Mineral Products Association Ltd (MPA), Hanson Cement, Imerys Aluminates, Forterra Building Products, Tarmac, University College London, University of Dundee.
To determine if lower value clays, currently discarded in UK quarry/brick production sites, could be used in cement and concrete.
A total of ten clays and two brick powders, with varying clay mineral constituents, were assessed as Supplementary Cementitious Materials (SCMs) at lab scale. Then four of these clays were calcined at pilot scale in a flash calciner and rotary kiln and rigorously analysed (along with 1 brick powder) for their strength and durability in cements and concretes.
The use of the materials manufactured in the pilot kilns, along with a brick dust source, were demonstrated at scale in precast self-compacting concrete. A number of L-shaped retaining wall elements were produced.
The findings of this study underscored the significant potential of reclaimed clays and finely ground bricks as SCMs, offering sustainable solutions for the construction industry while contributing to the circular economy objectives of the UK. All of the calcined clays produced using the pilot facilities, including clays with low kaolinitic content performed exceptionally in both standard and self-compacting concrete mixes. A strengths class of 42.5 N was easily obtained by cements with calcined clay as a component and continued strength gain beyond 28 days. This provides the industry with the necessary confidence that calcined clays perform similarly to mainstream SCMs and in some cases, performed better.
The cements were analysed against BS 8615:2019 (Specification for pozzolanic materials for use with Portland cement – High reactivity natural calcined pozzolana) and results are being used to make minor revisions to the standard with the removal of the 90 day activity index requirement and a relaxation of the water requirement.
Currently 79% of the UK cement market sales is CEM I, with a total market of 10 million tonnes per annum. Of the new cements trialled in the project - one has a CO2 profile 40-60% lower than CEM I. If fully deployed this would result in a reduction in direct emissions from cement production of over 4 million tonnes of CO2 every year. This work has removed potential barriers to manufacture and use of calcined clays in the UK.
The Report is in 2 parts, a summary report and an appendix report:
This project was part funded by Innovate UK through the Industrial Strategy Challenge Fund (ISCF) Transforming Foundation Industries (TFI) large collaborative R&D projects competition. This funding is aimed at improving the productivity and competitiveness of foundation industry companies and supply chains, by funding cross-sector collaborative research and development projects.