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This study examines the potential of using calcium‐rich precursors to improve the strength of alkali‐activated slag (AAS) cement at low temperature. To achieve this target, the effect of calcium‐rich precursors on the early strength development of AAS mortars cured at 5°C was assessed. The strength development was investigated along with its internal temperature, microstructure and reaction products. It is found that the calcium‐rich precursors can improve the early strength of AAS around 35% and the group with Portland cement clinker gave the highest strength. Calcium oxide can also increase the compressive strength of AAS cement, but its effectiveness is not as good as the sample with clinker. Adding calcium sulfoaluminate can increase the early strength, while no significant contribution to 28‐day strength could be found. The results highlight that compressive strength of modified AAS mortar can reach 15 MPa at 6 h and 20 MPa at 24 h at 5°C, suggesting that this binder could be a valuable alternative for low temperature construction. [ABSTRACT FROM AUTHOR]

Clustering is a common method for finding patterns in underlying data in data mining applications. The majority of conventional clustering methods are restricted to datasets with numeric or categorical characteristics. In real-world data mining applications, however, datasets containing various kinds of characteristics are frequent. To address this issue, we offer a new divide-and-conquer strategy in this article. To begin, the original mixed dataset is split into two sub-datasets: pure category and pure numeric. Then, to generate matching clusters, existing well-established clustering algorithms intended for various kinds of datasets are used. The superiority of our method is shown by comparisons with existing clustering algorithms on real-world datasets. Clustering is a well-known data mining method for pattern detection and retrieval of information. The data in the first clustering dataset may be categorised or numerical. Each kind of data has its own method for clustering. The k-means method for clustering numeric datasets and the k-modes technique for categorical datasets are proposed in this area. The transformation of categorical characteristics into numeric measurements and direct application of the k-means algorithm instead of the k-modes method is one of the major issues in achieving the clustering process on categorical values. In this article, it is suggested to test a method based on the preceding problem, which involves converting categorical data into numeric values by utilising the relative frequency of each modality in the characteristics. [ABSTRACT FROM AUTHOR]

The chemical compositions of the aqueous phases in alkali-activated slag (AAS) paste and Portland cement (PC) paste were determined up to 28 d with the aim of obtaining a better understanding of the stability of the hydration products in the two binder systems. The saturation levels with respect to the hydration products of PC and AAS were obtained by thermodynamic modelling. The main findings of this study were: the effective saturation index for portlandite in the AAS system was always below zero and the sulfate-bearing phases were not stable in the AAS system compared with those in the PC; strätlingite and hydrotalcite phases were stable in the AAS paste due to the high magnesium and silicon concentrations in the pore solution; both the ionic strength and alkalinity of the AAS pore solution were higher than those of the PC pore solution, which were responsible for more severe efflorescence in the AAS paste and the higher conductivity of the AAS pore solution. According to thermodynamic estimations, tobermorite-based C–S–H was dominant in the AAS system after 7 d, while jennite-based and tobermorite-based C–S–H gels were present in the PC system up to 28 d. The results suggest that in PC and AAS pastes, different solid phases are formed during the hydration, which change with time, and the reactions and equilibria in both binders are completely different. [ABSTRACT FROM AUTHOR]

Determining the water permeability of concrete in structures remains a conundrum because of difficulties in removing the influences of moisture. This study describes the extended flow-net theory developed on the basis of the two-pressure-head concept, which provides a means of measuring permeability under the partially saturated condition. Surface-mounted tests and standard laboratory water penetration tests were carried out to verify this approach. Before determining the water permeability, steady-state flow rates at two different pressure levels were evaluated and the effects of initial moisture conditions on flow behavior were investigated. The results indicate that the proposed approach does offer a useful means of determining the water permeability of structural concrete, although it cannot be claimed to be universally applicable for all moisture conditions likely to be encountered in practice. [ABSTRACT FROM AUTHOR]

This paper reports the findings of research on the environmental performance of two case-study houses, a retrofit and new build. The retrofit was completed to a Passivhaus standard while the new build was completed to current Irish building regulations. Environmental performance of the retrofit and new build was measured using life-cycle assessments, examining the assembly, operational and end-of-life stage over life spans of 50 and 80 years. Using primary information, life-cycle assessment software and life-cycle assessment databases the environmental impacts of each stage were modelled. The operational stage of both case studies was found to be the source of the most significant environmental damage, followed by the assembly and the end-of-life stage respectively. The relative importance of the assembly and end-of-life stage decreased as the life span increased. It was found that the retrofit house studied outperformed the new build in the assembly and operational stage, whereas the new build performed better in the end-of-life stage; however, this is highly sensitive, depending on the standards to which both are completed. Operational energy savings pre- and post-retrofit were significant, indicating the future potential for adoption of high-quality retrofitting practices. [ABSTRACT FROM AUTHOR]

The presence of chloride ions is one of the primary factors causing the degradation of reinforced concrete structures. An investigation to monitor ingress of chlorides during a 24-week wetting and drying exposure regime to simulate conditions in which multiple-mode transport mechanisms are active was conducted on a variety of binders. Penetration was evaluated using free and total chloride profiles. Acid extraction of chlorides is quantitatively reliable and practical for assessing penetration. X-ray diffraction was used to determine the presence of bound chlorides and carbonation. The ability of the cement blends to resist chloride penetration was, from best to worst, ground granulated blast-furnace slag, microsilica, pulverised-fuel ash, Portland cement. The effect of carbonation on binding capability was observed and the relative quantity of chlorides also showed a correlation with the amount of chlorides bound in the form of Friedel's salt. [ABSTRACT FROM AUTHOR]

Tetralogy of Fallot (TOF) is the most frequently diagnosed congenital cyanotic heart disease. It is often associated with additional findings, such as atrial septal defect(i.e., pentalogy of Fallot) or right sided aortic arch. Association of this pentalogy of Fallot with situs inversus totalis is rarely reported in paediatric literature and it can cause technical challenges to intracardiac repair. We report the case of pentalogy of Fallot with dextrocardia and situs inversus presenting as parieto-occipital abscess in a 12-year-old child. Complicated cardiac malformation like this when associated with brain abscess pose several challenges to the anaesthetist due to the altered haemodynamics and warrant a meticulous anaesthetic as well as surgical plan. [ABSTRACT FROM AUTHOR]