three antibiotic classes, with the range of elasticity values obtained from an estimate of the distribution of own price elasticities of demand of veterinary antibiotics  [Antibiotics with “first-line” identities were assumed to have higher elasticities due to the availability of alternative antibiotics, and that the elasticities of successive antibiotic classes decrease due to having fewer alternatives. The cross-PED was higher for antibiotics next in “priority” to the taxed antibiotic (e.g. antibiotic class 1 to 2), with an assumption that veterinarians are more likely to switch to the antibiotic next in therapeutic “importance”.2.4t = 8.22 years or 3000 days): 1) Taxation applied across all antibiotics , 2) single taxation to highest, medium and lowest resistance antibiotic classes (ST) or 3) a differential taxation scheme (DT).Three taxation strategies were modelled, fixed at a baseline rate of 50% (increase in price of 50%) introduced after the prevalence of resistance reaches an endemic equilibrium  relative to the prevalence of resistance in the taxed antibiotic class . As an example, assuming an 0.8, 0.5 and 0.25 resistance prevalence across the three antibiotic classes, changes to the taxation rate would be: 1.6× for class 1 (0.8/0.5), 1× for class 2 (0.5/0.5), and 0.5× for class 3 (0.25/0.5).status quo of antibiotic usage interventions, in highest, medium, or lowest resistance antibiotic classes. Note that all non-differential taxation interventions were constant throughout the intervention period.Taxation strategies were compared against bans on antibiotic usage to identify if similar impacts can be achieved when compared to the 2.5t = 10,000 days or 20 years). The first two criteria were calculated relative to the change in overall antibiotic usage (Eq. 1.2–1.3).To compare the efficacy of the intervention strategies, we considered three criteria relevant to AMR in food-producing animals: 1) maximising decreases to average resistance across all antibiotics, 2) preventing increases to overall infections and animal disease due to a loss in antibiotic pressure (due to changes in usage) and 3) maximising the average number of available antibiotics  over the course of the modelled intervention period (1 + σ2 + σ3 = 1 to 0). These relative criteria also enable direct comparisons between interventions.These relative performance criteria identify “efficient” interventions that have the greatest reductions in AMR for a given change in antibiotic usage . The distribution of effect sizes for each intervention across each criterion was also assessed.This metric was weighted by the probability of intervention failure, defined as an increase of both usage and resistance resulting from the intervention  and production systems .Scenario analyses were conducted to assess the robustness of the model to changes in model assumptions. This included alterations to the baseline taxation rate , cross-elasticity of demand (0.4 or 0.6), varying the entire PED matrix (sampling the cross-PED from 0 to 1 and own-PED from −2 to 0), varying the threshold for an “effective antibiotic” , the number of modelled antibiotics (two or four) and modelling specific food-producing animals  for each taxation strategy, information was combined on: 1) model output on the % increases in price (taxation rate) over the 20-year intervention period for each intervention, and 2) the yearly market value of different antibiotic classes in food-producing animals.Supplementary Material. Antibiotic price data from the US and China were used as proxies to represent high-income countries (HICs) and low/middle-income countries (LMICs) respectively. Pricing data was identified from online retailers and harmonised to US Dollars (US$) using a conversion rate from Chinese Yuan  [To generate an estimate for the yearly market value of veterinary antibiotics, information on the sales and price of different antibiotic classes in food-producing animals was combined for each country globally. Details of the included antibiotic classes can be found in the aterial) ,28. The aterial) ,30. Thisaterial) .Salmonella spp. and Campylobacter spp. was obtained from the 2021 NARMS report (US) and resistancebank.org (China) [Supplementary Material).Elasticity values were next assigned to each antibiotic class based on their respective level of resistance, classifying antibiotics as one of the three antibiotics modelled  in the synthetic PED matrix (eq. 1.1). Prevalence data on resistance for each antibiotic class in  (China) ,33. High33.11 + σ2 + σ3 = 1) to no usage (σ1 + σ2 + σ3 = 0), would result in a median reduction of the proportion of resistant infections in food-producing animals ranging between 0.26  to 0.37   A across 5, 1.17) B. Additi5, 1.17) C. The exHowever, bans (HR and MR) on antibiotic usage were identified as the “best” performing intervention according to the performance metric to minimise average resistance , minimise increases in overall infection  and maximise the average number of available antibiotics  .Differential taxation was the most similar strategy to bans to maximise the average number of available antibiotics and with the smallest range of intervention failure rates (0.9% - 5.2%). Taken together across all three criteria, this suggests that taxation strategies can perform as effectively as bans on antibiotic usage for the range of parameters explored. To explore the similarity in effect size between taxation and bans, the taxation rate (HR) was incremented from 1% to 100%. A linear change in effect size to reduce resistance was observed, plateauing to a level comparable to bans at 60% taxation  .The results were found to be robust when alternative performance criteria were used: 1) absolute changes in resistance/infection, and 2) % changes to resistance/infections per % decrease in usage . However, an exception was with an improved performance of single taxation to reduce resistance in the second alternative criteria. The results were also unchanged when the hierarchy of fitness costs assumption was removed .3.2β = 0.5 or 50; λ = 1/365−1 or 1/42−1 days) and the threshold for the resistance for which an antibiotic is considered “available”  , altering the PED matrix , the number of antibiotic classes (two vs four), a case study with cattle and broiler chicken production systems (and 35%) .Fig. 3PrThe qualitative pattern of best performing interventions was maintained across alternative scenarios, with bans on antibiotic usage maintained as the being the best performing strategy to reduce average resistance and overall infection . The exc3.3The median global yearly revenue averaged across all considered taxation strategies was $1.11 billion  A. DifferSupplementary Material). This analysis was also explored with alternative tax rates of 25% and 75%, with median global yearly revenue of $0.61  and $1.52  billion respectively .The average yearly median revenue across all taxation strategies was higher in HICs  when compared to LMICs , attributable to the higher average price of antibiotics in the former case study  such as taxation and its near equivalent of a cap and tradeable permit scheme also have benefits over bans, allowing for flexibility in the usage of antibiotics, with bans being punitive of all users irrespective of their relative cost of abatements . MBIs alUse of extensive production systems with lower transmission will also impact the efficacy of interventions, increasing the average availability of effective antibiotics and reducing intervention failure . Mode ofHowever, the main advantage of bans over taxation is the certainty in reductions to usage. In contrast, the efficacy of MBIs will be sensitive to uncertainty in market dynamics and some users may simply opt to pay a tax rather than altering consumption patterns . There aDifferential taxation was identified as an effective strategy in this study, dynamically controlling resistance across the portfolio of antibiotics by promoting periods of high and low resistance ,41,42. THowever, the cyclical nature of differential taxation may mean antibiotics critical for food-producing animals such as glycopeptides and streptogramins undergo periods of high resistance . DiffereDespite HICs only making up 20.4% of global sales of veterinary antibiotics, HICs were estimated to contribute the majority of global revenue from taxation. However, the variation surrounding this estimate suggests scenarios where revenue can be twice higher than the median, or close to levels observed in LMICs. Risk-averse policy makers may opt for flat taxation, with little variation in revenue expected if this is the primary goal. The result of this analysis also introduces a series of ethical questions: is the unequal contribution from HICs fair, considering the historical usage of veterinary antibiotics and higher GDP in HICs? Additionally, what would be the implications of these taxes be on small-holding farmers in LMICs? Could a scheme be introduced to compensate farmers in LMICs for potential losses in productivity, or to implement taxation in HICs only?Two scenarios demonstrated relatively higher rates of intervention failure: 1) high cross elasticity of demand, or 2) targeting the lowest resistance antibiotic class. Both can be attributed to the impact of compensatory increases in usage beyond what is being reduced through the intervention. Implementation of future economic interventions must avoid scenarios which lead to this increased risk of intervention failure, which has been identified in the implementation of pesticide taxation .By integrating an epidemiological model with the price elasticity of demand, this study provides a first quantitative exploration into the viability and efficacy of taxation as a potential strategy to tackle AMR in food animals. We highlight taxation, as a potential tool for AMR control in agriculture, which should be explored through further modelling work. However, this must also be done in tandem with improvements to surveillance and an increased understanding of the elasticity of antibiotics for use in food animals. It is vital that we continue to explore tools and strategies that can effectively reduce AMR to tackle the ongoing AMR crisis in both food animals and in humans.ALKM participated in the study design, carried out model analysis and drafted the manuscript. TPVB participated in the study design and provided feedback on manuscript drafts. DM provided feedback on manuscript drafts.ALKM and TPVB were supported by the Swiss National Science Foundation Eccellenza Fellowship (No 181248) and the Branco Weiss Foundation. DM wishes to acknowledge UKRI funding under grant numbers BB/W018152/1, BB/T004436/1.All authors declare that they have no conflicts of interest.


BackgroundAntibiotic overuse is a critical global health issue, and patient attitudes and expectations play a significant role in the inappropriate use of antibiotics. Limited research has been conducted on patient knowledge, attitudes, and perceptions of antibiotic use in Saudi Arabia. This survey aimed to assess patients' knowledge and attitudes related to antibiotic use in Jeddah, Saudi Arabia.MethodsA cross-sectional survey using a convenience sampling method was conducted in Saudi Arabia. An online self-administered questionnaire was used to collect demographic data, antibiotic knowledge, and attitudes.ResultsThe study included 400 patients, with a mean age of 39 years and an equal gender distribution . Most participants (75%) had not used antibiotics in the past year. Patients demonstrated moderate knowledge about antibiotics, with 81% recognizing that antibiotics can cause side effects and 69% knowing that overuse can lead to resistance. However, only 44% knew that antibiotics are not effective for all infections, and only half (50%) knew that antibiotics work against bacteria, not viruses. Patients held mixed attitudes toward antibiotic prescribing, with 25% believing it was essential to take antibiotics for every infection and 44% believing healthcare providers should prescribe antibiotics for respiratory tract infections. Logistic regression analyses showed that patient expectations for antibiotic prescribing were strongly associated with inappropriate antibiotic use. In contrast, patient satisfaction with antibiotic prescribing was negatively associated with inappropriate antibiotic use. Lower health literacy levels were also associated with inappropriate antibiotic use.ConclusionThe study underscores the need for interventions that promote patient education and communication to ensure appropriate antibiotic use in primary care. Patient attitudes and beliefs, such as their expectations for antibiotic prescribing and health literacy levels, were identified as significant predictors of inappropriate antibiotic use. Antimicrobial resistance poses a substantial hazard to public health, impacting all countries. It is estimated that it will account for 10 million fatalities annually by 2050 .In primary care settings, antibiotics are frequently prescribed for respiratory tract infections, despite most of these infections being viral and not requiring antibiotics . PatientAdditionally, patient knowledge about antibiotics and their consequences can influence prescribing practices -5. Poor To address this growing concern, it is essential to understand patient perceptions and attitudes toward antibiotic use in primary care settings. A cross-sectional study conducted in Saudi Arabia aims to assess patient knowledge, attitudes, and perceptions of antibiotic use in primary care. The study will involve surveying patients attending primary care clinics and will focus on identifying factors that influence patient expectations for antibiotics, as well as patient knowledge about antibiotic resistance and appropriate antibiotic use.Study design and settingThis cross-sectional survey aimed to assess patients' knowledge and attitudes related to antibiotic use in Jeddah, Saudi Arabia. The study was conducted in accordance with the principles outlined in the Declaration of Helsinki.Study participantsAdult patients who had visited any primary care clinic in Jeddah within the past six months were eligible to participate in this study. Participants were recruited using a convenience sampling method through an online survey platform, which was distributed through social media platforms, online groups, and forums related to healthcare and medicine. Participants were informed that participation was voluntary, and informed consent was obtained from all participants before they started the survey.Survey instrumentFor this study, an online self-administered questionnaire was developed by the researchers to collect data on patients' antibiotic knowledge, attitudes, and practices. The questionnaire was divided into three sections, including demographic information such as age, gender, educational level, income, and occupation; antibiotic knowledge, which included questions about antibiotics and their usage, benefits, risks, and appropriate use; and antibiotic attitudes and practices, which included questions about patients' attitudes toward antibiotic use, perceptions about the effectiveness of antibiotics, willingness to follow physician advice on antibiotic use, and previous experiences with antibiotic use. The knowledge subsection included questions about what antibiotics are used for, whether antibiotics are effective for all infections, whether antibiotics can cause side effects, and whether participants knew what antibiotic resistance is and that overuse of antibiotics can lead to resistance. The attitudes subsection included questions about the importance of taking antibiotics for every infection, whether healthcare providers should prescribe antibiotics for respiratory tract infections, whether participants would be dissatisfied if their healthcare provider did not prescribe antibiotics for a respiratory tract infection, and whether participants expected their healthcare provider to prescribe antibiotics if they ask for them. The questionnaire was developed based on a literature review and was reviewed by two experts in the field of family medicine for face validity. A pilot test was conducted on a sample of 20 patients to assess its reliability and validity.Data collectionData was collected using the online survey platform (Google Forms). The survey link was distributed through various online platforms related to healthcare and medicine. Participants were requested to share the survey link with others who may be interested in participating. However, only responses meeting the criteria were considered in the data analysis. The survey was open for two months, from January 1, 2023, to February 28, 2023. The responses were anonymous, and the participants were assured of confidentiality.Data analysisDescriptive statistics were used to summarize the demographic characteristics of the sample and to describe patient knowledge and attitudes toward antibiotic use. Logistic regression analysis was used to examine the factors associated with inappropriate antibiotic use, including patient expectations and satisfaction with prescribing practices, as well as health literacy levels. The data analysis was conducted using statistical software, and a p-value of less than 0.05 was considered statistically significant. The data analysis was done using SPSS Statistics version 26 .Demographics of the study populationTable Antibiotic knowledge of study participantsOverall, patients had moderate knowledge about antibiotics. Most participants correctly identified that antibiotics can cause side effects n=324, 81%) and that overuse of antibiotics can lead to resistance . However, fewer patients correctly identified that antibiotics are not effective for all infections . Additionally, only half  of the participants recognized that antibiotics work against bacteria, not viruses  believed that it was important to take antibiotics for every infection, and under half of participants  believed that healthcare providers should prescribe antibiotics for respiratory tract infections. However, a smaller percentage of patients  reported that they would be dissatisfied if their healthcare provider did not prescribe antibiotics for a respiratory tract infection. Only 48 (12%) patients expected their healthcare provider to prescribe antibiotics if they asked for them  were strongly associated with inappropriate antibiotic use. Patients who expected their healthcare providers to prescribe antibiotics were more likely to report having used antibiotics in the past year. Conversely, patient satisfaction with antibiotic prescribing  was negatively associated with inappropriate antibiotic use. Patients who were satisfied with their healthcare provider's decision not to prescribe antibiotics were less likely to report having used antibiotics in the past year. Additionally, health literacy levels  were found to be associated with inappropriate antibiotic use, with patients having lower health literacy levels being more likely to report having used antibiotics in the past year.The results of this study provide important insights into patient attitudes and beliefs about antibiotic use in primary care. Patients had moderate knowledge about antibiotics, with most recognizing the potential side effects and risks associated with their use. However, patients also held several misconceptions about antibiotics, including their effectiveness against viruses and the need for antibiotics for every infection. These findings are consistent with previous research that has shown a lack of knowledge and misunderstandings about antibiotics among the general public .The misuse of antibiotics was significantly linked to patient demands for antibiotic prescriptions. Those patients who held the belief that antibiotics should be prescribed for all types of infections and those who expected their healthcare provider to prescribe antibiotics for respiratory tract infections were more likely to have used antibiotics within the previous year . This diIt is noteworthy that patient satisfaction regarding antibiotic prescription had an adverse association with the misuse of antibiotics. Patients who expressed satisfaction with their healthcare provider's decision to refrain from prescribing antibiotics were less likely to report antibiotic usage in the past year. This observation indicates that approaches to antibiotic prescribing that prioritize patient preferences and involve shared decision-making between patients and healthcare providers could be efficacious in decreasing superfluous antibiotic use. Prior investigations have demonstrated that patient-centered antibiotic prescribing methods can enhance patient satisfaction and lower the rates of antibiotic prescriptions -13.The findings underscore the significance of health literacy in the context of antibiotic use. Individuals with lower educational levels were more inclined to disclose having utilized antibiotics within the preceding year. This finding aligns with earlier studies that have linked health literacy to medication usage ,15. InteThe study has some constraints worth noting. Firstly, the survey used self-reported information, which may be affected by recall bias and social desirability bias. Secondly, the sample was limited to patients from primary care clinics in Jeddah only, which might not accurately represent other patient groups. Future investigations should endeavor to confirm these results in larger and more diverse patient cohorts. Additionally, longitudinal studies could be carried out to analyze the evolution of patient attitudes and convictions regarding the use of antibiotics over time.This study highlights the importance of patient education and communication interventions in promoting appropriate antibiotic use in primary care. Patients' attitudes and beliefs, including their expectations for antibiotic prescribing and their health literacy levels, were found to be strong predictors of inappropriate antibiotic use. Overall, the study emphasizes the need for a collaborative effort between healthcare providers and patients to promote the appropriate use of antibiotics and preserve the effectiveness of these important medications.