Modification and validation of piezoelectric ring actuator technique to monitor setting and hardening of cement-based materials

A period of cement hydration is one of critical in the life span of concrete structures. One of the reasons of collapse of concrete structural elements during and after construction is the error in determining the concrete characteristics at early age. Recently, non-destructive test emerged as a popular way to evaluate the properties of cement-based materials. This test offers continuous measurements of concrete properties as well as ability to monitor any changes in the current state of structural materials. In the existing research, some of these methods fail to capture well properties of the materials in the plastics stage. A new piezoelectric pulse testing device (Piezoelectric Ring Actuators Technique), (P-RAT ) was initially developed at the University of Sherbrook as a non-destructive test (NDT ) for soil. This technique is considered a completely new, versatile, advanced and accurate. The development of the new technique (P-RAT ) was done on two main bases: the first was the development of piezoelectric ring actuators set-up and the second is the development of the interpretation method. The setup is composed of two main units; emitter and receiver, and is capable of measuring shear and compression wave velocities in specimens. With this technique, many problems of pulse tests, which make interpretation of results difficult and ambiguous, were solved in soil. The P-RAT overcomes wave reflections at boundaries (end-caps and sides), sample disturbance, weak shear coupling between soil and device (interaction) as well as the fixation problems, low resonant frequency and limited input voltage of the existing device. The previous method is exploited forward to measure the hydration properties of cement-based material. To apply this test method, it is necessary to determine how the evolution of shear wave velocity can be related and sensitive to the hydration of cement-based materials. Validation of the P-RAT with four conventional test setups that can be used to monitor early setting and hydration of cement-based materials is carried out. These tests include penetration resistance to monitor initial and final setting respectively, calorimetric to monitor heat of hydration, electrical conductivity to monitor change in continuity of the pore structure and compressive strength at 24 hours. The phase one of this investigation included trial tests to investigate the possibility of employing the original setup used for soil (P-RAT ) to determine setting and hardening properties of cement-based material. Based on the results of the preliminary test, two modifications were conducted to the previous test device to fit with cement based material and to obtain adequate resonant frequency for cement-based materials. These modifications are the design of the container and changing the dimensions of the rings. The resultant version of P-RAT after the modification was referred to be as P-RAT2 . Calibration of the P-RAT2 with water specimen was undertaken using the compression wave velocity and resulted in 99.33% accuracy. One paste mixture was tested three times to determine the experimental error of the P-RAT2 . The repeatability carried out on the P-ART2 proved the ability of this setup to capture accurate results of the shear wave velocity. This relative error is limited to 9 %. A number of series of validation was performed on cement paste and mortar mixtures proportioned with various water cement ratios (w/cm ) as well as chemical admixtures. The w/cm ratio ranged between (0.35 and 0.50). The investigated chemical admixtures comprise of high-range water-reducing agent, viscosity-modifying agent, set-accelerating agent, and set-retarding agent. The presented validations examine the ability of a P-RAT2 to monitor the hydration of the cement-based materials. The hydration is characterized by setting time, heat of hydration, electrical conductivity, and compressive strength at 24 hours. The results obtained using the P-RAT2 was correlated to those obtained using the conventional tests and strength measurement. The results enable to validate the ability of P-RAT2 to accurately detect variations in the hydration of cement-based materials. In addition, the initial and final time of setting can be determined from the derivation of velocity vs. time curve. The results show that conductivity, resistivity, has a bilinear relationship to shear wave velocity. The compressive strength at 24 hours was correlated to both the shear wave velocity and shear modulus obtained using the P-RAT2 . Furthermore, analytical model was derived to estimate the w/cm in mortar mixture by measuring the shear wave velocity (V[subscript s] ) and the corresponding time (t )||Résumé : La période d'hydratation du ciment est l'une des périodes clé du cycle de vie des structures en béton. L'une des raisons de l'effondrement d'éléments structuraux en béton pendant et après la construction peut être attribuée à une détermination des caractéristiques au jeune âge erronée. Depuis quelques années, l’auscultation des structures est devenue une méthode très populaire pour évaluer les propriétés des matériaux cimentaires. Cette méthode permet d'obtenir les propriétés du béton en continue et possibilité un suivi de changements dans I'état des matériaux structuraux. Dans I'état actuel de la recherche dans ce domaine, certaines méthodes ne sont pas adéquates pour bien mesurer les propriétés des matériaux à I'état plastique. Un nouvel appareil d'essai à impulsions piezoélectriques (Piezoelectric Ring Actuators technique), (P-RAT) a initialement été développé à l’Université de Sherbrooke comme technique d'auscultation des sols. Cette technique est considérée complètement nouvelle, polyvalente, évoluée et précise. Le développement de cette nouvelle technique (P-RAT) a été effectué en deux volets : la première sole est le développement du dispositif de vérin de commande annulaire piezoélectrique et le deuxième est le développement d'une méthode d'interprétation. Le dispositif d'essai est composé de deux unités principales, un émetteur et un récepteur. Et permet de mesurer la vitesse de propagation des ondes de cisaillement et de compression. Grâce à cette technique, plusieurs des problèmes associés aux dispositifs d'essais par impulsion des ondes, qui rendent les résultats ambigus et difficiles à interpréter, ont été résolu pour les sols. Le dispositif P-RAT surmonte les problèmes de réflexion des ondes aux limites (embouts et côtés), la perturbation de l’échantillon, le couplage de cisaillement faible entre le sol et l'appareil (interaction) ainsi que les problèmes de fixation, la faible résonnance des fréquences et le voltage d'entrée limité du dispositif. La méthode décrite a été utilisée pour mesurer les propriétés d'hydratation des matériaux cimentaires. Pour pouvoir appliquer cette méthode, il faut déterminer comment l’évolution de la propagation des ondes de cisaillement peut être reliée à l'hydratation des matériaux cimentaires et être sensible à ces dernières. La validation de la méthode P-RAT est réalisée, à l'aide de quatre configurations conventionnelles que l’on peut utiliser pour faire le suivi de la prise et de l'hydratation des matériaux cimentaires. Ces essais consistent à la résistance à la pénétration afin de pouvoir déterminer la prise initiale et finale, la calorimétrie pour suivre l’evolution de la chaleur d'hydratation, la conductivité électrique pour effectuer le suivi de la structure des pores et la résistance à la compression à 24 heures. La phase 1 de l'étude comprend des essais pour évaluer la possibilité d'utiliser la configuration originale utilisée pour les sols (P-RAT) pour déterminer les propriétés de prise et de durcissement des matériaux cimentaires. Selon les résultats des essais préliminaires, deux modifications ont été effectuées à l'appareil original pour permettre son utilisation avec des matériaux cimentaires et pour obtenir une fréquence de résonnance raisonnable sur les matériaux cimentaires. Les modifications effectuées sont la conception du contenant et un changement de la dimension des anneaux. La version modifiée du P-RAT est designée P-RAT2. La calibration du P-RAT2 à l'aide d'échantillon liquide sous propagation d'ondes de compression a été menée, avec des résultats d'une précision de 99,33 %. Un mélange a été testé trois fois pour déterminer l'erreur expérimentale du P-RAT2. La répétitivité des essais sur le PART2 a démontré la capacité de cet appareil à produire des résultats de cisaillement de propagation des ondes de cisaillement très précis. L'erreur relative se limite à 9 %. Une série d'essais de validation a été menée sur des mélanges de pâte de ciment et de mortier de rapport eau/ciment variés (e/c) ainsi qu'avec des adjuvants. Le rapport e/c variait entre 0,35 et 0,50. Les adjuvants utilisés étaient des supers plastiflants (réducteur d'eau), des agents de viscosité, des agents accélérateurs de prise et des agents retardateurs de prise. Les validations présentées ont pour but de valider la capacité du P-RAT2 à suivre l'hydratation des matériaux cimentaires. L'hydratation est caractérisée par le temps de prise, la chaleur d'hydratation, la conductivité électrique et la résistance à la compression à 24 heures. Les résultats obtenus à l'aide du P-RAT2 ont été comparés à ceux obtenus à l'aide d'essais de mesure des caractéristiques physiques et de résistance traditionnels. Ces résultats permettent de valider la capacité du P-RAT2 à détecter avec précision les variations dans l'hydratation des matériaux cimentaires. De plus, le dispositif P-RAT2 peut avoir une correction avec mesure obteniez avec les appareils traditionnels. II est aussi possible de déterminer le temps de prise initial et final à l'aide d'une courbe de propagation vs le temps. Les résultats montrent que la conductivité et la résistivité ont une relation bilinéaire à la propagation des ondes de cisaillement. La résistance à la compression à 24 heures a été comparee à la fois à la propagation des ondes de cisaillement et au module de cisaillement obtenus avec le P-RAT2. De plus, un modèle analytique a été établi pour estimer le rapport e/c dans le mélange de mortier en mesurant la propagation des ondes de cisaillement (V) correspondant au temps (t)

Myeloid ABCG1 Deficiency Enhances Apoptosis and Initiates Efferocytosis in Bronchoalveolar Lavage Cells of Murine Multi-Walled Carbon Nanotube-Induced Granuloma Model

The use of carbon nanotubes has increased in the past few decades. Carbon nanotubes are implicated in the pathogenesis of pulmonary sarcoidosis, a chronic granulomatous inflammatory condition. We developed a murine model of chronic granulomatous inflammation using multiwall carbon nanotubes (MWCNT) to investigate mechanisms of granuloma formation. Using this model, we demonstrated that myeloid deficiency of ATP-binding cassette (ABC) cholesterol transporter (ABCG1) promotes granuloma formation and fibrosis with MWCNT instillation; however, the mechanism remains unclear. Our previous studies showed that MWCNT induced apoptosis in bronchoalveolar lavage (BAL) cells of wild-type (C57BL/6) mice. Given that continual apoptosis causes persistent severe lung inflammation, we hypothesized that ABCG1 deficiency would increase MWCNT-induced apoptosis thereby promoting granulomatous inflammation and fibrosis. To test our hypothesis, we utilized myeloid-specific ABCG1 knockout (ABCG1 KO) mice. Our results demonstrate that MWCNT instillation enhances pulmonary fibrosis in ABCG1 KO mice compared to wild-type controls. Enhanced fibrosis is indicated by increased trichrome staining and transforming growth factor-beta (TGF-β) expression in lungs, together with an increased expression of TGF-β related signaling molecules, interleukin-13 (IL-13) and Smad-3. MWCNT induced more apoptosis in BAL cells of ABCG1 KO mice. Initiation of apoptosis is most likely mediated by the extrinsic pathway since caspase 8 activity and Fas expression are significantly higher in MWCNT instilled ABCG1 KO mice compared to the wild type. In addition, TUNEL staining shows that ABCG1 KO mice instilled with MWCNT have a higher percentage of TUNEL positive BAL cells and more efferocytosis than the WT control. Furthermore, BAL cells of ABCG1 KO mice instilled with MWCNT exhibit an increase in efferocytosis markers, milk fat globule-EGF factor 8 (MFG-E8) and integrin β3. Therefore, our observations suggest that ABCG1 deficiency promotes pulmonary fibrosis by MWCNT, and this effect may be due to an increase in apoptosis and efferocytosis in BAL cells

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study

Summary Background Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated with mortality. Methods We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis, exomphalos, anorectal malformation, and Hirschsprung’s disease. Recruitment was of consecutive patients for a minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause, in-hospital mortality for all conditions combined and each condition individually, stratified by country income status. We did a complete case analysis. Findings We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal malformation, and 517 with Hirschsprung’s disease) from 264 hospitals (89 in high-income countries, 166 in middleincome countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male. Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3). Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups). Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in lowincome countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries; p≤0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88–4·11], p<0·0001; middle-income vs high-income countries, 2·11 [1·59–2·79], p<0·0001), sepsis at presentation (1·20 [1·04–1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention (ASA 4–5 vs ASA 1–2, 1·82 [1·40–2·35], p<0·0001; ASA 3 vs ASA 1–2, 1·58, [1·30–1·92], p<0·0001]), surgical safety checklist not used (1·39 [1·02–1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed (ventilation 1·96, [1·41–2·71], p=0·0001; parenteral nutrition 1·35, [1·05–1·74], p=0·018). Administration of parenteral nutrition (0·61, [0·47–0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65 [0·50–0·86], p=0·0024) or percutaneous central line (0·69 [0·48–1·00], p=0·049) were associated with lower mortality. Interpretation Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between lowincome, middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger than 5 years by 2030

Modification and validation of piezoelectric ring actuator technique to monitor setting and hardening of cement-based materials

A period of cement hydration is one of critical in the life span of concrete structures. One of the reasons of collapse of concrete structural elements during and after construction is the error in determining the concrete characteristics at early age. Recently, non-destructive test emerged as a popular way to evaluate the properties of cement-based materials. This test offers continuous measurements of concrete properties as well as ability to monitor any changes in the current state of structural materials. In the existing research, some of these methods fail to capture well properties of the materials in the plastics stage. A new piezoelectric pulse testing device (Piezoelectric Ring Actuators Technique), (P-RAT ) was initially developed at the University of Sherbrook as a non-destructive test (NDT ) for soil. This technique is considered a completely new, versatile, advanced and accurate. The development of the new technique (P-RAT ) was done on two main bases: the first was the development of piezoelectric ring actuators set-up and the second is the development of the interpretation method. The setup is composed of two main units; emitter and receiver, and is capable of measuring shear and compression wave velocities in specimens. With this technique, many problems of pulse tests, which make interpretation of results difficult and ambiguous, were solved in soil. The P-RAT overcomes wave reflections at boundaries (end-caps and sides), sample disturbance, weak shear coupling between soil and device (interaction) as well as the fixation problems, low resonant frequency and limited input voltage of the existing device. The previous method is exploited forward to measure the hydration properties of cement-based material. To apply this test method, it is necessary to determine how the evolution of shear wave velocity can be related and sensitive to the hydration of cement-based materials. Validation of the P-RAT with four conventional test setups that can be used to monitor early setting and hydration of cement-based materials is carried out. These tests include penetration resistance to monitor initial and final setting respectively, calorimetric to monitor heat of hydration, electrical conductivity to monitor change in continuity of the pore structure and compressive strength at 24 hours. The phase one of this investigation included trial tests to investigate the possibility of employing the original setup used for soil (P-RAT ) to determine setting and hardening properties of cement-based material. Based on the results of the preliminary test, two modifications were conducted to the previous test device to fit with cement based material and to obtain adequate resonant frequency for cement-based materials. These modifications are the design of the container and changing the dimensions of the rings. The resultant version of P-RAT after the modification was referred to be as P-RAT2 . Calibration of the P-RAT2 with water specimen was undertaken using the compression wave velocity and resulted in 99.33% accuracy. One paste mixture was tested three times to determine the experimental error of the P-RAT2 . The repeatability carried out on the P-ART2 proved the ability of this setup to capture accurate results of the shear wave velocity. This relative error is limited to 9 %. A number of series of validation was performed on cement paste and mortar mixtures proportioned with various water cement ratios (w/cm ) as well as chemical admixtures. The w/cm ratio ranged between (0.35 and 0.50). The investigated chemical admixtures comprise of high-range water-reducing agent, viscosity-modifying agent, set-accelerating agent, and set-retarding agent. The presented validations examine the ability of a P-RAT2 to monitor the hydration of the cement-based materials. The hydration is characterized by setting time, heat of hydration, electrical conductivity, and compressive strength at 24 hours. The results obtained using the P-RAT2 was correlated to those obtained using the conventional tests and strength measurement. The results enable to validate the ability of P-RAT2 to accurately detect variations in the hydration of cement-based materials. In addition, the initial and final time of setting can be determined from the derivation of velocity vs. time curve. The results show that conductivity, resistivity, has a bilinear relationship to shear wave velocity. The compressive strength at 24 hours was correlated to both the shear wave velocity and shear modulus obtained using the P-RAT2 . Furthermore, analytical model was derived to estimate the w/cm in mortar mixture by measuring the shear wave velocity (V[subscript s] ) and the corresponding time (t )||Résumé : La période d'hydratation du ciment est l'une des périodes clé du cycle de vie des structures en béton. L'une des raisons de l'effondrement d'éléments structuraux en béton pendant et après la construction peut être attribuée à une détermination des caractéristiques au jeune âge erronée. Depuis quelques années, l’auscultation des structures est devenue une méthode très populaire pour évaluer les propriétés des matériaux cimentaires. Cette méthode permet d'obtenir les propriétés du béton en continue et possibilité un suivi de changements dans I'état des matériaux structuraux. Dans I'état actuel de la recherche dans ce domaine, certaines méthodes ne sont pas adéquates pour bien mesurer les propriétés des matériaux à I'état plastique. Un nouvel appareil d'essai à impulsions piezoélectriques (Piezoelectric Ring Actuators technique), (P-RAT) a initialement été développé à l’Université de Sherbrooke comme technique d'auscultation des sols. Cette technique est considérée complètement nouvelle, polyvalente, évoluée et précise. Le développement de cette nouvelle technique (P-RAT) a été effectué en deux volets : la première sole est le développement du dispositif de vérin de commande annulaire piezoélectrique et le deuxième est le développement d'une méthode d'interprétation. Le dispositif d'essai est composé de deux unités principales, un émetteur et un récepteur. Et permet de mesurer la vitesse de propagation des ondes de cisaillement et de compression. Grâce à cette technique, plusieurs des problèmes associés aux dispositifs d'essais par impulsion des ondes, qui rendent les résultats ambigus et difficiles à interpréter, ont été résolu pour les sols. Le dispositif P-RAT surmonte les problèmes de réflexion des ondes aux limites (embouts et côtés), la perturbation de l’échantillon, le couplage de cisaillement faible entre le sol et l'appareil (interaction) ainsi que les problèmes de fixation, la faible résonnance des fréquences et le voltage d'entrée limité du dispositif. La méthode décrite a été utilisée pour mesurer les propriétés d'hydratation des matériaux cimentaires. Pour pouvoir appliquer cette méthode, il faut déterminer comment l’évolution de la propagation des ondes de cisaillement peut être reliée à l'hydratation des matériaux cimentaires et être sensible à ces dernières. La validation de la méthode P-RAT est réalisée, à l'aide de quatre configurations conventionnelles que l’on peut utiliser pour faire le suivi de la prise et de l'hydratation des matériaux cimentaires. Ces essais consistent à la résistance à la pénétration afin de pouvoir déterminer la prise initiale et finale, la calorimétrie pour suivre l’evolution de la chaleur d'hydratation, la conductivité électrique pour effectuer le suivi de la structure des pores et la résistance à la compression à 24 heures. La phase 1 de l'étude comprend des essais pour évaluer la possibilité d'utiliser la configuration originale utilisée pour les sols (P-RAT) pour déterminer les propriétés de prise et de durcissement des matériaux cimentaires. Selon les résultats des essais préliminaires, deux modifications ont été effectuées à l'appareil original pour permettre son utilisation avec des matériaux cimentaires et pour obtenir une fréquence de résonnance raisonnable sur les matériaux cimentaires. Les modifications effectuées sont la conception du contenant et un changement de la dimension des anneaux. La version modifiée du P-RAT est designée P-RAT2. La calibration du P-RAT2 à l'aide d'échantillon liquide sous propagation d'ondes de compression a été menée, avec des résultats d'une précision de 99,33 %. Un mélange a été testé trois fois pour déterminer l'erreur expérimentale du P-RAT2. La répétitivité des essais sur le PART2 a démontré la capacité de cet appareil à produire des résultats de cisaillement de propagation des ondes de cisaillement très précis. L'erreur relative se limite à 9 %. Une série d'essais de validation a été menée sur des mélanges de pâte de ciment et de mortier de rapport eau/ciment variés (e/c) ainsi qu'avec des adjuvants. Le rapport e/c variait entre 0,35 et 0,50. Les adjuvants utilisés étaient des supers plastiflants (réducteur d'eau), des agents de viscosité, des agents accélérateurs de prise et des agents retardateurs de prise. Les validations présentées ont pour but de valider la capacité du P-RAT2 à suivre l'hydratation des matériaux cimentaires. L'hydratation est caractérisée par le temps de prise, la chaleur d'hydratation, la conductivité électrique et la résistance à la compression à 24 heures. Les résultats obtenus à l'aide du P-RAT2 ont été comparés à ceux obtenus à l'aide d'essais de mesure des caractéristiques physiques et de résistance traditionnels. Ces résultats permettent de valider la capacité du P-RAT2 à détecter avec précision les variations dans l'hydratation des matériaux cimentaires. De plus, le dispositif P-RAT2 peut avoir une correction avec mesure obteniez avec les appareils traditionnels. II est aussi possible de déterminer le temps de prise initial et final à l'aide d'une courbe de propagation vs le temps. Les résultats montrent que la conductivité et la résistivité ont une relation bilinéaire à la propagation des ondes de cisaillement. La résistance à la compression à 24 heures a été comparee à la fois à la propagation des ondes de cisaillement et au module de cisaillement obtenus avec le P-RAT2. De plus, un modèle analytique a été établi pour estimer le rapport e/c dans le mélange de mortier en mesurant la propagation des ondes de cisaillement (V) correspondant au temps (t)

Micro-chemo-mechanical features of ultra-high performance glass concrete (UHPGC)

The development of Ultra-High Performance Concrete (UHPC) opened new research directions for enhancing the architectural design, sustainability and serviceability of concrete structures. However, the costs and resource intensiveness trigger the need for innovative UHPC mix design incorporating alternative materials, such as post-consumption Glass Powder (GP). This works aims at disclosing the microstructure features of UHPGC, in which the constituents can be partially replaced by different fineness of GP without impacting the long-term strengths. By using the latest NI-QEDS technique (coupling NanoIndentation and Quantitative Energy-Dispersive Spectroscopy), as well as image analysis applied to EDS chemical mappings, it was possible to investigate mechanical properties of the microstructure constituents and their volume fractions. A conventional UHPC microstructure was compared to a similar system with 30% replacement of cement by GP and to another system with 50% replacement of silica fume by Fine GP (FGP). The results showed the key role of GP anhydrous particles contributing to the rigid skeleton of anhydrous inclusions, as well as their bond quality with the surrounding cement paste. The reduction of cement and silica fume was thus possible without impairing the micromechanical properties of the hydrates, by improving the particle packing density in the hardened state. As major conclusion, replacing cement and silica fume with GP and FGP without impairing both micro-scale and macro-scale mechanical properties provides a promising means to reduce the environmental footprint of current UHPC mix design

Ground Glass Pozzolan in Conventional, High, and Ultra-High Performance Concrete

Ground-glass pozzolan (G) obtained by grinding the mixed-waste glass to same fineness of cement can act as a supplementary-cementitious material (SCM), given that it is an amorphous and a pozzolanic material. The G showed promising performances in different concrete types such as conventional concrete (CC), high-performance concrete (HPC), and ultra-high performance concrete (UHPC). The current paper reports on the characteristics and performance of G in these concrete types. The use of G provides several advantages (technological, economical, and environmental). It reduces the production cost of concrete and decrease the carbon footprint of a traditional concrete structures. The rheology of fresh concrete can be improved due to the replacement of cement by non-absorptive glass particles. Strength and rigidity improvements in the concrete containing G are due to the fact that glass particles act as inclusions having a very high strength and elastic modulus that have a strengthening effect on the overall hardened matrix

Ground Glass Pozzolan in Conventional, High, and Ultra-High Performance Concrete

Ground-glass pozzolan (G) obtained by grinding the mixed-waste glass to same fineness of cement can act as a supplementary-cementitious material (SCM), given that it is an amorphous and a pozzolanic material. The G showed promising performances in different concrete types such as conventional concrete (CC), high-performance concrete (HPC), and ultra-high performance concrete (UHPC). The current paper reports on the characteristics and performance of G in these concrete types. The use of G provides several advantages (technological, economical, and environmental). It reduces the production cost of concrete and decrease the carbon footprint of a traditional concrete structures. The rheology of fresh concrete can be improved due to the replacement of cement by non-absorptive glass particles. Strength and rigidity improvements in the concrete containing G are due to the fact that glass particles act as inclusions having a very high strength and elastic modulus that have a strengthening effect on the overall hardened matrix

Lead, Mercury, and Cadmium Concentrations in Blood Products Transfused to Neonates: Elimination Not Just Mitigation

Lead (Pb), mercury (Hg), and cadmium (Cd) are identified as potent developmental neurotoxicants. Neonates are the main group receiving multiple blood transfusions. The exposure of neonates to these heavy metals (HMs) can occur through blood transfusions. This study aimed to determine the concentrations of lead (Pb), mercury (Hg), and cadmium (Cd) in various blood products (plasma, platelets, packed red blood cells (pRBCs), and whole blood (WB)) to explore the probability of concurrent exposure of these HMs and to identify the metal load per transfusion with risk assessment. Residual bloods from blood bank bags were collected after neonatal transfusion. Pb, Hg, and Cd concentrations were determined in 120 samples of blood products by inductively coupled plasma mass spectrometry (ICP-MS). Pb and Cd levels were over the normal levels in 19.2 and 5.9% of all blood units, respectively. In 35 and 0.8% of blood units, the Pb and Cd concentrations, respectively, were higher than that recommended for transfusions in premature neonates. The anticipated safe value was surpassed by 2.5% for Cd of all transfusions, primarily because of WB. However, Hg was detected only in 5.8% of all samples and their concentrations were within the normal range. The concurrent neonatal exposure to Pb, Hg, and Cd was statistically significant. Hazard quotients of Hg and Cr were >1 and Pb cancer risk was 2.41 × 10−4. To the best of our knowledge, this study is the first report examining Pb, Hg, and Cd in blood products other than WB and pRBCs using ICP-MS. This study demonstrated the exposure of neonates to Pb, Hg, and Cd during transfusion with a considerable amount of Pb. It confirms the significant concurrent exposure to the three HMs, which maximize their potential developmental neurotoxicity with a high probability of developing non-carcinogenic and carcinogenic health effects