Antibiotic resistance is a global threat to human health, and inappropriate use of antibiotics in humans and animals is widely considered to be a key driver of antibiotic resistant infections. Antibiotic use in humans and animals is growing rapidly in low- and, particularly, middle-income countries. However, there is little detailed understanding about practices related to the use of antibiotics in humans and animals within community settings in such countries. Here we aimed to understand the antibiotic practices of rural households across Cumilla district, Bangladesh, in relation to household members and their domestic animals.In 2018 we conducted a cross-sectional survey using representative cluster sampling methods. We collected self-reported information from 682 female and 620 male household heads, with women also asked about their children’s antibiotic practices.Only 48%  of women and men had heard of antibiotics, and among those women and men who were aware of antibiotics and the children of those women 70%  reported having previously taken antibiotics, while among these individuals who reported previously taking antibiotics 21%  said they had done so most recently within the last month. Risky/inappropriate antibiotic practices in humans and animals were often reported. For example, among women and men who were aware of antibiotics and the children of those women 52%  reported previously taking antibiotics for a “cough/cold”, despite antibiotics being typically inappropriate for use against viral upper respiratory tract infections. Among poultry-owning respondents who were aware of antibiotics 11%  reported previously giving healthy poultry antibiotics, mainly for growth/prophylaxis, while among cattle-owning respondents who were aware of antibiotics and reported previously giving their cattle feed 20%  said the feed had contained antibiotics at least sometimes.Our results highlight the need for context-adapted interventions at both the community level and the health systems level to reduce inappropriate antibiotic use among humans and domestic animals in rural Bangladesh. Successfully reducing inappropriate use of antibiotics among humans and animals is a required and critical step in tackling antimicrobial resistance.The online version contains supplementary material available at 10.1186/s12889-021-10457-w. Antibiotic resistance (ABR) is recognised as one of the biggest global challenges for future human health and development, as shown by the creation of global action plans by international institutions such as the World Health Organization (WHO), World Organisation for Animal Health (OIE), and the Food and Agriculture Organization of the United Nations (FAO) . GloballMany academic studies and global action initiatives have therefore called for a better understanding of how antibiotics are being used in humans and animals in LMICs, particularly in rural settings where most LMIC populations live . Lookinghttp://data.worldbank.org/about/country-and-lending-groups]. Our main aim was to understand rural household practices in relation to antibiotic use in humans and households’ domestic animals, to understand the prevalence of key potential drivers of ABR in this context.Therefore, in this study we surveyed rural households in villages across a typical district within Bangladesh, a lower-middle-income country [We conducted our cross-sectional, rural household survey across Cumilla district, Bangladesh, between May and June 2018, but we excluded the two predominantly urban sub-districts of Sadar and Sadar Dakshin leaving 14 mainly rural sub-districts. Cumilla had an estimated population of 5.4 million in 2011, and has an economy that is based primarily on agricultural production and agricultural product processing, mainly via cottage industries . As is tWe collected all data using a structured paper questionnaire with Bengali-language based questions. The questions were informed by 1) related surveys –19, 2) WWe used a two-stage cluster sampling approach and stratified our sampling by sub-district . In the We calculated our sample size based on a generic binary outcome because almost every question in our questionnaire would result in categorical responses where each category level (e.g. yes/no/don’t know) can be treated as a separate binary outcome, with the proportion/percentage of respondents providing each category-level response estimated along with its 95% confidence interval. Based on logistical resources considerations and desired levels of precision, we estimated that if we sampled 720 households, and therefore 720 women and 720 men , then we would have a sufficient sample size to estimate any binary outcome, separately for women or men, with a precision  of 6.9 percentage points or less . This esDuring field work the research team monitored progress remotely, and the field teams returned to the research team offices every week to hand over the questionnaire data sheets, which the research team then checked 5% of for data quality. After data collection the research team trained separate data entry staff, who entered all data from the paper questionnaires into a specially designed SPSS database, which was then checked for obvious errors and anomalies and cleaned by both the Bangladeshi research team and then checked again by JPH.We produced descriptive statistics to describe the key sociodemographic characteristics of the sample, and we produced inferential statistics in the form of point estimates and 95% confidence intervals to draw conclusions about responses given to questions. These were either in the form of percentages and their associated 95% confidence intervals for categorical questions, i.e. questions where the responses were categorical, or in the form of means and their associated 95% confidence intervals in the very few cases of numerical questions, i.e. questions where the responses were numerical. Depending on the question the estimated response percentages were specific to either female respondents, male respondents, the children of female respondents, household poultry, household cattle, or household goats and/or sheep (collectively).For all categorical questions the 95% confidence intervals were calculated using a “logit” method that involved fitting a logistic regression model before computing a Wald-type interval on the log-odds scale, which was then transformed to the probability-scale. For categorical questions related to human antibiotic practices we also produced “overall” estimates based on combining the responses from all female and male respondents, and, if applicable, the responses of female respondents in relation to their children. We also estimated how responses to categorical questions differed between women, men and children, or between the different animal groups, as appropriate to the question. We did this by treating each response category (e.g. “where did you last obtain antibiotics?”: “from a pharmacy”) as an individual binary outcome (i.e. response selected/not selected by responder) and using a binomial regression model  we estimsurvey [sryvr [survey package’s “average” option, where “the stratum contribution to the variance is taken to be the average of all the strata with more than one PSU.” [We used R  statistisurvey , 27 and y [sryvr  packagesy [sryvr . Where sne PSU.” , 27 In aBetween May and June 2018, across the 14 chosen subdistricts of Cumilla we selected 28 villages (two per subdistrict) and household clusters (one per village). Across the selected households there were 691 eligible female household heads and 672 eligible male household heads, with 682 (98.7%) and 620 (92.3%) female and male household heads agreeing to participate respectively. Female and male respondents’ ages were broadly evenly distributed across the eligible age range, both were mostly married (97%), and a substantial proportion (37%) of both either had no education or had not completed primary education. However, while 74% of men reported having worked for cash or in-kind payment in the last month only 20% of women did so  of women and men said they had heard of antibiotics, and we refer to these individuals as being “antibiotic-aware” from here on. Among these antibiotic-aware women and men 80%  and 76% , respectively, reported having ever taken antibiotics, while 56%  of antibiotic-aware women with children under 15 reported that at least one of their children had ever taken antibiotics. Across all women, men and children who reported taking antibiotics overall 21%  reported having taken antibiotics within the last month. See Table We asked those antibiotic-aware respondents who reported that they or any of their children had previously taken antibiotics what illnesses or main symptoms they had ever taken antibiotics for. Overall the most frequently reported condition was undifferentiated “fever”  followed by “cough/cold” . For all other illnesses/main symptoms the overall results were substantially less than 50%, but notably “sore throat”, a common symptom of viral URTIs, was reported by 24% . See Table 73%  of households reported owning poultry , mainly chickens and ducks, while 32%  reported owning cattle , and 9%  reported owning goats and/or sheep . See Table Animal illness was frequently reported, particularly for poultry. Among poultry-owning households 65%  reported at least one of their poultry had previously been ill or died suddenly, and among poultry-owning households reporting previous poultry illness 77%  reported that the most recent illness was within the last 6 months. Among cattle-owning households 27%  reported at least one of their cattle had previously been ill or died suddenly, and among cattle-owning households reporting previous cattle illness 57%  reported that the most recent illness was within the last 6 months.Ill cattle appear more likely to be treated than ill poultry. Among animal-owning households that reported ever previously seeking treatment for ill animal(s) 75%  of these households that owned poultry and 98%  of these households that owned cattle reported that the treatment involved either “western medicines”  or “food with added medicine/drugs”. Among poultry-owning households that reported ever treating their animal(s) when they were ill only 1%  and 4%  respectively, reported having previously used a government or private veterinarian, while the most frequently reported previous source of treatment was a drug seller/pharmacist . However, among cattle-owning households that reported ever treating their animal(s) when they were ill 25%  and 32% , respectively, reported having previously used a government or private vet, although 14%  still reported previously using a drug seller/pharmacist, and 27%  a village doctor/paramedic/private medical practitioner. See Table In relation to antibiotics, we asked antibiotic-aware respondents of animal-owning households who reported previously having ill animal(s) treated whether such treatment ever involved antibiotics, and this was reported by 24%  of these households that owned poultry and 36%  of these households that owned cattle. We also asked antibiotic-aware respondents if any of their animals had ever been given antibiotics when they were not ill, and this was reported by 11%  of poultry-owning households and 2%  of cattle-owning households. Additionally, 14%  of antibiotic-aware poultry-owning households said they “sometimes/usually/always” bought commercial feed for their animals, and 21%  of those who responded in this way said that this feed “sometimes/usually/always” contained antibiotics. For antibiotic-aware cattle-owning households the corresponding figures were 63%  and 20%  respectively Table . UnfortuTo our knowledge, our study provides the first comprehensive information from Bangladesh about rural households’ antibiotic practices in relation to humans and domestic animals. We found a substantial lack of awareness about the existence of antibiotics as a distinct class/type of medicine in this context, which necessarily restricted our ability to understand antibiotic practices among non-aware individuals. This problem is faced by all similar surveys of rural LMIC communities, with levels of awareness varying substantially but typically being moderate to low –32, althLike similar surveys from other LMICs, including those in urban settings, our data indicate high levels of antibiotic consumption among rural community members , 33–36. However, despite this clear evidence from across the world that highlights just how problematic inappropriate antibiotic prescribing is within formal and informal primary care settings, appropriately used antibiotics are obviously critical and irreplaceable tools that can substantially reduce mortality from communicable diseases within LMICs, particularly among children. And yet in most LMICs there is still actually often a lack of access to appropriate antibiotics in primary care settings . There iWe found that the main reported sources for antibiotics were private providers, particularly pharmacies, which in practice may also mean informal and unregulated drug sellers, again consistent with similar surveys , 32, 35.Antibiotic-aware respondents who reported using antibiotics did not report deviating from the WHO’s recommended best practices very frequently. For example, most such respondents reported that they and/or their children purchased antibiotics most recently using a prescription. However, contextual knowledge along with studies from Bangladesh and similar contexts suggest that prescriptions are rarely required to obtain medicines from private sources –62. SimiAnimal-owning respondents frequently reported previous experience of animal illness, and that treatments primarily involved “western medicines” or “drugs”. They also reported seeking treatment for ill cattle far more often than ill poultry, probably reflecting the far higher value of cattle. Evidence from rural areas within another Bangladeshi district suggests such generic terms might sometimes/often reflect the use of antibiotics, but this was based on small numbers of qualitative interviews . As therWe also found some evidence of limited use of antibiotics in healthy poultry or cattle, potentially to increase growth or production of eggs/milk/meat or as prophylactics. There is clear and growing evidence linking the indiscriminate use of antibiotics within small- and large-scale agriculture to the development of antibiotic resistant microbes –69, and A key limitation of our study is that we had to restrict our inferences for most questions to the sub-populations who were able to answer them, particularly the sub-population of individuals who had heard of antibiotics. With hindsight we would have been able to estimate the rest of our results (other than the question of antibiotic awareness) with more precision had we planned our sampled size to only include individuals who were aware of antibiotics, but while still collecting information on the key question of antibiotic awareness during an eligibility screening phase, for example. However, this does not affect the level of any bias in our results. A closely related limitation is that we sometimes ended up with impractically small sample sizes for some key questions that only small sub-populations within our sample could respond to. In terms of generalisability, the respondents remaining in our sub-population analyses are very unlikely to be representative of the complete rural communities that we sampled. Therefore, when generalising any of our sub-population results it is important to be clear that they can only be robustly applied to the relevant sub-populations within the sampled target population of adult (aged 18–49) female and male household heads, and the children of those females, within rural communities in Cumilla district. For example, our results on the frequency with which adult female household heads have previously taken antibiotics can only robustly be generalised to the population of adult female household heads living in rural communities who have also heard of antibiotics. Generalisations beyond this group would be questionable. The final obvious key limitation of the study is that we relied on self-reported responses, which are inevitably prone to respondent recall bias and social desirability bias. Obtaining more objective data in such surveys and contexts is very difficult, but future work could test possible methodological innovations .Our study provides rare, community-based data on antibiotic practices among humans and their domestic animals living in rural Bangladeshi communities. Given the lack of awareness about antibiotics and the human and animal practices currently identified that can lead to the development of antibiotic resistant microbes/infections, along with the risk that such practices will increase in the future, from a community perspective we argue that community-led, well informed and context-appropriate behaviour change education (BCE) is required as a first step. Our team has previously synthesised the key components necessary for delivering rural BCE on these issues in LMICs , and hasAdditional file 1: Table S1. Reported antibiotic awareness and use among household members. Table S2. Reported illnesses/main symptoms that have ever resulted in taking antibiotics. Table S3. Reported sources ever used to obtain antibiotics. Table S4. Reported behaviours relating to the WHO’s key recommended best practices for obtaining and using antibiotics for human illness when last obtaining and using antibiotics. Table S5. Reported current household ownership of domestic animals kept for small-scale husbandry. Table S6. Reported length of time households have owned poultry, cattle and/or goats/sheep that they currently own. Table S7. Reported risky animal husbandry practices and basic antibiotic use in households’ domestic animals. Table S8. Reported domestic animal illness and domestic animal treatment practices involving antibiotics. Table S9. Reported vaccination awareness, coverage and future preferences/desires.


The objective of this paper is to focus on consolidated and more recent improvements in clinical strategies that should be adopted in hospitalized patients to ameliorate their infectious diseases’ outcome and to reduce the antibiotic resistance risk through judicious use of antibiotics. We present 13 common clinical scenarios, the respective suggested interventions and the explanations of the supporting evidence, in order to help clinicians in their decision-making process. Strategies including the choice of antibiotic and dose optimization, antibiotic spectrum narrowing , shortening of duration, shift to oral route or outpatient parenteral antibiotic (including elastomeric pumps), and biomarkers are described and discussed.  Bacteria are continuously evolving and antibiotic resistances are significantly increasing, with 33,000 people in Europe, 35,000 in United States and >38,000 in Southeast Asia dying each year from antibiotic-resistant infections ,2,3. TheClostridioides difficile potential [Despite AMS currently being an extensively used medical term, it lacks a universally endorsed definition. Many doctors believe that AMS sums up and embodies what both infectious diseases physicians and generally all antibiotic prescribers should do. Recently, Dyar et al. tried to provide a definition for AMS: the authors suggested “viewing AMS as a strategy, a coherent set of actions which promote using antimicrobials responsibly”, stressing the continuous need for “responsible use” to be defined and translated into context-specific and time-specific actions . Severalotential . HoweverEnterobacteriaceae (CRE) urinary tract infections, using biomarkers and urinary antigens as stewardship tools, re-using old antibiotics, antibiotic allergy de-labelling . In addition, the literature data support the administration of beta-lactam antibiotics through continuous infusion for both increasing antibacterial activity and reducing sepsis-associated mortality [Neutropenic patients are at risk of severe infections especially due to Gram-negative organisms such as ortality .Streptococcus pyogenes.A 49-year old female obese patient, receiving insulin for diabetes mellitus, was admitted to the intensive care unit for septic shock and left leg ulcerative cellulitis. Empirical therapy with intravenous ceftriaxone was commenced. Two blood cultures yielded Shift from intravenous ceftriaxone to intravenous penicillin G.C. difficile. C. difficile has become the main cause of nosocomial infections in the western world [C. difficile emergence [C. difficile infection. Antibiotic therapy is a risk factor for developing infections from extended spectrum beta lactamases (ESBL)-producing bacteria and rn world . Third gmergence ,14. In EA 67-year old male underwent a recent hemicolectomy for left colon cancer. Four days after surgery, he developed fever, tachypnea and altered mental status. No intra-abdominal collections were found by computed tomography scan. Empirical therapy with piperacillin/tazobactam and metronidazole was commenced. Following two days of antibiotic therapy, the patient clinically improved. No microbial growth was demonstrated in blood cultures.Maintaining piperacillin/tazobactam while discontinuing metronidazole.Another frequently faced situation is the double anaerobic coverage in patients with intra-abdominal infections. Unnecessary double anaerobic coverage has been related to increased hospital costs, risk of drug-resistant pathogen acquisition, and the development of adverse reactions . Almost Streptococcus mitis showing penicillin minimum inhibitory concentration (MIC) ≤0.12 µg/mL. Her vital signs were stable and within normal limits. The echocardiographic examination showed mitral valve prolapse, evidence of an 8 × 13 mm vegetation, but no valve regurgitation or other abnormalities. No need for cardiac surgery was established. Targeted antibiotic therapy with ceftriaxone was started.A 39-year old female patient had native mitral valve endocarditis due to Fever disappeared at 36 h of antibiotic therapy and the patient’s vital signs remained stable. Therefore, after 10 days, antibiotic treatment was shifted from intravenous to oral regimen with amoxicillin 1 g orally every 6 h + rifampin 600 mg orally every 12 h.Streptococcus spp., Enterococcus faecalis, Staphylococcus aureus or coagulase-negative staphylococci [p = 0.4) [There is evidence that a shift from intravenous to oral antibiotic regimens in stable patients with left sided endocarditis is non-inferior to continued intravenous antibiotic treatment. The Danish trial published in 2018 included endocarditis due to A 55-year old man with persistent fever and lumbar pain was diagnosed with lumbar vertebral osteomyelitis (L4-L5). No neurological abnormalities were found. Diagnosis of probable vertebral osteomyelitis (L4-L5) was obtained by magnetic resonance imaging. The tissue culture from bone biopsy grew methicillin-susceptible S. aureus. Intravenous therapy with oxacillin 2 g every 4 h was commenced.After 7 days, the intravenous antibiotic therapy was changed to an oral regimen including levofloxacin 500 mg every 12 h plus rifampicin 450 mg every 12 h. The shift from intravenous to oral antibiotic therapy in bone and joint infections has been associated with a shorter length of hospital stay and fewer complications. In the trial by Li et al. published in 2019, there were no differences in terms of treatment failure in patients with bone or joint infection shifted to oral therapy within 7 days after surgery  vs those who continued intravenous antibiotic treatment [Bacteremic urosepsis due to Escherichia coli was diagnosed in a 65-year-old male with an indwelling urinary catheter for benign prostate hyperplasia. The patient developed fever and chills without other symptoms; his vital signs were stable and within normal limits. Bacteremic urosepsis due to E. coli was diagnosed and the urinary catheter was promptly replaced, and intravenous antibiotic therapy with ceftriaxone was administered, leading to defervescence, and the fever disappeared after 48 h of treatment.Stop antibiotic therapy after 7 days of treatment.A recent trial compared a 7-day vs 14-day course of antibiotic therapy for Gram-negative bacteremias. Patients who were afebrile and hemodynamically stable for at least 48 h were randomized in two arms to receive 7 or 14 days of intravenous antibiotics. The primary outcome at 90 days was a composite of all-cause mortality, relapse, suppurative, or distant complications, and readmission or extended hospitalization (>14 days). Patients with uncontrolled source of infection were excluded, as well as neutropenic, transplanted or HIV-seropositive. There were no significant differences in the primary outcome between the two groups .A diabetic 70-year-old female was diagnosed with native joint arthritis of her left knee. A synovial fluid culture grew methicillin-susceptible S. aureus. Intravenous oxacillin was commenced and surgical drainage was performed. Stop antibiotic therapy after a 2-week course of therapy following successful surgical drainage.A trial published in 2019 compared 77 patients treated with a 2-week course with 77 patients treated with 4-week course of antibiotic therapy . NowadayP. aeruginosa resistant to ciprofloxacin. Intravenous antibiotic therapy with piperacillin/tazobactam was commenced, with improvement in the patient’s clinical conditions and normalization of vital signs within 3 days.A 66-year-old male, affected by chronic obstructive pulmonary disease, was diagnosed with fever, worsening of cough and chest pain on the left side. His past medical history was remarkable for chronic obstructive pulmonary disease. A chest X-ray showed a left upper lobe infiltrate consistent with a lung abscess. A sputum culture demonstrated On day 3 of antibiotic therapy, the patient’s clinical conditions greatly improved and his vital signs returned to normal limits. On day 7, a midline catheter was inserted and the patient was discharged. He was referred to an outpatient service to continue continuous infusion of piperacillin/tazobactam (18 g daily), administered through an elastomeric pump, for 5 weeks. There is growing evidence that infusion pump  use is an effective outpatient parenteral antibiotic therapy strategy to facilitate de-hospitalization, especially in patients treated with time-dependent antibiotics . When anE. coli. A 74-year old man with relapsing urinary tract infections and benign prostatic hyperplasia was scheduled for transurethral biopsy of the prostate. One month before, he was treated for urinary tract infection; at that time, the urine culture grew 100,000 CFU/mL of ESBL-producing per os given once before bedtime the day before prostate biopsy was prescribed. Fosfomycin trometamol 3 g Fosfomycin trometamol has an excellent urinary concentration with mean peak urinary concentrations (within 4 h from administration) ranging from 1053 to 4415 mg/L after a single 3 g dose . Such a E. coli treated with fosfomycin trometamol 3 g per os every 48 h 3 times reported a clinical and microbiological success rate of 94% and 78%, respectively [A recent systematic review of the studies on fosfomycin in comparison with fluoroquinolones to prevent trans-rectal ultrasound-guided prostate biopsy-related infectious complications showed that patients who received fosfomycin prophylaxis were less likely than those who received fluoroquinolone prophylaxis to develop infections overall, as well as severe and resistant infections. The difference was explained by fluoroquinolone resistance and ESBL production in pathogens causing post-biopsy infections. A retrospective study on 52 patients with urinary tract infections from ESBL-producing ectively .Klebsiella pneumoniae carbapenemase (KPC)-producing Klebsiella pneumoniae, including colistin-resistant strains [Apart from ESBL-producing bacteria, fosfomycin has been demonstrated to be a viable option for infections sustained by CRE. In fact, fosfomycin is active against approximately 80% of CRE, especially  strains , and repA 65-year-old female patient with no previous medical history was diagnosed with community-acquired pneumonia. Intravenous ampicillin/sulbactam and clarithromycin were commenced. Urinary pneumococcal antigen tested positive.Clarithromycin was discontinued and ampicillin/sulbactam de-escalated to penicillin G.Streptococcus pneumoniae pneumonia, de-escalation to penicillin G is safe when penicillin G MIC in pneumococci ≤2 µg/mL .Macrolides are overprescribed antibiotics and represent an easy target for AMS interventions. It has been demonstrated that the hospital rate of pneumococcal urinary antigen testing was strongly correlated with de-escalation following a positive test , suggestHaemophilus influenzae was established. Procalcitonin on diagnosis was 10 µg/L . After 5 days of oral oseltamivir and intravenous ampicillin/sulbactam, the patient experienced significant clinical amelioration and procalcitonin dropped to 0.5 µg/L.A 50-year-old male affected by obesity and diabetes mellitus was admitted to an intensive care unit for sepsis with severe respiratory insufficiency. A diagnosis of influenza complicated by bacterial pulmonary superinfection due to Antibiotic therapy was stopped after 5 days.p < 0.0001) and this was also associated with a significantly reduced mortality in the procalcitonin-guided group  [Procalcitonin has been used as a tool to support clinical decisions on antibiotic discontinuation. A prospective, multicenter, randomized, controlled, open-label intervention trial compared two strategies in Dutch intensive care units. The authors included 761 patients in the procalcitonin-guided group and 785 patients in the standard-of-care group. In the procalcitonin-guided group, non-binding advice to discontinue antibiotics was provided if procalcitonin concentration had decreased by 80% or more of its peak value or to 0.5 µg/L or lower. The results show that the median duration of treatment was 5 days in the procalcitonin-guided vs 7 days in the standard-of-care-guided group  .6 CFU/mL of ESBL-producing K. pneumoniae. The strain was resistant to piperacillin/tazobactam (MIC 32 µg/mL), and fosfomycin but susceptible to temocillin (MIC 4 µg/mL).A 70-year-old man with history of nephrolithiasis and benign prostatic hyperplasia developed dysuria and high-grade fever accompanied by shaking chills. Urine culture grew 10Intravenous temocillin: 2 g loading dose followed by 6 g in 24 h continuous infusion was started with progressive amelioration of clinical signs and symptoms and improvement of biochemical parameters.Enterobacteriaceae. It is a forgotten antibiotic, recently rediscovered and used for bacteremia, urinary tract infection and lower respiratory tract infection. The cumulative percentage of a 24 h period during which the free drug concentration exceeds the minimum inhibitory concentration (fT > MIC) is the best pharmacokinetic/pharmacodynamic index [Temocillin is a carboxypenicillin active against ESBL, KPC and AmpC-producing ic index . The datic index . TemocilCutibacterium acnes 100 CFU/mL, and three out of four additional bone samples were positive for the same microorganism. The patient’s medical history revealed an allergy to penicillin. The patient was started on ceftriaxone 2 g every 24 h intravenously.A 75-years old man underwent the removal of a shoulder prosthesis for a prosthetic joint infection six months previously. His postoperative course seemed to be uneventful, but he did not stop complaining of stress-induced and nocturnal resting pain, and poor mobility. Revision was performed with the removal of the prosthesis. Sonication fluid grew The patient was sent to allergology clinics and the immediate type of allergy to penicillin was excluded by skin test. After 14 days of parenteral therapy, the patient was switched to oral treatment with amoxicillin 1000 mg every 8 h for additional 4 weeks.Antibiotic allergy labels that reflect variable adverse drug reactions are found in 10–30% of hospitalized patients. The labels lead to the substitution of antibiotics of choice with second line drugs that are often associated with microbial resistance, higher cost or even sub-optimal patient outcomes. Antibiotic allergy in-depth review has been shown to remove the label in more than 90% of cases, and may contribute to better antibiotic use . De-labeAntibiotic misuse or overuse is still highly prevalent in the hospital setting. Indeed, previous reports have shown that infectious disease specialist consultation can lead to resource-saving advices in more than 40% of cases . The impIn our manuscript, we have described several clinical scenarios frequently occurring during routine clinical practice, and we have proposed targeted practical interventions to optimize antibiotic therapy. Each scenario elucidates how the main principles of AMS could be applied at a patient level. Narrowing the antibiotic spectrum (intervention 2) is the mainstay of correct antibiotic usage and, when correctly applied, has the potential to obtain clinical success while minimizing the risk of increasing resistance. It is strictly dependent on microbiological data such as a continuous monitoring of local resistance epidemiology, but also the development of methods for accurate and rapid identification of pathogens and characterization of their resistance profile . UrinaryThe optimal use of antibiotics can also be obtained by the optimization of dosage or administration modes on the basis of their pharmacokinetic/pharmacodynamics properties (intervention 1). A shift from intravenous to oral therapy when the patient is stable (interventions 4–5), especially to drugs with high oral bioavailability , is one AMS programs should also take into account all scenarios characterized by antibiotic misuse. The double anaerobic coverage (intervention 3) is frequently observed in the management of intra-abdominal infections and should generally be avoided. Moreover, in patients with reported penicillin allergy, de-labelling is preferred over using a second-line drug, which is often a broad spectrum antibiotic with a higher impact on resistance spread (intervention 13).In conclusion, we provided a series of real-life clinical scenarios in order to discuss the main current topics of AMS. The aim of the present manuscript was to furnish practical cues for physicians involved in the management of bacterial infections. Some of the interventions described are already well established and supported by a large volume of evidence, while the others are based on recently published studies and look promising for at least some patients. The evidence is expected to change over the time, and, to improve antibiotic prescribing, we need to include it meaningfully in our clinical practice. There is a role for AMS teams to introduce new evidence and promote the use of well-established practices, but at the same time every prescribing physician should improve his knowledge on up-to date antibiotic treatments in his field of expertise.


Critical state-of-the-art review of pH and Cl− sensors revealed that the majority of the sensors have high sensitivity, reliability, and stability in concrete environment, though the experiments were carried out for relatively short periods. Among the reviewed works, only three attempted to monitor Cl− wirelessly, albeit over a very short range. As part of the feasibility study, this work recommends the use of internet of things (IoT) and machine learning for autonomous corrosion condition assessment of RC structures.In this work, technological feasibility of autonomous corrosion assessment of reinforced concrete structures is studied. Corrosion of reinforcement bars (rebar), induced by carbonation or chloride penetration, is one of the leading causes for deterioration of concrete structures throughout the globe. Continuous nondestructive in-service monitoring of carbonation through pH and chloride ion (Cl Building and infrastructure accounts for 47% of the world gross domestic product . DespiteCorrosion of reinforcement bars (rebar) is one of the major causes for degeneration of RC structures throughout the world, especially those exposed to aggressive environments ,6,7. Stu− or by the carbonation of the concrete [2 from the neighboring environment into the concrete through pores in the matrix where the CO2 reacts with hydrated cement [− is also the primary cause for rebar corrosion in concrete environment. Like carbonation, the penetration of Cl− does not typically cause harm directly to the concrete. Nonetheless, when the amount of Cl− concentration at the rebar reaches a certain threshold, depassivation occurs that cause corrosion initiation [− by mass of binder) as it is controlled by several factors including composition of the concrete, the type of rebar, and the exposure conditions [Naturally, concrete cover provides a high level of protection to the embedded rebar against corrosion since the pore solution of the concrete is alkaline with a pH of 12–13. Under this amount of alkalinity, rebar persists passivated. However, the passivation of rebar is breakdown due to the presence of Clconcrete . Carbonad cement ,16. Althd cement ,17,18,19itiation ,22,23,24nditions ,26. Both− concentrations in the concrete is crucial. Measurement of pH of the concrete can indicate the risk of corrosion caused by carbonation. The conventional methods for evaluating carbonation and the Cl− content in concrete is often semi-destructive, time-consuming, and demand periodic repetition [− concentrations in the concrete are determined using chemical and/or physical laboratory tests of samples taken from in-service structures. Due to these facts, the conventional techniques cannot be applied for frequent measurements. In addition, performance investigation of RC structure either in the field or laboratory (by taking sample from the structure) usually incur a high amount of direct and indirect costs [− concentration in concrete along with accurate corrosion assessment method is indispensable, which ultimately makes the service-life management of RC structures efficient from economy and safety perspectives. Corrosion initiation time must be precisely estimated to carry out in-time and cost-effective maintenance decisions to prevent RC structures from corrosion-induced damage. To do so, continuous assessment of pH of the concrete and the amount of Clpetition . In thesct costs . For insct costs . After ect costs . This un− penetration in RC structures. The contributions of this work are threefold: (i) in-depth review of state-of-the-art Cl− and pH sensing devices that can be embedded in concrete structures, (ii) study on the potential of IoT system for continuous Cl− and pH monitoring, and (iii) a critical insight into the integration of IoT systems and intelligent data analytics to achieve autonomous corrosion assessment of RC structures. The objective of this work is to carry out feasibility study on autonomous assessment of rebar corrosion due to carbonation and Cl− and pH in concrete environment are critically reviewed. The possibility of integrating the physical infrastructure with digital technologies by employing internet of things based continuous Cl− and pH monitoring system is presented in The structure of the remainder of the paper is as follows. In − concentration can deliver information about the state of the rebar embedded in the concrete well before corrosion initiates, serving as early alerting systems. Hence, this paper focuses in reviewing only Cl− and pH sensors that monitor chloride concentration and pH of the concrete pore solution. In addition, pH and Cl− sensors can be used for controlling concrete repair works. For example, repair work to passivate rebar using electrochemical chloride extraction and re-alkalization methods [The risk of structural disintegration of infrastructure caused by rebar corrosion fosters the development of sensing devices for continuous nondestructive monitoring that enable early detection of corrosion. Over the past years, embeddable sensors have been developed and installed in concrete structures for monitoring the corrosion state of rebar. There are even commercially available corrosion monitoring systems based on different approach including measurements of macrocell, resistivity, and electrochemical polarization dynamics. The drawback of these types of sensors is that they provide information about the corrosion state of the rebar after corrosion has initiated. While sensors that can monitor pH of the pore solution and Cl methods .− and pH sensing devices that can be embedded in concrete structures, databases of the Scopus and Web of Science were selected for analysis. Both are abstract and citation databases of peer-reviewed literature, delivering a complete citation search by giving access to numerous databases. A set of queries that comprise the manuscript’s title, topic, abstract, and keywords were carried out on every database in order to choose works reporting Cl− and pH sensing devices that can be embedded in concrete structure. Since one of the focuses is to evaluate the current development Cl− and pH sensors, the lifespan of the search criteria for both databases were set to 10 years. Any duplicated records from the databases were removed and then manually checked to select suitable ones. To perform a thorough study on the recent development of Cl− concentrations in concrete. ISEs are firmly established and have been adopted in several areas. For instance, in the area of analytical chemistry, ionic activity of some specific species had been examined using a potential measurement [In the past few decades, several electrochemical sensors based on potentiometric ion-selective electrodes (ISEs) have been developed to monitor change of Clsurement . The worsurement . One of surement . R is the gas constant [− [The potential of a potentiometric sensor is estimated using the Nernst equation, described by Equation (1) , which d2Cl2), silver/silver chloride (Ag/AgCl), manganese dioxide (MnO2), copper/copper sulphate (Cu/CuSO4)) have constant potential values. All the polarizable electrodes, except lead (Pb), showed potential values with a fluctuation range of ±20 [The widely used reference electrodes and their potentials with respect to the regular hydrogen electrode (NHE) is given in e of ±20 ,35. Amone of ±20 ,37. This− concentrations for a long time while providing accurate and reliable results. Moreover, the stability of the Cl− sensors to pH changes and other major interfering ions (which come from the environment and/or the concrete ingredients) should be assured. There are studies that have evaluated the performance of potentiometric ISEs in monitoring Cl− concentration in concrete [Though the fundamental principles of potentiometric ISEs based sensors are well established and widely applied in the field of electrochemistry, their applicability in concrete must be assessed. Sensors that can be mounted in concrete should operate in high alkaline environment and in a wide range of Clconcrete ,46,47,48− using Ag/AgCl electrodes in hardened mortar was documented in the early 1990s [− sensors based on Ag/AgCl electrodes have been developed. − and pH potentiometric sensors and their performance in concrete environment. The performance of the sensors was evaluated using simulated concrete pore solutions, mortar, and concrete.Ag/AgCl electrodes are the most commonly utilized and commercially available chloride ion selective electrodes ,43. It cly 1990s . Since t−, it reliably measures the Cl− concentration. The authors concluded that Ag/AgCl electrode can satisfactorily be applied to monitor the amount of Cl− in RC structures exposed to chloride-laden environments. Montemor et al. [− in concrete environment. The evaluation was performed in mortar and concrete specimens at different depths by exposing to a broad range of Cl− concentrations. The reported results revealed that the Ag/AgCl based chloride sensor is reasonably stable. Femenias et al.  investigr et al.  evaluate− and pH values. The claimed test results showed that the influence of pH on the potential value of the sensor is trivial at Cl− concentrations of > 4 mM. This makes Ag/AgCl based sensors are practical to monitor the change of Cl− in concrete structures since Cl− concentration of 4 mM is much under than the usually stated thresholds that initiate rebar corrosion in concrete. As the pH has a notable effect on the reading of the sensor at low Cl− concentration (<4 mM), it is vital to monitor the pH value and Cl− concentration simultaneously for accurate measurement of Cl− content. Similar phenomenon was also observed regarding the influence of pH on measuring Cl− concentration in concrete made by another study [− concentration in concrete specimens composed of different mineral admixtures at different depths. On the basis of the potential analysis of the embedded Cl− sensor, the authors concluded that continuous monitoring of Cl− concentration in RC structure could be achieved. They also remarked that extra efforts are required to produce inexpensive, robust, and reliable Cl− potentiometric sensors that can be utilized in concrete environment.Pargar et al.  characteer study . Jin et er study  applied − concentration in concrete structure. The alkaline stability of the sensor and the coating material were evaluated in synthetic concrete pore solution and characterized using advanced tests, including half-cell potential, scanning electron microscopy (SEM), X-ray diffraction (XRD). The sensor was calibrated in wide range of Cl− concentrations using three different solutions: (i) saturated KCl solution, (ii) distilled water solution, and (iii) synthetic concrete pore solution. Then the sensor was embedded in the concrete at the depths of 5, 10, 20, 30, and 40 mm for 90 days.Karthick et al.  produce − concentration in concrete structure. Gao et al. [− sensor employing MnO2 and Ag/AgCl electrodes. The potentiometric response and stability of the sensor was examined in synthetic concrete pore solutions with diverse NaCl concentrations ranging from 0.05–5.0 M. The performance of the sensor with the existence of interfering ions of K+, Ca2+, Na+, and SO42− was tested. The authors reported that the potentiometric response of the sensor to chloride is slightly influenced by the interfering ions, but considerably affected by the pH at low-chloride concentration.Based on the findings, the authors claimed that the sensor has excellent chloride sensing ability and well stable in an alkaline medium, and thus it is suitable to monitor Clo et al.  produce − monitoring in concrete environments. Indeed, the authors recommend the pH of the concrete pore solution to be simultaneously monitored to accurately determine the Cl− in slightly chloride contaminated concrete. Gao et al. [− sensor in synthetic concrete pore solutions with a wide range of NaCl concentrations ranging from 0.005–1.0 M.Meanwhile, over the range of 5–45 °C, the sensor’s potential reading linearly grows with the solution temperature. The sensor reveals outstanding polarization behaviour as proven by galvanostatic and potentiodynamic tests. Based on these facts, the author concluded that the sensor has excellent potential for Clo et al. , in anot− concentrations in concrete structures. However, the main hurdles in realizing these sensors for monitoring concrete structures are the lack of appropriate sensors, which desirably have to be inexpensive, robust, and easily maintainable. Commercially available potentiometric chloride sensors typically utilize ISEs which show durability problems and can be costly. To address these problems, Gandía-Romero et al. [− sensors made of Ag/AgCl resistive pastes, aiming to produce accurate, miniaturized, long-term, and inexpensive electrodes for monitoring Cl− concentration in concrete. This technology is based on a printing method, which comprises a rubber palette to transfer inks via a display on the substrate surface. Screen-printed sensors are generally robust, inexpensive, and allow integration of multiple sensors in a small space. Sensors based on this technology are ideal for industrial mass production since it is possible to utilize resistive pastes, which are readily available in the market. The developed thick-film Ag/AgCl sensors are illustrated in − concentration in concrete specimens at different depths. The author concluded that the thick-film Ag/AgCl is a promising Cl− sensor for concrete structure since it is robust, miniaturized, low cost, and have long-term stability.All the above short- and long-term evaluations of potentiometric Ag/AgCl based chloride sensors performed in pore solutions, mortar and concrete specimens demonstrated that Ag/AgCl electrode is stable and reliable in alkaline environments, and thus they could be suitable to monitor Clo et al.  develope− sensors is through cables. There are few studies which demonstrate the possibilities of wireless monitoring of Cl− in concrete element using potentiometric sensors. Abbas et al. [− concentrations using sensor based on Ag/AgCl electrodes. The block diagram of the proposed wireless method for monitoring Cl− using Ag/AgCl electrode is shown in − concentration. Using near-field coupling, the resonance frequency is reflected on an antenna. The communication does not need battery/external power. The authors were able to reliably measure the Cl− concentrations (0.01 to 0.2 M) up to 35 mm between readout and sensor coil.The data transmission method of all the above mentioned potentiometric Cls et al.  were abl− concentration in concrete. The sensor is based on radio-frequency identification (RFID) communication protocol, which comprises an energy harvesting and management circuit, low-dropout (LDO) voltage regulator, microcontroller unit (MCU), RFID tag chip and three pairs of electrodes. These are: (i) calomel reference electrode, (ii) platinum, Pt, reference electrode, and (iii) Ag/AgCl electrode. The sensor tag powers its circuitry by harvesting energy which is radiated by the RFID reader. The authors also adopted a wavelet denoising approach to filter out the noise from the raw data which are corrupted by the noises in the wireless channel. In addition, monitoring software to display real-time measurements was developed. The performance of the sensor was tested in concrete with different Cl− concentration. The authors claimed that the sensitivity of the developed wireless Cl− sensor is high and the response time of the electrodes are sufficiently fast. The sensor reliably measures the Cl− content in concrete within a communication distance of 16.3 m.Zhou et al.  proposed− content in concrete as well as open circuit potential and corrosion current density of rebar, electrical resistivity of concrete, oxygen availability, and inner temperature. The Cl− sensor was developed based on Ag/AgCl electrodes. The evaluation of the sensors, in solutions of different pH values, exhibited acceptable stability and great reproducibility. The sensors have also demonstrated reasonably good stability when embedded in mortar for two years.There are also studies which demonstrate the possibilities of integrating potentiometric sensors to monitor different parameters in a concrete environment. For instance, Duffó and Farina  develope2, Ag/Ag2O, Ti/IrO2, W/WO3, and MO electrodes are used in recent time to monitor pH in a concrete environment. Femenias et al. [x) electrodes. They continuously monitor pH at different depths over time in mortar specimens subjected to accelerated carbonation. The authors claimed that the utilized pH sensors can provide insight into the carbonation process and in the kinetic processes, for example, transport and phases transformations. These authors, in another work [x electrodes for long-term continuous pH monitoring in a concrete environment, focusing on its reproducibility, stability, accuracy, and oxygen dependency. The sensor was exposed to highly alkaline solutions (pH 9–13.5) for about two years and they were able to measure with a maximum error of 0.5 pH units. They also examined its performance by embedding in mortar for about 160 days. The authors concluded that IrOx electrodes-based sensors are stable, accurate, oxygen independent, and have outstanding ability for pH monitoring in a concrete environment. The formed (10–25 μm) thickness of the oxide layer is beneficial for long-term stability in concrete structure. Indeed, the authors indicated the essentiality of the IrOx electrodes conditioning in highly alkaline solutions for a minimum of 3–4 months in order to achieve precise and reproducible potential responses. The response time of the electrodes are adequately fast for pH monitoring in a concrete environment. The schematic illustration and stereomicroscopy image of an IrOx electrode that is developed to monitor pH in a concrete environment is shown in Monitoring the pH of the concrete is vital since the alkalinity of the concrete has paramount importance in protecting the embedded rebar against corrosion. Though the use of potentiometric sensors for pH measurement is a common practice in various application areas, its use in monitoring the pH of the concrete pore solution is very limited. It can be noticed from s et al.  utilizedher work , examine3-based chloride sensor by exposing it to saturated calcium hydroxide solution for 10 months. The sensitivity was slightly decreased within the pH range of 5–12, but the response was stable and repeatable in high-alkaline solutions (pH > 12). The sub-Nernstian response was observed within the pH range of 2–5. None of the analysed interfering ions, SO42−, K+, and Cl−, had a substantial impact on electrode potential. The W/WO3 electrode is robust, simple, low cost, and temperature resistant. By considering all these facts, the author reported that W/WO3 electrode is applicable for the long-term monitoring of Cl− in concrete environment.Kolar et al.  examined2O potentiometric pH sensor using thick-film technology and examined the performance of the sensor in simulated concrete pore solutions and concrete specimens. The performance evaluation of the sensor confirmed its reproducibility, reversibility, and acceptable response time. Based on these facts, the authors concluded that the screen-printed Ag/Ag2O sensors can be embedded into concrete to continuously monitor pH in real time, which in turn provide insight regarding the carbonation front.Similar to chloride sensors, Gandía-Romero et al.  developex), and a reference electrode (Ag/AgCl), a thermistor, a voltage sensing circuit and an interrogator coil which is inductively connected to the inductor of the sensor. The sensor was calibrated with a range of 25–55 °C and 1.5–12 for temperature and pH, respectively. By utilizing temperature compensation, a sensitivity of less than 0.1 pH was achieved with a response time of below 1 s. Nonetheless, this sensor is unstable to interference by the existence of other ionic matters. The authors claimed that the temperature compensation capacity and the design simplicity of the sensor make it suitable to be integrated by printed technology, so that the sensor will be used to remotely monitor pH in a concrete environment [Bhadra et al.  reportedironment . − concentrations and pH at rebar/concrete interface is imperative for detecting rebar corrosion at early stage and to make sound decisions. In this regard, there are some attempts which show the possibility of integrating chloride and pH sensors to monitor both parameters  simultaneously. For example, Du et al. [− concentration at the interface of rebar and concrete. The pH and the chloride sensors are based on Ir/IrO2 and Ag/AgCl electrodes, respectively. The sensor was embedded in the concrete to simultaneously monitor pH of the pore solution and the amount of Cl− concentrations. The reported test results revealed that the integrated sensor is stable and robust, indicating the potential of the sensor to realize continuous in-service monitoring of pH and Cl− concentrations in concrete. Monitoring of Clu et al.  develope− sensors, which are integrated with other sensors that monitor different parameters in concrete environment. For example, Yu and Caseres [− concentrations, pH, microcell corrosion current, and localized concrete resistivity, respectively. The long-term sensitivity and reliability of the prototype sensor was evaluated by embedding it in a cement paste cylinder. The claimed results (based on a year of monitoring) indicated that the pH and the other integrated sensors were reliable and stable, showing its potential to be implemented in real RC structures. − concentration in concrete, corrosion current, and equilibrium potential of rebar. The pH sensor was developed from Ti/IrO2 electrode, while the Cl− sensor from Ag/AgCl electrode. The reported results of the investigation demonstrated that all the sensors (including pH and Cl−) were stable and reliable while providing great potential responses. Hence, this multifunctional sensor is suitable for long-term in-service monitoring of corrosion causing parameters. There are also pH and Cl Caseres  developeAs ISEs measurement, optical techniques are one of the oldest and well-established methods for detecting chemical analytes and have shaped the foundation for several chemical sensors. The optical based sensing technology is not based on a single concept but on a variety of optical phenomena that can be applied to measure a wide range of chemical and physical parameters ,58. The In the past four decades, there has been substantial research attempt in developing optical fiber- based sensors for both chemical and physical analytes. Accordingly, several interesting schemes have been made and continue to be the subject of significant research. Application areas for chemical analysis involve laboratory-based analysis, environmental monitoring, and clinical diagnosis applications. Every area of specific application has their own prerequisites for selectivity, sensitivity, accuracy, robustness, and cost. The studied physical state of the analytes comprised gases, dissolved gases, liquids, ions in solution, and solids . With FO− concentrations in concrete environment was developed. Ding et al. [− sensor using a suspended-core optical fiber for in-situ real-time monitoring. The predominant property of suspended-core optical fiber is its big air holes running throughout its length, and thus sensitive material could be stored into the holes. This type of optical fiber has extended interaction length, powerful light-matter interaction and utilization of small sample amounts [+, Ca2+, Mg2+, SO42−, and OH−) that can be occurred in concrete was tested. The authors claimed that the sensor works in high-alkaline environments. Na+, Ca2+, and Mg2+ have minor influence on Cl− detection of the fiber-optics sensor and high amount of SO42− slightly hamper the process of lucigenin quenching. The OH− has a major interference in Cl− detection of the sensor. Based on the results, the authors claimed that the developed sensor could be successfully applied for Cl− monitoring in concrete structure. Laferrière et al. [− concentrations in concrete pores. It uses Cl− sensitive fluorescence indicator dye. The performance of the developed sensor was tested in mortar specimens at various depths in two simulated climatic conditions: (i) hot maritime and (ii) cold environment. The authors reported that it is possible to precisely quantify the Cl− concentrations in both climatic conditions, indicating its applicability for scientific studies and condition monitoring of concrete structure. The schematic representation of the optical fiber based Cl− sensor measurement setup and the components of the sensor is illustrated in Recently, few numbers of fiber optic-based sensors to monitor Clg et al.  have dev amounts . They ine et al.  has deveThough fiber-optic fluorescence techniques are applied to measure pH in various fields of study, its application in concrete environments is yet limited. Nguyen et al. ,61 produAs discussed earlier, the operational technique of the potentiometric and fiber-optic sensors is different. Since both types of sensing devices are based on their own specific principles; they are affected by different parameters. Thus, the comparison between them is focused on their production process, invasiveness, and performance. − and pH in the concrete element. The production process of potentiometric sensors is simple which adopts the well-known electrochemical processes, whereas the fiber-optic sensors are highly technical and complicated. Regarding invasiveness, both types of sensing devices have negligible effect on the structural behaviour of the infrastructure because they are small compared with the size of the structural element under investigation. They also have no impact on the surrounding environment during measuring ClThe overall performance of the potentiometric sensors largely depends on the types and preparation of the electrodes. As several of the parameters  presented in − and pH sensors presented above can be embedded in real RC structures for corrosion monitoring as almost all the authors concluded that both potentiometric and fiber-optic sensors are reasonably precise, stable, and reliable. This allows avoiding the conventional laboratory based destructive testing and paves a way for continuous monitoring. All but three of the sensors that are presented in The ClThe IoT is a networked system where distributed sensors monitor physical events and transmit the measurements through wireless communication medium to a remote user. IoTs have been proposed for a number of different applications, such as healthcare ,65,66, eVarious low-power communication technologies are developed for transmitting the data from the computing device to the gateway. These technologies differ in their communication range, spectrum usage, bandwidth requirement and power consumption. For corrosion monitoring of RC structures, communication technologies that have 100 m or longer communication range, such as Zigbee , LoRa 77, SigfoxIoT-based corrosion monitoring system has advantages over wired sensors with datalogger systems in terms of continuous measurements, cost effectiveness, flexibility, remote monitoring, ease of deployment and maintenance. There have been proposals on the use of wireless sensor networks for corrosion detection ,79,80,81− permeability [− diffusion coefficient [With the emerging IoT based low-cost continuous monitoring system, speculating about where the future might lead in corrosion assessment of RC structures is interesting. It is well known that smart environments based on IoTs and complex data analytical techniques represent the next evolutionary development step in various disciplines, including transport , militareability ,125,126,eability ,128, Cl−fficient ,131,132,fficient ,133, andfficient .Continuous in-situ monitoring of parameters that initiate and accelerate rebar corrosion in concrete structure is crucial to avoid corrosion associated damage. An early detection of corrosion risks assists engineers to plan optimal maintenance measures in a timely and cost-effective manner. Long-term in-situ monitoring of such parameters has also the utmost importance in better understanding of the complex corrosion phenomenon. With the current development of sensing technology, realization of miniaturized sensors, that are stable, accurate, robust, and low-cost, for monitoring durability performance of RC structures will grow in years to come. These sensors can be employed in RC structures to monitor factors that control corrosion of rebar or other deterioration mechanisms, even in remote locations that are normally inconvenient to access. Data acquired from several sensors will be fused using machine learning and/or deep learning methods. The fused data will then be used to evaluate the status of the structures autonomously by applying appropriate algorithm(s). Several machine learning algorithms such as k-nearest neighbors, linear models, decision trees, ensembles of decision trees, and support vector machine as well as deep learning algorithms such as convolutional neural network, recurrent neural networks, long short-term memory networks and deep belief networks, have the potential to be employed for realizing autonomous corrosion assessment method. Thus, the application of IoT systems and intelligent data analytics will form a principal element in lifecycle management of RC structures.Autonomous corrosion assessment utilizing IoT systems and advanced data analytics is illustrated in − sensors that are proposed for monitoring the carbonation front and Cl− concentration in concrete environment are critically reviewed. Based on their measuring principles, the sensors utilized in concrete environment for monitoring pH and Cl− concentration can be categorized into two: potentiometric and fiber optic. The majority of the studied pH and Cl− sensors have showed high sensitivity, reliability, and stability in concrete environment, though the experiments were carried out for relatively short periods. The review work also identified three cases that attempted to monitor the Cl− in concrete wirelessly albeit very short range. In addition, this work speculates where the future might lead in corrosion condition assessment of RC structures. With the technology development of sensors along with IoT-based systems, and machine learning, autonomous corrosion condition assessment remotely in a cost-efficient manner will become feasible. The collected sensor data can be analysed further by engineers and scientists for greater understanding concerning the intricate corrosion phenomena. The new scientific knowledge will help scientists to design optimum solutions that increase the durability of infrastructure and to build proactive maintenance plans.Continuous monitoring of corrosion-causing factors in a reliable and cost-effective manner is vital to plan accurate condition-based maintenance strategies for RC structures. In this paper, state-of-the-art pH and Cl


The study follows a series of experiments on the fresh, hardened, and durability properties of PLC concrete with different replacement rates of nano CaCO3. Incorporation of 1% nano CaCO3 into PLC concrete provided the optimal performance, where the 56 days compressive strength was increased by approximately 7%, and the permeability was reduced by approximately 13% as compared to Ordinary Portland Cement (OPC) concrete. Further, improvements were observed in other durability aspects such as Alkali-Silica Reaction (ASR) and scaling resistance. Additionally, nano CaCO3 has the potential to be produced within the cement plant while utilizing the CO2 emissions from the cement industries. The integration of nanotechnology in PLC concrete thus will help produce a more environment-friendly concrete with enhanced performance. More in-depth study on commercial production of nano CaCO3 thus has the potential to offer a new generation cement—sustainable, economical, and durable cement—leading towards green infrastructure and global environmental sustainability.Despite lower environmental impacts, the use of Portland Limestone Cement (PLC) concrete has been limited due to its reduced later age strength and compromised durability properties. This research evaluates the effects of nano calcium carbonate (CaCO Sustainable approaches are, therefore, required to effectively control the environmental impact of cement production. A recent report published by Chatham House [Approximately 4.1 billion metric tons of cement are currently produced globally every year, accounting for about eight to ten percent of global anthropogenic carbon-dioxide CO emission2 of the cement [Portland Limestone Cement (PLC) has often been used as an environment-friendly alternative to Ordinary Portland Cement (OPC) . PLC is e cement .European countries were the early users of PLC. The European Standard EN 197 allows two types of Portland limestone cements: Type II/A-L containing 6–20% and Type II/B-L containing 21–35% limestone powder . More reTo compensate for these limitations, use of other Supplementary Cementitious Materials (SCMs) has been a common practice. One of the commonly used SCM is fly ash, and several studies have concluded that addition of fly ash helps improve concrete properties ,12. Howe3) as partial replacements  of PLC in concretes and identifies changes in fresh and hardened concrete properties including durability. Nano CaCO3, as compared to several other nano materials such as nano TiO2, nano SiO2, nano Al2O3, nano Fe3O4, nano ZrO2, carbon nanotubes, and carbon nanofibers, is economical and easily available [3 can provide comparable benefits to other higher-cost nanomaterials [3 can be produced within the cement plant utilizing the waste CO2 using an integrated approach for green and economical cement production [3 can mitigate the shortcomings of PLC concrete.This paper evaluates the use of nano calcium carbonate  images. While advancing the current knowledge in the field, the findings from this research provide research directions for the future to achieve the sustainability goals in the construction industries.To the authors’ knowledge, the performance of PLC incorporated with nano CaCOno CaCO3 . This re2/kg and Type IL-PLC with Blaine fineness of 450 m2/kg were used as binders. Commercially available Type I/II-OPC was used while Type IL PLC was obtained from a local source and was produced by inter-grinding Type I cement clinker with 15% of limestone by weight in the cement plant. 3 (98% pure) with an average diameter of 40 nm and a specific surface area greater than 40 m2/g was used. On average, the size of nano CaCO3 is 2.5 times smaller, and the specific surface area is twice as large as those of silica fume. 3 under SEM.Type I/II-OPC with Blaine fineness of 390 m3 (control sample) and samples with nano CaCO3 at varying replacement rates of 1%, 2%, and 3%.The properties evaluated in this study include: (a) slump and setting of fresh concrete, (b) compressive strength and modulus of elasticity of hardened concrete, and (c) concrete durability properties—permeability, alkali silica reaction (ASR), and scaling resistance. In addition, the microstructure was investigated using SEM images and EDS analysis. Concrete samples were prepared as per ASTM guidelines for both OPC and PLC and consisted of samples without nano CaCO3 on concrete properties, two different concrete mixing methods were evaluated. In one method, CaCO3 was introduced to the mixer right after cement addition, which is called regular mixing in this paper. In the other method, nano CaCO3 and cement were placed in an electrically driven mechanical mixer and blended under high speed for three to four minutes; this is called modified mixing in this paper. This modified mixing is considered to disperse nano CaCO3 more effectively, reducing the agglomeration of nano materials as observed in a concrete made by a regular mixing  of concrete are given in 3 (650 lbs per 1 cy) of concrete. Despite the common practice of using chemical admixtures in concrete production, no chemical admixtures were used in this experiment to limit the interference of other chemicals on the effects of using nano CaCO3. A study by Shaikh et al. [The mixture proportions for 0.76 mh et al.  shows thSlump and setting tests were conducted as per ASTM C143  and ASTM2 (4 × 8 in2) were tested at 3, 7, 28, and 56 days. The specimens were fabricated and moist cured in accordance with ASTM C192 [2 (4 × 8 in2) were cured for 56 days, as per ASTM C192 [2 (4 × 2 in2) as prescribed by ASTM C1202 [3 (1 × 1 × 10 in3) as per ASTM C1260 [3 (6 × 6 × 24 in3) with plastic dikes of 19 mm (0.75 in) height for the chloride solution.For compressive strength and elastic modulus, cylindrical concrete specimens of 100 × 200 mmSTM C192 . Rapid CSTM C192  using thSTM C192 . The curTM C1202 . An alkaTM C1260 , where sTM C1260  at 5, 10TM C1260 . The tes3 on the microstructural changes in concrete. The specimens were prepared as per ASTM C305 [SEM image and Energy Dispersive Spectroscopy (EDS) analyses were conducted to investigate the effects of nano CaCOSTM C305 . A Zeiss3 and its replacement rates on fresh and hardened concrete properties, including mechanical properties and durability of concretes made with OPC and PLC. All the testing results presented in this paper are the averages of three specimens, except for scaling resistance (single specimen).Test results were analyzed to evaluate the effects of nano CaCO3 on slump. Since the specific surface area of nano CaCO3 is about twice as large as that of silica fume, the incorporation of nano CaCO3 in concrete could adversely affect the workability of concrete, which can be an issue from a practical standpoint. Slump loss of 13 mm (0.5 in) was observed for both OPC and PLC at replacement rates of 2% and 3%. It appears that large surface areas of nano CaCO3 have negative effects on concrete workability, as observed in concretes with silica fume. However, 1% replacement of nano CaCO3 did not change the slump for either concretes, indicating that the effect of large surface area of nano CaCO3 on workability is minimal at a 1% replacement rate.Concrete setting is controlled by the hydration rate, where the set time varies inversely with the hydration rate, i.e., an increase in the hydration rate leads to reduced set times. Limestone powder fills the microstructure space between hydration products, reducing the set time . Limesto3 would serve as a catalyst for hydration rates. The setting tests conducted on concretes with different replacement rates of nano CaCO3 shown in 3. The exact mechanism has not been identified; however, it could be possibly due to the inefficient dispersion of nanomaterials as no special mixing techniques were used in this study. This could lead to agglomeration of nano particles thus increasing the size from nano to micro as shown in 3 in concrete, the higher the chances for agglomeration. Also, it appears that the increased rate of nano CaCO3 accentuated the dilution effect resulting in a decreased rate of hydration.Further, a study by Kakali et al.  has show3, PLC concrete has higher strength than OPC concrete up to 7 days, while at 28 days, both the concretes have comparable strengths. Limestone powder acts as an inert filler, creating a dense structure in concrete through improved packing and helps in the early hydration of cement due to a nucleation effect, thus improving early age strength of PLC. However, at 56 days, the strength of PLC concrete is a little lower than OPC concrete. At later ages, this reduction could be attributed to the pronounced dilution effect being more dominant, resulting in lower strength of PLC concrete.Strength of concrete mainly depends on the amount of hydration products, porosity of concrete, and packing of the microstructure. 3, increased compressive strength for both OPC and PLC concretes. The effects of nano CaCO3, however, are more pronounced at the early ages for OPC concrete. Addition of nano CaCO3 accelerates the rate of C3S hydration as explained by Sato et al. [3S broke earlier during the induction period. This break reduces the induction period, thereby accelerating the C3S hydration rate and increasing the early age strength.Replacement of cement, especially with 1% nano CaCOo et al. , where t3 at 1% increased 3-day strength of OPC concrete by 52%; however, the strength increase diminishes with time, with only about 7% increase at 56 days. A similar trend was observed for PLC concrete, but at a lower scale, with 6% increase at 3 days and only 2% at 56 days. The large difference in strength increase of concretes with and without nano CaCO3 between early and later ages, especially for OPC concrete, might be due to a more prominent nucleation effect of nano CaCO3 at the early ages. 3 at 2% and 3% resulted in lower strengths than at 1% replacement rate for both concretes and at all ages. It appears that, as far as concrete strength is concerned, the optimum replacement rate of nano CaCO3 is 1%. Even though it is not known why additional nano CaCO3 beyond 1% resulted in reduced strength, it could be due to the enhanced dilution and filler effect [Replacement of nano CaCOr effect .3 in improving concrete strength or other mechanical properties. Other methods such as sonification could also be used for better dispersion of nano materials [Additionally, the test results were compared between two different mixing sequences. The samples with modified mix sequence (MOP-1 and MPL-1) had better strength at all ages, with the maximum increment at three days, as compared with regular mix (OP-1 and PL-1) concrete. The findings thus signify the importance of proper dispersion of nano CaCOaterials .3 on porosity or denseness of hydrated cement paste. The modulus of elasticity was slightly higher for concrete specimens with nano CaCO3 and a modified mixing sequence. For instance, elasticity at three days was approximately 6% higher for MOP-1 as compared to OP-1 and about 4% higher for MPL-1 as compared to PL-1.3 at 56 days: OP-0, OP-1, MOP-1, PL-0, PL-1, and MPL-1. This testing measures concrete resistivity, not permeability; however, a correlation exists between concrete resistivity and permeability [3 were not included in this testing since compressive testing results positively indicated an optimum replacement rate of 1%. This decision was also aided by several other studies [It is well known that concrete durability depends primarily on the permeability of concrete. For the evaluation of concrete permeability, rapid chloride penetration tests (RCPT) were conducted on six different concrete mixes with 1% replacement rate of nano CaCOeability . Other r studies ,44.3, and (2) modifying the mixing sequence, or effective dispersion of nano CaCO3. Replacement of cement with 1% nano CaCO3 reduced chloride permeability by 28% and 11% for OPC and PLC, respectively. This reduction could be the effect of enhanced pore structures and more hydration products due to a nucleation effect, as shown in the increased compressive strengths of concretes with 1% nano CaCO3 at 56 days. Improved packing density, formation of supplementary hydration products such as calcium carboaluminates, and carbosulfoaluminates, compact structures, and refined pores were some of the changes in microstructure that helped to reduce the porosity of concrete with the addition of nano CaCO3 [no CaCO3 ,45.Further reduction in chloride permeability for concretes with modified mixing (MOP-1 and MPL-1) signifies the importance of proper dispersion of the nano particles in concrete mixing on achieving the maximum improvements of concrete properties. Proper dispersion effects were also observed in the compressive strength .3.As PLC concrete showed higher slump when compared to OPC, the w/b ratio can be reduced for PLC, thus alleviating the adverse effects of limestone powder on chloride permeability of PLC concrete. Also, studies have shown that PLC with a lower w/b ratio provided better performance . More reAlkali silica reaction (ASR) in concrete occurs when reactive silica present in the aggregates reacts with hydroxide ions in the pore solution to form expansive silica gel, which could cause micro cracks in the concrete when moisture is absorbed. The expansion of concrete due to ASR depends on several factors such as the alkali content of the cement, the amount, and the reactivity of the silica present in the aggregates, the availability of moisture, and the porosity of the concrete.Substantial research has been conducted to identify the mechanisms of ASR ,47. The 3 did not reduce the expansion below an acceptable limit of 0.1%, it reduced the expansion substantially, especially for OPC mixes. The expansion of MOP-1 concrete is about half of the control (OP-0). The exact mechanism of this reduction in expansion for 1% replacement of cement with nano CaCO3 is not known. The alkalinity of the soak solution in ASTM C1260 [3.TM C1260  is quiteTM C1260 . Thus, t3, but on a lower scale. The expansion for MPL-1 was reduced by approximately 18% as compared to PL-0. This reduced effectiveness of nano CaCO3 on PLC concrete could be due to the higher permeability of PLC as compared to OPC concrete. On the contrary, the ASR expansion for PL-0 is approximately 22% lower as compared to OP-0, despite its higher chloride permeability.A similar effect was observed for PLC concrete with nano CaCOScaling is the removal of a concrete surface in repeated freezing and thawing environments, and mainly occurs in concrete structures where salt is used as a de-icing agent. There are four theories involved in scaling of concrete: osmotic pressure theory, hydraulic pressure theory, critical saturation degree theory, and water absorption theory ,50,51,52There are a number of factors that affect the scaling resistance of concrete, including porosity or strength, w/b ratio, method of curing, air entrainment, and type of coarse aggregates used ,54; of t3 experienced the least mass loss. In this study, concrete did not contain any entrained air. It is interesting that quite comparable mass losses were observed for OPC with 1% nano CaCO3 and PLC with no nano CaCO3. However, PLC with 1% nano CaCO3 significantly reduces the mass loss of concrete due to scaling.3 improved scaling resistance for both concretes, even though MOP-1 and PL-0 concretes show a similar trend when it comes to the mass of concrete scaled off  and gypsum form ettringite or calcium sulfoaluminates, and as the gypsum is depleted, calcium sulfoaluminates convert to monosulfoaluminates [3 react with C3A in the concrete to form calcium carboaluminates [3A in the presence of CaCO3 retards or stops the conversion of ettringite to monosulfoaluminates. Moreover, study shows that the addition of CaCO3 replaces the sulfate ions in calcium sulfoaluminates and monosulfoaluminates by carbonate ions, further stabilizing the ettringites or calcium sulfoaluminates [In OPC concrete, reactions between tri-calcium aluminate  of nano CaCO3 in PLC were investigated where 1% replacement provided the optimal performance, as summarized below.To make Portland cement environment-friendly and economical, limestone powder is incorporated during the manufacture of cement. This cement type, called PLC (Portland Limestone Cement), has environmental benefits due to the reduced clinker production required. However, the use of PLC has been limited primarily due to its reduced later age strength. The use of CaCO3. However, with larger replacements of 2% and 3%, concrete workability decreased. The setting time for the concrete, especially the final set, was affected by the incorporation of nano CaCO3. The final setting was accelerated for PLC concretes with up to 2% nano CaCO3 replacements; however, at 3% replacement, the trend was reversed with longer set times.The workability of PLC concrete was not adversely affected by 1% replacement of cement with nano CaCO3. The strength, however, exceeded the strength for OPC by 7% when a modified mixing sequence was used.A comparable 56-day compressive strength was observed for PLC with 1% nano CaCO3 in PLC.Permeability at 56-days and ASR expansion at 14-days were reduced by approximately 33% and 20%, respectively with the replacement of 1% nano CaCO3 in both OPC and PLC concretes helps in densifying the pore structure and in increasing the amount of hydration products, thus improving the strength and durability properties of both concretes.SEM images showed that nano CaCO3 was investigated by modifying the way nano CaCO3 was introduced. Compared with adding nano CaCO3 to cement during concrete mixing, pre-mixing of nano CaCO3 with cement prior to concrete mixing improved both the mechanical properties and the durability of both OPC and PLC concretes.Also, the effect of dispersion of nano CaCO3 in the presence of chemical admixtures was not investigated. Further study is recommended to evaluate the effect of nano CaCO3 in combination with different types of admixtures.In this study chemical admixtures were not used. The effect of nano CaCOInefficient dispersion of nanomaterials in the concrete mix has been identified as one of the major challenges and process costs for the industries. As observed in this study, pronounced effects on performance of concrete was observed when a modified mixing sequence was adopted. Further research is needed to identify the optimum mixing method to achieve efficient dispersion of the nanomaterials.