Effect of Mix Proportions on Rheological and Hardened Properties of Composite Cement Pastes

There is an increasing need to identify the effect of mix composition on the rheological properties of composite cement pastes using simple tests to determine the fluidity, the cohesion and other mechanical properties of grouting applications such as compressive strength. This paper reviews statistical models developed using a fractional factorial design which was carried out to model the influence of key parameters on properties affecting the performance of composite cement paste. Such responses of fluidity included mini-slump, flow time using Marsh cone and cohesion measured by Lombardi plate meter and unit weight, and compressive strength at 3 d, 7 d and 28 d. The models are valid for mixes with 0.35 to 0.42 water-to-binder ratio (W/B), 10% to 40% of pulverised fuel ash (PFA) as replacement of cement by mass, 0.02 to 0.06% of viscosity enhancer admixture (VEA), by mass of binder, and 0.3 to 1.2% of superplasticizer (SP), by mass of binder. The derived models that enable the identification of underlying primary factors and their interactions that influence the modelled responses of composite cement paste are presented. Such parameters can be useful to reduce the test protocol needed for proportioning of composite cement paste. 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 which are highlighted. The multi parametric optimization is used in order to establish isoresponses for a desirability function of cement composite paste. Results indicate that the replacement of cement by PFA is compromising the early compressive strength and up 26%, the desirability function decreased.

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.

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.

Neural Network Modeling of Rheological Parameters of Grouts Containing Viscosity-Modifying Agent

The development of artificial neural network (ANN) models to predict the rheological behavior of grouts is described is this paper and the sensitivity of such parameters to the variation in mixture ingredients is also evaluated. The input parameters of the neural network were the mixture ingredients influencing the rheological behavior of grouts, namely the cement content, fly ash, ground-granulated blast-furnace slag, limestone powder, silica fume, water-binder ratio (w/b), high-range water-reducing admixture, and viscosity-modifying agent (welan gum). The six outputs of the ANN models were the mini-slump, the apparent viscosity at low shear, and the yield stress and plastic viscosity values of the Bingham and modified Bingham models, respectively. The model is based on a multi-layer feed-forward neural network. The details of the proposed ANN with its architecture, training, and validation are presented in this paper. A database of 186 mixtures from eight different studies was developed to train and test the ANN model. The effectiveness of the trained ANN model is evaluated by comparing its responses with the experimental data that were used in the training process. The results show that the ANN model can accurately predict the mini-slump, the apparent viscosity at low shear, the yield stress, and the plastic viscosity values of the Bingham and modified Bingham models of the pseudo-plastic grouts used in the training process. The results can also predict these properties of new mixtures within the practical range of the input variables used in the training with an absolute error of 2%, 0.5%, 8%, 4%, 2%, and 1.6%, respectively. The sensitivity of the ANN model showed that the trend data obtained by the models were in good agreement with the actual experimental results, demonstrating the effect of mixture ingredients on fluidity and the rheological parameters with both the Bingham and modified Bingham models.

Notating the Unpredictable

Notation can be seen to sit comfortably between theory and practice as it symbolizes practice, generates and implements theory, and produces practice. Historically, its presence changes in significance across the development of activities such as music or architecture. From design tool to canonic text, notational artefacts both solidify and formalize practice, as will be expanded below. How, then, does the role and function of notation change with specific contemporary practices, which are by definition ill-defined and feed off fluidity and change? What is the nature of notation in distributed and collaborative practices such as improvised music or network music performance?

Protic ionic liquids based on the dimeric and oligomeric anions: [(AcO)(x)Hx-1](-)

We describe a fluidity and conductivity study as a function of composition in N-methylpyrrolidine-acetic acid mixtures. The simple 1 : 1 acid-base mixture appears to form an ionic liquid, but its degree of ionicity is quite low and such liquids are better thought of as poorly dissociated mixtures of acid and base. The composition consisting of 3 moles acetic acid and 1 mole N-methylpyrrolidine is shown to form the highest ionicity mixture in this binary due to the presence of oligomeric anionic species [(AcO)(x)Hx-1](-) stabilised by hydrogen bonds. These oligomeric species, being weaker bases than the acetate anion, shift the proton transfer equilibrium towards formation of ionic species, thus generating a higher degree of ionicity than is present at the 1 : 1 composition. A Walden plot analysis, thermogravimetric behaviour and proton NMR data, as well as ab initio calculations of the oligomeric species, all support this conclusion.

Hopanoid Production Is Required for Low-pH Tolerance, Antimicrobial Resistance, and Motility in Burkholderia cenocepacia

Hopanoids are pentacyclic triterpenoids that are thought to be bacterial surrogates for eukaryotic sterols, such as cholesterol, acting to stabilize membranes and to regulate their fluidity and permeability. To date, very few studies have evaluated the role of hopanoids in bacterial physiology. The synthesis of hopanoids depends on the enzyme squalene-hopene cyclase (Shc), which converts the linear squalene into the basic hopene structure. Deletion of the 2 genes encoding Shc enzymes in Burkholderia cenocepacia K56-2, BCAM2831 and BCAS0167, resulted in a strain that was unable to produce hopanoids, as demonstrated by gas chromatography and mass spectrometry. Complementation of the Delta shc mutant with only BCAM2831 was sufficient to restore hopanoid production to wild-type levels, while introducing a copy of BCAS0167 alone into the Delta shc mutant produced only very small amounts of the hopanoid peak. The Delta shc mutant grew as well as the wild type in medium buffered to pH 7 and demonstrated no defect in its ability to survive and replicate within macrophages, despite transmission electron microscopy (TEM) revealing defects in the organization of the cell envelope. The Delta shc mutant displayed increased sensitivity to low pH, detergent, and various antibiotics, including polymyxin B and erythromycin. Loss of hopanoid production also resulted in severe defects in both swimming and swarming motility. This suggests that hopanoid production plays an important role in the physiology of B. cenocepacia.

Optimisation of rheological parameters and mechanical properties of superplasticised cement grouts containing metakaolin and viscosity modifying admixture

The objective of this research was to optimise the rheological parameters, hardened properties, and setting times of cement grouts containing metakaolin (MTK), viscosity-modifying agent (VMA) and superplasticiser (SP). All mixes were made with water-to-binder ratio (W/B) of 0.40. The replacement of cement by MTK was varied from 6% to 20% (by mass), and dosages of SP and VMA were varied from 0.3% to 1.4%, and 0.01% and 0.06% (by mass of binder), respectively. Increased SP led to an increase in fluidity, reduction in flow time, plate cohesion, rheological parameters, and an increase in the setting times. Increased VMA demonstrated a reduction in fluidity, an increase in Marsh cone time, plate cohesion, yield stress, and plastic viscosity. Results indicate that the use of MTK increased yield stress, plastic viscosity, cohesion plate, and flow time due to the higher surface area associated with an increase in the water demand. MTK reduced mini-slump and setting times, and improved compressive strength.

Social mobility in Ireland in the 1990s: Evidence from the 1994 living in Ireland survey

In this paper we seek to update findings relating to class mobility outcomes and processes in the Republic of Ireland employing data from the Living in Ireland Survey which was carried out in 1994. We also provide an evaluation of a measured variable model of the mobility process developed on an earlier data set. Our findings confirm that transformation of the class structure has been associated with substantial levels of social mobility. At the same time inequalities of opportunity as reflected in the underlying patterns of social fluidity remain substantial and are constant across cohorts. Gender differences are almost entirely a consequence of occupational segregation and there is no evidence that the underlying processes of class disadvantage operate differently for men and women.

GENDER AND CLASS MOBILITY - EVIDENCE FROM THE REPUBLIC-OF-IRELAND

Gender has frequently been identified as the most controversial issue confronting class analysis. In this paper we make use of data from the Republic of Ireland to assess the extent to which the incorporation of women in class mobility analysis alters our understanding of the central processes of social mobility. We find that for married women their husband's class is a more powerful predictor of household poverty and life-style than their own 'class' as indicated by current or previous occupation. With regard to employment mobility we find that the sole source of gender variation in mobility chances relates to differences in the objective opportunity structures faced by men and women. Applying a measured variable model to 'men only' and 'complete' mobility tables reveals only modest differences in the patterns of social fluidity. The inclusion of women in class mobility tables requires little in the way of substantial modification of our understanding of the pattern of class relationships underlying the observed pattern of mobility.

FROM ASCRIPTION TO ACHIEVEMENT - ORIGINS, EDUCATION AND ENTRY TO THE LABOR-FORCE IN THE REPUBLIC OF IRELAND DURING THE 20TH-CENTURY

This paper examines the relationship between class of origin, educational attainment, and class of entry to the labour force, in three cohorts of men in the Republic of Ireland using data collected in 1987. The three cohorts comprise men born (i) before 1937; (ii) between 1937 and 1949; and (iii) between 1950 and 1962. The paper assesses the degree of change over the three cohorts in respect of (a) the gross relationship between origins and entry class; (b) the partial effect (controlling for education) of origin class on entry class; (c) the partial effect of education (controlling for origins) on class of entry. In broad terms the liberal theory of industrialism would imply a movement, over the three cohorts, towards (a) increasing social fluidity; (b) a weakening of the partial effect of origin class; (c) a strengthening of the partial effect of education. These latter two trends should be particularly noticeable in the youngest cohort, which would, to some degree, have benefited from the introduction of free post-primary education in Ireland in 1967.

Our results provide almost no support for these hypotheses. We find that patterns of social fluidity in the origin/entry relationship remain unchanged over the cohorts. The partial effect of class remains relatively constant; and, while the partial effect of education on entry class changes over the cohorts, the most striking result in this area is the declining returns to higher levels of education. While the average level of educational attainment increased over the three cohorts, the advantages accruing to the possession of higher levels of education simultaneously diminished. Taken together our results suggest that, in Ireland, those classes that have historically enjoyed advantages in access to more desirable entry positions in the labour market have been remarkably adept at retaining their advantages during the course of industrialization and through the various educational and other labour market changes that have accompanied this process.

Economic boom and social mobility:The Irish experience

In this paper we examine the consequences for social mobility of the recent unprecedented period of economic growth experienced in Ireland and the implications of such developments for current theories of social fluidity. Contrary to suggestions that the "Celtic Tiger" experience has been associated with deepening problem marginalization, we found evidence for a substantial upgrading of the class structure, increased levels of social mobility and increased social fluidity in relation to long-range hierarchical mobility. Such increased openness could not be explained by changes in the mediating role of education. The pattern of change suggests that both the upgrading of the class structure and the recent unprecedented tightness of the labour market have led employers to increasingly apply criteria other than education in a manner that has facilitated increased social fluidity. The Irish case provides further support for the argument for reconsidering the balance that mobility research has struck between social fluidity and absolute mobility and encouraging increased attention to the evolution of firms and jobs. It also suggests that, in circumstances where policies in advanced industrial societies have shown an increasing tendency to diverge, increased social fluidity may come about as a consequence of very different economic and social policies. © 2006 Elsevier Ltd. All rights reserved.

Brucella abortus and its closest phylogenetic relative, Ochrobactrum spp., differ in outer membrane permeability and cationic peptide resistance

The outer membrane (OM) of the intracellular parasite Brucella abortus is permeable to hydrophobic probes and resistant to destabilization by polycationic peptides and EDTA. The significance of these unusual properties was investigated in a comparative study with the opportunistic pathogens of the genus Ochrobactrum, the closest known Brucella relative. Ochrobactrum spp. OMs were impermeable to hydrophobic probes and sensitive to polymyxin B but resistant to EDTA. These properties were traced to lipopolysaccharide (LPS) because (i) insertion of B. abortus LPS, but not of Escherichia coli LPS, into Ochrobactrum OM increased its permeability; (ii) permeability and polymyxin B binding measured with LPS aggregates paralleled the results with live bacteria; and (iii) the predicted intermediate results were obtained with B. abortus-Ochrobactrum anthropi and E. coli-O. anthropi LPS hybrid aggregates. Although Ochrobactrum was sensitive to polymyxin, self-promoted uptake and bacterial lysis occurred without OM morphological changes, suggesting an unusual OM structural rigidity. Ochrobactrum and B. abortus LPSs showed no differences in phosphate, qualitative fatty acid composition, or acyl chain fluidity. However, Ochrobactrum LPS, but not B. abortus LPS, contained galacturonic acid. B. abortus and Ochrobactrum smooth LPS aggregates had similar size and zeta potential (-12 to -15 mV). Upon saturation with polymyxin, zeta potential became positive (1 mV) for Ochrobactrum smooth LPS while remaining negative (-5 mV) for B. abortus smooth LPS, suggesting hindered access to inner targets. These results show that although Ochrobactrum and Brucella share a basic OM pattern, subtle modifications in LPS core cause markedly different OM properties, possibly reflecting the adaptive evolution of B. abortus to pathogenicity.

An Ethical Production of Place:A Case for Economy in Architectural Design

Architects typically interpret Heidegger to mean that dwelling in the Black Forest, was more authentic than living in an industrialised society however we cannot turn back the clock so we are confronted with the reality of modernisation. Since the Second World War production has shifted from material to immaterial assets. Increasingly place is believed to offer resistance to this fluidity, but this belief can conversely be viewed as expressing a sublimated anxiety about our role in the world – the need to create buildings that are self-consciously contextual suggests that we may no longer be rooted in material places, but in immaterial relations.
This issue has been pondered by David Harvey in his paper From Place to Space and Back Again where he argues that the role of place in legitimising identity is ultimately a political process, as the interpretation of its meaning is dependent on whose interpretation it is. Doreen Massey has found that different classes of people are more or less mobile and that mobility is related to class and education rather than to nationality or geography. These thinkers point to a different set of questions than the usual space/place divide – how can we begin to address the economic mediation of spatial production to develop an ethical production of place? Part of the answer is provided by the French architectural practice Lacaton Vassal in their book Plus. They ask themselves how to produce more space for the same cost so that people can enjoy a better quality of life. Another French practitioner, Patrick Bouchain, has argued that architect’s fees should be inversely proportional to the amount of material resources that they consume. These approaches use economics as a starting point for generating architectural form and point to more ethical possibilities for architectural practice