Paramètres de composition des mélanges de particules de chènevotte pour l'élaboration de béton de chanvre

National audienceThis study is located in a green building approach axed on the eco-materials and innovative construction complexes for building insulation and sustainable development. The shive (a co-product of hemp) may be one of the first used plants for this purpose. To determine the concrete mix with vegetable fibers, three levels of milling were applied to the same shives and these fractions were analyzed in terms of size and packing densities. Two methods are used to characterize the particle size: sieve analysis and image analysis. Grain size analysis by sieving gives only a partial description of the distribution. Image analysis completes the grain size distribution and its parameters (Féret diameter, throbbing, etc.) are useful in optimizing plant skeleton. Packing densities (on individual shive and on a series of mixture) bring new elements to understand the relationship controlling the granular stack of vegetable fibers.L'étude se place dans une démarche d'éco-construction avec pour principal axe la conception d'éco-matériau et de complexes constructifs innovants destinés à l'isolation des bâtiments de basse consommation (BBC) notamment. La chènevotte issue du chanvre est un co-produit de plus en plus appréciée pour cet usage. Afin d'établir la composition de bétons incorporant ces fibres végétales, trois niveaux de broyage ont été appliqués sur une même chènevotte, et ces fractions ont été analysées du point de vue de la morphologie et de la compacité des particules. Deux méthodes sont employées pour la caractérisation granulométrique : l'analyse par tamisage et l'analyse d'images. Compte tenu de l'élancement élevé de la plupart des fibres, le tamisage ne donne qu'une description partielle de la distribution granulaire. L'analyse d'images complète l'identification, et ses paramètres (diamètre de Féret, élancement, etc.) sont utiles à l'optimisation du squelette végétal, sous l'aspect de sa compacité notamment. Des mesures de compacité individuelles et des mesures complémentaires sur des mélanges apportent des éléments nouveaux pour comprendre les relations contrôlant l'empilement granulaire des fibres végétales

Impact of opioid-free analgesia on pain severity and patient satisfaction after discharge from surgery: multispecialty, prospective cohort study in 25 countries

Background: Balancing opioid stewardship and the need for adequate analgesia following discharge after surgery is challenging. This study aimed to compare the outcomes for patients discharged with opioid versus opioid-free analgesia after common surgical procedures.Methods: This international, multicentre, prospective cohort study collected data from patients undergoing common acute and elective general surgical, urological, gynaecological, and orthopaedic procedures. The primary outcomes were patient-reported time in severe pain measured on a numerical analogue scale from 0 to 100% and patient-reported satisfaction with pain relief during the first week following discharge. Data were collected by in-hospital chart review and patient telephone interview 1 week after discharge.Results: The study recruited 4273 patients from 144 centres in 25 countries; 1311 patients (30.7%) were prescribed opioid analgesia at discharge. Patients reported being in severe pain for 10 (i.q.r. 1-30)% of the first week after discharge and rated satisfaction with analgesia as 90 (i.q.r. 80-100) of 100. After adjustment for confounders, opioid analgesia on discharge was independently associated with increased pain severity (risk ratio 1.52, 95% c.i. 1.31 to 1.76; P < 0.001) and re-presentation to healthcare providers owing to side-effects of medication (OR 2.38, 95% c.i. 1.36 to 4.17; P = 0.004), but not with satisfaction with analgesia (beta coefficient 0.92, 95% c.i. -1.52 to 3.36; P = 0.468) compared with opioid-free analgesia. Although opioid prescribing varied greatly between high-income and low- and middle-income countries, patient-reported outcomes did not.Conclusion: Opioid analgesia prescription on surgical discharge is associated with a higher risk of re-presentation owing to side-effects of medication and increased patient-reported pain, but not with changes in patient-reported satisfaction. Opioid-free discharge analgesia should be adopted routinely

Propriétés mécaniques et physico-chimiques de Bétons autoplaçants exposés à une température élevée

The use of Self-consolidating concrete (SCC) has considerably developed during the last years and a growing attention has been brought to the study of its mechanical properties at hardened state. The mixture proportions of SCC (large paste volume, high content of mineral admixtures, coarse to fine aggregates ratio close to 1, . . .) in relation with its placing conditions could modify its mechanical behaviour, comparatively to traditional vibrated concrete. The behaviour of SCC subjected to high temperature has in particular to be evaluated. The materials tested are 3 concretes which 2 SCC and a TC (Traditional concrete). The characteristic of SCC is the important volume. Mechanical tests (Compressive strength, flexural strength and modulus of elasticity) were realized. Alongside that, the water porosity, apparent density, loss of mass as well as gas permeability allowed having additional parameters to characterize the behaviour. But, microscopic observations coupled with images analyses and thermal analyses help to have a vision more physical and chemical of the behaviour. The experimental results show significant behaviours between the SCC and TC. The compressive strength allowed distinguishing an increase in compressive strength between 150 and 300°C. This increase is explained by a rehydration of the cement paste due to water migration through the pores for the SCC, and also by the creation of stronger hydrates. The rehydration concerned the anhydrous elements of the cement paste. Alongside this study, a work in collaboration with the University of Alabama concerning the behaviour at high temperature of lightweight self-compacting concrete (LW-SCC). This study allowed characterizing the mechanical properties and the physico-chemical properties of lightweight self-compacting concrete (made in University of Alabama (USA)). For that, prismatic and cylindrical specimens underwent two different thermal treatments : a fire ISO-834 and a slow heating to 1°C/min. Through this study, the LW-SCC presented a better thermal stability to a fire ISO-834. About physico-chemical properties, we noted a behaviour similarity between LW-SCC and SCC in water porosity, density, thermal analyses. Nevertheless, a decrease in porosity is observed at 400°C. It can be attributed to a shrinkage due to a decrease in volume. About mechanical properties, LW-SCC present a better residual compressive and residual flexural strength than SCC. Therefore, lightweight aggregates improves the residual mechanical behaviour.L'utilisation des Bétons autoplaçants (BAP) s'est considérablement développée au cours des dernières années et une attention grandissante est portée à l'étude de leurs propriétés mécaniques à l'état durci. Les spécificités de formulation de ces bétons (volume de pâte important, dosage élevé en additions minérales, rapport G/S (Gravillons/Sable) proche de 1, . . .) liées à leurs exigences de mise en oeuvre pourraient modifier leur comportement mécanique à l'état durci, comparativement aux bétons traditionnels vibres. Le comportement des BAP à haute température doit en particulier être évalué. Les matériaux testés sont 3 bétons de résistance courante dont 2 BAP et un BV. La particularité des BAP est le volume de pâte important. Des essais mécaniques (résistance à la compression, à la traction par flexion 4 points et mesure du module d'élasticité) ont été réalisés. Parallèlement à cela, la détermination de la porosité à l'eau, de la densité apparente, de la perte de masse ainsi que de la perméabilité aux gaz ont été étudiées. De plus, des observations microscopiques couplées à des analyses d'image et des analyses thermiques aident à préciser les causes physico-chimiques des phénomènes macroscopiques observes. Les résultats expérimentaux montrent des comportements significatifs entre les BAP et BV. Les essais de résistance à la compression ont permis de distinguer un gain de résistance entre 150 et 300°C. Ce gain est expliqué par une réhydratation de la matrice cimentaire due à la migration de l'eau à travers les pores pour les BAP, mais aussi à de meilleures propriétés liantes des hydrates formés. La réhydratation concerne les éléments anhydres de la pâte de ciment. Parallèlement à cette étude, un travail en collaboration avec l'Université d'Alabama concernant le comportement à haute température des bétons autoplaçants de granulats légers a été réalisé. Cette étude a permis de caractériser les propriétés mécaniques et les propriétés physico-chimiques de BAP de granulats légers (fabriques a Université d'Alabama (USA)). Pour cela, des éprouvettes prismatiques et cylindriques ont subi deux traitements thermiques différents : un chauffage de type incendie ISO-834 et un chauffage lent à 1°C/min. A travers cette étude, les BAP GN ont présenté une meilleure stabilité thermique à un incendie ISO-834. En ce qui concerne les propriétés physico-chimiques, nous avons constaté une similitude des comportements entre BAP GL et BAP GN du point de vue de la porosité, densité, analyses thermiques. Néanmoins, une diminution de la porosité est observe à 400°C. Elle peut être attribuée à un retrait des éprouvettes causant une diminution de volume. D'un point de vue mécanique, les BAP GL présentent une meilleure résistance résiduelle à la compression et à la flexion que le BAP GN. Donc, l'utilisation de GL améliore le comportement mécanique résiduel

Propriétés mécaniques et physico-chimiques des bétons autoplaçants exposés à une température élevée

L'utilisation des Bétons autoplaçants (BAP) s'est considérablement développée au cours des dernières années et une attention grandissante est portée à l'étude de leurs propriétés mécaniques à l'état durci. Les spécificités de formulation de ces bétons (volume de pâte important, dosage élevé en additions minérales, rapport G/S (Gravillons/Sable) proche de 1, . . .) liées à leurs exigences de mise en oeuvre pourraient modifier leur comportement mécanique à l'état durci, comparativement aux bétons traditionnels vibres. Le comportement des BAP à haute température doit en particulier être évalué. Les matériaux testés sont 3 bétons de résistance courante dont 2 BAP et un BV. La particularité des BAP est le volume de pâte important. Des essais mécaniques (résistance à la compression, à la traction par flexion 4 points et mesure du module d'élasticité) ont été réalisés. Parallèlement à cela, la détermination de la porosité à l'eau, de la densité apparente, de la perte de masse ainsi que de la perméabilité aux gaz ont été étudiées. De plus, des observations microscopiques couplées à des analyses d'image et des analyses thermiques aident à préciser les causes physico-chimiques des phénomènes macroscopiques observes. Les résultats expérimentaux montrent des comportements significatifs entre les BAP et BV. Les essais de résistance à la compression ont permis de distinguer un gain de résistance entre 150 et 300C. Ce gain est expliqué par une réhydratation de la matrice cimentaire due à la migration de l'eau à travers les pores pour les BAP, mais aussi à de meilleures propriétés liantes des hydrates formés. La réhydratation concerne les éléments anhydres de la pâte de ciment. Parallèlement à cette étude, un travail en collaboration avec l'Université d'Alabama concernant le comportement à haute température des bétons autoplaçants de granulats légers a été réalisé. Cette étude a permis de caractériser les propriétés mécaniques et les propriétés physico-chimiques de BAP de granulats légers (fabriques a Université d'Alabama (USA). Pour cela, des éprouvettes prismatiques et cylindriques ont subi deux traitements thermiques différents : un chauffage de type incendie ISO-834 et un chauffage lent à 1C/min. A travers cette étude, les BAP GN ont présenté une meilleure stabilité thermique a un incendie ISO-834. En ce qui concerne les propriétés physico-chimiques, nous avons constaté une similitude des comportements entre BAP GL et BAP GN du point de vue de la porosité, densité, analyses thermiques. Néanmoins, une diminution de la porosité est observe à 400C. Elle peut être attribuée à un retrait des éprouvettes causant une diminution de volume. D'un point de vue mécanique, les BAP GL présentent une meilleure résistance résiduelle à la compression et à la flexion que le BAP GN. Donc, l'utilisation de GL améliore le comportement mécanique résiduel.The use of Self-consolidating concrete (SCC) has considerably developed during the last years and a growing attention has been brought to the study of its mechanical properties at hardened state. The mixture proportions of SCC (large paste volume, high content of mineral admixtures, coarse to fine aggregates ratio close to 1, . . .) in relation with its placing conditions could modify its mechanical behaviour, comparatively to traditional vibrated concrete. The behaviour of SCC subjected to high temperature has in particular to be evaluated. The materials tested are 3 concretes which 2 SCC and a TC (Traditional concrete). The characteristic of SCC is the important volume. Mechanical tests (Compressive strength, flexural strength and modulus of elasticity) were realized. Alongside that, the water porosity, apparent density, loss of mass as well as gas permeability allowed having additional parameters to characterize the behaviour. But, microscopic observations coupled with images analyses and thermal analyses help to have a vision more physical and chemical of the behaviour. The experimental results show significant behaviours between the SCC and TC. The compressive strength allowed distinguishing an increase in compressive strength between 150 and 300C. This increase is explained by a rehydration of the cement paste due to water migration through the pores for the SCC, and also by the creation of stronger hydrates. The rehydration concerned the anhydrous elements of the cement paste. Alongside this study, a work in collaboration with the University of Alabama concerning the behaviour at high temperature of lightweight self-compacting concrete (LW-SCC). This study allowed characterizing the mechanical properties and the physico-chemical properties of lightweight self-compacting concrete (made in University of Alabama (USA). For that, prismatic and cylindrical specimens underwent two different thermal treatments : a fire ISO-834 and a slow heating to 1C/min. Through this study, the LW-SCC presented a better thermal stability to a fire ISO-834. About physico-chemical properties, we noted a behaviour similarity between LW-SCC and SCC in water porosity, density, thermal analyses. Nevertheless, a decrease in porosity is observed at 400C. It can be attributed to a shrinkage due to a decrease in volume. About mechanical properties, LW-SCC present a better residual compressive and residual flexural strength than SCC. Therefore, lightweight aggregates improves the residual mechanical behaviour.CERGY PONTOISE-BU Neuville (951272102) / SudocSudocFranceF

Using aggregate flowability testing to predict lightweight self-consolidating concrete plastic properties

International audienceThis paper presents the results of an experimental study on the flow properties of lightweight self-consolidating concrete (LWSCC) which utilizes a new test relating aggregate flow to concrete flow. Three types of LWSCC were tested containing differing proportions of lightweight and normal weight, coarse and fine aggregates, as well as a normal weight self-consolidating concrete (NWSCC) as a control. The flow properties of the aggregate mixes used in the LWSCC and NWSCC specimens were tested using a V-funnel. The concrete flow properties were also tested for comparison, as were the compressive and tensile strengths of the various mixtures. A relationship between the aggregate frictional resistance and the traditional concrete flowability tests-i.e., slump flow, J-ring, and T-500-was demonstrated. Compressive strengths were greater in LWSCC mixes that contained smaller sized coarse and normal weight aggregates. Finally, a design procedure is introduced that utilizes the aggregate frictional resistance, paste flow properties, and aggregate void ratio to predict the plastic properties of the concrete

Effectiveness of the Concrete Equivalent Mortar Method for the Prediction of Fresh and Hardened Properties of Concrete

Modern concrete mix design is a complex process involving superplasticisers, fine powders, and fibres, requiring time and energy due to the high number of trial tests needed to achieve rheological properties in the fresh state. Concrete batching involves the extensive use of materials, time, and the testing of chemical admixtures, with various methodologies proposed. Therefore, in some instances, the required design properties (physical and mechanical) are not achieved, leading to the loss of resources. The concrete equivalent mortar (CEM) method was introduced to anticipate concrete behaviour at fresh and hardened states. Moreover, the CEM method saves time and costs by replacing coarse aggregates with an equivalent sand mass, resulting in an equivalent specific surface area at the mortar scale. This study aims to evaluate the performance of fibre in CEM and concrete and determine the relationships between the CEM and the concrete in fresh and hardened states. Steel and polypropylene fibres were used to design three series of mixtures (CEM and concrete): normal-strength concrete (NSC), high-strength concrete (HSC), high-strength concrete with fly ash (HSCFA), and equivalent normal-strength mortar (NSM), high-strength mortar (HSM), and high-strength mortar with fly ash (HSMFA). This study used three-point bending tests and digital image correlation to evaluate load and crack mouth opening displacement (CMOD) curves. An analytical mode I crack propagation model was developed using a tri-linear stress–crack opening relationship. Post-cracking parameters were optimised using inverse analysis and compared to actual MC2010 characteristic values. The concrete slump is approximately half of the CEM flow; its compressive strength ranges between 78% and 82% of CEM strength, while its flexural strength is 60% of CEM strength. The post-cracking behaviour showed a significant difference attributed to the presence of aggregates in concrete. The fracture energy of concrete is 28.6% of the CEM fracture energy, while the critical crack opening of the concrete is 60% of that of the CEM

Multi-criteria study for recycled concrete aggregate separation process

Construction and demolition waste stream has generated news materials that may be reintroduced into new concrete, e.g. as recycled aggregates. The specific feature of recycled concrete aggregates (RCA) is the presence of hardened mortars influencing their behaviour. This study aims to distinguish processes that allow the complete separation and quantification of attached mortar. The laboratory developed method has to be transferable on a wider scale to be exploited on a real recycling platform. This study is linked to the RECYBETON National Research Project involving public research laboratories, institutes and private companies. Several methods are tested in laboratory conditions to determine their efficiency. They are based on mechanical, chemical and physical principles. The definition of this efficiency concept and the mortar content denomination are also discussed. Originality of this study consists in optimizing hot or cold thermal processes combined with a mechanical treatment. To perform that, a multi-criteria phase experiment was carried out and several values of the multi-criteria parameters were optimized. Results allow for a thorough knowledge of treatment efficiency. However, it appears that not any one method is 100% satisfactory as aggregates are never completely cleaned and/or are damaged

Clinicopathological Characteristics of Hirschsprung’s Disease With Emphasis on Diagnosis and Management: A Single-Center Study in the Kingdom of Saudi Arabia

Introduction : Hirschsprung’s Disease (HD) is a motor disorder of the gut caused by the failure of neural crest cells to migrate craniocaudally into the bowel during intestinal development, resulting in a functional obstruction. The majority of patients with HD are diagnosed in the neonatal period when they present with symptoms of distal intestinal obstruction. Aim : This study aims to identify the clinic-pathological characteristic of HD patients in our institution in KSA and comparing it with local and international data. Materials and Methods : This retrospective cohort study was conducted in King Abdulaziz Medical City (KAMC), a tertiary care center in Riyadh, Kingdome of Saudi Arabia (KSA). Results : A total of 54 patients (72% male) were diagnosed with HD. Forty-eight patients (89%) were born at term, and 6 were pre-term. Sixty-three percent of the patients presented in the neonatal period. Twenty-two patients (41%) underwent one-stage endorectal pull-through procedure, 23 patients (43%) two-stage endorectal pull-through, and 9 patients (16%) had three-stage endorectal pull-through. Five out of 54 patients had ganglion cells seen on FS but were absent in the permanent section. Therefore, the concordance rate was 90.8%. Conclusion : FS biopsy is a necessary method to determine the level of aganglionosis intraoperatively in HD, but the definitive diagnosis should be with permanent section. Also, the choice of surgical operation type (single-stage or multi-stage pull-through) depends on the patient’s clinical condition