B has been reported to regulate neurogenesis and vasoregulation in foetal development. Its dysfunction was known to cause HSCR, an aganglionic colonic disorder with syndromic forms reported to associate with both small heads and developmental delay. We therefore asked, "is CNS maldevelopment a more general feature of ETB mutation?" To investigate, we reviewed the micro-CT scans of an ETB−/− model animal, sl/sl rat, and quantitatively evaluated the structural changes of its brain constituents.ETB+/− cross breeding were sacrificed. Micro-CT scans were completed following 1.5% iodine-staining protocols. All scans were reviewed for morphological changes. Selected organs were segmented semi-automatically post-NLM filtering: TBr, T-CC, T-CP, OB, Med, Cer, Pit, and S&I Col. Volumetric measurements were made using Drishti rendering software. Rat genotyping was completed following analysis. Statistical comparisons on organ volume, organ growth rate, and organ volume/bodyweight ratios were made between sl/sl and the control groups based on autosomal recessive inheritance. One-way ANOVA was also performed to evaluate potential dose-dependent effect.Eleven neonatal rats generated from ETsl/sl rat has 16.32% lower body weight with 3.53% lower growth rate than the control group. Gross intracranial morphology was preserved in sl/sl rats. However, significant volumetric reduction of 20.33% was detected in TBr; similar reductions were extended to the measurements of T-CC, T-CP, OB, Med, and Pit. Consistently, lower brain and selected constituent growth rates were detected in sl/sl rat, ranging from 6.21% to 11.51% reduction. Lower organ volume/bodyweight ratio was detected in sl/sl rats, reflecting disproportional neural changes with respect to body size. No consistent linear relationships exist between ETB copies and intracranial organ size or growth rates.B−/− mutant has a normal CNS morphology, significant size reductions in brain and constituents were detected. These structural changes likely arise from a combination of factors secondary to dysfunctional ET-1/ET-3/ETB signalling, including global growth impairment from HSCR-induced malnutrition and dysregulations in the neurogenesis, angiogenesis, and cerebral vascular control. These changes have important clinical implications, such as autonomic dysfunction or intellectual delay. Although further human study is warranted, our study suggested comprehensive managements are required for HSCR patients, at least in ETB−/− subtype.Although ETThe online version contains supplementary material available at 10.1186/s12868-021-00646-z. B) is a widely expressed seven-transmembrane G-protein coupled receptor (GPCR) with multiple regulatory controls on embryological development, vasoregulation, and endothelin metabolism [B mutation has been well documented to cause Hirschsprung’s disease (HSCR), a paediatric intestinal disease affecting 1/5000 live births, we suspect concurrent intracranial changes is also likely due to the impaired neurogenesis [B mutation by studying the changes detected in spotting-lethal (sl/sl) rat, a HSCR animal model. We hope these findings can provide additional evidence to support ETB’s importance on anatomical development and the notion that HSCR is likely a multi-organ disease, at least in ETB−/− subtype.Endothelin receptor B (ETtabolism –4. Althoogenesis . In thisB), endothelin-3 (ET-3), SOX10, endothelin converting enzyme-1 (ECE-1), neurturin (NTN), and Smad interacting protein 1 (SIP1) genes [B (5%) and ET-3 genes (< 5%) [B gene of an inbred kindred can result 74% and 21% risks for HSCR development in homozygotes and heterozygotes, respectively [B and the likely underestimation in its true impact on HSCR and embryological development, possibly due to ETB’s multi-regulatory functions. This notion is further supported by the increasing identifications of novel ETB mutations and polymorphism in sporadic HSCR patients, which further emphasizes its developmental importance [Although HSCR is best known for its clinical manifestations of intestinal dilatation and toxic megacolon sequelae, multi-organ dysfunctions have also been documented , 8. Inde1) genes , 13. Amos (< 5%) . Puffenbectively . This suportance , 17.A and ETB) have been reported to involve in the neurogenesis of both central and peripheral nervous systems. Mutations in endothelin receptors and endothelin  can cause defective embryonic development in neural crest derived structures, in particular melanocytes and enteric nervous systems (ENS) from ETB mutations [B signalling for migrating neural crest cells of ENS development is well documented, maintaining the pluripotency of neural crest cells, its impact on the development of central nervous system remains unclear [B is widely expressed in mammalian brains, including medulla oblongata, cerebral cortex, hippocampus, cerebellum, and striatum [Endothelin receptors  and antagonist (BQ-788) promotes and inhibits the remyelination processes, respectively [B-knockout mice, Swire et al. (2019) reported significantly reduced myelin sheaths in ETB-deficient oligodendrocytes. This phenotypically coincided with the decreased sociability among the affected animals [B deficient animals [B exerts a positive impact on neurogenesis.ET control –28. Pastocephaly , 29. Cononist BQ-20 and an animals . Further animals –34. ThesB inhibition may be beneficial for remyelination, possibly through its regulation on astrocyte proliferation and vascular control. Back et al. (2005) have reported high molecular weight hyaluronan produced by astrocytes can inhibit oligodendrocyte progenitors (OPCs) maturation, which is vital to remyelination post-injury [B signalling in astrocytes enables oligodendrocyte progenitor cell maturation and promotes remyelination following brain injury [B antagonist, BQ-788, to rat corpus callosum can suppress the upregulations of reactive astrogliosis following acute demyelination injury. Further studies on cell culture suggested this ET-1/ETB activated astrocyte proliferation is mediated by ERK- and JNK- dependent pathways. Inhibitions of these pathways or ETB deficiency may therefore be beneficial to myelination [B antagonist can suppress cerebral hypoperfusion by inhibiting the vasoconstriction in cerebral arteries. Together, these studies suggested ETB−/− mutants may exhibit neuroprotection through the absence of ETB signalling [B and its obvious multimodal actions on neural structures and functions, we adopted a macroscopic approach to investigate its effect on brain anatomy and growth.On the other hand, several reports have suggested ETt-injury . Consistn injury . Gadea elination . Furthergnalling , 39. GivB on myelination. Although increased neural apoptosis has been reported in ETB deficient animals using immunohistochemistry methodology, to the best of our knowledge, no macroscopic analysis has been completed to evaluate the intracranial changes associated with ETB mutations or HSCR. At most, one anecdotal inference was made from a cohort study showing the regional prevalence of intracranial abnormalities associated with Mowat-Wilson syndrome, a HSCR-associated syndrome caused by mutations in ZEB2 gene; however, no direct comments have been made on the physical brain size [B’s importance on the brain development and to clarify potential correlation between HSCR and intracranial changes.Prior cell culture studies have suggested possible bimodal actions of ETain size . We aimesl/sl rat as the study subject. It is a naturally occurred ETB−/− animal model analogous to human WS-IV syndrome with the following characteristics: HSCR, hypopigmentation, and congenital hearing loss [B gene leading to defective G-protein-coupled receptor, yielding sl/sl rat [sl/sl rat follows autosomal recessive inheritance  with 95% genetic penetrance for HSCR phenotype, supporting sl/sl rat as a good candidate for studying the phenotype of ETB mutation.In this study, we have chosen ing loss . Confirml/sl rat , 41. Segsl/sl rat and the control group [sl/sl rat has not reached growth maturity and may suffer HSCR-induced growth impairment, organ growth rate and organ volume/bodyweight ratios were also determined for comparison.Image acquisitions were performed using X-ray micro-computed tomography (micro-CT) and previously described tissue-preparation methods to examine neuroanatomical difference between ol group . ThorougB−/− animals.Gross intracranial morphology may be preserved in ETB−/− animals with respect to those of the control group (ETB+/+ & ETB+/−). Reducing trends may also extend to the organ growth rate and organ volume/bodyweight ratios of ETB−/− animals.Reductions in brain and constituent sizes may be presented in ETB mutation may be presented across different neural constituents; effect of ETB mutation on neuroanatomy may be regional-dependent.Non-uniform anatomical changes associating with homozygous ETIn this study, we hypothesized the following:All tissues and animals used in this study were handled with strict compliance to both approval bodies: Australian Capital Territory Health-Human Research Ethics Committee (ACTH-HREC) and Australian National University-Animal Experimentation Ethics Committee (ANU-AEEC), approval project number A2011/67.B+/−). The breeding colony was initially derived from a natural-occurring mutation; this colony has been maintained in the Australian National University (ANU) over the past 15 years.Rat samples were generated from cross breeding the heterozygous rats  series over four days: 20%, 50%, 70%, and 90% for 1 day each. These tissue preparations were finalized by seven days of iodine-staining with 1.5% iodine solution in 90% EtOH.All micro-CT datasets of the rats were acquired using a commercially available Caliper Quantum FX in vivo micro-CT scanner. At the expense of 4.5 min scanning time per scan, acquired in vivo micro-CT data has an image-resolution of 20 µm/voxel. The resultant images were stored as DICOM series with average dataset size of 256 MB.Prior to quantitative analysis, images of in vivo micro-CT scans were validated with two sets of ex vivo micro-CT scans for quality control. The ex vivo micro-CT scans were acquired by scanning two of the eleven rat-tissues using a custom-built micro-CT system at the Applied Mathematic Department of Australian National University. Because ex vivo micro-CT scans have significantly higher signal-to-noise ratio than in vivo micro-CT images, they provided good reference for image quality control; however, accesses to ex vivo micro-CT scanner were limited. Ex vivo micro-CT data with resolution of 10.7 µm/voxel required fifteen hours of scanning time followed by eight hours of image-processing time via Australia National Computational Infrastructure (NCI) services. The resultant images were stored as netCDF files with each dataset size of 12 GB. All datasets were visualized and analysed with FIJI and Drishti, opensource image rendering software , 44.All acquired in vivo micro-CT raw data were denoised using non-local means (NLM) algorithms to improve signal-to-noise ratio and hence image clarity for segmentation . This cost cervical spine for comparison across different samples. Cerebral cortex and caudate putamen were segmented and analysed in respective left and right hemispheres prior to amalgamation of measurements. Superior and inferior colliculus were measured together due to poor differentiation between the two regions on micro-CT scans.Following image denoising, micro-CT images were segmented semi-automatically through individual CT-slices for organs of interest using Drishti paint. This segmentation was verified by two operators. A number of neural organs were selected based on prior literature and organ differentiation on micro-CT scan: total brain (TBr), total cerebral cortex (T-CC), total caudate putamen (T-CP), olfactory bulb (OB), medulla (Med), cerebellum (Cer), pituitary gland (Pit), and superior and inferior colliculus (S&I Col). The posterior border of TBr was standardized to 1Lastly, the segmented data were rendered, visualized, and volumetrically measured with Drishti for volumetric exploration and presentation .H&E light microscopy was completed for two of eleven rats following micro-CT scanning for verification of neuroanatomical detail presented by micro-CT scans. The tissue processing was conducted in the following steps. The iodine-stained tissues were sectioned longitudinally into blocks of 4 mm in thickness and placed in cassettes. Contrast washout and dehydration were then performed in 90% EtOH for 48 h prior to paraffin embedment at 60 °C. Next, the samples were sliced with a microtome for tissue-sheets of 4 µm in thickness. These tissue-sheets were then laid in water bath of 5–6 °C while being positioned onto labelled-glass slides. These slides were dried overnight at 37 °C.Progressive H&E staining was then performed. The slides were placed in alum-hematoxylin solutions until the visualization of dark red colour. This was followed by washing and ‘bluing’ with lithium carbonate solution. Finally, the slides were washed before counter-staining with 0.5% eosin alcoholic solution.All H&E slides were examined with an Olympus IX71 microscope with 4 × magnification.B+/+), three heterozygotes (ETB+/−), and five sl/sl (ETB−/−) rats were identified. The average ages of wild-type, heterozygotes, and sl/sl groups were 90.7 h, 96 h, and 83.2 h, respectively.Genotyping was completed following the completion of the quantitative image analysis of rat data to avoid observational bias. It was completed by standard PCR methods. Three wild types  by the side. Electrophoresis gel was visualized with Gel Documentation System DOC-Print VX5 (Vilber Lourmat).PCR genotyping was processed through the following. Five-millimetre tail tips from each of the eleven rats were isolated for lysis using Proteinase K in lysis buffer, which consisted of 100 mM Tris pH 8, 5 mM EDTA, 0.2% SDS, and 200 mM NaCl in distilled water. The DNA was extracted via vortex heating and centrifuging to separate DNA-containing supernatant from the undigested materials. Afterwards, the supernatant was further vortexed and centrifuged to isolate the DNA pellet, followed by 70% EtOH washing and drying. The DNA was then suspended and quantified with spectrophotometry. Next, PCR was completed with “Master-Mix” reagent: 10*PCR buffer Qiagen-contained MgCl2, dNTP (10 mM), Primer PS7 , Primer PS15  and DNA polymerase . The Massl/sl rat phenotype followed autosomal recessive inheritance  with high genetic penetrance, up to 95% of sl/sl rat exhibited HSCR, statistical comparisons were made between sl/sl (ETB−/−) and the control group (ETB+/+ & ETB+/−) to determine the effect of ETB on structural changes and growth. This approach was consistent with the autosomal recessive inheritance of human WS-IV, a disease caused by ETB−/− genotype. Nonetheless, we have also performed one-way ANOVA analysis and post hoc Tukey to assess the potential relations between ETB gene dose and the following selected parameters.Based on segregation analysis on cumulative colony data showing The parameters included for comparison were as follows: bodyweight (g), bodyweight growth rates (g/Hr), organ volume (mL), organ volume growth rates (mL/Hr), and organ volume/bodyweight ratios (mL/g). The bodyweight growth rate (g/Hr) was calculated by dividing each rat’s bodyweight (g) to its respective age (Hr) at culling and followed by statistical comparison between the control and mutant groups. Similarly, organ volume growth rate (mL/Hr) and organ volume/bodyweight ratios (mL/g) were calculated from respective volumetric measurements (mL), age (Hr), and bodyweight (g) at times of culling.B. All parameters were expressed as mean ± sem in figures. The relative parametric difference (%) between sl/sl and the control group was also calculated and reported throughout this study for better appreciation on the degrees of difference.Standardized comparisons of organ volume growth rate and organ volume/bodyweight ratios were made to exclude potential confounding factors of age and body-size variance. Additionally, these measures provided estimating metrics for the organ changes upon developmental maturation of the animals. Moreover, the proportionality of individual neural substituent with respect to the total brain  was compared to explore potential regional-dependent effect of ETB−/− mutation. As shown by Fig. sl/sl rat has 16.32% lower bodyweight than the control group, p-value = 0.03. Although not reaching statistical significance, a 3.53% deduction in growth rate was also detected, Fig. B mutation may be associated with body growth impairment in an autosomal recessive manner.We compared the bodyweight of the studied animals to evaluate potential growth reduction associated with ETsl/sl rat scan  migration failure and thus marked craniofacial defects . Howevercan Fig. B demonstcan Fig. C. As shosl/sl mutants. As demonstrated by Fig. sl/sl rat, p-value = 0.02. Furthermore, an average of 20% volumetric reduction was detected across all neural constituents analysed in the sl/sl rat. Structures with statistically significant difference between sl/sl and the control groups were as follow: T-CC ; T-CP ; OB ; Pit . Although not reaching the statistical power, the reducing trend in sl/sl rat was also evident in the following: Med , Cer ; S&I col .While the gross morphology might be preserved, moderate volumetric reductions of the brain and constituents were detected in sl/sl and heterozygous group; consistent ETB dose-dependent trend was not seen in the wild type, as shown by Additional file Additionally, one-way ANOVA showed statistically significant variation in TB, T-CC, and Pit volumes of the three genotypes, as shown by Additional file sl/sl group; however, this margin of reduction was smaller than that detected in the volumetric changes. An approximately 10% reduction in growth rate was observed across various brain components in sl/sl rat.Reduced intracranial organ growth rate was observed in sl/sl rat was 7.35% lower than that of the control group, p-value = 0.07. Consistent decreasing trends were also presented in the following: T-CC , T-CP , and OB . Furthermore, although not reaching the statistical power, similar reductions were observed in the medulla  and pituitary gland  of sl/sl rat. Unexpectedly, no significant change was detected in the growth rate of Cer  and S&I Col . Lastly, no consistent linear relationship was detected between the neural growth rates and ETB gene dose, as shown by one-way ANOVA analysis in Additional file As shown by Fig. B mutation was associated with reduced neural growth rate during development, an effect likely to persist until maturation age.Overall, we found homozygous ETsl/sl rat has disproportionally larger reductions in its brain volumes than the decreases in its bodyweight. As illustrated by Fig. sl/sl rat has lower organ volume/bodyweight ratios than the control group: TBr , T-CC , T-CP , OB , Med , and Pit . Albeit statistically underpowered, these findings suggested neural development was more sensitive to ETB dysfunction than the bodily growth. And although homozygous ETB mutation seemed to predominantly affect growth negatively, sl/sl rat was found to have larger organ/bodyweight ratios in its Cer  and S&I Col . This raised the possibility that a potential protective mechanism associated with ETB−/− may be presented, albeit this protective effect was likely small. Additionally, non-uniform changes were recorded from different neural structures of sl/sl rat, suggested the impact of ETB mutation on anatomical development might be dependent on organ location.sl/sl rat and the control group shared subtle difference between their respective neural organ/TBr indices. Although these differences may be small, ranging from 2 to 8%, they reflected disproportional changes in different neural constituents of ETB−/− rat. These variations suggested that the effect of ETB on structural growth may be influenced by the target organ locations within the brain.As showed by Fig. B mutation and associated HSCR were likely linked with intracranial changes, at least in the sense of volumetric measurements. This finding was consistent with previous in vitro studies and clinical reports citing HSCR’s associations with neurological deficits, as exemplified by Down’s syndrome, Haddad syndrome, Mowat-Wilson syndrome, and WS-IV [As evidenced by the anatomical changes detected, we supported the notion that homozygous ETnd WS-IV , 48–51.A pathway system can lead to marked craniofacial dysmorphism. [sl/sl rat, as demonstrated by Fig. B mutation may disrupt enteric neural crest cell migration, its direct impact on the migration of cephalic and vagal neural crest precursors may be limited. On the other hand, neurogenic modelling mediated by ETB signalling and the clinical reporting of HSCR-associated mental retardation supported the notion that ETB may possess an adjunct but important role in neural development [It has been suggested that disruption in ET-1/ECE/ETorphism. . And ageorphism. , 52. Regelopment , 53. QuaB receptors in olfactory bulb, cerebral cortex, caudate putamen, thalamus, hypothalamus, pituitary gland, brain stem and limbic system through the combined use of immunohistochemistry and ETB’s agonist or antagonists, supporting its importance in brain structures and functions [Many previous studies have demonstrated the presence of ETunctions –57.B stimulation by IRL-1620 can lead to neurogenic remodelling, which was likely achieved by increased neurogenesis and angiogenesis via elevated vascular endothelial growth factor (VEGF) and nerve growth factor (NGF) [B by ET-1 can trigger vasodilation of basilar artery through the production of nitric oxide [B activation promotes neuroprotection. This was indeed consistent with the overall brain size reduction observed in sl/sl rat, which lacks functional ETB during its development. On the other hand, in vitro studies using U0126, a mithramycin A (MitA) or mitogen-activated protein kinase (MEK) 1/2 inhibitor, blocks the elevation of ETB-mediated vasoconstriction following cerebral ischemic events, suggesting ETB stimulation in vascular smooth muscle cells (VSMC) may worsens neural damage [B on brain growth may be dynamic and regional-dependent, a pattern consistent with our finding, Fig. Consistently, two-dimensional 2D) immunofluorescence studies have demonstrated ETD immunofor (NGF) , 58. Addic oxide , therebyl damage , 60, 61 p-value = 0.02) was found in the brain volume of sl/sl rat at the age of 88 h. Consistently, a reduction of 7.35%  in brain growth rate also suggested its structural impairment would likely worsen upon developmental maturity. Several factors could have contributed to these impairments. As previously reported by McDougall et al. [sl/sl rat based on our colony data of 864 rats, we did record a bodyweight reduction of 16.32% at the age of 88 h in our studied rats, Fig. B-mediated vasodilation can be achieved in the heterozygous parents of sl/sl rat [sl/sl rat may later suffer the negative effect of HSCR-induced malnutrition and ETB−/−-mediated mesenteric hypoperfusion [sl/sl rat can be partially explained by this bodily growth impairment, disproportionally larger reductions in sl/sl rat brain with respect to changes in its bodyweight, as shown by Fig. B mechanisms on the brain development. Indeed, this was supported by sl/sl rat exhibiting 1.26% to 11.18% smaller organ volume/bodyweight indices in TBr, T-CC, TCP, OB, Med, and Pit. Interestingly, opposite trend was seen in Cer and S&I Col measurements, with sl/sl rat having 3.17% and 6.84% higher indices, respectively. In conjunction with ETB’s functional duality on vasoregulation and neurogenesis reported previously, our observations likely reflected a potential regional-specific neuroprotection by ETB mutation despite its overwhelming negative effects [Despite the presentation of a grossly normal brain morphology, a significant structural reduction of 20.33%  showed ETB-stimulation by IRL-1620 accelerates interkinetic nuclear migration (INC) of cortical neural progenitor cells (NPC), whereas inhibition by BQ-788 results in INC deceleration and subsequent mislocalization of NPC [B stimulation increases vascular endothelial growth factor A (VEGF-A), thereby triggering VEGF-receptor signalling in cerebrum but not hippocampus. This suggested regional-dependent neuroprotective effect of ETB, possibly via vascular control [B-mediated clearance caused significant elevation of ET-1 in sl/sl rat, thus leading to ET-1/ETA-mediated hyper-vasoconstriction in cerebral vasculature [B stimulation was also lost in sl/sl rat [sl/sl rat, small elevation in Cer/bodyweight and S&I Col/bodyweight indices lend some support to the argument that regional brain development may benefit from increased perfusion secondary to reduced ETB-mediated vasoconstriction, for instance, in the VSMC of collicular artery [A effect [Dysregulation in the neurogenesis, angiogenesis, and cerebral vascular tone have likely contributed to the observed structural changes in n of NPC . Additio control . Moreoveculature . Albeit l/sl rat , 68. Togr artery . HoweverA effect , 61, 69.B triggers the release of dopamine [sl/sl rat [sl/sl rat were consistent with the ETB distribution [B−/− individuals were therefore likely to worsen. Hence, more prominent structural impairments were likely to reflect HSCR-associated functional declines upon maturity.If our finding was extrapolatable to human subjects, then the observed structural impairments lend supports to several HSCR-associated clinical anomalies. For instance, marked reductions in total brain 20.33%), cerebral cortex 24.60%), and caudate putamen (24.68%) were not only consistent with prior observations of mental delay in some HSCR patients and but also raised the questions that these patients may be more susceptible to Parkinson’s disease or depression secondary to potential dopamine deficiency , 71. Inddopamine . Moreovedopamine , 72. In dopamine . This wal/sl rat , 34. Lasribution –24, 73. .60%, andribution –76. It w3%, cerebB. While heterozygote has significantly larger TB, TCC and Pit than those of sl/sl rats, no linear relationship can be drawn from its comparison with the wild-type rat, Additional file B gene may be sufficient to prevent neuroapoptosis and mediate ET-1 clearance in some structures, thereby improving cerebral perfusion and exerting some neuroprotection [B mutation impairs brain structures. Our findings were consistent with ETB mutation acting as an autosomal recessive condition with high penetrance.Lastly, we compared the structural differences among the three genotypes to explore potential dose-dependent effect of ETotection , 61, 67.B−/− animal model. These detrimental effects were not uniform across different brain structures and minor protective effects may be presented, Fig. B, including regulations on angiogenesis, neurogenesis and vasoconstriction [Bs have predominantly neuroprotective benefits during neonatal development.In summary, we provided quantitative 3D evidence illustrating structural changes in the brain associating with HSCR, at least in ETtriction , 66, 69.B mutation affects brain growth, further study was warranted. We acknowledged a larger sample size would be beneficial along with more efficient image-analysing software to improve statistical power; nevertheless, current finding cannot be overlooked. More importantly, given that we have macroscopically identified ETB-affected neural organs, future cell proliferation studies using 5-bromo-2’-deoxyuridine (BrdU) labelling can be useful in confirming reduced neural proliferation microscopically [sl/sl rats [B [Although we have shown ETopically . Moreove rats [B .B−/− HSCR model. With no significant differences between wild-type and heterozygous animals, these changes associated with ETB mutation were consistent with autosomal recessive inheritance. The non-uniform neuroanatomical changes observed across different constituents supported prior studies on differential ETB distribution, neurogenesis, and vasoregulation in the brain. Interestingly, a regional-dependent protective effect of ETB may be presented, potentially corresponding to the circulatory distribution through ET-1/ETB-mediated vasoregulation. Overall, our model findings supported the notion that ETB−/− HSCR patients may exhibit neuroanatomical impairments, consistent with prior clinical reports. Although further study involving human subjects was encouraged, this study supported the importance to a more comprehensive management plan for HSCR patients.Despite exhibiting a grossly normal cranial morphology, an average of 20% volumetric reduction was detected in the brain and constituents of ETAdditional file 1: Table S1: No significant variation was detected in the mean bodyweight (p = 0.0551) or mean body growth (p = 0.9096) of the studied rats, which consisted of three genotypes: ETB+/+, ETB±, and ETB−/−. This suggested bodily growth restriction associated with ETB mutation, if presented, was not a dose-dependent relationship.Additional file 2: Table S2: One-way ANOVA showed statistically significant variations in the TBr, TCC, and Pit volumetric means of the studied rats: ETB+/+, ETB+/−, and ETB−/−. On the contrary, no significant variation was detected in other organ measurements of the three genotypes, as shown by A Post-hoc Tukey showed significant volumetric difference between the heterozygote (ETB+/−) and sl/sl (ETB−/−) in TBr , TCC , and Pit . However, measurement of wild type (ETB+/+) was not significantly different from those of the other two groups, as shown by B.Additional file 3: Table S3: One-way ANOVA comparison showed no significant difference was detected in the mean organ growth (A), volumetric/bodyweight ratios (B), and organ/whole-brain ratios (C) of the three genotype rats: ETB+/+, ETB+/−, and ETB−/−. These findings suggested that effect of ETB mutation was likely non-linear to gene doses.


One of the biggest challenges in the development of a biological self-healing concrete is to ensure the long-term viability of bacteria that are embedded in the concrete. In the present study, a coated expanded clay (EC) is investigated for its potential use as a bacterial carrier in biological concrete. Eight different materials for coatings were selected considering cost, workability and accessibility in the construction industry. Long-term (56 days) viability analysis was conducted with a final evaluation of each coating performance. Our results indicate that healing efficiency in biological concrete specimens is strongly related to viable bacteria present in the healing agent. More viable bacteria-containing specimens exhibited a higher crack closure ratio. Our data suggest that the additional coating of EC particles improves long-term bacterial viability and, consequently, provides efficient crack healing in biological concrete. When the cracks open, oxygen and water start to penetrate the concrete, which easily triggers the metabolic activity of bacteria. Several biological pathways have been proposed for the precipitation of CaCO3, such as metabolic conversion of organic acids, ureolysis or denitrification [Biological concrete combines the advantages of traditional concrete and autonomous crack repair. The self-healing effect is achieved by using calcium carbonate  in the cement. In fact, the actual concentration of these metal oxides may exceed the claimed minimal inhibitory concentration (MIC) several times, causing rapid viability loss [Expanded clay (EC) and expanded perlite (EP) have been widely investigated for their potential use as bacterial carriers ,13,14. Tity loss .It appears that protection of bacteria by immobilization into the EC or EP alone may be insufficient, as bacterial viability drastically decreases during the early setting (0–7 days) of concrete . To solvSimilarly to EC, several different coatings for EP have been explored . CoatingB. pseudofirmus bacterial strain, commonly used as a producer of a healing agent, was selected [Here, we report a detailed study on the influence of an additional coating layer of bacteria-embedded EC particles on the bacterial viability in a biological concrete. To evaluate the performance of coating materials, the selected ,19,20. CBacillus pseudofirmus DSM 8715 was purchased from the German Collection of Microorganisms and Cell Cultures, Braunschweig, Germany. Bacteria were routinely cultured in liquid alkaline nutrient medium according to the manufacturer’s recommendations. Alkaline nutrient medium contained 5 g/L of peptone, 3 g/L of meat extract, 0.42 g/L of NaHCO3 and 0.53 g/L of Na2CO3. Bacteria were incubated at 30 °C overnight.Alkaliphilic 2PO4, 0.166 g/L of CaCl2, 0.476 g/L of KCl, 0.2 g/L of MgSO4·7H2O, 0.2 g/L of MnSO4·H2O, 4.2 g/L of Na2CO3 and 5.3 g/L of NaHCO3. Bacteria were aerobically incubated at 30 °C with shaking until the concentration reached 109 cells/mL. The sporulation of B. pseudofirmus was quantified using light microscopy after staining [Spores were prepared in a sporulation medium containing 3.5 g/L of sucrose, 4 g/L of yeast extract, 0.02 g/L of KHstaining . After 48 CFU/mL of bacterial spores. EC particles were dried at room temperature for 72 h until constant mass. Scanning electron microscope (SEM)  images of dried EC particles are shown in 7 bacterial spores were immobilized into 1 g of dry EC on average. EC (Liapor 4–8 mm) was impregnated by vacuum pressure of 0.1 MPa. Impregnation solution contained 80 g/L of calcium lactate pentahydrate, 1 g/L of yeast extract and 1 × 10Eight different coatings listed in To distribute the coating material evenly, EC particles were immersed into a prepared protective solution. Then, the coatings were left to air-dry for 48 h at room temperature. All studied coatings are shown in ®, Aalborg, Denmark), tap water and EC aggregates . Concrete mix proportion was adopted from [Cylindrical concrete specimens A were cated from  and is gEach concrete sample was mixed in a separate plastic cup, sealed and left to cure for 7 days A. After The surface of the coated bacteria-immobilized EC particles was examined using JEOL JSM-7600F Field Emission Scanning Electron Microscope (SEM) at an accelerating voltage of 10 kV. The distance between the SEM and the specimen surface was 7–11 mm. Imaging with secondary electron detectors (SEI and LEI) was used to recreate the surface topography. Samples were completely dried in the oven at 60 ± 5 °C for 72 h. The dried samples were covered with an electrically conductive thin layer of gold by evaporating a gold electrode in vacuum using a Quorum Q150R ES instrument . The survival rate of bacterial spores in the concrete matrix was determined in 7, 14, 21, 35 and 56 days after the preparation of concrete specimens. For each viability test, 6.53 g of concrete was crushed to powder, which contained approximately 1 g of bacteria-embedded EC. The powder was suspended in sterile 10 mM Tris-HCl buffer (pH 9) and homogenized by vortexing. Then, samples were serially diluted in the same buffer. Aliquots of suitable dilutions were plated on alkaline nutrient agar and incubated at 30 °C overnight. The colonies were counted after 24 h.Crack healing progress was measured after 7, 14, 28 and 56 days of the healing period in all concrete samples. To avoid the reflective brightness from water, specimens were dried one day before measurement. Crack images were taken using a digital microscope equipped with a camera . Two or three measuring areas were selected in each sample and marked using waterproof markers. To ensure that the results were representable and correct, each crack location was selected carefully: parallel cracks, missing aggregates or pieces of cement matrix as well as other irregularities were avoided. Four measurement points were selected in each area. An example of crack measurement with a target area and measuring points is presented in Our preliminary data have shown that bacterial viability drastically decreases at an early age (0–7 days) . After t7 CFU/g, see The main results of the bacterial viability in concrete specimens with differently coated EC particles are illustrated in The potassium magnesium phosphate cement (MKPC)-based coating had almost no impact on the bacterial viability whatsoever A. SurpriThe remaining five coatings  demonstrated considerably good shielding activity, increasing the bacterial survivability by almost 10-fold B,C,F–H. High protective characteristics were also detected for the MgO-based coating, although a visible uniform shell, as with styrene–acrylate emulsion, was not observed during the preparation of the coating F. As desEven though this viability study generated fairly scattered results, all tested coating materials may be divided into two groups: coatings displaying low protection and highly protective coatings  and 1 (full crack closure). Along with bacterial viability studies, crack healing in concrete specimens with coated EC particles was optically assessed. The healing progress was monitored at 14, 28 and 56 days after concrete samples’ preparation. The representative results are summarized in ficiency . Hc may c = 0.31) was observed after 56 days in the specimen with embedded bacteria yet no coating 2 may improve long-term autogenous healing. A more detailed long-lasting statistical analysis with a larger sample number and broader variety is required to verify this effect.Crack healing progress in the double-negative control specimen is depicted in  coating B. The nu05 CFU/g J. The faNevertheless, our results indicate that healing efficiency in biological concrete specimens is strongly related to viable bacteria cells present in the healing agent. More viable bacteria-containing specimens exhibited a higher crack closure ratio. Consequently, additional coating of EC particles is essential to prolong bacterial viability and enhance crack healing in biological concrete.B. pesudofirmus bacteria in concrete specimens produced with differently coated EC particles was carried out. Optical measurement of crack healing in biological concrete specimens was also performed. Based on the aforementioned data, the following conclusions may be drawn. First, a concrete matrix is a harsh environment even for EC-embedded bacterial spores. Notably, the porous structure of EC may facilitate the diffusion of the metal oxide nanoparticles that at certain concentrations are lethal to bacteria. Moreover, a surface coating of EC particles may improve bacterial viability by almost 10-fold. To ensure the high survival rate of bacteria, the coating material must block the surface pores of EC. In addition, styrene–acrylate- and MgO-based coatings were characterized as excellent protectors. Indeed, these materials may be further used for the development of a coating-based encapsulation technique. Undoubtedly, future research is needed to assess the protective capabilities of styrene–acrylate- and MgO-based coatings for other bacterial strains suitable for biological concrete production. Finally, healing efficiency in biological concrete specimens is related to viable bacteria cells present in the healing agent. The more viable bacteria, the higher the crack closure ratio is.In the present study, a detailed investigation on the viability of


Mechanical properties and data analysis for the prediction of different mechanical properties of geopolymer concrete (GPC) were investigated. A relatively large amount of test data from 126 past works was collected, analyzed, and correlation between different mechanical properties and compressive strength was investigated. Equations were proposed for the properties of splitting tensile strength, flexural strength, modulus of elasticity, Poisson’s ratio, and strain corresponding to peak compressive strength. The proposed equations were found accurate and can be used to prepare a state-of-art report on GPC. Based on data analysis, it was found that there is a chance to apply some past proposed equations for predicting different mechanical properties. CEB-FIP equations for the prediction of splitting tensile strength and strain corresponding to peak compressive stress were found to be accurate, while ACI 318 equations for splitting tensile and elastic modulus overestimates test data for GPC of low compressive strength. Initial research on geopolymers carried out by Davidovits  was on t2) will be released into the atmosphere, and the related reports indicate that the cement industry contributes around 8% of the worldwide yearly CO2 emission . cE is measured in MPa and R2 for this equation is 0.857 better than that of Equation (5), indicating a strong relation between elastic modulus and concrete density. It is worth checking the accuracy of some proposed equations when used for calculating elastic modulus of GPC. It is of interest to perform regression analysis to develop an equation for the elastic modulus taking into account the effect of concrete density, because there are proposed equations based on both compressive strength and density of concrete such as that given by ACI 318 . Data coc’υ/f) and compressive strength. 2). From regression analysis, the final form of the equation for predicting Poisson’s ratio is given byCompared with the other properties of geopolymer concrete, there is limited test data for this property. In this study, total of 99 data samples were collected. Additionally, it seems that equations for the prediction of Poisson’s ratio of GPC are not available. 2 for the above equation is 0.793, and c′f is measured in MPa. The mean  value of Poisson’s ratio for GPC was found to be 1.04, indicating the accuracy of the proposed equation accompanying with safety.Ro) taken is that of normal concrete. The authors think that it is better to derive equations for this parameter, since test data obtained by some researchers are available. Additionally, there is a chance to assess the accuracy of the assumed εo basically derived the for normal concrete. To do this, there is a need to review the related works performed on the compressive stress- strain relationship of GPC. This property was experimentally investigated by Hardjito [o) was picked up and found that there are 27 strain values. o with compressive strength, from which one can find that there is a weak correlation, identical to that of Poisson’s ratio.This property has a great importance to assess accurately the compressive stress-strain relationship of GPC. Those models proposed for compressive stress-strain response of GPC are based on some equations proposed basically for normal concrete, and the parameter of strain corresponding to peak stress  value is 0.975. Now, it is worth checking the accuracy of some proposed equations for calculating εo applied on test data on GPC. Mean value of test/calculated strain was found to be 0.999 for the equation proposed by Albitar et al. [For the above, Equation Rr et al. , indicatr et al.  and Euror et al. , respectAlkali-activated materials are considered to be very suitable from the point of view of sustainable development. This novel concrete meets many of the requirements including high strength, use of secondary materials, low carbon trace, minimum greenhouse gas emissions, good frost resistance, etc. A revised data analysis on the mechanical properties of geopolymer concrete was made in this study and equations were proposed for each property. The outcome of the study is interesting, because the proposed equations derived for the mechanical properties are accurate since they were based on a relatively large amount of test data. These equations can be used in the design of GPC structural members and to prepare a state-of-art report on GPC. Furthermore, the following conclusions can be drawn.I.Different properties of geopolymer concrete (GPC) can be correlated with compressive strength; however the correlation strength usually reduced as the number data taken for analysis increased.II.The effect of initial curing temperature was not important for correlation between different properties and compressive strength, and from this basis, a single equation was proposed using regression analysis. For the splitting tensile strength and flexural strength, power equation (Equations (3) and (4)) was found accurate, while there is a linear equation (Equation (5)) for the elastic modulus.III.There is a better prediction of the elastic modulus based on both compressive strength and concrete density. Because of very low correlation, it was better to correlate normalized Poisson’s ratio and strain corresponding to peak stress with compressive strength. From this basis, Equations (7) and (8) were obtained from regression analysis.IV.Accuracy of most important past equations were checked against the large number of test data collected, and found that the equation of CEB-FIP  is accurV.In general, most of the proposed equations are safe for predicting flexural strength, while the equation given by ACI 318  overesti


Background: To identify and address the potential overuse of antibiotics, it is important to ascertain the prescribing practices of physicians. We, therefore, conducted this prescription analysis to document URTI-specific antibiotic prescription frequency in a public primary healthcare setting of Quetta city, Pakistan.Methods: A retrospective record review was conducted of all prescriptions for URTIs in Combined Military Hospital, Quetta from 1 March to 31st May 2021. The Mann-Whitney U and Jonckheere–Terpstra test was used to evaluate the association between the tendencies of a different group of prescribers. p-value of <0.05 was of statistical significance.Results: Over the 3 months, 50,705 prescriptions were screened and analyzed according to the established inclusion and exclusion criteria. A total of 4,126 (8.13%) URTI prescriptions met the inclusion criteria, of which 2,880 (69.80%) prescriptions contained antibiotics. Among all antibiotics, penicillins (Amoxicillin + Clavulanate) were the most prescribed antibiotic, constituting 1,323 (45.9%) of total antibiotics prescribed for all cases, followed by the Macrolide group 527 (18.2%). The Jonckheere–Terpstra test revealed a statistically significant association between the status of the prescriber and the diagnosis (p = 0.002). Furthermore, a moderate positive trend was reported with specialists being more competent in antibiotic prescribing based on their diagnosis, followed by postgraduates and house officers (τ = 0.322).Conclusion: The prescribing patterns for the management of URTIs in the hospital were inconsistent with current guidelines. Strict adherence to guidelines must be ensured and antibiotic prescribing for URTIs should be discouraged. Upper respiratory tract infections (URTIs) are acute infections involving the nose, paranasal sinuses, pharynx, larynx, trachea, and bronchi . Often mThe inappropriate and over-prescribing of antibiotics in ambulatory care is frequently reported in the literature , 14, 15.Quality use of antibiotics is getting worse in the Asian region. Antibiotics consumption between the years 2000–2015 increased from 3.2 to 6.5 billion DDDs (103%) in India, from 2.3 to 4.2 billion DDDs (79%) in China, and 0.8 to 1.3 billion DDDs (65%) in Pakistan . RoutinePakistan despite having an essential drug list is facing issues of lacking standard guidelines for the treatment of infectious diseases . In PakiCorrelating irrational use of antibiotics in URTI, large variations in antibiotics prescribed for URTIs exist that are difficult to explain . Within A retrospective prescription analysis was conducted whereby all prescriptions from 1st March 2021 to 31st May 2021 were screened and retrieved for further investigation. Prescriptions with mentioned diagnosis of “URTI,” “tonsillitis,” “pharyngitis,” “rhinitis,” “common cold,” “sore throat,” “cough,” or “otitis media” were included in the study , Quetta. Combined Military Hospital is a tertiary care teaching hospital situated in Quetta Cantonment and is operated by Pakistan Armed Forces. After British colonization, it was established as British Military Hospital (BMH) in 1854, which was converted to the Indian Army Medical Corps (IAMC) in 1927. After partition in 1947, it was handed over to Pakistan Army and was named CMH. Combined Military Hospital is one of the biggest hospitals of the city and in the access of the public. All departments are well established here with facilities and modern machinery.p-value of < 0.05 was of statistical significance.The data was coded and entered into Statistical Package for the Social Sciences (SPSS), version 21 for further analysis. The Kolmogorov-Smirnov test was used for testing the normality of the sample distribution. Both descriptive and inferential statistics were used for data elaboration. Frequencies and percentages were used to summarize the data. The Mann-Whitney test was used to associate dichotomous variables. The Jonckheere–Terpstra test was used to evaluate the trend of association between the tendencies of a different group of prescribers. Where significant associations were reported, the effect size was calculated by using the Kendall tau correlation coefficient. The ethics committee of the Faculty of Pharmacy & Health Sciences, University of Baluchistan, Quetta approved the study. Permission for data collection was also taken from the Commandant CMH, Quetta. Being a record review, consent for publication was not required.Over the 3 months, 50,705 prescriptions were screened and analyzed according to the established inclusion and exclusion criteria. A total of 4,126 (8.13%) URTI prescriptions met the inclusion criteria, of which 2,880 (69.80%) prescriptions contained antibiotics. Nearly 40% of the prescriptions were diagnosed as non-specific URTI followed by cough  and rhinitis . Thirty percent of prescriptions were from the pediatrics unit and the majority  of the prescription with URTIs were prescribed by postgraduates .Among all URTI cases, Amoxicillin + Clavulanate was the most favored antibiotic in more than 50% of cases, except for sinusitis and nasopharyngitis. Levofloxacin was preferred as the treatment of choice in sinusitis (12.1%) while Cefixime was prescribed for Nasopharyngitis (20%). The antibiotic prescription against specific diagnoses is described in p = 0.002). Furthermore, a moderate positive trend was reported with specialists being more competent in antibiotic prescribing based on their diagnosis, followed by postgraduates and house officers (τ = 0.322). No significant association, however, was reported among other study variables.The Jonckheere–Terpstra test revealed a statistically significant association between the status of the prescriber and the diagnosis  for URTIs from Quetta city, Pakistan, and the published literature provides mixed results in this context. By and large, the prescription rate for URTI in the current study was higher than the rates observed from the Asian region. Antibiotics were prescribed to 51.6% of the patients in Bahrain  and 31.8As documented in the literature and guidelines, only a very limited number of patients with URTIs warrant antibiotic treatment , 44, 45.The trend of association reported specialists being more competent in antibiotic prescribing based on their diagnosis, followed by postgraduates and house officers. From the clinical perspective, the reported trend is comprehensible. As experience increases, healthcare professionals also expand their skills and knowledge while practicing safe patient care. Also, experienced healthcare professionals are often more prepared mentally and are equipped with proficiency in dealing with a medical crisis. In line with what is being discussed, Lewis et al. , in theiThe prescribing patterns for the management of URTIs in the hospital were inconsistent with current guidelines. Quality use of antibiotics can help prevent the emergence of AMR; consequently, a better understanding of appropriate antibiotic prescribing must be fostered among prescribers. Strict adherence to guidelines must be ensured and antibiotic prescribing for URTIs should be discouraged. We also urge the policymakers to introduce antimicrobial stewardship programs and guidelines in healthcare institutes that will help with planning future initiatives among the primary healthcare centers of Pakistan.In a single-centered study, the generalizability of the findings is always an issue. Also, the diagnoses of URTIs were based on the written diagnosis on the prescription and we did not verify the accuracy of the clinical examination and diagnosis with the prescribers due to the reasons described earlier. We, therefore, recommend a comprehensive study involving multiple (public and private) healthcare institutes with a confirmed diagnoses of URTI in consultations with the prescribers.The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.The Ethics Committee of the Faculty of Pharmacy and Health Sciences, University of Baluchistan, Quetta approved the study. Permission for data collection was also taken from the Commandant CMH, Quetta. Written informed consent was not required in this study in accordance with the national legislation and the institutional requirements.HH, NS, AS, and AR conceptualized and designed the study. FB, SR, QI, and SH collected the data while SU, MM, and AT analyzed and interpreted the data. The study was supervised by AK and FS. All authors have met the criteria for authorship and had a role in preparing the manuscript. Also, all authors approved the final manuscript.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.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.


To improve the photocatalytic performance of TiO2, the Nano SiO2-TiO2 (NST) has been developed by coating TiO2 with SiO2 as a support using the sol-gel method. The environmental performance of concrete blocks incorporating NST as an additive was evaluated using both laboratory and full-scale chamber experiments. It was observed from laboratory environment chamber testing that the NO reduction efficiency of concrete blocks with 4% NST ranged from 16.5 to 59.1%, depending on the UV intensity. Results of the full-scale chamber test on NST concrete blocks indicated that the NO and SO2 reduction efficiencies were 22.3% and 14.4% at a 564 W/m2 of solar radiation, respectively. It was found that the increase in UV intensity and solar radiation had a positive effect on decreasing NO and SO2 concentration. In the future, the NST will be applied at in-service photocatalytic block pavements to validate the environmental performance in field conditions. The use of titanium dioxide in concrete block pavements is a promising approach to reduce air pollution in the roadside. When TiO NOx emitted from road mobile sources such as vehicles and stationary sources including industrial factories power generation facilities is a harmful air pollutant; NO emitted from vehicles is especially a serious problem in metropolitan areas   was used as the precursor of TiO2; TEOS   as the precursor of SiO2; nitric acid (HNO3)  as the catalyst; and ethanol (EtOH) and iso-propanol (IPA) as the solvent . The NST was processed as shown in As for starting materials, TTIP [Titanium Isopropoxide; Ti , which had a density of 3.14 g/cmThe fine aggregate used in this study, silica sand , was used instead of general natural fine aggregate, and the physical properties of silica sand were shown in The coarse aggregate used in this study was crushed stone . The grain size of the aggregate was 5 to 8 mm, and the physical properties of the coarse aggregate were shown in 2, the nucleation and filling effects of NST, and the formation of pores smaller than 50 nm within the mortar matrix. Accordingly, 4% was found to be the optimal amount of NST to mix in order to obtain the target strength and flow value without using excessive chemical admixture.As a result of testing the mortar mixed with NST, the flow rate of the mortar decreased, and the strength increased as the NST replacement rate increased. The increase in the strength could be attributed to the pozzolan reaction of SiOx pollutants. The laboratory testing device  with environment chamber was manufactured to evaluate the photocatalytic efficiency of concrete block specimens. The test setup was adapted from ISO 22197-1 (2007): “Test method for air-purification performance of semiconducting photocatalytic materials-Part1: Removal of Nitric Oxide” and UNI 11247: 2010: “Determination of the degradation of nitrogen oxides in the air by inorganic photocatalytic materials: continuous flow test method”. The developed experimental setup consisted of a pollutant source (gas cylinder of NO), zero air source, adjustable valves, humidifier, calibrator, photoreactor, and chemiluminescent NOx analyzer, as shown in A laboratory experiment was conducted to assess the capacity of the concrete block with NST to remove the NOx concentration flowing into the environment chamber, and a pressure gauge and a valve were in place to control NOx inflow. A T-shaped connector before the photoreactor was linked to the NOx analyzer to measure the concentration in the inlet. A gas mixture of NOx and zero air filled the photoreactor at the controlled humidity, flow, and NOx concentration.The calibrator controlled the NOThe chamber’s photoreactor (500 × 500 × 500 mm) was fully sealed to maintain the controlled environment. All tests were performed at a temperature of 25 ± 2 °C and a humidity level of 40 ± 5%. UV light was placed above the photoreactor to simulate for photocatalysis.x was set to be 1.00 ppm by adding a gas mixture of NOx and zero air before the testing. The light source of the UV lamp was irradiated under three conditions of 10, 20, and 30 W/m2 for more than five hours to measure changes in the NOx concentration at one-minute intervals.The concrete block was placed in the center of the photoreactor, and the concentration of NO3. This chamber was fabricated from transparent ETFE (Ethylene Tetrafluoroethylene) film to enable natural sunlight and ambient temperatures to govern the photochemical reactions occurring inside the chamber. The ETFE film was selected as the membrane material for the full-scale chamber structure because of its lightweight, high tensile strength, good durability, and high solar transmittance [The full-scale environment chamber  had been constructed to evaluate the air pollutant reduction technologies on the roadside at the Korea Institute of Civil Engineering and Building Technology (KICT) near Yeoncheon, Korea . The chamittance ,45. A prmittance .The environment chamber was divided into reference and testing chambers. The membrane layer was installed in the middle of chamber for perfectly blocking the transportation of aerosol and gas materials between the two chambers. The test data measured in the reference chamber was used to determine the wall loss rates and leakage rates of gaseous reactants and particles. It was applied to calibrate the measurement data in the testing chamber for the analysis. The temperature and humidity control systems were implemented at each chamber to maintain the designed environment condition. A total of 16 sensors at different heights were installed to monitor the temperature and relative humidity data inside the chamber during the testing.2 reduction efficiency of concrete blocks with TiO2 application using a full-scale environment chamber. The chamber was purged with rural background air prior to the experiment. The diesel and gasoline exhaust gas were generated from a 2010 Hyundai Star Rex  and 2019 Sonata engine , which were run under idling conditions. An air fan was used to uniformly diffuse the exhaust gas inside the chamber within a short period of time.The testing was conducted to determine NO/SO2 of coverage area. The concrete blocks were exposed to natural sunlight for photocatalytic reaction by removing the aluminum cover after ensuring an equilibrium condition. The environment parameters such as temperature, relative humidity, and solar radiation were monitored during the testing at one-minute intervals.A total of 50 concrete blocks were placed at the center of the testing chamber with 4mx concentration during the laboratory environment chamber test for the concrete block sample treated with 4% of NST replacement rate under 30W/m2 of UV intensity. The inlet concentration reached equilibrium at 1 ppm before the light was turned on. After turning on the UV light, a fast drop of NO and NOx concentration in the outlet was exhibited, and the NO2 was produced from the NO oxidation. The light and gas supply were turned off after five hours of testing. For the test condition shown in x reduction was 51.8%.x reduction efficiency. Results presented in x reduction efficiency doubled with an increase of 10 W/m2 in UV intensity. As a result of the experiment, the concrete blocks using NST were capable of reducing the NOx concentration through photocatalysis. This fact proved that NST does not penetrate the cement pores and was evenly dispersed in the surface layer of the concrete blocks, since negative charges were formed due to the Ti-O-Si bond and activated interface.2 material. As shown, the NO concentration rapidly increased in both chambers, by injecting the exhaust gas for roughly 40 min, until NO concentration inside the chamber reached approximately 800 ppb. After stopping the gas injection, it took 20 min to ensure equilibrium conditions inside the chambers. Once the concrete blocks were exposed to natural sunlight in the testing chamber, a fast drop of NO concentration was exhibited due to the photocatalytic reaction of TiO2 material. To determine NO/SO2 reduction efficiency of TiO2 concrete blocks in the environment chamber, two hours of measured data were compared between the reference and testing chambers. The measured data in the reference chamber was used to calculate the absolute reduction of NO/SO2 concentration by considering wall loss and leaking phenomenon. The testing was conducted at different weather conditions and times to investigate the effects of solar radiation on NO/SO2 reduction efficiency.2 of solar radiation was not enough for activating a photocatalytic reaction of concrete blocks with TiO2 application.As shown in 2 concentrations measured in the testing and reference chambers. It was observed from this figure that the SO2 concentration in the testing chamber could be reduced using TiO2 at 358 and 564 W/m2 solar radiation. Similar to the NO measurement results, the SO2 reduction efficiency of concrete blocks with TiO2 applications tended to increase with an increase of solar radiation. It was also found from the test results that the reduction efficiencies of SO2 were slightly lower than those of NO at high solar radiation levels.2 reduction efficiencies for the concrete block that was treated with TiO2. It was found that the use of TiO2 photocatalyst materials had an SO2 reduction of 14.4% at 564 W/m2 of average solar radiation.2 as a support was prepared using the sol-gel method and blended with a conventional concrete binder at 4% of replacement rate for concrete blocks. Prepared concrete block samples were evaluated for the NOx reduction performance using laboratory and full-scale chamber experiments. Based on the results of the experimental programs, the following conclusions may be drawn:This study evaluated the environmental effectiveness of incorporating NST as an additive to concrete blocks. The NST coated with SiOx pollutants in the air stream. The NO reduction efficiency ranged from 16.5 to 59.1%, and the highest NO reduction efficiency was achieved with a UV intensity of 30 W/m2. The increase in UV intensity positively affected the effectiveness of the NOx reduction capacity.(1) Based on the results of the laboratory chamber test, the concrete blocks using NST were effective in reducing NO2 pollutants. The maximum environmental performance was achieved at a 564 W/m2 with NO and SO2 reduction efficiencies of 22.3% and 14.4%, respectively.(2) Results of the full-scale environmental chamber test showed that the concrete blocks with NST was effective in reducing NO and SOx and SO2 reduction efficiencies by considering various influencing parameters. In order to improve the photocatalysis efficiency of TiO2, the TiO2 material has been developed as an anatase crystal phase with larger specific surface area and excellent photodissociation. Various attempts have been made, including sputtering, a process in which TiO2 is directly and physically coated on a proper and solid support.(3) In the future, the field application of NST as a road material is required to validate the NO


A total of 5 steel and 21 rectangular composite concrete-filled steel tube (CFST) columns of moderate slenderness were tested to investigate their ductility under axial compression. The importance of the vertical ductility of columns was discussed, and a novel ductility measure was proposed and utilized to examine the ductility of tested specimens. The analyses showed that the ductility of axially compressed CFST columns highly depends on their failure mode. The key feature influencing the ductility is their ability to dissipate the energy of imposed loads. The larger the volume of a material that may permanently deform and consequently dissipate the energy, the greater this ability. In consequence, the ductility of specimens exhibiting local failure mode was higher in comparison to the columns that underwent global or mixed global—local failure. It was found that both steel and composite columns were able to carry axial loads in the post-critical state; but due to the limitations of local buckling of the steel cross-section in the concrete core and concrete confinement, all tested composite columns showed greater ductility than their steel counterparts. The vertical ductility of columns is an essential parameter when considering the responses of structures subjected to accidental events, such as fires, impacts, strong earthquakes, and explosions a–c. SuchStructural design analysis;Comparison of the ductility of structural elements.In the literature, the word ductility is often used to describe the deformability of tested specimens and to categorize them in terms of their ductility without using any direct measure ,6,7,8,9.In the first case, the ductility of the structure is calculated in order to check its stability in an accidental event. The calculations check whether the ductility demand for a given excitation is lower than the available ductility of a structure. In the latter, the ductility is calculated as one of many parameters in addition to strength, stiffness, durability, etc., which characterize the elements tested and enable a comparative analysis of a given design solution in relation to other types of structures. Depending on the measure of ductility adopted for calculations, the ductility of elements may differ .yx, mx, and x0,85, which denote yield displacement, the displacement at the ultimate strength, and the post-peak displacement when the load carrying capacity has undergone a 15% reduction in load, respectively. The available ductility of a column is in fact the post peak displacement for a given reduction in load, and yx or mx are used mainly for normalization purposes.Several definitions of vertical ductility measures of columns have been used in the literature see . All of The ductility measures defined in L/D = 15, where for circular cross-section D is its diameter and for rectangular one D is a length of its shorter side, L—column length) and moderately slender (L/D = 9.4) steel and composite columns. In total, 21 composite and 5 steel elements were tested. A comparative analysis of the vertical ductility of the tested specimens was conducted. The variable parameters were structural solution—steel or composite concrete-filled steel tubes (CFST)—column slenderness, wall thickness, concrete strength, and grade of structural steel. The experimentally obtained equilibrium paths and failure modes were analyzed for comparative purposes.In this paper, the importance of the vertical ductility of columns is discussed in the context of their stability under accidental loads. Based on the concept of the ultimate bearing capacity of columns for extreme situations, a novel vertical ductility measure of axially compressed columns is proposed. A series of experiments was carried out on axially compressed slender , whereas columns with rectangular cross-sections showed the same behavior only with thick steel walls (D/t < 20). In [ξ = afyA/cfcA, where sA and cA are the areas of the steel and concrete cross-sections, respectively, and yf and cf are the yield strength of the steel and concrete, respectively. The use of a thicker steel casing caused greater confinement of the concrete, which resulted in crushing of the concrete over a greater length of the stub column, which increased its ductility.In , test repe 3. In , the verm/xy see , is grea 20). In , it was  20). In  the behacf = 173 ÷ 184 MPa) in circular CFST columns resulted in a significant decrease in the vertical ductility of the tested elements. This phenomenon was attributed to the inadequate ability of steel casing (yf = 420 MPa) to confine high strength concrete. It was stated that in order to increase the efficiency of confinement, thicker steel walls should be used and the steel contribution ratio in the cross-section should be at least 30%. Similar conclusions were drawn from the analyses carried out in [D/t = 30.The use of a higher class of concrete increases the load capacities of CFST stub columns but decreases their ductility. In , it was d out in , where iβ = h/b. Ductility index was defined based on strains DI = ε85%/uε, where uε is the strain at the ultimate load, and ε85% is the strain when the load falls to 85% of the ultimate load. The increase in the steel contribution ratio had a positive effect on the ductility of rectangular CFST stub columns. The inverse relationship can be noticed when analyzing the influence of the cross-sectional shape factor β. Columns with square cross-sections exhibited the greatest ductility, and the elongation of one of the cross-section sided has a negative effect on its ductility. Similar observations were presented in [In  the ductented in .The influence of the aspect ratio of the cross-section on the ductility of a CFST stub column was also noticed in , where eThe above considerations concern mainly the CFST stub columns—eliminating slenderness from the analysis is helpful to identify the behavior of steel and concrete and the mutual interaction between the two materials at the cross-sectional level. In  it was fB/t and B/D, where B and D are the larger and smaller cross-section dimensions, respectively, the ductility of the elements decreased. The decrease in ductility also occurred with an increase in the class of concrete used.In  the behaIn the literature, there is lack of investigations considering the ductility of rectangular CFST columns with moderate slenderness that are most used in practice. Either stub or very slender CFST columns were tested, and their behavior is described in the literature. Therefore, it was necessary to carry out the investigation on the vertical ductility of axially compressed, moderately slender, rectangular CFST columns.RN, whereas N0 = RωN is an equivalent axial force in the column prior to the extreme event. A reduction parameter ω is used to account for the influences of various combinations of actions’ coefficients and material safety factors in the permanent and accidental design situation, the reserve factor, and the strain rate behavior of the steel and concrete. Assuming that the utilization of the element in the permanent design situation is equal to 100% and that the typical safety factors for concrete and steel are equal to 1.4 and 1.0, respectively, an upper limit of this coefficient for composite steel-concrete columns is equal to approximately 0.8. Increasing the column’s reserve factor in permanent design situation results in a decrease in the ω coefficient.In ωμ of axially compressed columns based on the displacements of the column top in the pre- and post-peak periods, x0 and ωx, respectively, is proposed  accumulated in the column at N0 load, and ωE is the energy in the column (accumulated and dissipated) when the force drops to N0 in the post-peak part of the equilibrium path. In fact, the energy ωE is the physical measure of the vertical ductility of a given column, and the energy E0 is introduced for normalization purposes. The advantage of the proposed measure of ductility is also the fact that for a given equilibrium path, E0 and ωE can be easily determined, since both x0 and ωx are explicitly defined as points of intersection of the equilibrium path with the ordinate N0. This avoids imprecise definition of the yield and failure points used in the conventional vertical ductility measures adopted from horizontal ductility factors widely used in seismic analysis [N0, failure of the column will occur.An energetic measure of the ductility osed see . The valanalysis . Those hThe number of publications on modelling of the behavior of composite CFST columns continues to rapidly rise. Fiber element models ,46 and FD/t and L/D, where D—height of the steel profile, t—wall thickness, L—total length of the column; ξ—steel contribution ratio; the number of elements tested in each series. The columns from series D were of moderate slenderness, and elements from series A and B were considered slender in relation to columns from series D.The experimental research was conducted on 26 cold-formed steel rectangular hollow section columns made of S235JR and S355JR-grade steel. The length of each element was 750 mm. The analysis included 3 types of composite steel–concrete column. For comparative studies, steel columns that had not been filled with concrete were also tested. A, B, and D describe columns made of RHS100 × 50 × 5, RHS100 × 50 × 3, and RHS120 × 80 × 3 profiles, respectively. S1 and S2 indicate the steel grades S235 and S355, respectively, and C1 and C2 indicate the concrete classes C20/25 and C50/60, respectively. In the experimental analysis, the variable parameters were the type of column , slenderness, wall thickness, concrete strength, and steel grade. Standardized steel and concrete samples were tested to obtain the material properties. A detailed description of the material and geometrical properties is provided in The columns were compressed in a hydraulic press. The applied force vs. column shortening was measured, along with the vertical strains of the steel profiles using strain gauges placed mid-length. In addition, the digital image correlation method (DIC)  was usedIn order to obtain equilibrium paths in the post-peak parts of the equilibrium paths of columns, a displacement control method was used in the analysis. For technical reasons, due to expected exceptionally large deformations of investigated elements and therefore a possibility of uncontrolled ejection of columns from the hydraulic press after buckling, the knife edged boundary conditions simulating pinned-pinned support boundary conditions were not used. The test elements were each placed on a rigid, non-deformable steel plate and compressed by a spherical traverse, embedded in a spherical seat; hence, columns’ ends were partially fixed due to friction. The experimental setup was as shown in The typical failure modes of the analyzed columns are shown in t = 3 mm), the failure mode of most test elements is local. Only in one specimen BS1C2_1 is the failure mode global.In moderately slender columns from series D, all failure modes were of the local type, and in slender columns with 5 mm wall thickness (series A), global type. This was due to the relative slenderness of the tested elements, which in the case of columns from series D was on average ξ is used in the literature to estimate the effectiveness of concrete confinement by the steel jacket in a composite column [ξ ≤ 1.51, (see ξ = 1.51). This suggests the influence of concrete confinement on the types of local failure modes of moderately slender composite columns. The greater this phenomenon, the greater the probability of a symmetrical failure mode such as “elephant’s foot.” On the other hand, in another column of this series, DS2C1_2, the “elephant’s foot” failure did not occur, which suggests the high complexity of phenomena occurring in rectangular CFST columns and their random nature.The steel contribution ratio e column ,49. The .51, see . The symt = 5 mm) in which the steel contribution ratio had of the highest values, 3.18 ≤ ξ ≤ 4.30, only global buckling was observed. As a result of significant confinement of concrete by the steel jacket, the concrete core was neither crushed (“elephant foot” failure) nor sheared (“shear and slip” failure). In these elements, the local load-bearing capacity and ductility of concrete increased by its confinement are high enough that they do not determine the load-bearing capacity of the entire element. Therefore, global sway buckling occurs, and in the middle of the column a plastic hinge is formed. Only after the buckling of the entire element, in the compression zone of the middle section, does the concrete undergo one-sided crushing, and the compressed part of the steel jacket is subject to local buckling (see In slender elements from series A (ling see a.t = 3 mm), the confinement of concrete (1.52 ≤ ξ ≤ 1.97) was not high enough to trigger the global buckling failure mode before the local shear of concrete. This was the case only in one specimen marked BS1C2_1 .A different conclusion can be drawn when analyzing the data presented in ξ in the DS2C1 and DS1C1 columns were equal to . In slender columns from series A and B that exhibited a global failure mode, the higher strength concrete filling had no significant influence on the ductility of the elements. However, in moderately slender columns from series D that exhibited local failure modes, the ductility of specimens filled with C1 was 22% higher in relation to those filled with C2. Similarly, it can be observed that the ductility of moderately slender columns from series D made of stronger steel S2 exhibited a 33% increase in ductility in relation to columns made of weaker steel S1. The wall thickness had a significant influence on the ductility of slender CFST columns—the ductility of elements from series AS1C1 with xxε, transverse yyε, and shear xyε strains of selected CFST specimens are presented in Contour plots of longitudinal On analyzing Significantly different strain localization patterns can be observed in A combination of the two previously described behaviors can be observed in It was previously observed that the ductility of moderately slender columns from series DS2C1 made of stronger steel S2 exhibited a 33% increase in ductility in relation to columns DS1C1 made of weaker steel S1. This was due to the greater concrete confinement in such elements. This may indicate that there is a correlation between the intensity of the occurrence of diagonal yield zones and the level of concrete confinement in elements that exhibit local shear and sliding or elephant foot-type failure. In CFST columns, concrete confinement is always accompanied by transverse tensile strains of the steel jacket. This can be observed in ξ = 4.12) and BS1C2_1 (ξ = 1.52), respectively. BS1C2_1 was the only specimen from series B that exhibited global buckling failure mode. The top and bottom strain contour plots were captured close to the ultimate force and in the post peak part of the equilibrium paths, respectively. In both specimens, a combination of global and local outward buckling occurred. In the middle of both columns, plastic hinges denoted by elliptical shapes representing the bulged steel jacket (showed in the lower contour plots) were formed. It seems interesting that similarly to series D columns, which all exhibited local failure modes, in the BS1C2_1 element, after reaching the ultimate force, the diagonal yield pattern also appeared, but was located below the plastic hinge that formed in the middle. The reason for this may be larger imperfections in this specimen that caused the global buckling to occur before the local concrete shear could have been fully developed. An outline of similar diagonal yield patterns was also observed in other specimens from series B, but not in any of the specimens from series A. This may indicate that the geometric and material properties of elements from series BS1C2 delimit the global and local failure modes of axially compressed CFST columns.In this study, a total of 21 composite CFST and 5 steel rectangular columns of moderate slenderness were tested to investigate their ductility under axial compression. The importance of the vertical ductility of columns was discussed, and a new ductility measure considering the equivalent preloading prior to the extreme event was proposed and utilized to examine the ductility of tested specimens. The test results were presented and analyzed in detail to provide information about the factors influencing the ductility of axially compressed CFST columns.The conducted analyses showed that the key feature influencing the ductility of axially compressed columns is their ability to dissipate the energy of imposed loads. The larger the volume of a material in the element that may permanently deform (in the case of steel) or crush (in the case of concrete) and consequently dissipate the energy, the greater this ability. Due to the confinement of a concrete core by a steel jacket, and most importantly, the limitation to local buckling of the steel cross-section by the concrete core, all tested composite columns showed greater ductility than their steel counterparts.The analysis concluded that the vertical ductility levels of axially compressed CFST columns with rectangular cross-sections highly depend on their failure modes. Therefore, the detailed conclusions were divided into two categories, taking into account the failure modes of the analyzed columns. In general, the ductility of specimens with local failure modes was higher in comparison to columns that exhibited global buckling failure.D/t ratios, the additional formation of diagonal yield zones in the other cross-sections of the columns occurred.The concrete core failure consisted of crushing the concrete in the plastic hinge on the side of the cross-section with high compressive stresses. In elements with large The higher strength concrete filling had no significant influence on the ductility of slender test elements.The increase in the wall thickness had a positive effect on the ductility of slender specimens.For elements that underwent the local failure mode:In shear and sliding failure mode, the concrete core failure consists of the formation of diagonal or horizontal yield zones along the height of the column, causing stress concentrations in the steel jacket, and in the weakest yield zone, shear solid wedge movements along a shear frictional surface develop. In elephant foot failure mode, the concrete core failure consists of crushing the concrete in the weakest cross-section of the column.Symmetrical elephant foot failure mode yielded higher vertical ductility in comparison to shear and sliding failure modes.The use of higher-grade steel increased the vertical ductility of the tested columns.The use of stronger concrete caused a decrease in the ductility of the test specimens.The conclusions for elements that underwent global buckling:


In order to study the mechanism of strength improvement of RAC, this paper takes NS and polyvinyl alcohol (PVA) fiber as variable parameters; uniaxial and triaxial compression tests were carried out on RAC with PVA fiber and NS, and the mechanical properties of RAC were investigated The result shows that within the range of 3% NS content, an increase in the NS substitution rate causes the mechanical properties of RAC to improve significantly. The compressive strength of RAC increases again after adding PVA fiber; through a SEM (scanning electron microscopy) analysis of the specimen, it was found that the NS filled the micro-pores and micro-cracks in the RAC, and the PVA fiber changed the contact range between recycled aggregate and mortar, so the microstructure of the material was more compact. The mechanism of RAC strength improvement is explained in the microcosmic view.In recent years, recycled aggregate concrete (RAC) has become a research hotspot in the field of urban construction because of its resource utilization of construction waste. However, compared with original concrete, its strength is still low, which requires additional nano-SiO As urbanization gains increasing momentum, many buildings are demolished, resulting in substantial construction waste . MeanwhiHowever, compared with natural concrete, recycled concrete has a much more complex structure. As recycled coarse aggregate boasts lots of micro-cracks, with the pressure of rolling, the old cement mortar and the aggregate will give rise to cracks. Influenced by the minor cracks in recycled aggregate, the interface transition coefficient of natural concrete is greater than recycled concrete . In addiIn recent years, surveys on recycled concrete mixing with PVA fiber have revealed that concrete with PVA fiber exhibits good ductility , inhibit2 (NS) in enhancing the mechanical properties and durability of concrete. The addition of NS into the concrete accelerates the hydration of cement, which reduces the consumption of cement, and improves the concrete strength from the micro perspective [Additionally, abundant studies have shown the capacity of nano-SiOspective . Generalspective . Gonzalez observed that with a mixture of 2% NS, the compressive strength of the cement mortar and the bending stiffness were improved by 50% and 16%, respectively . GesogluBased on previous studies on recycled concrete, PVA fiber concrete and NS concrete, this paper makes the uniaxial and triaxial compression tests on NS recycled aggregate concrete with and without PVA fiber and studies its impact on the work performance, mechanical strength and ultimate stress of the concrete from a macro perspective. Utilizing scanning electron microscopy (SEM), we discuss the influence of PVA fiber and nano NS on the microstructure of recycled aggregate concrete, which shows that the microstructure performance is in good agreement with the macroscopic mechanical properties. This paper also illustrates how NS fills the micro-pores and micro-cracks of the recycled aggregate, and how PVA fiber improves the contact surface of the new and old mortar. To sum up, the collaboration of PVA fiber and NS enhances the strength of recycled concrete, providing an efficient and effective purpose for its application. 2/g and a pH within 5 to 7. The sample fibers used in our work are PVA fibers , and 3.The introduction has described the current research towards PVA fiber concrete and summarized that PVA fiber enhances concrete strength ,9, as shThe design of concrete mix ratio is shown in With the completion of curing, all samples went through uniaxial compression and traditional triaxial compression tests. After casting formation, the test piece was put into a standard curing room ((20 ± 2) °C, (95 ± 3)% RH) for 3 days, and then the mold was removed. As the test block without mold continued to stay in the standard curing room for a certain period of time, the test samples were examined on the DYS-2500 high temperature and pressure rock triaxial testing machine , with 3 samples subjected to 3 values of confining pressures . Finally, the average of the test results was regarded as the final value. The loading path involves 2 stages: First, the confining pressure continued to increase at a speed of 0.25 MPa/s until the target confining pressure was reached; Second, under a constant confining pressure, the displacement rate was controlled at 0.06 mm/s.By comparing the failure modes of NS-recycled aggregate concrete with PVA fibers and the concrete without PVA fibers under the confining pressure, we found that the failure mode of the sample was related to the content of NS, the value of the confining pressure and whether it contained PVA fiber. Among them, the sample exhibited vertical splitting failure under uniaxial compression and oblique shear failure under triaxial compression. As there was no confining pressure in the lateral direction, the concrete was under uniaxial compression. With the content of NS within 3%, an increased content of NS gradually increased the elastic limit value of the recycled concrete and damaged the aggregate concrete. Furthermore, the addition of PVA fiber further improved the elastic limit value of the recycled concrete. As the load exceeded the elastic limit value, vertical cracks appeared in the middle of the test piece and extended to both ends and, at the same time, new small transverse cracks were generated. Compared with NS-recycled aggregate, the one mixed with PVA fiber produced fewer small cracks, and when the load reached the maximum, the bearing capacity of the sample lasted longer, but all the final samples showed split failure.In triaxial compression, as the sample withstood the confining pressure from the lateral restraint, the interior structure could endure greater pressure. In contrast with uniaxial compression, the sample showed larger and more cracks. With the increase of the NS, the sample exhibited large cracks, but the width of the small cracks decreased. In the face of the corresponding confining pressure and NS replacement ratio, the PVA fiber could shoulder the load with concrete as the PVA fibers were arbitrarily allocated in the sample to construct a web system. Compared with the NS-recycled aggregate concrete, the concrete blended with PVA fiber showed higher durability and more compact cracks. Observation of the failure surface revealed that when the confining pressure value was 5 MPa, the interface between the recycled coarse aggregate and the cement paste was mainly sheared, but the coarse aggregate was hardly sheared. As the confining pressure value rose to 10 MPa, the recycled aggregate and the cement collision between the recycled aggregates were sheared and destroyed.In conclusion, the failure mode of the specimen changes significantly with the increase of the confining pressure value. When the confining pressure value is 0, it is mainly the splitting failure of the interface between the coarse aggregate and cementitious body; with the increase of the confining pressure value, the vertical cracks gradually change into oblique cracks, and when the confining pressure value reaches 10 MPa, shear failure appears on the recycled aggregate. Compared with the failure mode of RAC without PVA, the aggregate at the failure surface of RAC with PVA is almost sheared into powder; at the failure surface of RAC with low nano silica content, the cement mortar wrapped with coarse aggregate is crushed into fine powder, and a small amount of coarse aggregate is sheared off.The compressive strength of the NS-recycled aggregate concrete with and without PVA fibers was compared, and the results are shown in When the content of NS is 3%, a 7.6% increase of the compressive strength is registered by the NS-recycled aggregate concrete containing PVA fibers. It shows that the addition of PVA fibers enhances the compressive strength of NS-recycled aggregate concrete. When the NS content remains low, PVA fibers exert minor impacts on the NS-recycled aggregate concrete. Meanwhile, with the rise of NS content, the compressive strength of NS-recycled aggregate concrete blended with PVA fiber is gradually improved, and NS is easily dispersed in the course of mixing the concrete. Thus, NS is prone to penetrating the interface of recycled aggregate, with the effective release of NS.(1) As the confining pressure exists, the stress-strain curve turns to develop smoothly without an obvious peak, which shows that the deformation of the sample and the micro-cracks in the section under the confining pressure can be virtually restrained. As the confining pressure rises from 0 MPa to 10 MPa, the ultimate strain range of the sample will be regulated. After the ultimate stress interval, the stress-strain curve presents plastic features; however, as the applied load surpasses the appropriate axial stress and reaches the utmost strength of the concrete, the sample is instantly squashed. In other words, the stress-strain curve drops abruptly.(2) With the confining pressure unchanged and the increase of the NS replacement ratio, the main compressive stress of the sample increases, along with a corresponding decrease in the axial strain. All in all, the curves of different NS replacement ratios show the same trend. When the NS replacement ratio remains constant, the rise of confining pressure leads to an increase in the main compressive stress and the axial strain. In contrast with the NS recycled aggregate concrete blended without PVA fiber, the concrete without fibers has a larger main compressive stress but a smaller axial strain. Owing to the confining pressure, the sample shows stronger plastic capacity and lasts longer in the triaxial test before it fails.Comparing the peak stress of NS-recycled aggregate concrete with and without PVA fiber, it is found that under the same loading conditions, the strength of the former is higher than the latter, which is attributed to the addition of PVA fibers. As micro-cracks are generated in the aggregate while crushing, the strength of the aggregate is reduced, but the PVA fibers restrain the development of internal cracks and weaken the impact of micro-cracks in the aggregate.By changing the replacement ratio of mixed NS  macroscopically, we compared the NS recycled aggregate concrete with PVA fibers and the one without in terms of mechanical properties, the failure process, deformation and other characteristics; meanwhile, the microstructure changes were analyzed by the SEM technique microscopically. In this way, we reached the following conclusions:(1) The addition of NS within a certain range greatly improves the mechanical properties of the concrete. However, as the NS content exceeds a threshold, the performance of concrete no longer improves for the dispersion of nanoparticles.(2) The synergistic effect of PVA fibers and NS improves the recycled aggregate concrete, which enhances the adhesive strength between new and old mortar, as well as aggregate in recycled concrete. Thus, the recycled concrete containing PVA fibers and NS shows higher compressive strength than that mixed with NS alone.(3) When the NS content is 3.0%, the compressive strength of concrete without and with PVA fiber reaches 43.2 MPa and 47.6 MPa, respectively. The addition of PVA fibers improves the compressive strength of recycled aggregate concrete containing different contents of NS. As the NS replacement ratio remains constant and the confining pressure rises, NS-recycled aggregate concrete with and without PVA fibers will show a larger principal compressive stress but their axial strain is smaller. Comparison of uniaxial compression test and triaxial compression test, the triaxial compression test shows that NS-recycled aggre-gate concrete with PVA fiber improves its containing elastic characteristic and the specimen will take longer to fail.(4) As the replacement ratio of NS remains constant and confining pressure increases, the peak stress of the concrete in the RCN group and the RCN-P group shows a linear increase. Under the condition of NS substitution, with rate substitution and confining pressure unchanged, the peak stress of the NS recycled aggregate concrete with PVA fibers is 1.21–1.40 times that of the concrete without PVA fibers.