Non-destructive evaluation of concrete using a capacitive imaging technique : preliminary modelling and experiments

This paper describes the application of capacitive imaging to the inspection of concrete. A two-dimensional finite-element method was employed to model the electric field distribution from capacitive imaging probe, and how it interacts with concrete samples. Physical experiments with prototype capacitive imaging probes were also carried out. The proof-of-concept results indicated that the capacitive imaging technique could be used to detect cracks on the surface of concrete samples, as well as sub-surface air voids and steel reinforcement bars

Scenarios for reducing the environmental impacts of the UK clothing economy

In the 21st century the carbon emissions, material consumption, and impact on planetary boundaries associated with clothing have increased dramatically, driven in large part by fast fashion. The UK represents a typical, affluent, import-reliant Global North country, with clothing consumption per capita at double the global average and the impacts largely offshored. Progress towards a sustainable, circular clothing economy in the UK has been sluggish, as it has been globally. Here, we develop scenarios exploring how, over the coming two decades, the UK clothing economy could achieve the ambitious reductions in environmental impacts necessary to bring humanity's impact back within planetary boundaries. The scenarios consider the impacts of production- and consumption-focused changes, and the modelling uses material flow analysis to develop an assessment of energy consumption, carbon emissions, water consumption, and land use. We find that cleaner production and recycling alone could provide significant benefits for land and water use, reducing footprints by 60–70% by 2040. But to meaningfully reduce energy use, transformational changes will be required throughout supply chains at consumer and post-consumer stages. The same is true if the UK clothing economy is to be on track for net-zero by 2050, which requires these changes to be well under way within the next decade in order to halve emissions. Given the scale of change required, it seems highly unlikely that current clothing business models are compatible with a sustainable future

Is carbon dioxide pricing a driver in concrete mix design?

The global cement industry is responsible for 7% of anthropogenic carbon dioxide emissions and, as such, has a vital role to play in the transition to a low carbon dioxide economy. In recent years, this has been achieved by technological advances and increased use of supplementary cementitious materials, but the authors have recently shown that there are other means of achieving comparable carbon dioxide savings, for example, by reducing workability. However, price remains a considerable barrier to the widespread implementation of low carbon dioxide concrete. Using the same model for concrete mix design as was used to determine embodied carbon dioxide (ECD), variations in the cost of the components of concrete have now been considered. Considering 24 different mix designs, each spanning a range of characteristic strengths from 20 to 100 MPa, measures to reduce the carbon dioxide footprint were also found to reduce the material cost of the concrete. As such, it may be considered that the construction industry is already encouraged to reduce its ‘carbon footprint’. However, the concept of the carbon footprint was then considered in a more nuanced fashion, considering the ECD per unit strength. On such a basis, the cheapest mixes did not have the lowest ECD. Therefore, the impact of levying a charge on the carbon footprint was considered. To ensure low carbon dioxide concrete is also the cheapest, carbon dioxide emissions would have to be priced approximately one to two orders of magnitude higher than current market value. This would become the dominant factor in construction, with serious consequences for the industry. Furthermore, such charges may pose ethical problems, being viewed as a ‘licence to pollute’ and therefore undermining society's efforts to reduce the carbon dioxide emissions of the construction industry

Embodied carbon dioxide in concrete: Variation with common mix design parameters

The transition towards a low-carbon infrastructure requires an understanding of the embodied carbon (eCO 2) associated with concrete. However, much current work on eCO 2 underestimates the complexity of its relationship with concrete mix design. This paper demonstrates how eCO 2 of concrete is not a simple function of strength. Rather, for a given strength, considerable eCO 2 savings can be made by careful attention to basic mix design. Replacement of cement with PFA (pulverised fuel ash) can achieve considerable savings; additionally, using a concrete of lower workability, employing a superplasticiser, using crushed rather than rounded aggregate and using a higher strength of cement can have comparably significant effects. The analysis is presented in terms of embodied carbon per unit strength; this shows that there is an optimum strength for all concretes (with regard to minimising eCO 2 per unit of structural performance) of between 50 and 70 MPa

Mechanical, chemical, biological : Moving towards closed-loop bio-based recycling in a circular economy of sustainable textiles

The textile industry is facing increasing criticism because of its intensive use of resources –both natural and fossil derived– and the negative environmental and societal impacts associated with the manufacturing, use and disposal of clothes. This has led to a desire to move towards a circular economy for textiles that will implement recycling concepts and technologies to protect resources, the environment and people. So far, recycling processes have been focused on the chemical and mechanical reuse of textile fibres. In contrast, bio-based processes for textile production and recycling have received little attention, beyond end-of-life composting. However, the selectivity and benign processing conditions associated with bio-based technologies hold great promise for circularising the textile life cycle and reducing the environmental impacts of textile production and processing. Developing circular and sustainable systems for textile production requires a revolutionary system approach that encompasses the choice of material and finishes being designed for recycling at the end of life, and in this context bio-based processes can help provide the means to maintain materials in a closed loop. This paper reviews established methods in mechanical and chemical recycling processes in closed-loop textile recycling of all fibre types, as well as bio-based processes that demonstrate open-loop textile recycling. Fermentation and enzymatic processes have been demonstrated for the production of all types of textiles, which in combination with enzymatic deconstruction of end of life cellulosic textiles could allow them to be recycled indefinitely. Within the context of the circular economy, bio-based processes could extend mechanical and chemical textile recycling mechanisms in the technical cycle, enabling greater circularity of textiles in the biological cycle before composting takes place

Critical materials for infrastructure: local vs global properties

Introducing new technologies into infrastructure (wind turbines, electric vehicles, low-carbon materials and so on) often demands materials that are ‘critical’; their supply is likely to be disrupted owing to limited reserves, geopolitical instability, environmental issues and/or increasing demand. Non-critical materials may become critical if introduced into infrastructure, owing to its gigatonne scale. This potentially poses significant risk to the development of low-carbon infrastructure. Analysis of this risk has previously overlooked the relationship between the ‘local properties’ that determine the selection of a technology and the overall vulnerability of the system, a global property. Treating materials or components as elements having fixed properties overlooks optima within the local–global variable space that could be exploited to minimise vulnerability while maximising performance. In this study, a framework for such analysis is presented along with a preliminary measure of relative materials criticality by way of a case study (a wind turbine generator). Although introduction of critical materials (in this case, rare earth metals) enhances technical performance by up to an order of magnitude, the associated increase in criticality may be two or three orders of magnitude. Analysis at the materials and component levels produces different results; design decisions should be based on analysis at several levels

Post-consumer plastic packaging waste in England: Assessing the yield of multiple collection-recycling schemes

The European Commission (EC) recently introduced a ‘Circular Economy Package’, setting ambitious recycling targets and identifying waste plastics as a priority sector where major improvements are necessary. Here, the authors explain how different collection modalities affect the quantity and quality of recycling, using recent empirical data on household (HH) post-consumer plastic packaging waste (PCPP) collected for recycling in the devolved administration of England over the quarterly period July-September 2014. Three main collection schemes, as currently implemented in England, were taken into account: (i) kerbside collection (KS), (ii) household waste recycling centres (HWRCs) (also known as ‘civic amenity sites’), and (iii) bring sites/banks (BSs). The results indicated that: (a) the contribution of KS collection scheme in recovering packaging plastics is higher than HWRCs and BBs, with respective percentages by weight (wt%) 90%, 9% and 1%; (b) alternate weekly collection (AWC) of plastic recyclables in wheeled bins, when collected commingled, demonstrated higher yield in KS collection; (c) only a small percentage (16%) of the total amount of post-consumer plastics collected in the examined period (141 kt) was finally sent to reprocessors (22 kt); (c) nearly a third of Local Authorities (LAs) reported insufficient or poor data; and (d) the most abundant fractions of plastics that finally reached the reprocessors were mixed plastic bottles and mixed plastics

Developing policies for the end-of-life of energy infrastructure: Coming to terms with the challenges of decommissioning

Energy sector policies have focused historically on the planning, design and construction of energy infrastructures, while typically overlooking the processes required for the management of their end-of-life, and particularly their decommissioning. However, decommissioning of existing and future energy infrastructures is constrained by a plethora of technical, economic, social and environmental challenges that must be understood and addressed if such infrastructures are to make a net-positive contribution over their whole life. Here, we introduce the magnitude and variety of these challenges to raise awareness and stimulate debate on the development of reasonable policies for current and future decommissioning projects. Focusing on power plants, the paper provides the foundations for the interdisciplinary thinking required to deliver an integrated decommissioning policy that incorporates circular economy principles to maximise value throughout the lifecycle of energy infrastructures. We conclude by suggesting new research paths that will promote more sustainable management of energy infrastructures at the end of their life