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    We have the opportunity to reduce the environmental impact of our work through both the effective management and delivery of construction projects. Beyond that, we can also do so via investment in research and innovation.

    Knights Brown has actively taken steps towards improving construction practices, driven by our ‘Goal 13’ working group established in 2021, named in reference to the 13th United Nations Sustainable Development Goal, Climate Action1.

    Knights Brown is a stakeholder in a collaborative research project at Cardiff University, focusing on the production of a low impact concrete alternative.

    The project looks to resolve significant waste management and emission problems from a range of industries, working with companies involved in both foundry and cast metal (Weir Group Plc), as well as waste and carbon utilisation (Carbon Upcycling Technology).

    In its most basic form, concrete is composed of four main ingredients: cement, fine aggregate, coarse aggregate and water. The project aims to prove the simultaneous replacement of raw materials, namely fine aggregate and cement, with specific industrial waste streams, is not only feasible but largely beneficial.

    A significant proportion of construction emissions can be attributed to cement, with approximately 0.6 tCO2 emitted for every tonne produced2.

    Working with materials provided by Carbon Upcycling Technology, the project aims to use treated industrial waste streams, such as fly ash and steel slag, to replace cement, the most carbon intensive proportion of the concrete mix. These materials are exfoliated and sequestered with CO2 to provide not only environmental benefits but also superior mechanical and durability properties.

    Carbon is of course, only one measure of sustainability, with raw material extraction and usage being others. A report by the United Nations has suggested 40 – 50 billion tonnes of aggregate is extracted from the natural environment annually,3 of which it is estimated over half is consumed by the concrete industry4. This extraction has consequences, such as natural resource depletion, on the natural environment.

    A partial solution may be the reuse of foundry waste material in a circular economy context. Waste foundry sand is the source of a significant waste management problem in the foundry industry; approximately 100 million tons is produced on an annual basis5, of which only 15% is recycled6.

    Working with material from Weir Group Plc, the project aims to prove the replacement of fine aggregate within concrete with such waste is feasible and produces a concrete with adequate mechanical, physical and durability properties.

    Preliminary testing has been conducted at Cardiff University, replacing fine aggregate with waste foundry sand. Results have proved promising, with the subsequent composite displaying evidence of structural grade concrete with desirable physical, mechanical and durability properties.

    Next we aim to conduct a full scale trial, the results of which, if successful, will contribute towards an adjustment in construction standards as a means of paving the way for the more standardized use of waste material within concrete.

    This post features research undertaken by Joseph Pugh for his PHD at Cardiff University. We assert his rights as author.


    1 United Nations (2023) The Sustainable Development Goals Report 2023: Special Edition. New York. Available at: https://digitallibrary.in.one.un.org/TempPdfFiles/8157_1.pdf (Accessed: 18 September 2023).

    2 IEA (2023) International Energy Agency (IEA) – Cement. Available at: https://www.iea.org/energy-system/industry/cement (Accessed: 19 January 2024).

    3 United Nations Environment Programme (2019) Sand and Sustainability: Finding New Solutions for Environmental Governance of Global Sand Resources. Available at: https://wedocs.unep.org/20.500.11822/28163. (Accessed: 9 June 2023).

    4 United Nations Environment Programme, U. (2014) Sand, Rarer than One Thinks: UNEP Global Environmental Alert Service (GEAS). Available at: https://wedocs.unep.org/20.500.11822/8665. (Accessed: 9 June 2023).

    5 Ahmad, J. et al. (2022) ‘Waste Foundry Sand in Concrete Production Instead of Natural River Sand: A Review’, Materials, 15(7). Available at: https://doi.org/10.3390/ma15072365.

    6 Tittarelli, F. (2018) ‘Waste foundry sand’, Waste and Supplementary Cementitious Materials in Concrete: Characterisation, Properties and Applications, pp. 121–147. Available at: https://doi.org/10.1016/B978-0-08-102156-9.00004-3.