The relationship between antibiotic use and antimicrobial resistance varies with cultural, socio-economic, and environmental factors. We examined these relationships in Kibera, an informal settlement in Nairobi—Kenya, characterized by high population density, high burden of respiratory disease and diarrhea.E. coli  were isolated and tested for susceptibility to nine antibiotics.Two-hundred households were enrolled in a 5-month longitudinal study. One adult (≥ 18 years) and one child (≤ 5 years) participated per household. Biweekly interviews (n = 1516) that included questions on water, sanitation, hygiene, and antibiotic use in the previous two weeks were conducted, and 2341 stool, 2843 hand swabs and 1490 drinking water samples collected. Presumptive E. coli were resistant to ≥ 3 antibiotic classes. Stool isolates were resistant to trimethoprim (mean: 81%), sulfamethoxazole (80%), ampicillin (68%), streptomycin (60%) and tetracycline (55%). Ninety-seven households reported using an antibiotic in at least one visit over the study period for a total of 144 episodes and 190 antibiotic doses. Enrolled children had five times the number of episodes reported by enrolled adults (96 vs. 19). Multivariable linear mixed-effects models indicated that children eating soil from the household yard and the presence of informal hand-washing stations were associated with increased numbers of antimicrobial-resistant bacteria . Rainy conditions were associated with reduced carriage of antimicrobial-resistant bacteria (1·19 to 3·26 log10 depending on the antibiotic tested).Eighty percent of presumptive Antibiotic use provided little explanatory power for the prevalence of antimicrobial resistance. Transmission of resistant bacteria in this setting through unsanitary living conditions likely overwhelms incremental changes in antibiotic use. Under such circumstances, sanitation, hygiene, and disease transmission are the limiting factors for reducing the prevalence of resistant bacteria. Numerous organizations have called attention to the increasing prevalence of antimicrobial resistance (AMR) worldwide . EffortsIn 2013 the United Nations Human Settlements Program estimated that a quarter of the world’s urban population lived in slums ; informaWe assessed the relationship between sanitation, antibiotic use, and antimicrobial resistance in Kibera. We surmise that socio-economic and environmental determinants likely impact both antibiotic use and antimicrobial resistance in Kibera and similar impoverished communities.2 . A reference plate (Mac without antibiotic) was prepared for each 96-well plate to confirm cell viability. Isolates were either scored resistant (visible growth) or susceptible (no growth). Partial growth (satellite colonies) relative to the reference plate was considered susceptible. For quality control, 248 presumptive E. coli CFU. This measure was chosen to reflect different reservoir “sizes” of resistant bacteria and to provide greater analytical power to detect modest changes in colonization that may not have been detectable with prevalence values. Load data were log10-transformed and analyzed as continuous variables. Linear mixed-effects models fit by the restricted maximum likelihood lme4 package in R [10) of resistant E. coli in stool samples. Separate models were constructed to predict household-level (adult and child samples) and individual-level (adult or child samples) AMR load. Antibiotic use, water, sanitation, and hygiene-related variables were tested as the main predictors for the carriage of antibiotic resistant E. coli. Demographic and environmental variables were additional predictors.Household survey data were checked for accuracy and completeness within a day of collection and were compiled in a Microsoft Access database . Sample data were managed in Microsoft Excel . The main outcomes of interest were “load of resistance” (stool samples only), prevalence of resistance and number of resistance patterns. The load of resistance was calculated as a product of the prevalence of resistance (proportion of stool isolates resistant to each antibiotic) and the quantified age in R  were useP < 0·2 in two or more univariable models were included in the multivariable regression analyses. To avert modeling problems resulting from collinearity, a Pearson’s correlation coefficient was used to identify correlated variables (r ≥ 0·7) after which one of a pair of correlated variables was removed. Variables with P < 0·05 in the multivariable analysis were considered significant predictors of the load of resistant E. coli.Effects due to household respondents were assumed to be constant across households. Consequently, only a household-specific random intercept (Household ID) was included in household-level models, and an individual-specific random intercept (Respondent ID) in individual-level models. This allowed us to account for variations due to repeated sampling of households and individuals, respectively. Each fixed effect was regressed independently against household or individual AMR load, applying the appropriate random intercept. Variables with Eighty-one percent 81%) of the 200 enrolled households participated in seven of the nine visits. Household participation dipped in visits 8 (64%) and 9 (58%) because some study respondents traveled elsewhere for holiday festivities  of the 200 households reported an antibiotic use episode in at least one visit over the 5-month period. This accounted for 144 episodes, i.e., reported case of antibiotic use by the enrolled adult, enrolled child, and/or other household member, and a total of 190 antibiotic “doses”. Enrolled children had five times the number of episodes reported by enrolled adults (96 vs. 19) and three times that by other household members (96 vs. 29). Episodes by enrolled children represented 67% (96/144) of household antibiotic use episodes. Fifteen different antibiotics were reported over the study period, 53% of which were beta-lactam antibiotics. Amoxicillin was the most used antibiotic within the household , followed by ampicillin , cotrimoxazole , erythromycin and metronidazole . Enrolled children commonly used amoxicillin  and cotrimoxazole ; Fig. Most households 92%) accessed water for their daily household needs from protected sources, and 81% spent < 15 min to make a return trip to the main water source (Table % accesseE. coli were isolated from 99·0% of stool (n = 2341), 12·1% hand (n = 2843) and 9·8% of water (n = 1490) samples. Phenotypic tests for 248 isolates confirmed that our selection criteria for E. coli was reliable (99·2% accuracy). Isolates  were tested against nine antibiotics from seven antibiotic classes. Of these, 23,981 (87·4%) stool isolates, 3020 (83·0%) hand swab isolates and 2354 (79.7%) water isolates were resistant to at least one antibiotic; 80% percent of all presumptive E. coli isolates were resistant to ≥ 3 antibiotic classes. The prevalence of resistance to ampicillin, streptomycin, sulfamethoxazole, tetracycline, and trimethoprim was > 15% across all sample types and > 50% among stool samples. Resistance to ceftazidime, chloramphenicol, ciprofloxacin, and kanamycin was < 15% across all specimen types  and hand swabs (19·6%), while SulTmp was the most abundant in isolates from water , and between 0·7 × 101 and 1·3 × 102 CFU/g for low-prevalence phenotypes . The distribution of resistant E. coli in adult and child stool samples was similar although on average, children had marginally higher loads of ampicillin and chloramphenicol-resistant E. coli  of both prevalence and load of resistant E. coli at household and individual levels. When these predictors were added to multivariable regression models, the level of significance (P < 0·05) varied depending on the antibiotic tested, and the level of analysis i.e. household or individual , among adults , and children .Enrolled children eating soil (β = 0·27 to 0·80 log increase) and presence of a common hand-washing station within the housing block (β = 0·22 to 0·51) were both associated with increased load of antimicrobial-resistant E. coli at the level household  of antibiotic-resistant ·26 log oE. coli in this population despite the common use of oral formulations , or discourage outdoor activities and thus reduce contact with contaminated environments. Furthermore, wet seasons are generally associated with lower ambient temperatures, which may reduce the environmental load of bacteria.Fecal environmental contamination likely explains why the variable “children eating soil” was a significant predictor for increased individual and household AMR load. This environmental connection is consistent with the negative association between the load of antibiotic-resistant E. coli. While this correlation seems counter-intuitive, it is consistent with these stations serving as fomites. Moist surfaces around wash stations favor bacterial survival and proliferation, and the inconsistent availability of soap likely contributes to this outcome. This interpretation is supported by the association between lack of a hand-washing station and lower Amp resistance, and by behavioral practices for which handwashing after use of public toilets was associated with increased Amp-resistant E. coli in children and increased Tet-resistant E. coli in adults.Unfortunately, when hand-washing stations were used by multiple households within the housing block they were a risk factor for a higher load of antibiotic-resistant E. coli in children [Like many communities in low-income countries –33, resichildren . While Kchildren , and migAs a community, Kibera suffers from poor sanitation and a dense population, conditions that favor transmission of infectious diseases. It is unclear what proportion of antibiotic use in this setting is justified. Nevertheless, antibiotics likely provide a much-needed health benefit while inadvertently selecting for antibiotic-resistant bacteria. AMR transmission is a density-dependent process. Thus, when resistant bacteria in environments with poor sanitation are enriched from antibiotic use, ideal conditions for a steady production of antibiotic-resistant bacteria are achieved. E. coli isolates for analysis. Colony morphology, while not a reliable diagnostic for species identity, was 99.2% consistent with E. coli based on a random subset of 248 isolates. We have successfully used this method for selecting E. coli for high-throughput assessment of antibiotic resistance in other studies [We acknowledge several limitations of our study. Firstly, self-reported data, inaccurate recall and biased responses could have increased variance in our results. Additionally, by sampling individuals who were available at home, our results may not be generalized to adult males and school-going children. Given that most enrolled adults were female household heads with extensive knowledge of household practices, and that household interactions facilitate “sharing” of germs, we surmise that our data were a reasonable representation of enrolled households. Secondly, we relied on colony morphology as the primary method to select presumptive  studies , 36–38. Kibera experiences sanitation challenges that promote disease transmission and demand for antibiotics within a highly dense population. Under these conditions it is likely that selection of antibiotic-resistant bacteria within the gut, their disposal and enrichment within the environment, and recurrent transmission to humans occurs continuously. For communities that suffer such scenarios, the fight against antibiotic-resistant bacteria will require significant reduction in the burden of infectious disease coupled with markedly improved sanitation at the household and community levels.Additional file 1. Water, Sanitation and Hygiene Questionnaire.Additional file 2. Antibiotic use Questionnaire.Additional file 3. Nine of the most abundant  resistance phenotypes out of 148 unique combinations. The number of isolates and their proportional representation (%) of the total are shown. Profile marked with an asterisk (*) denotes the penta-resistant phenotype.Additional file 4. Multivariable regression analysis for antimicrobial resistance load (Log10 CFU) at the household level. Only variables with P < 0·2 in the univariable mixed-effects model were included in the multivariable model. Regression estimates (β) and 95% confidence intervals with P < 0·05 are shown in bold. P = 0·00 indicates P < 0·01.Additional file 5. Multivariable regression analysis for antimicrobial resistance load (Log10 CFU) at the adult level (≥18 years). Only variables with P < 0·2 in the univariable mixed-effects model were included in the multivariable model. Regression estimates (β) and 95% confidence intervals with P < 0·05 are shown in bold. P = 0·00 indicates P < 0·01.Additional file 6. Multivariable regression analysis for antimicrobial resistance load (Log10 CFU) for children aged 0–5 years. Only variables with P < 0·2 in the univariable mixed-effects model were included in the multivariable model. Regression estimates (β) and 95% confidence intervals with P < 0·05 are shown in bold. P = 0·00 indicates P < 0·01.


CORR) of the rebars and, therefore, an increase in durability. In fact, after subjecting specimens to wetting–drying cycles in a 0.5 M sodium chloride solution for 630 days, corrosion is considered negligible in fly ash concrete with 10% or 20% lime (iCORR less than 0.2 µA/cm2), while in fly ash concrete without lime, corrosion was low (iCORR of the order of 0.3 µA/cm2) and in the reference concrete made with Portland cement, only the corrosion was high (iCORR between 2 and 3 µA/cm2).The main objective of this study was to analyze the influence that the addition of finely ground hydrated lime has on chloride-induced reinforcement corrosion in eco-efficient concrete made with 50% cement replacement by fly ash. Six tests were carried out: mercury intrusion porosimetry, chloride migration, accelerated chloride penetration, electrical resistivity, and corrosion rate. The results show that the addition of 10–20% of lime to fly ash concrete did not affect its resistance to chloride penetration. However, the cementitious matrix density is increased by the pozzolanic reaction between the fly ash and added lime. As a result, the porosity and the electrical resistivity improved , giving rise to a lower corrosion rate (i The pozzolanic reaction largely depends on temperature; according to Hanehara et al. , when cohlorides . As a rehlorides ,11.2 required for the pozzolanic reaction of fly ash may be insufficient and may reduce the pH [When fly ash is used as a partial cement replacement, not as an addition, the early strength of fly ash concrete is reduced due to the slow pozzolanic reaction of the ash ,13. Nevee the pH ,25,30,31Lime increases the availability of portlandite in concrete ,32,33, tTo date, studies of HVFA concrete with added lime have been scarce and have focused on analyzing their mechanical properties and microstructure ,25,32,36Four different concrete mixes were made with w/b (water/binder) ratio of 0.5: a reference concrete made with Portland cement only (C-0) and three mixes with 50% of the cement replaced by fly ash. Varying amounts of hydrated lime were also added to the three mixes: the first with 0% by weight of fly ash (CFA-0L), the second with 10% (CFA-10L), and the third with 20% (CFA-20L).The lime content was limited to a maximum of 20%, because with this content, Lorca et al.  obtained2, a density of 2.3 g/cm3, a particle size distribution similar to the fly ash, and with an average particle size of 22.8 μm. The grading curves of the fly ash and lime were determined by laser diffraction fraction . The cheSetting time was also measured in concrete mixes (ASTM C 403-08), to obtain further information on the influence of replacing cement by fly ash and adding lime . The 50%Compressive strength was tested according to European standard EN 12390-3. Tests were made at five different ages: 7, 28, 90, 180 and 365 days. Three batches were made from each mix, and two samples from each batch were tested at each age.To analyze the extent of chloride corrosion in the different concretes, six types of measurements were performed: mercury intrusion porosimetry, chloride migration coefficient, accelerated chloride penetration test, electrical resistivity, and corrosion rate. Electrical conductance tests were also carried out on different solutions of lime and fly ash in order to analyze the influence of adding lime on pore water conductivity.Different types of specimens were used and were removed from their molds 24 h after casting. Then, they were placed in the curing chamber at 20 °C and above 95% RH until the age of 28 days. As the pozzolanic reaction of fly ash is quite slow and only occurs in the presence of water, the specimens were subsequently immersed in water at 20 °C until the tests started.At 28 and 180 days, pore size distribution was determined by a Micromeritics AutoPore IV-9500 mercury porosimeter . The test was carried out on small drilled cores (12 mm diameter × 23 mm high) weighing approximately 6 g. The cored samples were obtained from the center of 100 × 100 × 100 mm cubic specimens. They were first dried in an oven  at 105 °C and then immersed in mercury under gradually increasing pressure. This technique can also measure total porosity of the sample.This test, performed to the NT BUILD 492 standard, provides a measure of the resistance of the concrete to chloride penetration. Cylindrical specimens with a diameter of 100 mm and a thickness of 50 mm were used. An external electrical potential was applied axially across the specimen to force the chloride ions outside to migrate into the specimen. At the time of the test, the specimen was axially split, and a silver nitrate solution was sprayed on the freshly split sections. Then, the chloride penetration depth could be measured from the visible white silver chloride precipitation, subsequently allowing the chloride migration coefficient to be calculated. The test was carried out at the age of 90 days. Three batches were made from each mix, and two samples from each batch were tested. The result was the arithmetic mean of all six values.To perform this test, 40 × 40 × 160 mm prismatic specimens were submerged in water until the age of 100 days and then exposed to successive wetting–drying cycles in a 0.5 M sodium chloride solution. The chloride concentration used is similar to that found in seawater. The time for each cycle was 7 days; the specimens were immersed in the solution for 4 days, then dried in an oven at 50 °C for 2 days, and finally cooled at room temperature for 1 day. The chloride penetration depth was measured at three different ages: after 3, 9, and 14 cycles . To perform the measurements, the specimens were axially split, and a silver nitrate solution was sprayed on the freshly split sections. Three batches were made from each mix, and two samples from each batch were tested. The result was the arithmetic mean of all six values.Electrical resistance was determined by the reference method (direct method) by applying a uniform electric field using two electrodes in contact with the specimen bases . Prismat2. The electrical contact for measurements was at the end of the bar, which was protected with Vaseline in order to prevent corrosion. After casting, the specimens were cured for 28 days and remained submerged in water until the age of 100 days. Then, the specimens were subjected to 7-day wetting–drying cycles in a 0.5 M sodium chloride solution  in the center were made. The bar protruded through one side of the specimen . The conCORR) was measured by the linear polarization resistance method [P) was obtained, and considering the ohmic drop between the bar and the reference electrode, iCORR was determined, iCORR = B/(A·Rp), where B is the Stern–Geary constant, which is assumed to be 26 mV [Corrosion current density . The total solid mass prepared for each mix was 2 g. First, a beaker was filled with 100 mL of distilled water, hermetically closed to prevent water loss by evaporation, and placed in a thermostated cell until the test temperature of 60 °C was reached. This temperature was chosen to speed up the reactions. Subsequently, the lime was added and conductance measured; then, fly ash was put inside, and conductance readings were obtained at different ages. The beakers were kept at a constant temperature of 60 °C ± 0.1 °C and under argon to avoid carbonation for the whole period. Likewise, the solutions were stirred continuously to facilitate the pozzolanic reaction . The conIn concrete mixes with fly ash , adding lime to the mixture improves the mechanical strength with the best performance at 20% lime. The increased strength is not significant at 7 days. At older ages, the added lime participates in the fly ash pozzolanic reaction, giving rise to new calcium silicate hydrates and therefore obtaining higher compressive strengths than in the concrete without lime. For example, at 1 year, the strength of CFA-10L and CFA-20L is respectively 11% and 18% higher than CFA-0L. At the same age, this increase in strength also enabled concrete mixes with 50% less cement and 20% added lime to be similar in strength to the reference concrete (C-0). These results agree with those obtained by Lorca et al.  and showAt the two ages studied, concretes with a 50% cement replacement by fly ash  have higher total porosity than the concrete made with Portland cement only (C-0) . These rAs it can be seen in the evolution of compressive strength, in C-0, the decrease in porosity from 28 to 180 days is very little (from 9.4% to 9.0%), which is probably due to the use of a high early strength cement and the absence of pozzolanic reaction. On the contrary, the porosity of fly ash concretes is reduced even more in the same period, matching the findings of other research groups ,42, and Regarding only the influence of hydrated lime on fly ash concrete mixes , the total pore volume is lower in concretes with added lime and is lowest with an addition of 20% . For exanssm) obtained at the age of 90 days. The chloride penetration for concretes made with 50% cement replaced by fly ash  is much lower than concrete without fly ash (mix C-0), giving Dnssm values of the order of 10 times lower. Differences in chloride permeability were also observed in the accelerated chloride penetration test  are similar to those for concrete without lime (CFA-0L). The chloride penetration depth in the specimens subjected to wetting–drying cycles is also similar, although it tends to be slightly higher in concretes with 10% and 20% of lime. As seen in Regarding only the influence of lime on the behavior of concretes made with fly ash , Electrical resistivity is a property that reflects the ability of a material to transport electric charge. In concrete, charge is transported through the ions dissolved in the pore solution, and therefore, the resistance provides an indication of pore connectivity. This parameter is also related to corrosion , since aConcretes made with a 50% cement replacement by fly ash  have much higher resistivity than the reference concrete (C-0), even though the latter’s total porosity is lower . For exa+, K+, and OH−; therefore, when this is reduced, conductivity also falls. Hussain and Rasheeduzzafar [− concentration decreases. In fact, when replacing part of the cement with fly ash, there is a decrease in the calcium hydroxide content (promoted simultaneously by the cement reduction and pozzolanic reaction), which consequently decreases the pH of the pore solution and therefore the OH− concentration, thus increasing the resistivity of concrete. Shi [+ and K+) generally decreases, leading to higher resistivity.Some additions are known to modify ion concentration in the pore solution ,48,49,50duzzafar  point ouete. Shi  or Yishuete. Shi  also fou2Oe). This is not the case of the fly ash used in the present study, in which the total equivalent sodium oxide content (Na2Oe) is less than 2.63% and with low lime and high silica content , To sum up, cement replacement by fly ash decreases the conductivity of the pore water, thus increasing the concrete resistivity, even though the total porosity may be higher. Furthermore, the addition of small quantities of hydrated lime does not significantly modify the pore water conductivity, but it does modify the concrete porosity, reducing it. In this case, it is the porosity that controls the mixture resistivity. As a consequence of all this, the resistivity of fly ash concretes with 10%–20% lime is higher than that of fly ash concrete without lime, and it is much higher than concrete made with Portland cement only.CORR is lower than 0.1 µA/cm2 (negligible corrosion). From a practical point of view, some researchers establish the onset of corrosion when an average sustained corrosion rate higher than 0.2 µA/cm2 is reached [According to Spanish standard UNE 112072 , the rei reached ,55.CORR evolution over time of rebars embedded in concrete specimens subjected to wetting–drying cycles in a 0.5 M sodium chloride solution. For all specimens, the iCORR value was not negligible during the first days, and afterwards, it quickly dropped below 0.1 µA/cm2. Thus, a little corrosion occurs initially, but later, a passivating layer is created around the rebar, stabilizing the iCORR.CORR value was always lower than 0.35 µA/cm2, while for C-0 concrete, a significant increase in the corrosion rate occurred 100 days after starting the wetting–drying cycles, reaching moderate values of iCORR (>0.5 µA/cm2) after 155 days and high values (>1.0 µA/cm2) after 210 days. Over 550 days, the corrosion rate tends to stabilize around values between 2 and 3 µA/cm2. These results are consistent with those reported in the accelerated chloride penetration test. As described in As shown in This better behavior against the chloride corrosion of fly ash concretes is due to two reasons: (a) the resistance to chloride penetration is higher than C-0 because the fly ash combines with some of the free chlorides, reducing its diffusion , and (b)CORR values are very similar; they always stayed below 0.15 µA/cm2 and 0.17 µA/cm2, respectively, and there are no visible signs of rebar corrosion , the addition of lime tends to slightly improve corrosion behavior. The corrosion rate was somewhat lower in CA-10L and CA-20L than CA-0L. For example, for concrete mixes with 10% and 20% added lime, the iorrosion b. Converbar ribs a. In thiTo sum up, 50% cement replacement by fly ash increases the electrical resistivity of concrete and its resistance to chloride diffusion, reducing the probability of rebar corrosion. The addition of hydrated lime to these concretes also favors fly ash hydration and allows making up for, in the long term, the loss of compressive strength and the increase in porosity that occurs as a result of the high cement substitution by fly ash. This improvement is greater with 20% than 10% lime. In this way, the rebar protection against corrosion increases and hence the concrete durability. Therefore, the addition of 20% lime to fly ash concretes improves their mechanical properties and durability, obtaining more sustainable concrete.The addition of finely ground hydrated lime to concretes with 50% cement replacement by fly ash improved compressive strength, this increase being greater with 20% than 10% lime. The addition of 20% allowed a compressive strength similar to that of concrete made entirely with Portland cement to be obtained after one year, which means that the fly ash has reacted in a significant way with the alkaline addition.Adding lime to fly ash concrete reduced porosity, and to a larger extent with 20% rather than 10% added lime. At 180 days, this reduction was on average 10% and 13% in CFA-10L and CFA-20L concrete mixes, respectively, compared to CFA-0L. Still, all fly ash concretes were more porous than concrete with Portland cement only.In fly ash concretes, the chloride penetration depth was around 10 times lower than in concrete made with Portland cement, despite having higher total porosity. This is due to the high alumina content of fly ash. The addition of 10–20% of lime to fly ash concrete did not affect its permeability to chlorides.Fly ash concretes had around 10 times higher resistivity than the reference concrete at the age of 180 days. The addition of 10–20% lime to fly ash concrete does not significantly modify the pore water conductivity but increases the concrete resistivity due to a decrease in porosity.CORR was of the order of 0.3 µA/cm2 in fly ash concrete without lime and less than 0.2 µA/cm2 in that with 10% or 20% lime.The corrosion rate in concrete with 50% cement replaced by fly ash was 85% lower than in the reference concrete due to higher resistance to chloride penetration and higher resistivity. Adding 10–20% lime to fly ash concrete slowed down the corrosion rate even more as a result of greater concrete resistivity. At 730 days, the iAs a general conclusion, the addition of 20% lime to high-volume fly ash concrete increases its mechanical properties and the reinforcement protection against chloride-induced corrosion, obtaining more sustainable concrete.The results obtained make it interesting to continue studying the durability of these concretes, specially carbonation-induced reinforcement corrosion in HVFA concrete, since fly ash concrete has a lower carbonation resistance. This loss of resistance is also higher with increasing fly ash content.The following conclusions can be drawn from the tests carried out on concretes with 50% cement replaced by fly ash:


Previous literature indicates a decrease in the mechanical properties of various concrete types that contain recycled aggregates (RA), due to their porosity and to their interface of transition zone (ITZ). However, other components of the RA concrete microstructure have not yet been explored, such as the modification of the new paste (NP) with respect to a reference concrete. This paper deals with the microstructure of the new paste of self-compacting concrete (SCC) for different levels of RA. The water to binder ratio (w/b) was kept constant for all concrete mixtures, and equal to 0.5. The SCC mixtures were prepared with percentages of coarse RA of 0%, 30%, 50% and 100%. Mercury intrusion porosimetry test (MIP) and scanning electron microscope (SEM) observations were conducted on the new paste of each concrete. The results indicated that the porosity of the new paste presents a significant variation for replacement percentages of 50% and 100% with respect to NP0 and NP30. However, RA contributed to the refinement of the pore structure of the new paste. The amount of macrospores the diameter of which is in the 50–10,000 nm range was reduced to 20% for NP50 and NP100, while it was about 30% for NP0 and NP30, attributed to the water released by RA. Compressive strength loss for SCC50 and SCC100 concretes are both influenced by porosity of RA, and by the NP porosity. The latter is similar for these two concretes with the 26% increase compared to a reference concrete. In the context of sustainable development, recycling of concrete waste is carried out with the main purpose of protecting the environment through the reduction of generated greenhouse gases and the preservation of natural resources. The reuse of concrete from demolition as aggregates in new concrete compositions reduces overheads and eases costs associated to waste management. Thus, this approach promotes the protection of natural resources, which are becoming increasingly difficult to obtain. Recycling of demolition waste has then witnessed a rather significant development. The European Directive on waste (2008/98/EC)  has fixeUsing recycled aggregates (RA) in self-compacting concrete (SCC) improves the ecological impact of concrete, since their microstructure properties are greater than normal vibrated concrete ,3,4. TheFew investigations have been conducted on the microstructure of SCCs made with RA. Unlike studies on conventional concrete, which showed the performance of recycled aggregate concrete is mainly due to the porosity caused by the old paste in RA ,11,12, t3), raising the question of RAC sample representativity of a RAC sample with respect to the real mix. Therefore, the current porosity will be fully identified using other techniques. Hence, it is necessary to propose a new approach to study the microstructure of RAC by MIP test. A suitable sampling method, especially considering the lower volume of coarse aggregate in SCC compared to conventional concrete, might ease the sampling of the new paste. Accordingly, this work proposes a sampling method to study the microstructure of the new paste (NP) of self-compacting concrete (SCC) for different levels of recycled aggregates (RA). The binder content was kept constant for all concrete mixtures, with a water to binder ratio (w/b) of 0.5. SCC mixtures were prepared with 0%, 30%, 50% and 100% of coarse RA. The pore distribution of the new paste was evaluated by MIP test, and its anhydrous content was quantified by SEM images analysis. Additionally, the contribution of the porosity of NP and RA to the decrease in compressive strength was investigated and demonstrated.The different components of an RAC  each generally occupy a significant volume, in the range of tens of cubic centimeters. On the other hand, MIP does need a small volume of the sample for testing (a few cm3 and a blaine specific surface of 3150 g/cm2. A limestone filler (LF) was used with a real density of 2.70 g/cm3 and a blaine specific surface of 4200 g/cm2. The chemical composition of both materials is provided in The type of cement used in all mixtures was CEM I/42.5 N with a real density of 3.16 g/cmTo obtain an SCC, the volume of the aggregates and their maximum size has been reduced to mitigate friction and to avoid blockages in confined areas. The maximum diameter of the coarse aggregates was fixed in our study at 15 mm. In this study, siliceous sand and crushed limestone sand were used as the fine natural aggregates. Natural coarse aggregates were made of crushed limestone aggregates and recycled coarse aggregates were obtained from construction and demolition waste (CDW). The grading curves of aggregates are presented in The main properties of the aggregates are displayed in In order to achieve equal consistency, and due to the higher water rate absorption of RA, the mixing of water had to be adjusted. This adjustment was achieved by using RA under the saturated surface dry (SSD) condition. If the aggregates are fully saturated, the surface moisture would increase the effective w/c ratio, the aim being that RA would have the same water absorption coefficient as NA. Thus, for each fraction of RA (3/8) and (8/15), the amount of water pre-saturation (M W.pre-sat) is defined as the difference between the water absorbed by RA and NA, and is calculated as follows:Despite the very rapid evolution of water absorption of the RA in the first five minutes, a pre-saturation time for 24 h was chosen. This is consistent with the relevant literature, in which it is indicated that absorption lasts for hours after its initial quick step ,30. This3), a water to binder ratio w/b ratio of 0.5 and a gravels/sand (G/S) ratio close to one. SCC-RA mixes were designed by replacing a volume of NA with RA. Four mixes were prepared with 0%, 30%, 50% and 100% recycled aggregates respectively labelled to SCC0, SCC30, SCC50 and SCC100 respectively. The mix designs of the concrete are shown in The mixing method used to design the compositions of the SCC is based on a composition of one with limestone fillers. The amount of components required for making one cubic meter of concrete was constant. They consisted in a paste volume of 37.5%  is one of the main methods for investigating the mesoporous structure (pore radius between 2 and 50 nm) and the macro-porous nature (apertures greater than 50 nm) of cementitious materials. Its effectiveness is based on the principle that to fill a non-wetting fluid into a pore of diameter d, a pressure P inversely proportional to this diameter must be applied. This pressure is given by the Washburn Equation (3):Here, the surface tension3), as shown in RA concretes (SCC30 and SCC50) are considered as multiphase composites in which the new paste (NP) is joined into coarse NA and coarse RA. The new paste consists of the binder and the sand, and represents 69% v/v of concrete. SCC0 consists in NP and coarse NA, while SCC100 in NP and coarse RA. As the common phase between the different concretes is the new paste, the study and the comparison between mixes focused on its microstructure. Each concrete type was sampled  of each concrete type. The study of the concrete microstructure of all RA-SCC samples was performed using a scanning electron microscope (SEM), Quanta 400 from FEI Company. Their observation was carried out through electron backscattered imaging (BSE) to identify the different phases of the microstructure. Before initiating SEM observation, to remove the free water, small samples of size 35 × 35 × 10 mm were dried under vacuum with silica gel at 45 °C for 14 days. The dry samples were then impregnated with epoxy resin; then, the samples were polished in various steps to create a smooth plane surface for SEM imaging. Because our samples were not conductive, we had to add a very thin gold metallic coat. Obtained BSE images were processed with the Stream Motion software to distinguish the different phases of the samples using a toll dedicated to contrast the grey levels. Images of NP were taken at random spots, with an analysis over a 10,000 µmThis result is widely accepted and consistent with the literature ,35. SomeDifferential intrusion curves of the NP in In the present study, NP0 and NP30 have a pore diameter distribution spread all over the whole measured range. No clear visible peaks in the capillary pores were observed besides the ones at 5 and 4.35 nm. A less rounded peak at the capillary pores for NP0 and NP30 is attributed to a large pore size distribution for this material phase, as stated by . It is pFor NP50 and NP100 pastes, a sharp peak is visible around 50–60 nm. It is associated with the minimum diameter of an interconnected capillary network, called the critical diameter. This diameter is determined from the inflection point of the curves in The SEM observations conducted on the NP of each SCC enables us to evaluate anhydrous content. The content of the anhydrous grains  is 31% in the total volume of concrete see . An estiThe microstructural characterization of self compacting concretes (SCC) containing recycled aggregates (RA) with the proposed sampling method enables us to evaluate the pore network of their different components as RA and NP.The replacement of coarse aggregates by RA at 30% does not affect the new paste of SCC. The pore size distribution of NP30 is similar to the reference concrete NP0 with a total introduced pore volume of 0.069 mL/g. While NP50 and N100 pastes present a total introduced pore volume of 0.09 mL/g.The porosity of the new paste presents a significant variation for 50% and 100% replacement in RA with respect to NP0 and NP30. NP50 and NP100 exhibit higher refinement of the porous structure. The number of macrospores of a diameter between 50 and 10,000 nm is reduced by 20% for NP50 and NP100 in comparison to NP0 and NP30, of which the reduction is about 30%. This is attributed to the release of water absorbed by the RA during the pre-saturation process that allows continuous hydration.The anhydrous rates in the NP decrease with increasing RA replacement percentage. The anhydrous content was 5.75% for NP0 and 5.04% for NP30, while it was 3.63% for NP50 and 1.21% for NP100. This validates the hypothesis that the water absorbed by RA during the pre-saturation process can migrate into the NP, generating less anhydrous and macrospores for high rate substitution of RA.The compressive strength loss for RA concretes SSC50 and SCC100 is influenced not only by the porous old paste of RA, but also by the porosity of the new paste. The paste is similar for these two concretes and shows an increase of 26% compared to the reference concrete.Further works will be conducted to study the microstructure evolution between 28 days and 90 days.The modification of the microstructure of the new paste (NP) of self-compacting concrete (SCC) for different levels of recycled aggregate (RA) at 90 days compared that to the reference concrete has been explored. The results obtained from this work can be summarized as follows:


Acute ischemic stroke (AIS) is a perpetual threat to life and functionality due to its high morbidity and mortality. In the past several decades, therapeutic hypothermia has garnered interest as an effective neuroprotective method in the setting of AIS. However, traditional hypothermic methods have been criticized for their low cooling efficiency and side effects. Intra-arterial cold saline infusion (IA-CSI), as a novel hypothermic method, not only minimizes these side effects, but is also perfectly integrated with widely accepted recanalization modalities in AIS, thereby serving as a promising prospect for clinical translation. In this article, we review the historical development of IA-CSI, summarize major studies of IA-CSI in rodents, large animals, and humans to date, and suggest insight into future development prospects in the field of AIS. We hope that this article will provide inspiration for the future application of hypothermia in AIS patients. Acute ischemic stroke (AIS) is an increasingly prevalent threat to human health , 2. A reNeuroprotective strategies offer this solution. The utility of neuroprotection has been long-recognized, and thousands of neuroprotective strategies have been evaluated, but among them, therapeutic hypothermia has demonstrated the most promise . The genHypothermia is a well-established therapy in the fields of cardiac arrest and neonatal hypoxic-ischemic encephalopathy. Two randomized controlled trials demonstrated almost simultaneously that patients with cardiac arrest could benefit from therapeutic hypothermia , 15. TheSystemic cooling, the technique used in cardiac arrest and neonatal hypoxic-ischemic encephalopathy, has been evaluated in AIS with discouraging results. A randomized, multicenter trial of endovascular cooling in AIS patients treated within 6 hours of symptom onset found that 18% of patients receiving hypothermia achieved favorable outcomes  at 90-day follow-up, compared to 24% of patients in the normothermia group . AnotherSince hypothermia in AIS is hindered by systemic effects, an optimal strategy would avoid systemic cooling altogether. To this end, local cooling methods have been devised. Cooling helmets were investigated , but tarIn recent years, IA-CSI has made significant progress in the field of AIS. From rodent to large animal studies, then to clinical studies , the proThe initial 2002 Ding papers evaluated the cooling efficacy of pre-reperfusion flushing in a rat stoke model . TransieBased on the success of pre-reperfusion flushing, the IA-CSI concept was put forth in three consecutive 2004 papers , 37, 38.Post-reperfusion flushing, a logical extension of pre-reperfusion flushing, has also demonstrated a significant neuroprotective effect with increased clinical relevance, since recanalization is of primary importance in care of the ischemic stroke patient. A 2012 study by Ji and colleagues used two methods to infuse cold saline after recanalization: the traditional continuous infusion method (uninterrupted IA-CSI), and infusion with 3 20 minute interruptions interspersed at regular intervals (interrupted IA-CSI) . While bIn addition to the tMCAO model, the IA-CSI concept has also demonstrated efficacy in a permanent MCAO rat model. Using immunohistological analysis, Kurisu and colleagues observed suppression of apoptosis and reactive gliosis in the ischemic penumbra of rats, despite permanent MCA occlusion . A sizabIA-CSI has also been found to augment the efficacy of other neuroprotective agents . In 2013While IA-CSI provides robust neuroprotective benefits in rodents, findings in rat models often translate poorly to human trials . In addiIn 2007, Furuse and colleagues first evaluated IA-CSI in large animals. Infusion into the common carotid artery of six adult canines using a 4-French angiographic catheter rapidly achieved target hypothermic temperatures in target brain parenchyma . IpsilatIA-CSI has also been evaluated in rhesus monkeys . InfusioA recent study by Caroff and colleagues was one of the first large animal studies to evaluate the optimal flow rate to balance cooling rate with judicious fluid administration . In a caMethods of local hypothermia induction using techniques other than IA-CSI have also been evaluated in several recent large animal studies. A pair of 2015 and 2016 papers evaluated the viability of a unique heat exchanger in a sheep model of cerebral ischemia. The heat exchanger was a novel closed-loop balloon cooling system, similar to the Zoll catheter  used in Mattingly and colleagues evaluated another alternative cooling method in a tMCAO swine model in 2016 . Using aGiven the rousing success of IA-CSI in benchtop research, several pilot human studies have recently been launched. The first group to assess the safety and feasibility of IA-CSI in humans was Choi and colleagues in 2010. This pilot study enrolled 18 patients with partially or completely treated cerebrovascular disease undergoing elective diagnostic cerebral angiographies . Upon coThe first implementation of IA-CSI in AIS patients was performed in a small 2016 observational study . This noFollowing the success of the 2016 trial, a larger prospective cohort study was designed to explore the safety and efficacy of IA-CSI in patients undergoing mechanical thrombectomy compared to mechanical thrombectomy without IA-CSI . Using tIt is essential to note that infusion volume optimization has not been evaluated in humans. A pilot study in healthy, conscious volunteers showed that a systemic 30 ml/kg cold saline bolus could be well tolerated without any significant hemodynamic consequences . HoweverClinicalTrials.gov number: NCT03163459) [Currently, another exploratory study   and a weThere now exists a robust body of preclinical data suggesting that therapeutic hypothermia provides a neuroprotective benefit to the ischemic brain, and that quicker onsets and longer durations enhance this neuroprotection. However, both variables share a common solution: higher infusion rates. As such, a major obstacle in the quest toward IA-CSI clinical implementation is the volume issue; how can we achieve maximally effective cooling while avoiding fluid overload? Here, we propose two possible solutions.The first solution is to improve hypothermic efficiency. While infusion temperature is often discussed in literature, infusion temperature at the catheter tip is rarely discussed. According to a prospective cohort study, cold saline (4 °C) infused at 10 ml/min through a femoral artery sheath heats to 20.2 °C when it reaches the internal carotid artery . IncreasThe second solution is to improve the method of IA-CSI. Several studies have evaluated the efficacy of hypothermic autologous arterial blood as the perfusate, which eliminates the concern for fluid overload, thereby alleviating any restriction on hypothermia duration. Previous pre-clinical studies have assessed this modified IA-CSI approach in rodents and large animals -68. In tAfter nearly 20 years of unrelenting efforts, the neuroprotective effects of IA-CSI in AIS have been gradually verified in rodent studies, large animal studies, and now in clinical investigations. Although the clinical study of IA-CSI in AIS is only just beginning, with the progress of medical technology and the development of new materials, IA-CSI will continue to become more effective and more attractive. Therapeutic local hypothermia, represented by IA-CSI, is ushering in a development opportunity, and as it gains momentum, clinical acceptance will likely follow.


The effect of fibre reinforcement on the chloride diffusion property of concrete is controversial, and the coupling effect of sulphate erosion and drying–wetting cycles in marine environments has been neglected in previous studies. In this study, the chloride diffusion property of hybrid basalt–polypropylene fibre-reinforced concrete subjected to a combined chloride–sulphate solution under drying–wetting cycles was investigated. The effects of basalt fibre (BF), polypropylene fibre (PF), and hybrid BP–PF on the chloride diffusion property were analysed. The results indicate that the presence of sulphate inhibits the diffusion of chloride at the early stage of erosion. However, at the late stage of erosion, sulphate does not only accelerate the diffusion of chloride by causing cracking of the concrete matrix but also leads to a decrease in the alkalinity of the pore solution, which further increases the risk of corrosion of the reinforcing steel. An appropriate amount of fibre can improve the chloride attack resistance of concrete at the early stage. With the increase in erosion time, the fibre effectively prevents the formation and development of sulphate erosion microcracks, thus reducing the adverse effects of sulphate on the resistance of concrete to chloride attack. The effects of sulphate and fibre on the chloride diffusion property were also elucidated in terms of changes in corrosion products, theoretical porosity, and the fibre-matrix interface transition zone. The marine economy has become an important part of the global gross national product, and the construction of marine projects such as offshore oil and gas fields, ports, and cross-sea bridges is underway. In marine engineering, reinforced concrete is still the most commonly applied engineering material because of its excellent performance and low cost. However, the marine environment contains a large amount of chloride, which corrodes the reinforcing steel in concrete. This seriously affects the durability of marine engineering structures, resulting in considerable economic losses . TherefoFibre-reinforced concrete has been widely used in the past few decades, especially steel fibre, which is widely used in decentralized reinforcement of industrial floors and pavements . AdditioWith the development of fibre-reinforced concrete, hybrid fibre-reinforced concrete has gradually become a research hotspot. Numerous studies have shown that blending two or more types of fibres can take full advantage of the properties of each fibre material compared to using a single type of fibre ,7,8,9,10Owing to the broad application prospects of hybrid basalt–polypropylene fibre, some researchers have conducted a series of studies on hybrid basalt–polypropylene fibre-reinforced concrete (HBPRC). Smarzewski et al. ,16 invesFrom the perspective of corrosion, the marine environment can be divided into atmospheric, wave splash, tidal, and underwater zones . Among t−/OH− ratio of concrete at the early and late stages of erosion were analysed. In addition, the composition of the corrosion products and changes in the physical phase components of the concrete were analysed using X-ray powder diffraction (XRD) and thermogravimetric (TG) testing, and the distribution of fibre inside the concrete and corrosion products were observed by scanning electron microscopy (SEM).In this study, BF and PF were used as reinforcing materials to study the chloride diffusion property of HBPRC subjected to a chloride–sulphate composite solution under drying–wetting cycles. The effects of fibre content, type of fibre, and hybrid form on the chloride content distribution, pore solution pH distribution, and ClTo prepare the HBPRC, P.O. 42.5R Portland cement (C) , silica fume (SF) , fly ash (FA) , and ground granulated blast-furnace slag (GGBS)  were used as cementitious materials. The chemical compositions of the cementitious materials are listed in The mix proportions of the HBPRC are summarised in To ensure uniform fibre dispersion, the mixing time of the concrete was extended appropriately, as depicted in 2SO4 was used as the erosion solution. The drying–wetting cycle system adopted was as follows: first, the concrete specimens were soaked in the composite solution for 24 h; then, they were dried in an oven at a temperature of 50 °C for 24 h. The solution was changed once a week during the test to maintain a constant ion concentration in the solution. Five erosion periods were set up for the test, namely, drying–wetting cycle for 30 days (15 times), 60 days (30 times), 90 days (45 times), 120 days (60 times), and 180 days (90 times).In this study, a composite solution of 3.5% NaCl and 5% NapX the negative logarithm of the molar concentration of chloride in the solution, After each erosion period, one specimen of each group was taken out and placed in a room to dry naturally for 3 days. Then, they were placed in an oven at 50 °C for 24 h. After drying, a concrete grinding machine was used to obtain powder from the surface of the specimen layer by layer. The powder was then passed through a 0.16 mm sieve and then placed inside a sealed bag. The free chloride content of the HBPRC was measured using a potentiometric method, which is in accordance with the Chinese Standard GB/T 50344-2004 . Before The pH of the pore solution was also measured using the potentiometric method. The pH test was carried out simultaneously with the free chloride content test, and a standard Pro2100/3C laboratory pH meter produced by Shanghai Yidian Scientific Instrument Co., Ltd. (China) was used to measure the pH of the pore solution for each group from the obtained filtrate.2 protective atmosphere). The microstructure of the HBPRC was observed using a Quanta 600 FEG-type cold field emission scanning electron microscope  before and after 180 days of erosion.The XRD test was carried out on the concrete samples using an Empyrean X-ray diffractometer manufactured by Panac , which has a scan range (2θ) of 5–40°. A Mettler Toledo TGA/DSC 2 thermogravimetric simultaneous differential thermal analyser  was used to test the HBPRC after different erosion periods. The mass of the test sample was approximately 15 mg, and the temperature range was 30–900 °C at a heating rate of 10 °C/min BW with high porosity will form on the fibre surface. The ITZ is the weakest area in the composite system and contains a large number of connected pores ,41. AlthWhen the amount of hybrid BF–PF reaches 0.2%, the excessive fibre blending reduces the dispersion of fibre. Consequently, the fibre tends to clump and entangle; this introduces a large number of air bubbles, resulting in numerous air voids in the hardened concrete. In addition, a large number of fibre-matrix ITZ will change the original pore structure of the concrete, making the pores interconnected along the fibre length direction. Therefore, the incorporation of excess fibre in specimen BPC-0.2 provides more channels for ions to enter the concrete, thus increasing the chloride penetration rate in concrete at the early stage of erosion.D the apparent chloride diffusion coefficient, The chloride content distribution of the HBPRC after 180 days of erosion is illustrated in Specimen BPC-0.1 exhibited the lowest apparent chloride diffusion coefficient after 180 days of erosion, which was 43.1% lower than that of specimen NC. Although the variability in the experimental results cannot be excluded, these results are also explainable. According to El-Hamrawy’s study, PF with a low elastic modulus can bridge microcracks and delay the development of microcracks into macrocracks, while BF with a high elastic modulus can inhibit the expansion of macrocracks . As a reD = A + Bt + Ct2, where t is the erosion time (days); A, B, and C are material property parameters determined from tests. It is obvious that the larger A is, the worse the concrete’s resistance to chloride attack at the early stages of erosion; the smaller B and the larger C are, the earlier sulphate attack begins to have an adverse effect on the chloride attack resistance of concrete. The regression analysis is carried out according to the experimental data, and the results are shown in From 2+ in the concrete pore solution and generates readily soluble NaOH. Because the pH of the erosion solution is much lower than that in the concrete pore solution, NaOH gradually diffuses to the outside. This leads to a gradual decrease in the alkalinity of the concrete pore solution, which seriously affects the stability of the concrete matrix [As indicated in Equations (7) and (9), the sulphate attack consumes Cae matrix . The pore matrix ,45, the 2(CH) in the solid phase of concrete will dissolve to maintain the alkalinity of the concrete pore solution. While CH is not only the basis for the stable presence of hydration products such as C–S–H gels, it is also an important component of the hardened cement paste itself [Similar to the difference in the degree of influence of the fibre on the chloride diffusion property at the early and late stages of erosion, the influence of the fibre on the degree of pH reduction of the concrete pore solution also differs. The fibre had minor beneficial effect on inhibiting the pH reduction at the early stage of erosion and the incorporation of 0.2% hybrid BF–PF even slightly accelerated the pH reduction. Take the pore solution pH at 4 mm from the surface of the specimen as an example. After 30 days of erosion, the pore solution pH values of specimens BC-0.1, PC-0.1, and BPC-0.1 are only 0.01–0.05 higher than that of specimen NC, whereas that of specimen BPC-0.2 is 0.09 lower. In contrast, after 180 days of erosion, the pore solution pH values of the specimens with fibres are all significantly higher than that of specimen NC, and the pore solution pH values of specimens BC-0.1, PC-0.1, BPC-0.1, and BPC-0.2 are approximately 0.06–0.12 higher than that of specimen NC. A higher liquid phase alkalinity is the basis for maintaining a stable concrete system. When the liquid phase alkalinity decreases, Ca(OH)e itself . Therefo−/OH−) can be used to assess the corrosion potential of reinforcing steel in a chloride-containing environment [−/OH− ratio was performed. Similarly, taking the location of 4 mm from the surface as an example, the chloride contents and Cl−/OH− ratios of the HBPRC after 30 days and 180 days of erosion are illustrated in −/OH− ratio is much higher than that of the chloride content for all specimens. For example, the Cl−/OH− ratio of specimen NC after 180 days of erosion is 7.7 times higher than that after 30 days of erosion, while the chloride content increases by only approximately two times. This result shows that sulphate severely affects the risk of reinforcement corrosion. First, it causes cracking of the concrete matrix, which increases the rate of chloride penetration. Second, it decreases the alkalinity of the concrete pore solution, which further increases the risk of reinforcement corrosion.In the case of reinforced concrete structures, the decrease in alkalinity of the concrete pore solution also decreases the stability of the reinforcement passivation film, thus increasing the risk of reinforcement corrosion. It is well known that the molar ratio of free chlorides to hydroxide ions , Friedel’s salt, ettringite, gypsum, gismondine, CaCO3, SiO2, and mirabilite. In this study, the focus is on the transformation of the hydration products and the variations in the Friedel’s salt, ettringite, and gypsum.The XRD patterns of specimen NC after different erosion periods are displayed in 4–AFm, C4AF, and C3A) in the hydration products to form ettringite, which is much more stable than Friedel’s salt [It can be seen from l’s salt ,46. Therl’s salt , the incThe ettringite diffraction peak (9.08° 2θ) and gypsum diffraction peak (11.54° 2θ) are also observed in The TG and derivative thermogravimetric (DTG) curves of specimen NC after different erosion periods are depicted in The porosity is an important factor that affects the chloride diffusion performance of concrete. The variations in the theoretical porosity of the HBPRC were calculated based on Equations (3)–(5), and the results are presented in Compared with the initial porosity, the porosity of the HBPRC decreases by 13.49–59.24% after 30 days of erosion. However, it should be noted that the change in porosity is not only caused by the corrosion products filling the pores. According to Haga et al. , the disTo better understand the effects of the hybrid BF–PF and sulphate on the resistance of concrete to chloride attack, the microscopic morphologies of the HBPRC before and after erosion were examined by SEM. The microscopic morphology of the HBPRC before erosion is depicted in The microscopic morphology of the HBPRC after 180 days of erosion is displayed in There is a peak at a certain depth from the specimen surface in the chloride content distribution curve due to drying–wetting cycles and the “ink bottle–bundle tube” like microstructure of concrete pores; however, the fibre and erosion time have little effect on the depth of the peak point. The peak depth was approximately 4 mm in each group of specimens after each erosion period.When the fibre content was 0.1%, the addition of BF, PF, and hybrid BF–PF improved the chloride attack resistance of concrete at the early stage of erosion. Adding 0.1% BF had the best effect, which reduced the apparent chloride diffusion coefficient by 8.5% after 30 days of erosion. Moreover, the chloride attack resistance of concrete at the early stage of erosion was reduced when 0.2% hybrid BF–PF was blended.−/OH− ratio was 2.8 to 3.9 times the growth rate of the chloride content.The sulphate in the composite solution decreased and increased the chloride penetration rate in the concrete at the early and late stages of erosion, respectively. In addition, sulphate erosion also led to a decrease in the alkalinity of the pore liquid phase of concrete, in which the growth rate of the Cl−/OH− ratios were reduced by 25.7–39.3%. The specimen blended with 0.1% hybrid BF–PF demonstrated the smallest apparent chloride diffusion coefficient and Cl−/OH− ratio at the late stage of erosion.The positive effect of the fibre gradually appeared as the erosion time was extended. After 180 days of erosion, the apparent chloride diffusion coefficients of the specimens with fibre were reduced by 29.4–43.1% compared with that of the control specimen NC, while the ClThe theoretical porosity of concrete decreases with the addition of fibre; however, an excessive amount of fibre increases the porosity. The SEM results show that BF has a better bonding performance with the concrete matrix and a thinner fibre-matrix ITZ with lower porosity compared with PF. The corrosion products filled the pores inside the concrete as well as the fibre-matrix ITZ during the erosion process, thus reducing the porosity of the concrete.The purpose of this study was to evaluate the effect of hybrid basalt–polypropylene fibre on the chloride diffusion property of concrete subjected to a chloride–sulphate composite solution under drying–wetting cycles. Based on the results, the following conclusions can be drawn:From the above conclusions, it can be found that fibres have little effect on the chloride diffusion properties of concrete in a chloride–sulphate composite solution under drying–wetting cycles at the early stages of erosion. Its effect is mainly reflected when the expansion products begin to produce expansion stress on the pore wall, which is mainly due to its anti-cracking effect. However, it is also clear from the above conclusions that an excessive amount of fibre increases the porosity of the concrete. There are two main reasons for this: on the one hand, the high porosity of the fibre-matrix ITZ; on the other hand, excessive use of fibre reduces the dispersion of the fibre, resulting in the introduction of air bubbles in the mixing process. For a single chloride attack environment, the increase of porosity reduces the chloride attack resistance of the concrete, because it provides more channels for chloride penetration. However, this effect may change for a chloride-sulphate composite environment. The matrix with high porosity can provide more space to accommodate sulphate erosion products, which can also inhibit the formation of sulphate erosion cracks, which is described by other scholars as the buffer capacity of pores. This mechanism may also play a very important role in the process of erosion resistance. Of course, high porosity will inevitably provide more channels for chloride penetration, and further research is needed to confirm the optimum mix ratio for a good balance between the two.


Left-hand dominant (LHD) batters were consistently overrepresented in the male YAC  and OAC  compared with the expected general population distribution. Male LHD batters exhibited a significantly (p < 0.05) higher batting aggregate , scored more runs , spent more time batting , and scored more boundary-4s per game , across both YAC and OAC groups with small effect sizes. No overrepresentation was present for either female group . Female LHD batters exhibited significantly higher batting aggregate (68.97 ± 53.17 vs. 102.96 ± 73.48), batting average (13.24 ± 10.88 vs. 17.75 ± 12.28), and spent more time batting per game (25.52 ± 15.08 vs. 37.75 ± 26.76 min), but only at the OAC level with small-moderate effects sizes. Finally, there were few performance advantages identified to batting with a reverse stance, with further work needed to clarify any potential biomechanical benefits. Team selection practices may exploit the left-handed advantage by over-selecting talented left-handed junior cricketers. Practical implications for coaches include creating practice environments that negate the negative frequency-dependent selection, such as providing more practice opportunities for their players against left-handed opponents.The purpose of this study was to examine performance advantages associated with batting stance, in the form of left- vs. right-handed dominant stance, and orthodox vs. reverse stance, of talented junior cricket batters within age-restricted competitions. Data were sourced from the national male younger age competition (YAC; Under-17;  For insnegative frequency-dependent hypothesis were apparent, then it might be reasonable to expect the advantage of the left-handed cricket batters to increase over time due to a progressive accrual of experience competing against right vs. left-handed opponents. While there is evidence that left-handedness—and perhaps a “reversed stance”—may be advantageous at the elite level of competition , much leThe aim of this study was to examine the magnitude of performance advantages associated with batting stance, in the form of left- vs. right-handed dominant stance, and orthodox vs. reverse stance, in junior cricket players within age-restricted competitions. Both male and female players were examined to account for any potential sex differences in performance due to handedness . We hypo1  and confirmed via the National Sporting body’s database. Players were then separated into whether they competed in the younger age competition  or the OAC . Batting handedness was determined by the players throwing hand, in line with previous work  number of innings batted. Relative measures included (i) batting average , (ii) runs per innings , (iii) strike rate , (iv) boundary-4s per game , (v) boundary-6s per game , and (vi) time per innings . Finally, the percentage of innings was recorded where the batter was (i) not dismissed , and where the batter had scored (ii) ducks  and (iii) centuries . Participant’s batting handedness was recorded as either right-hand dominant (RHD) or LHD. Batting stance was also recorded as being orthodox (dominant hand placed on the bottom of the bat) if the dominant hand matched the batting handedness  or reversed (dominant hand placed on top off the bat) if the dominant hand did not match the batting handedness .Measures of batting performance were collated from the tournament database. Two measures of absolute performance were recorded: (i) d, and reported as 0.2, 0.5, and 0.8 as small, moderate, and large, respectively  with the alpha level set at ≤ 0.05 and descriptive information expressed as mean ± standard deviation. First, any over- or underrepresentation of left-handedness, when compared with the proportions expected from the general population , whereas the advantage in the OAC group for LHD batters was marginal (p = 0.07). LHD batters also exhibited significantly less ducks in the YAC group only, and significantly more centuries scored in the OAC group (p < 0.05). All other variables across both YAC and OAC groups were similar, including the number of matches, innings, boundary-6s, and strike rate, with all exhibiting a small ES  while no other significant differences between batting variables were evident between the different stances . There were no other significant differences evident between the different stances for OAC level  compared with orthodox stance batters . No other differences were evident between reverse and orthodox stance for the YAC group. There were also no significant differences between stances for any performance measure at the OAC level  and boundary-4s (OAC) for males, and greater runs scored and batting time for female cricket batters (YAC). These findings demonstrate evidence of a small left-handed advantage in cricket batting, with limited performance advantage for either orthodox or reverse batting stance at the youth representative level.Left-handed male cricket batters were found to be more prevalent in junior elite competition when compared to the proportion expected from the general population . Similarnegative frequency effect may influence the acquisition of perceptual or strategic skills required to outperform a left-handed opponent  would mean that there are also less practice opportunities against left-handers, which may partially explain the left-hander’s performance advantage for female cricket. Further, this study provided evidence for the reverse stance hypothesis contributing a limited performance advantage to cricket batting. Together, these findings highlight the emergence of selection and performance biases occurring at the male and female youth representative level. Practical implications for coaches include creating practice environments that minimize the negative frequency effect, such as providing more practice opportunities against left-handed opponents. Future performance analysis research is encouraged to examine whether selecting a greater number of left-handers increases the likelihood of winning matches.All datasets generated for this study are included in the article/The study was conducted according to the ethical guidelines of the authors’ affiliated institution. Written informed consent from the participants’ legal guardian/next of kin was not required to participate in this study as analyzed data were archival data available in the public domain.JC contributed to the conception and design of the work, writing of the manuscript, and analysis and interpretation of data. DM, AL, and KD contributed to the writing and critiquing of the manuscript and interpretation of data. M-AG contributed to the critiquing of the manuscript, data analysis, and interpretation of the data. All authors contributed to the article and approved the submitted version.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


A reduced carbon footprint and longer service life of structures are major aspects of circular economy with respect to civil engineering. The aim of the research was to evaluate the interfacial bond properties between a deteriorated normal strength concrete structure and a thin overlay made of Eco-UHPC containing 50 wt% of limestone filler. Two types of formwork were used: untreated rough plywood and surface treated shuttering plywood. The normal strength concrete elements were surface scaled using water jets to obtain some degradation prior to casting of the UHPC overlay. Ultrasonic pulse velocity (UPV), bond test (pull-off test), and Scanning Electron Microscopy (SEM) combined with Energy Dispersive Spectrometry (EDS) were used for analysis. Elements repaired with the Eco-UHPC showed significantly improved mechanical properties compared to the non-deteriorated NSC sample which was used as a reference. The bond strength varied between 2 and 2.7 MPa regardless of the used formwork. The interfacial transition zone was very narrow with only slightly increased porosity. The untreated plywood, having a rough and water-absorbing surface, created a surface friction-based restraint which limited microcracking due to autogenous shrinkage. Shuttering plywood with a smooth surface enabled the development of higher tensile stress on the UHPC surface, which led to a more intensive autogenous shrinkage cracking. None of the formed microcracks penetrated through the entire thickness of the overlay and some were partly self-healed when a simple water treatment was applied. The project results showed that application of UHPC as repair material for concrete structures could elongate the lifespan and thus enhance the sustainability. Deterioration of concrete is commonly related to its porous microstructure and deleterious chemical change in the binder matrix. One method to elongate the lifespan of an affected structure is to cover it with an external protective layer made of a more durable material. Ultra-High Performance Concrete (UHPC) is one of the most promising materials for such applications . Its hig/c ratio ,11,12,13/c ratio . However/c ratio .3) compared to ordinary concrete (320–450 kg/m3). This cement consumption consequently emit 2–3 times more CO2 and thus significantly higher carbon footprint [2 emission, but will also lower the production cost, lower the shrinkage, and reduce the crack risk [3A to form calcium carboaluminate (CCA), which tended to increase the compressive strength [Curing is yet another factor, which directly influences the bond properties. UHPC covered NSC which was cured at high temperature produced high early shrinkage and thus decreased the interfacial bond compared to ambient temperature cured specimens. Furthermore, interfacial shear properties of Z-shaped single sided push-out test were determined on untreated, rough, and water jet grooved substrate specimens. The bond strength was higher for rough and grooved substrates ,16. Otheootprint ,22. It hootprint ,24,25. Hack risk ,29,30,31ack risk ,34. Calcstrength ,36,37.The primary aim of this research was to study the interfacial bond behavior between treated normal strength concrete (NSC) and repair ECO-UHPC overlay and to determine the effects of the used type of formwork.Normal strength self-compacting concrete (NSC) was used to produce the reinforced specimens. NSC was produced by locally available ready-mix concrete distributor . Portland cement type CEM II/A-V 52.5N was produced by “Cementa” , as superplasticizer MasterGlenium SKY 823  was used. The maximum aggregate size was 16 mm. The Eco-UHPC concrete contained Portland cement CEM I 42.5N, condensed micro-silica 920D from Elkem , limestone powder “Nordkalk Limus 40” from Nordkalk AB, Norquartz 45 from Sibelco Nordic  as well as micro sand B15 (150 µm) and B35 (350 µm) provided by Baskarpsand AB . A polycarboxylate-based superplasticizer type “MasterGlenium ACE 30” from BASF  was added. Steel fibers having lengths of 6 mm and 13 mm were provided by Krampe Harex-Germany . The detailed mix proportions and mechanical properties are shown in 3 and three steel-reinforced concrete columns of dimension 300 × 300 × 2500 mm3 (Test samples included twelve cubes having dimensions of 150 × 150 × 150 mm2500 mm3 a. Four r2500 mm3 b. The ovTwo types of formwork—untreated plywood (UTT) (rough surface) and shuttering plywood (STT) (smooth surface)—were used for casting composite columns . The UHPUHPC was dry mixed for 2 min, followed by an addition of water with superplasticizer and mixed for another 5–6 min. Steel fibers were added and mixed for another 2 min. In total, the mixing time was approximately 9–10 min.3 cubes at 1, 7, and 28 days. The SS-EN 12390-3:2019 standard was followed, and the applied loading rate was 10 kN/s [3 was measured at 7 and 28 days after casting of the UHPC layer. The reference NSC cubes of 150 × 150 × 150 mm3 were tested at the same day as the composite concrete samples. The substrate concrete and the NSC-only sample were of the same age. For larger cube samples, the loading rate was set to 13.5 kN/s, following the SS-EN 12390-3:2019 standard [1 = d2 = 300 mm and d1 = d2 = 360 mm for NSC and composite concrete, respectively.Fresh properties of Eco-UHPC were evaluated using the slump flow test, in accordance with the SS-EN 12350-8:2019 standard . The comstandard . The use1, Blue B-B1) as described in The ultrasonic pulse velocity (UPV) test was used to detect internal cracking and debonding between layers of new and old concrete following the SS-EN 12504-4:2004 standard . The UPVPf = bond (pull-off) strength (MPa); F = failure load (N); d = diameter of core (mm).The pull-off test was performed to measure the interfacial bond strength between the substrate concrete and the repair UHPC overlay. This test is a conventional way to analyze the bond strength, as it neglects the friction between interfacial surfaces or any other form of stresses ,42. The Bond failure modes were classified into four types determined by a visual observation, The crack depth in the UHPC overlay was assessed for the composite columns. A layer of epoxy resin was applied on randomly selected cracks a,b. AfteNote: The diameter of core used for pull-off test was 50 mm, as per ASTM C1583 standard—while, to measure the depth of shrinkage cracks penetration, separate cores of 35 mm were drilled, followed by visualizing the macrocracks using digital optical microscope Dino-Lite Pro AM-413T.The interfacial transition zone between NSC and UHPC was analyzed using a Scanning Electron Microscope (SEM)—JSM-IT100  coupled with an energy-dispersive spectrometer (EDS) from Bruker . For the analysis, a piece of the interface extracted from the core was immersed in isopropanol for 24 h to stop the hydration, followed by 12 h of drying. The specimens were vacuum-impregnated with a low-viscosity resin. After hardening of the resin, the specimens were polished using a set of grinding plates and diamond spray with particles sizes of 9, 3, and 1 µm with lamp oil as a lubricant and coolant . SEM imaSelf-healing of shrinkage-induced cracks was observed on the surface of the UHPC layer, which was subjected to water curing. The images of the healed cracks were acquired approximately 4 months after curing. A digital light microscope, type Dino-Lite Pro AM-413T with 1.3 MP camera and a field of view of 1280 × 1024 pixels was used to obtain the crack photographs.The slump flow of UHPC mix reached 800 mm for concrete without fibers and 900 mm when fibers were present. Steel fibers presumably enhanced the breaking and dispersion of the condensed silica fume during the mixing process. The small size of the fibers and the small amount prevented the occurrence of the interlocking mechanism commonly present for regular steel fibers ,52. The The comparison of compressive strength values measured for NSC and composite concrete cubes (NSC with UPHC overlay applied on 4 sides) is shown in The average measured transit time from composite columns is shown in The bond strength between NSC and the UHPC overlay tested on different levels of the casted columns varied between 2.0 and 2.7 MPa . The obtw/c ratio directly on the interface. This could lead to a lower bond strength [The bond strength is mostly affected by the substrate roughness and moisture content. According to Benoit Bissonnette et al., the dry substrate concrete tends to absorb water from the fresh overlay concrete leading to a lower hydration degree and weaker bond strength ,67. Othestrength ,68.The UHPC overlay showed autogenous shrinkage cracks. Interestingly, the number of cracks was lower on surfaces casted against the untreated plywood (UTT). The formed surfaces were also visibly rougher in comparison with elements casted against the smooth shuttering plywood. None of the studied cracks penetrated the full depth of the UHPC overlay, SEM analysis of the polished and resin-impregnated samples did not detect significant differences between samples cast against the STT and UTT plywood formwork, W/C and pores filled with the concentration of Ca(OH)2 reacted with silica fume to produce silica rich C-S-H. On the contrary, higher water absorption occurred at the NSC binder-UHPC interface resulted in the locally lower W/C ratio and partially inhibited the reaction with silica fume—thus, relatively showing higher calcium content in C-S-H corresponding to binder–UHPC interface. The Ca/Si ratio varied between 1.2 and 1.6. In general, these results showed that the formed ITZ is very much narrow and does not exceed 20 μm, which resulted in a very good bond strength and failure was only observed on the weaker NSC substrate side.The chemical composition of the C-S-H was analyzed using SEM-EDS as a function of the distance from the interface. The analyzed spots were chosen based on the grey level in the SEM-BSE images corresponding to C-S-H only. Both specimens (column using untreated and shuttering plywood) showed a slightly higher Ca/Si atomic ratio at the binder-UHPC interface compared to the aggregate–UHPC interface, Several cracks were found to be partially filled with light-colored healing products, No delamination between the layers, despite loading parallel to the bond surface being observed indicating the bond strength exceeding the strength of the weaker NSC.Bond strength varied between 2 and 2.7 MPa regardless of the used formworkThe type of the plywood used as formwork affected the microstructure and crack formation of the external layers of the UHPC overlay.W/C ratio on top of the UHPC surface layer leading locally to a lower hydration degree. At the same time, the surface roughness created a surface friction-based restraint which limited the microcracking due to the autogenous shrinkage.The rough and water-absorbing untreated plywood reduced the Shuttering plywood with smooth surface enabled the development of higher tensile stress on the UHPC surface, which led to more intensive autogenous shrinkage cracking.None of the autogenous shrinkage related microcracks developed on the UHPC surface penetrated through the entire thickness of the UHPC overlay.Detected ITZ was very narrow, less than 20 μm. The estimated Ca/Si based on the SEM-EDS analysis and corresponding to the C-S-H was uniformly distributed on the interface as well as in the bulk zone with only minor statistically insignificant variations.The UHPC overlay showed signs of a limited self-healing when treated with water.Repair of degraded NSC using UHPC overlay has a high potential for full-scale application, due to its enhanced bond strength, dense microstructure.The aim of this study was to characterize the interfacial transition zone forming between water jetted NSC concrete and UHPC overlay simulating repair strengthening operation of deteriorated concrete columns. Additionally, the effects of formwork plywood to limit the development of autogenous microcracks were determined. The following conclusions were drawn:


Immunoglobulin G4-related disease (IgG4-RD) is an immune-mediated inflammatory disorder that can involve multiple organs. It is characterized by IgG4-positive plasma cell-rich storiform fibrosis and obliterative phlebitis associated with a high serum IgG4 level. There are few reports of gastric IgG4-RD, especially those detected prior to systemic or other organ involvement.Case presentation: A 70-year-old man was diagnosed with type 0–IIc gastric cancer at the anterior wall of the gastric corpus by upper gastrointestinal endoscopy. In addition, a submucosal tumor (SMT) 7 mm in diameter was found at the greater curvature of the angulus. Laparoscopic distal gastrectomy with regional lymph node dissection was performed. Pathology revealed a poorly differentiated adenocarcinoma in the type 0–IIc lesion and storiform fibrosis with infiltration of a large number of IgG4-positive plasma cells in the SMT. Postoperative laboratory testing showed elevation of serum IgG4 levels; thus, we diagnosed the SMT as IgG4-RD. Intriguingly, the gastric IgG4-RD lesion demonstrated IgG4-positive plasma cell-rich arteritis as well as typical obstructive phlebitis. The patient has been followed for 2 years after surgery without recurrence of cancer, but skin lesions of IgG4-RD have appeared.We report a rare case of IgG4-RD presenting as a gastric SMT, accompanied by early-stage gastric cancer. Our case may support a newly proposed relationship between IgG4-RD and malignancies. The gastric IgG4-RD lesion showed arteritis as well as obliterative phlebitis, potentially providing novel insight into IgG4-related vascular lesions. IgG4-RD is an immune-mediated inflammatory disorder that involves multiple organs. It is characterized by IgG4-positive plasma cell-rich storiform fibrosis and obliterative phlebitis associated with a high serum IgG4 level . GastricA 70-year-old man was diagnosed with type 0–IIc gastric cancer by upper gastrointestinal endoscopy and referred to our hospital for further examination. The type 0–IIc lesion was 30 × 15 mm in size and located at the anterior wall near the greater curvature of the gastric corpus. In addition to gastric cancer, a submucosal tumor (SMT) 7 mm in diameter was revealed at the greater curvature of the angulus Fig. .Fig. 1a Pathology revealed the type 0–IIc lesion to be poorly differentiated adenocarcinoma with signet-ring cells Fig. a. The caFurther histological examination of the resected tissue revealed several IgG4-related inflammatory foci discontinuously distributed throughout the stomach. They were predominantly located in the submucosa and muscularis propria, occasionally causing wall thickening. Regional lymph nodes also contained fibrotic foci with lymphoplasmacytic infiltrate, occasionally with obliterative phlebitis.In addition to obliterative phlebitis, small-sized arteries were thickened and narrowed with marked intimal and medial inflammation by lymphoplasmacytic infiltrate Fig. a–d. The A postoperative laboratory test revealed elevation of the serum IgG4 level , with no increase in myeloperoxidase anti-neutrophil cytoplasmic autoantibodies (MPO-ANCA), proteinase 3(PR3)-ANCA, or interleukin 6 (IL-6). There was no clinical evidence of systemic vasculitis.The postoperative course was uneventful, and the patients were discharged on the 15th postoperative day. The patient has been followed for 2 years after surgery without recurrence of cancer, during which time only skin lesions of IgG4-RD have appeared. Cutaneous IgG4-related lesions have shown repeated exacerbations and remissions despite corticosteroid treatment.Multiple lines of evidence indicate that IgG4-RD is an autoimmune condition; however, the exact pathogenesis remains incompletely understood. There is an emerging consensus that the IgG4 antibodies in IgG4-RD are not pathogenic, and that T cells, especially CD4+ cytotoxic and T-follicular helper cells, have a more important role . ElevatiIn our case, gastric IgG4-RD was discovered during the preoperative examination for gastric cancer. Recent data have suggested that a history of IgG4-RD may be a risk factor for malignancies. In their analysis of 106 cases of IgG4-RD, Yamamoto et al. reported that IgG4-RD patients had a 3.8-fold elevated risk of malignancies compared to same-age cohorts . NotoharAlthough the mechanism underlying the association of IgG4 and carcinogenesis is not fully understood, several findings have been reported on how IgG4 is involved in cancer development. IgG4 was found to positively correlate with regulatory T cells and to negatively correlate with cytotoxic T cells, supporting its involvement of immune tolerance in cancer . KaragiaVascular involvement of IgG4-RD frequently occurs in the aorta and branching medium-sized arteries, such as the coronary arteries, superior mesenteric artery, and iliac arteries; by contrast, small-sized peripheral arteritis is rare . IgG4-reOther forms of vasculitis, such as polyarteritis nodosa and ANCA-associated vasculitis can be considered differential diagnoses of this disorder. They are necrotizing vasculitis of medium or small arteries with neutrophil infiltrates and fibrinoid necrosis. Our case lacked the clinical features of systemic vasculitis with no increase in ANCA; the inflamed arteries were almost exclusively localized in the SMT where inflammation was most prominent. There is the possibility that obliterative arteritis may be a secondary arterial involvement of interstitial inflammation.It has been reported that gastric IgG4-RD lesions are mainly localized in the muscularis propria and are often difficult to diagnose by endoscopic biopsy . When thWe report a case of a 70-year-old man with IgG4-related gastric disease presenting as a submucosal tumor and early-stage gastric cancer. Our case may support the newly proposed relationship between IgG4-RD and malignancies. The IgG4-related gastric lesion showed arteritis as well as obliterative phlebitis, potentially providing novel insight into IgG4-related vascular lesions.