28 research outputs found

    Usability of mortar for predicting shear strength development at rest of fresh self compacting concrete

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    Determining the relationship between the rheological parameters of the model mortar and the rheological parameters of SCC (Self-Compacting Concrete) was the aim of the work. The static yield stress and the thixotropy coefficient AT were determined, which are important due to the development of the shear strength at rest and the formwork pressure generated during SCC casting. Shear strength of SCC reflected as static yield stress gs at rest develops mainly due to a self-compaction ability of SCC. And in the longer term, gs develops due to the progressive hydration of the cement and the disappearance of the HRWR impact (loss of fluidity). The static yield stress gs depends on w/c ratio, the type of HRWR (High Range Water Reducers) and cement. SCCs with a higher w/c ratio develop static yield stress gs faster, but up to 40 min the influence of w/c ratio decreases. The stiffening of SCC due to thixotropy increases the shear strength of SCC, but at the same time, it slows down the self-compaction of concrete. Thixotropy coefficient AT depends primarily on w/c ratio, and with the same w/c, on the type of cement and HRWR. The thixotropy coefficient AT increases in the initial period of SCC being at rest. The SCC with higher w/c ratio are characterized by higher thixotropy coefficient AT but at the same time by lower static yield stress gs. The significance of the thixotropic effect for shear strength disappears in time

    A home for all within planetary boundaries: Pathways for meeting England's housing needs without transgressing national climate and biodiversity goals

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    Secure housing is core to the Sustainable Development Goals and a fundamental human right. However, potential conflicts between housing and sustainability objectives remain under-researched. We explore the impact of current English government housing policy, and alternative housing strategies, on national carbon and biodiversity goals. Using material flow and land use change/biodiversity models, we estimate from 2022 to 2050 under current policy housing alone would consume 104% of England's cumulative carbon budget (2.6/2.5Gt [50% chance of < 1.5 °C]); 12% from the construction and operation of newbuilds and 92% from the existing stock. Housing expansion also potentially conflicts with England's biodiversity targets. However, meeting greater housing need without rapid housing expansion is theoretically possible. We review solutions including improving affordability by reducing demand for homes as financial assets, macroprudential policy, expanding social housing, and reducing underutilisation of floor-space. Transitioning to housing strategies which slow housing expansion and accelerate low-carbon retrofits would achieve lower emissions, but we show that they face an unfavourable political economy and structural economic barriers

    Mapping material stocks of buildings and mobility infrastructure in the United Kingdom and the Republic of Ireland

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    Understanding the size and spatial distribution of material stocks is crucial for sustainable resource management and climate change mitigation. This study presents high-resolution maps of buildings and mobility infrastructure stocks for the United Kingdom (UK) and the Republic of Ireland (IRL) at 10 m, combining satellite-based Earth observations, OpenStreetMaps, and material intensities research. Stocks in the UK and IRL amount to 19.8 Gigatons or 279 tons/cap, predominantly aggregate, concrete and bricks, as well as various metals and timber. Building stocks per capita are surprisingly similar across medium to high population density, with only the lowest population densities having substantially larger per capita stocks. Infrastructure stocks per capita decrease with higher population density. Interestingly, for a given building stock within an area, infrastructure stocks are substantially larger in IRL than in the UK. These maps can provide useful insights for sustainable urban planning and advancing a circular economy

    Emisyjność głównych materiałów budowlanych – co przyniesie przyszłość. (Emissions of major building materials – What brings the future?)

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    Industry accounts for almost 40% of global energy consumption and almost a quarter of direct CO2 emissions. Steel, cement and aluminium production alone represents 12% of global energy consumption and 13% of global CO2 emissions. By keeping emissions at the current level, we will use the remaining 2050 carbon budget in 12 years. In order to reduce carbon dioxide (CO2) emissions and thereby stop the global warming process, the International Energy Agency (IEA) has proposed scenarios that can lead to the reduction of emissions by 2060: for steel by 70%, for cement – by 20%, and for aluminium – by 30 even under the assumption of a rapid increase in demand for these materials. The IEA assumes a decrease in global CO2 emissions in the energy sector by almost 75%, inter alia by a reduction of materials consumption and an improvement in the use of materials in final products, including the construction sector. This article presents developed scenarios, includes their explanations and brings more in-depth analysis

    Can Material Passports lower financial barriers for structural steel re-use?

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    The building and construction sector is responsible for more than half of global steel consumption. Recycling is common practice. Yet, this is an energy intensive process, even when using the best currently available technology. A strategy that avoids energy use for remelting and significantly reduces negative environmental impacts is re-use. Steel element re-use is technically feasible and economically attractive in certain cases. However, re-use rates in the UK remain low. Cost and timing are identified to be among the main barriers for re-use across the structural steel value chain. Re-used steel is estimated to be about 8-10% more expensive than new steel, taking into account all required reconditioning processes. This study investigates how data/information services like BAMB Material Passports can facilitate structural steel re-use in the UK by lowering financial barriers. It shows that relevant data has the potential of reducing costs in sourcing, testing, reconditioning and fabrication, ranging from 150-1000 /t, depending on the re-use path followed (remanufacture or direct re-use of elements/structures). Key stakeholder groups are stockists and fabricators, which will be both the suppliers and customers of the data. It should be noted that data alone is not sufficient to overcome all barriers. Next to shortening or vertical integration of the supply chain, value redistribution across the chain can align incentives of different stakeholders. Regulations and perceptions (on quality) also play a key role. Finally, reversible design/design for dismantling can be a game changer in the transition towards more structural steel re-use, since it can significantly reduce deconstruction costs

    Application of programmable logic devices for acquisition of ECG signal with pacemaker pulses

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    The paper describes implementation of a new technology of digital systems design in case of medical measurement interface of IMPULS system used for acquisition of ECG signal from pacemaker patients. Similarly as in other applications, the processor circuit is a base of digital system, however - regarding large number of performed tasks - it is assisted by additional peripheral logic circuits. At the beginning, there were used standard elements (logic gates, counters, registers, etc.), however a growing complexity of beyond processor operations encouraged designers to apply the programmable circuits. The paper presents the stages of digital system development that has been implemented in medical measurement interface. It is the excellent example of possibility to integrate several standard elements in one integrated circuit

    Testing the greenhouse gas emissions reduction potential of alternative strategies for the english housing stock

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    Buildings account for around a third of global energy and process emissions, but have been delivering much smaller emissions savings than other sectors. Although clear standards of new building construction and retrofitting options have been developed and are able to reduce building emissions, there is need for a clear prioritisation of policy options capable of delivering the greatest reduction in emissions at minimal costs. This requires an assessment of the trade-offs between new construction and retrofitting in terms of the pace of adoption of improved building standards and the emissions savings achieved to meet current climate targets. In this paper, a dynamic material flow analysis is used to explore the impact of combined mitigation strategies on both new and existing buildings capable of reducing embodied and operational emissions in the English domestic housing stock. The results show that progress in the use of low carbon materials in construction and the deployment of zero-carbon buildings at scale would not be enough to deliver a reduction of building emissions of the scale required nationally (–66% from current levels by 2050). Improvement in building standards for both new and pre-existing construction is essential to meet targets, but its costs are likely to be unreasonable without a reduction in the demand for floor area per capita by promoting flexible design of buildings, house sharing or telecommuting, which are likely to produce far-reaching implications in social organisation and urban planning

    Mortar as a model to predict self-compacting concrete rheological properties as a function of time and temperature

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    © 2016 Elsevier Ltd The design of self-compacting concrete (SCC) is a time consuming and expansive process. We propose a new method for designing SCCs from equivalent mortars. For the purpose of this research, we investigated four methodologies to design equivalent mortars. They are all based on the assumption that the fresh materials, mortar and concrete can both be described as Bingham fluids. Thus, the measure of the rheological parameters of the mortars can be directly related to the equivalent parameters in concrete. Good models exhibit the same sensitivity as concrete to temperature, choice of superplasticizer and w/c changes as concrete. We propose two methods which conserve the w/c of concrete by calculating the appropriate paste-to-aggregate ratio. The results were validated experimentally for 3 temperatures, 2 superplasticizers, 2 cement types and 2 w/c ratios
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