10118595Recycled concrete fines, a low-carbon cement substitute: Tackling barriers to commercial uptakeClosedDemonstratorInnovate UKA widely adopted practice to lower carbon emissions from concrete use is minimising Portland cement (or CEM I) consumption. For this purpose, CEM I is partially replaced by other materials. Slag and fly ash are the most used types, but their availability is either very limited in the UK or they are fully utilised. To fill the gap in the slag or fly ash supply, the industry is looking to replace CEM I not only by these materials, but also by limestone. However, this solution is only temporary, as slag and fly ash will become scarcer. Other solutions currently being explored include calcined clay, but concerns are rising that too much reliance on clays will hinder resource efficiency in the UK. An alternative approach is to treat recycled concrete fines (RCF) and use them as slag or fly ash substitute. RCF typically constitutes about 15% of the total recycled concrete. In the UK, the coarse fraction of recycled concrete is commonly used as a substitute for natural aggregates in some applications, while the fines are downcycled or landfilled. However, recent advancements have made it possible to separate the fines from the coarse fraction, especially the hydrated cement fraction, and use them for other purposes, including partial CEM I replacement. Using RCF as CEM I substitute is not considered by the UK concrete standards (BS 8500), partly due to its low reactivity. However, there are ways to improve RFC reactivity. Improved reactivity is anticipated to enable about 50% CEM I substitution, a level comparable to what is typically achieved with slag. The aim of this project is twofold. First, it will address the RCF reactivity. To do this, RCF will be either carbonated or calcined. Second, concretes made with a range of cement compositions based on RCF will be rigorously tested against the current EU/UK standards. This is to revise BS 8500 to allow for high CEM I substitution with RCF. Revising BS 8500 will remove barriers to the wider adoption of RCF in the UK market. As a result, this project will enhance UK supply chains by providing alternatives to slag and fly ash for the concrete industry, addressing waste management and circularity challenges in the concrete industry. Doing so will enhance the UK's economic performance and GVA levels, making the concrete supply chain resilient. The construction industry has shown interest in using RCF as soon as BS 8500 permits.