Cement manufacture is responsible for 5-7 % of world CO 2 emissions. Cement is primarily used in concrete, the most used material on the planet and a critical part of any analysis of emissions reduction strategy. To estimate the potential for reducing demand, this work analyses material flow in the cement industry, using the uk in 2014 as a case study. Combining published data, analytic assumptions, and interviews we estimated the material flow of cement from the production to a breakdown of its use in applications. Having broken down the demand for cement into 25 applications, multiple material efficiency techniques were considered: substituting cement for calcined clay and limestone, reducing the cement content of concrete, post-tensioning floor slabs, using more precast building elements, reducing construction waste, and reducing the overdesign in construction. We produce a final estimate of the total reduction in emissions achievable from material efficiency: 51.3 %. Due to overlap and interactions between the methods, the attribution of the carbon abatement depends on the sequence of application. In this analysis, we have applied the reduction of overdesign last, because it is independent of the others, and would require a cultural change. We show then that cement demand from floors, repairs and maintenance, concrete beams, and applications within the transport sector should be targeted. The substitution of cement with calcined clay and limestone has the biggest potential to reduce cement demand (27 %) and carbon emissions in the uk. Reducing the amount of cement in concrete has the next highest * Corresponding author Preprint submitted to Elsevier today potential (10 %), followed by post-tensioning floor slabs (3 %).

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Although steel reuse has been identified as an effective method to reduce the carbon and energy impact of construction, its occurrence is shrinking in the uk. This can be partly explained by the many barriers which have been identified in the literature, but a detailed analysis of how these barriers affect different parts of the supply chain is still lacking. We show that there is a contrast between perceived higher costs and time required to employ reused steel and the assessments of realised projects. Using a novel ranking method inspired from the field of information retrieval (tf-idf), we have analysed interviews of actors across the supply chain to determine the acuteness of the perception of each barrier. We show that demolition contractors, stockists, and fabricators face specific barriers which each need to be addressed at their level. This is in contrast with more generic barriers present throughout the value chain which we show are probably more perception than reality. Finally, we suggest how supply chain integration could facilitate reuse and make it economically viable at scale.

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The built environment accounts for 39% of global energy related CO2 emissions, and construction generates 13% of global GDP. Recent success in reducing operational energy and the introduction of strict targets for near-zero energy buildings mean that embodied energy is becoming the dominant component of whole life energy consumption in buildings. One strategy that may be key to achieving emissions reductions is to use materials as efficiently as possible. Yet research has shown that real buildings use structural material inefficiently, with wastage in the order of 50% being common. Two plausible mechanisms are 1) that some engineers hold individual misconceptions, or 2) that inefficiency is a cultural phenomenon, whereby engineers automatically and unquestioningly repeat previous methods without assessing their true suitability. This paper presents a survey of 129 engineering practitioners that examined both culture and practice in design relating to material efficiency. The results reveal wide variations and uncertainty in both regulated and cultural behaviours. For the first time, we demonstrate that embodied energy efficiency is not a high priority, with habitual over-design resulting in more expensive buildings that consume more of our material resource than necessary. We show wide variability in measures that engineers should agree on and propose research through which these culture and individual issues might fruitfully be tackled within the timeframes required by climate science.