Statistical Analysis of the Mechanical Properties and Weight of Reinforcing Bars

The variability of the mechanical properties and weight of steel reinforcing bars produced in the United States and Canada under ASTM A 615, A 616, and A 706 in 1997 is evaluated and expressions are developed to represent the probability distribution functions for yield and tensile strength. Thirty-four mills were invited to submit data on yield strength, tensile strength, elongation, and percent of nominal weight. Of these, 29 mills submitted data on a heat-by-heat basis, three mills provided average values (no data on a heat-by-heat basis), one mill provided data on “No Grade” bars (these were not used in this analysis), and one mill did not respond to the request for data. A statistical analysis of bar properties is conducted. Trends in the data are evaluated based on grade, bar size, and production mill. Beta functions are developed to represent the probability distribution functions for yield and tensile strength for each bar size, grade, and steel type, as well as for all bars for each grade and steel type. The analyses show that less than 0.1% of the steel heats failed to meet minimum ASTM standards for yield strength, and less than 0.1% of the steel heats failed to meet minimum ASTM standards for tensile strength. Approximately 1.2% of the steel heats failed to meet minimum ASTM standards for elongation, but no heats failed to meet the minimum ASTM standard for weight. The beta distributions for yield strength covering all A 615 Grade 40 and all A 615 Grade 60 bars provide good representations for the distributions for individual bar sizes within each of these grades, with the exception of A 615 No. 14 and No. 18 bars, which exhibit significantly different distribution functions. Both normal and beta distribution functions (for the individual bars and all bars) can be used to represent the distributions of yield strength for A 615 Grade 75, A 616, and A 706 bars. For tensile strength, the distribution for all bar sizes is recommended for A 615 Grade 40 bars. The beta functions developed for the individual bar sizes for A 615 Grade 60 bars provide a good match with the actual tensile strength distributions, with the exception of No. 3 through No. 5 and No. 7 bars. Both normal and beta distribution functions can be used to represent the distributions of tensile strength for A 615 Grade 75, A 616, and A 706 bars for both individual bar sizes and all bars

Stabilisation of heavy metal containing dusts by reaction with phosphoric acid: study of the reactivity of fly ash

International audienceWater-washed fly ash was reacted with phosphoric acid in order to transform available heavy metals into insoluble metal phosphate compounds. The temperature, pH and concentration of free phosphate were monitored during the first 80 min of reaction. Phosphoric acid reacted rapidly with second order kinetics and an apparent rate constant of 0.015 l/(mol s m(2)). Analysis of the evolution of the concentrations of other major elements of fly ash shows that the reaction follows a dissolution-precipitation type mechanism. The solubility of trace heavy metals tends to increase at low pH values. Various heat and mass transfer coefficients are derived and help understand the phosphate stabilisation procedure and design industrial reactors for this purpose. Calcium phosphates are formed which can trap heavy metals in a stable apatite mineral structure

Stabilization of minerals by reaction with phosphoric acid - Evolution of model compounds

International audienceThe mechanisms of heavy metal stabilization from mineral residues were investigated. The reaction of phosphoric acid with municipal waste incinerator fly ashes and some of its major constituents was assessed. The reaction was monitored by analysis of soluble phosphate contents as a function of time, as well as by pH and temperature variations. Evolution of the solids was followed by X-ray diffraction. Various phosphoric acid concentrations were used and yielded different end products for the case of little and limestone. Silica and calcium sulphate were found to remain inert, while alumina consumed part of the soluble phosphate. Melilite showed it complex process of dissolution and precipitation of amorphous aluminium phosphates. These results help on understanding the phosphate reaction used to stabilize a mineral matrix like fly ash and demonstrate that insoluble minerals are formed such as calcium phosphates which may effectively trap heavy metal ions

Macroscopic behavior of bidisperse suspensions of noncolloidal particles in yield stress fluids

We study both experimentally and theoretically the rheological behavior of isotropic bidisperse suspensions of noncolloidal particles in yield stress fluids. We focus on materials in which noncolloidal particles interact with the suspending fluid only through hydrodynamical interactions. We observe that both the elastic modulus and yield stress of bidisperse suspensions are lower than those of monodisperse suspensions of same solid volume fraction. Moreover, we show that the dimensionless yield stress of such suspensions is linked to their dimensionless elastic modulus and to their solid volume fraction through the simple equation of Chateau et al.[J. rheol. 52, 489-506 (2008)]. We also show that the effect of the particle size heterogeneity can be described by means of a packing model developed to estimate random loose packing of assemblies of dry particles. All these observations finally allow us to propose simple closed form estimates for both the elastic modulus and the yield stress of bidisperse suspensions: while the elastic modulus is a function of the reduced volume fraction $\phi/\phi_m$ only, where $\phi_m$ is the estimated random loose packing, the yield stress is a function of both the volume fraction $\phi$ and the reduced volume fraction

Streamlining cell therapy manufacturing: Automated production and integrated data management

The manufacturing of cell therapy is a complex sequence of different unit operations. The substantial amount of manual and/or (semi-)automated manufacturing steps in a strictly regulated environment raise the need for scalable manufacturing and data management tools. Bioreactors have long been advocated as enabling technology for manufacturing of cell-based products. Automated bioreactors are not only able to substitute manual culture operations, but provide real-time monitoring and control of the culture environment, ultimately leading to improved process robustness. Additionally, they can be more easily integrated in an ‘Industry 4.0’ framework where data integration is required in real-time for process planning, regulatory compliance, etc. This work presents the integration of new a new bioreactor and a software platform, allowing more automation and efficient streamlining of the cell therapy manufacturing processes. On one hand, a closed benchtop perfusion bioreactor system with a reduced footprint was developed that is suitable for point-of-care use. Precise monitoring of the culture environment (pH, DO2 and T°) was achieved thanks to flexible sensor ports. The perfusion circuit was designed as a closed, single-use silicone tubing circuit linking a culture medium reservoir to a perfusion chamber via a peristaltic pump (cfr. Figure 1). A reusable cassette enclosed the disposable circuit and contained all the electronics required for bioreactor operation and environment control. A proof of concept study provided validation of the system on the perfusion culture of skeletal progenitor cells seeded onto 3D scaffolds. Regular sampling of the medium was performed during culture to measure glucose and lactate concentrations. Metabolic profiles, Live/Dead staining and DNA quantification of the constructs indicated similar cell growth kinetics compared to previously validated perfusion cultures of identical constructs. Please click Additional Files below to see the full abstract

Phosphatation de résidus minéraux

International audienceThe incineration of municipal solid waste generates mineral residues which contain soluble chlorides and heavy metal pollutants. The mineral residue is currently landfilled after a cement solidification. An alternative treatment, the new patented by Solvay process uses phosphoric acid to stabilise mineral residue by the formation of stable minerals such as calcium phosphates which are insoluble in natural environments and can incorporate heavy metals inside their crystalline structure. Two different water-washed municipal solid waste incinerator mineral residues are investigated during the phosphate treatment. Phosphoric acid reacts exothermically with mineral residues with rapid kinetics of the dissolution-precipitation type. Second order rate is observed with respect to the phosphate concentration and activation energies for the phosphate reaction are found to be small (near 20 kJ/mol). Mineral residues react with phosphoric acid mainly as calcium carbonate does. Precipitated amorphous calcium phosphates coat the more inert particles (silicoaluminates, silicates, and calcium sulphates…). The two mineral residues with different compositions show similar behaviour. This indicates the phosphate stabilisation procedure can be widely applied. This chemical treatment can be considered as a first essential step in the effective insolubilisation of extractable trace heavy metals in a mineral material that could find in the future an beneficial reuse after further processing as secondary raw materialSolvay a breveté un nouveau procédé de stabilisation de résidus minéraux contaminés par des métaux lourds et des composés organiques dont l’une des étapes fondamentales est le traitement chimique à l’acide phosphorique. Son objectif est de former des phosphates de calcium de grande stabilité chimique et thermique, capables d’incorporer dans leur structure cristalline les métaux lourds. L’étude de la cinétique de phosphatation montre que la réaction est exothermique. Les phosphates calciques formés enrobent les particules les plus inertes. L’énergie d’activation faible (20 kJ/mol), caractéristique d’une réaction acide-base, est proche de celle de la réaction avec le carbonate de calcium. Les expérimentations menées et les paramètres observés indiquent que la phosphatation peut être généralisée pour tous les résidus minéraux et constituer une première étape dans l’insolubilisation effective des métaux lourds. Ceci permet d’envisager pour le futur une possible revalorisation des résidus minéraux phosphatés et calcinés comme matière première secondaire

Influence of water vapour on the propagation speed and mean energy of an atmospheric non-equilibrium diffuse discharge in air

We report results on the influence of humidity on the propagation and the energy of a pin-to-plane nanosecond pulse discharge at atmospheric pressure. Water vapour only impacts discharges in saturated gas mixtures, for which propagation is first slowed down, but accelerates faster than usual close to the plane. Energy is unchange