Experimental Design to Optimize High-Volume Ash Grout in the Presence of Welan Gum and Superplasticizer

Applications such as soil, rock and oil-well grouting all require enormous amounts of cement and are good examples of areas where a high volume of fly ash could partially replace cement to produce low-cost, environmentally safe and durable concrete. There is an increasing need to identify the rheological properties of cement grout using a simple test to determine the fluidity, and other properties of underwater grouts such as washout resistance and compressive strength. This paper presents statistical models developed using a fractorial design which was carried out to model the influence of key parameters on properties affecting the performance of underwater grout. Such responses of fluidity included mini-slump and flow time measured by Marsh cone, washout resistance, unit weight and compressive strength. The models are valid for mixes with 0.40 to 0.60 water-to-cementitious materials ratio, 0.02 to 0.08% of anti-washout admixture, by mass of binder, and 0.6 to 1.8% of superplasticizer, by mass of cementitious materials. The grout was made with 50% of pulverized-fuel ash replacement, by mass ofcementitious materials. Also presented are the derived models that enable the identification of underlying primary factors and their interactions that influence the modelled responses of underwater cement grout. Such parameters can be useful to reduce the test protocol needed for proportioning of underwater cement grout. This paper highlighted the influence of W/CM and dosage of antiwashout admixture and superplasticizer on fluidity, washout resistance and compressive strength and attempted also to demonstrate the usefulness of the models to improve understanding of trade-offs between parameters.

Factorial Design of Modelling Mix Proportion Parameters of Underwater Composite Cement Grouts

There is an increasing need to identify the rheological properties of cement grout using a simple test to determine the fluidity, and other properties of underwater applications such as washout resistance and compressive strength. This paper reviews statistical models developed using a factorial design that was carried out to model the influence of key parameters on properties affecting the performance of underwater cement grout. Such responses of fluidity included minislump and flow time measured by Marsh cone, washout resistance, unit weight, and compressive strength. The models are valid for mixes with 0.35–0.55 water-to-binder ratio (W/B), 0.053–0.141% of antiwashout admixture (AWA), by mass of water, and 0.4–1.8% (dry extract) of superplasticizer (SP), by mass of binder. Two types of underwater grout were tested: the first one made with cement and the second one made with 20% of pulverised fuel ash (PFA) replacement, by mass of binder. Also presented are the derived models that enable the identification of underlying primary factors and their interactions that influence the modelled responses of underwater cement grout. Such parameters can be useful to reduce the test protocol needed for proportioning of underwater cement grout. This paper attempts also to demonstrate the usefulness of the models to better understand trade-offs between parameters and compare the responses obtained from the various test methods that are highlighted.

Designing ionic liquids: Imidazolium melts with inert carborane anions

A new class of low-melting N,N'-dialkylimidazolium salts has been prepared with carborane counterions, some of the most inert and least nucleophilic anions presently known. The cations and anions have been systematically varied with combinations of 1-ethyl-3-methyl-(EMIM+), 1-octyl-3-methyl-(OMIM+), 1-ethyl-2,3-dimethyl- (EDMIM+), and 1-butyl-2,3-dimethyl- (BDMIM+) imidazolium cations and CB11H12-CB11H6Cl6-, and CB11H6Br6- carborane anions to elucidate the factors which affect their melting points. From trends in melting points, which range from 156 degrees C down to 45 degrees C, it is clear that the alkylation pattern on the imidazolium cation is the main determinant of melting point and that packing inefficiency of the cation is the intrinsic cause of low melting points. C-Alkylation of the anion can also contribute to low melting points by the introduction of a further packing inefficiency. Nine of the thirteen salts have been the subject of X-ray crystal structural determination. Notably, crystallographic disorder of the cation is observed in all but one of these salts. It is the most direct evidence to date that packing inefficiency is the major reason unsymmetrical N,N'-dialkylimidazolium salts can be liquids at room temperature.

Optimization of Cement Grouts Containing Silica Fume and Viscosity Modifying Admixture

There is an increasing need to identify the effect of mix composition on the rheological properties of cementitious grouts using minislump, Marsh cone, cohesion plate, washout test, and cubes to determine the fluidity, the cohesion, and other mechanical properties of grouting applications. Mixture proportioning involves the tailoring of several parameters to achieve adequate fluidity, cohesion, washout resistance and compressive strength. This paper proposes a statistical design approach using a composite fractional factorial design which was carried out to model the influence of key parameters on the performance of cement grouts. The responses relate to performance included minislump, flow time using Marsh cone, cohesion measured by Lombardi plate meter, washout mass loss and compressive strength at 3, 7, and 28 days. The statistical models are valid for mixtures with water-to-binder ratio of 0.37–0.53, 0.4–1.8% addition of high-range water reducer (HRWR) by mass of binder, 4–12% additive of silica fume as replacement of cement by mass, and 0.02–0.8% addition of viscosity modifying admixture (VMA) by mass of binder. The models enable the identification of underlying factors and interactions that influence the modeled responses of cement grout. The comparison between the predicted and measured responses indicated good accuracy of the established models to describe the effect of the independent variables on the fluidity, cohesion, washout resistance and the compressive strength. This paper demonstrates the usefulness of the models to better understand trade-offs between parameters. The multiparametric optimization is used to establish isoresponses for a desirability function for cement grout. An increase of HRWR led to an increase of fluidity and washout, a reduction in plate cohesion value, and a reduction in the Marsh cone time. An increase of VMA demonstrated a reduction of fluidity and the washout mass loss, and an increase of Marsh cone time and plate cohesion. Results indicate that the use of silica fume increased the cohesion plate and Marsh cone, and reduced the minislump. Additionally, the silica fume improved the compressive strength and the washout resistance.

Prevalence and Management of Anaemia in Renal Transplant Recipients: Data from Ten European Centres.

Background: Although it is a known predictor of mortality, there is a relative lack of recent information about anaemia in kidney transplant recipients. Thus, we now report data about the prevalence and management of post-transplant anaemia (PTA) in Europe 5 years after the TRansplant European Survey on Anemia Management (TRESAM) study. Methods: In a cross-sectional study enrolling the largest number of patients to date, data were obtained from 5,834 patients followed at 10 outpatient transplant clinics in four European countries using the American Society of Transplantation anaemia guideline. Results: More than one third (42%) of the patients were anaemic. The haemoglobin (Hb) concentration was significantly correlated with the estimated glomerular filtration rate (eGFR) (r = 0.4, p < 0.001). In multivariate analysis, eGFR, serum ferritin, age, gender, time since transplantation and centres were independently and significantly associated with Hb. Only 24% of the patients who had a Hb concentration <110 g/l were treated with an erythropoiesis-stimulating agent. The prevalence of anaemia and also the use of erythropoiesis-stimulating agents were significantly different across the different centres, suggesting substantial practice variations. Conclusions: PTA is still common and under-treated. The prevalence and management of PTA have not changed substantially since the TRESAM survey.

A refined physical model of the clarinet using a variable air jet height

A time-domain formulation of a lumped model ap-
proximation of a clarinet reed excitation mechanism is presented.
The lumped model is based on an analytical representation of
the ow within the reed channel, incorporating a contraction
coefcient (vena contracta factor) that is dened as the ratio of
the effective ow over the Bernoulli ow. This coefcient has
been considered to be constant in previous studies focusing on
sound synthesis. In this paper it will be treated as a function
of the reed opening, varying between 0 and 1 as predicted by
boundary layer ow theory. Focussing on a specic mouthpiece
geometry, the effect of modelling a variable air jet height on the
synthesised sound is analysed.

"The pride of noise": drums and their repercussions in early modern England

This article draws on a wide range of literary and archival sources in order to explore the cultural resonances of drumming in England during the 16th and 17th centuries. It concentrates not on instrument design and playing techniques but on the varied meanings that contemporaries attached to the ubiquitous sound of the drum. The discussion begins and ends with the unmistakable military associations of drumming. In between, consideration is also given to a range of interconnected but sometimes contradictory resonances that appear to have endowed drums with considerable cultural significance. Drums spoke, for example, of authority and they worked hard to impose order in urban streets. They also played their part in the contemporary culture of punishment, and many miscreants were subjected to the humiliation of public percussion. Beyond this, drums were particularly potent in their ability to express masculinity, and female drummers were rare and remarkable. The primal potency of the instrument also rendered it valuable to the insubordinate, and rioters—like soldiers— were regularly called together 'by the drum'. Lastly, the sound of the drum was sometimes intensely festive and could also be used to publicize special events such as dramatic performances and the display of curiosities. The repercussions of drumming were thus varied, and confusion sometimes resulted when the different possibilities became entangled.