61 research outputs found
Rehabilitation of Mass Housing as a Contribution to Social Equality: Insights from the East-West European Academic Dialogue
No full textMass housing neighbourhoods (MHN) represent the leading pattern of urban transformation and expansion in the second half of the 20th century, and accordingly evaluation, regeneration and redesign of the MHN represent a necessary and challenging task in the contemporary research context. In the practical scope of MHN rehabilitation, various holistic approaches and design strategies are identified that affirm both ecological transition and social transformation of these urban settings. However, the level of application of such approaches across Europe varies greatly, and requires research initiatives of a comparative nature that open a cross-geographical debate at the European level. Although there is a series of evidence-based studies that define the conceptual framework of MHN, i.e., large-scale housing settlements, through historical-interpretative and chronological analyses, the academic debate on practical and feasible MHN rehabilitation and their sustainable integration into the urban development of cities at European level is underdeveloped. The specific objective of this paper is to establish preliminary insights into the current level of MHN rehabilitation and to identify challenges for further actions through (1) a comparative analysis of MHN role models from the second half of 20th century, and through (2) insights from an implemented expert questionnaire. The research engages a comparative case study analysis as the primary method and analyses MHN in Germany (as a representative of Western Europe) and in the two ex-Yugoslav countries, North Macedonia and Serbia (as representatives of Eastern Europe). This research has highlighted the main obstacles and challenges for MHN rehabilitation and demonstrated the importance of a multiscale approach to MHN analysis, having in mind that through the distribution of design values at the analysed spatial levels (neighbourhood level, building level, and apartment level) the application of affirmative indicators within different design values group is recognised.Heritage & Technolog
Prescribing by mental health nurses: the UK perspective
No full textPURPOSE. This article aims to discuss the growth of mental health nurse (MHN) prescribing in the United Kingdom as an exemplar for readers to compare progress in their own countries and context. This study also aims to provide a historical overview of this process in the United Kingdom where MHNs prescribe safely and competently.
CONCLUSIONS. Finally, evidence has shown that MHNs with prescriptive authority are competent when prescribing when compared to psychiatrists.
PRACTICE IMPLICATIONS. Despite organizational barriers and educational concerns, MHN prescribing is becoming embedded in the healthcare context in the United Kingdo
3D Monte Carlo simulation of backscattered electron signal variation across pore-solid boundaries in cement-based materials
No full textThree-dimensional (3D) Monte Carlo simulation was used to study the variation of backscattered electron (BSE) signal across pore-solid boundaries in cement-based materials in order to enhance quantitative analysis of pore structure. The effects of pore size, depth and boundary inclination angle were investigated. It is found that pores down to 1 nm can generate sufficient contrast to be detected. Visibility improves with larger pore size, smaller beam probe size and lower acceleration voltage. However, pixels in shallow pores or near pore boundaries display higher grey values (brightness) than expected due to sampling sub-surface or neighbouring solid material. Thus, cement-based materials may appear less porous or the pores appear smaller than they actually are in BSE images. Simulated BSE images were used to test the accuracy of the Overflow pore segmentation method. Results show the method is generally valid and gives low errors for pores that are 1 μm and greater
Natural carbonation of concrete: a data-driven analysis
No full textThis study presents a data-driven analysis of long-term natural carbonation in concrete, using a newly compiled database comprising 1079 mixes and 8194 carbonation depth measurements over 65 years, representing one of the largest natural carbonation datasets assembled to date. Four different tree-based machine learning models (CatBoost, XGBoost, Random Forest and Decision Tree) were evaluated for predicting carbonation rate (k), with CatBoost emerging as the most effective. Partial dependence and SHAP analyses were used to quantify the relative importance of 13 features influencing k, including binder composition, mix proportion, curing and exposure conditions. The water-to-calcium oxide (w/CaO) ratio emerges as the most important feature, encapsulating the effects of porosity, carbonatable content, and supplementary cementitious material (SCM) type and content. Higher SCM replacement levels increase carbonation, while aggregate-related features show comparatively less pronounced effects. Carbonation environment is a more important feature than curing condition in predicting k. By combining machine learning with interpretable SHAP analysis, the model independently recognised trends consistent with literature findings. This study offers a comprehensive dataset and robustly selected features to facilitate future machine learning-based predictions of concrete carbonation
3D pore structure and mass transport properties of blended cementitious materials
No full textThe effect of supplementary cementitious materials on three-dimensional pore structure and how this influences mass transport properties are not well understood. This paper examines the effect of silica fume, fly ash and ground granulated blastfurnace slag on 3D structure of capillary pores (>0.24 μm) within 1003 μm3 cement paste for the first time using laser scanning confocal microscopy, combined with backscattered electron imaging and mercury intrusion porosimetry. Pastes containing different binder types, w/b ratios and curing ages were tested. Results show that SF enhances 3D pore structure from early ages whereas PFA and GGBS show improvements at later ages. SCMs not only reduce the volume and size of accessible pores, but also decrease connectivity and increase tortuosity, pore coordination number and formation factor. Measured 3D pore parameters were used as modelling inputs to estimate diffusivity and permeability. Predictions to within a factor of five from measured values were obtained
3D Pore Structure Characterisation of Blended Cement Pastes using Laser Scanning Confocal Microscopy
No full textDetermining the slag fraction, water/binder ratio and degree of hydration in hardened cement pastes
No full textA method for determining the original mix composition of hardened slag-blended cement-based materials based on analysis of backscattered electron images combined with loss on ignition measurements is presented. The method does not require comparison to reference standards or prior knowledge of the composition of the binders used. Therefore, it is well-suited for application to real structures. The method is also able to calculate the degrees of reaction of slag and cement. Results obtained from an experimental study involving sixty samples with a wide range of water/binder (w/b) ratios (0.30 to 0.50), slag/binder ratios (0 to 0.6) and curing ages (3 days to 1 year) show that the method is very promising. The mean absolute errors for the estimated slag, water and cement contents (kg/m3), w/b and s/b ratios were 9.1%, 1.5%, 2.5%, 4.7% and 8.7%, respectively. 91% of the estimated w/b ratios were within 0.036 of the actual values
3D imaging of cement-based materials at submicron resolution by combining laser scanning confocal microscopy with serial sectioning
No full textIn this paper, we present a new method to reconstruct large volumes of nontransparent porous materials at submicron resolution. The proposed method combines fluorescence laser scanning confocal microscopy with serial sectioning to produce a series of overlapping confocal z-stacks, which are then aligned and stitched based on phase correlation. The method can be extended in the XY plane to further increase the overall image volume. Resolution of the reconstructed image volume does not degrade with increase in sample size. We have used the method to image cementitious materials, hardened cement paste and concrete and the results obtained show that the method is reliable. Possible applications of the method such as three-dimensional characterization of the pores and microcracks in hardened concrete, three-dimensional particle shape characterization of cementitious materials and three-dimensional characterization of other porous materials such as rocks and bioceramics are discussed
Effect of autogenous shrinkage on microcracking and mass transport properties of concrete containing supplementary cementitious materials
No full textIt is well-known that supplementary cementitious materials (SCMs) and low water-to-binder (w/b) ratio increase autogenous shrinkage, but the impact on microcracking and long-term transport properties is less understood. This paper examines the effect of microcracking induced by autogenous shrinkage on transport properties of concretes cured up to ~3.6 years. Variables include SCM type (9% SF, 70% GGBS), w/b ratio (0.20–0.45), maximum-aggregate-size (MSA: 5–20 mm) and shrinkage reducing admixture (SRA). Oxygen diffusivity, permeability and water sorptivity were correlated with microcracks characterised using laser scanning confocal microscopy and 3D X-ray microtomography. Results show greater microcracking in mixes containing SCMs, low w/b ratio and large MSA. At the same w/b ratio and binder type, strong positive correlations are observed between transport and microcracking with increasing MSA, confirming the negative impact of autogenous shrinkage. SRA was effective in reducing these effects. The significance is compared with drying shrinkage and implications for durability are discussed
Analysis of autogenous shrinkage-induced microcracks in concrete from 3D images
No full textA new image analysis procedure for quantifying microcracks from three-dimensional (3D) X-ray microCT images of concrete is presented. The method separates microcracks from air voids and aggregates by combining filtering and morphological operations. It was applied to study the effects of supplementary cementitious materials (SCMs) and curing age on autogenous shrinkage-induced microcracks in low w/b ratio concretes, and to determine the representative elementary volume (REV) for various properties of microcracks and air voids. Results showed that slag and silica fume significantly increased autogenous shrinkage and related microcracking. These SCMs increased volume fraction, width, length, dendritic density, anisotropy, and connectivity of microcracks, but decreased specific surface and tortuosity. Similar trends were observed with age. Comparison between 3D and 2D measurements was made. REV analysis showed that a sampling volume of ~20 × 20 × 25 mm3 is sufficient for characterising most parameters of autogenous shrinkage microcracks and air voids in concrete
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