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Interview with Andrew McIntosh, Director of R&D, banah UK Ltd

Andrew talks to Ashtrans about the role of calcined clay pozzolan in replacing flyash, and banah UK Ltd’s research into geopolymer binders

You can hear more from Andrew at Ashtrans Europe in Barcelona on 26 - 27 October.

Ashtrans Europe (AE): This year’s Ashtrans Europe will facilitate a discussion into alternative products.  From that perspective, what role do you think calcined clay pozzolan can play to replace the conventional flyash?

Andrew McIntosh (AM): In discussions with concrete producers across the UK and Western Europe, we are finding that the majority are really struggling to secure supplies of good quality fly ash for use in cementitious products. There are warnings that what has happened to fly ash will also be repeated with GGBS in the near future. However, these are not the only supplementary cementitious materials (SCMs) that may be used to substitute Portland cement clinker. Pozzolans such as metakaolin and silica fume are often used as high performance SCMs, but their use is limited due to the high cost of these materials. This has left a gap in the market for a pozzolan that offers good performance, but at a reasonable cost. This is where calcined clays fit in – with raw materials readily available in almost any country in the world, a consistent and highly reactive product can be manufactured that will produce concrete with reduced chloride ingress and permeability, and with increased resistance to sulfate attack, alkali silica reaction and strength.

AE: The geopolymer binder is expected to replace cement. Can geopolymers replace all the cement and fly ash in regular concrete formulations?

AM: Your question has two answers – I will give both. In terms of individual geopolymer concrete formulations, the geopolymer binder replaces all of the cement content. We have carried out considerable work along with Queen’s University Belfast looking at concrete mix design with these new binders and comparing this to existing Portland cement methods. We now understand how that water/binder solids ratios and binder content influence the workability and performance of banahCEM-based concretes.

The second possible answer is – no, I do not believe that geopolymers will ultimately replace all Portland cement in the concrete industry. However, I do believe that they will become much more commonplace and that there will be a range of cements available to the specifier who will make their selection based on the application.

AE: Finally, you’re speaking at Ashtrans Europe this October. What are you most looking forward to hearing about?

AM: I am looking forward to hearing how those directly involved with the supply of ashes perceive the future of these materials – getting opinion directly from the coalface, if you like. Also looking forward to assessing the opportunities for alternative materials - like calcined clays.

This content is provided by Coaltrans Conferences for informational purposes only, and it reflects the market and industry conditions and presenter’s opinions and affiliations available at the time of the presentation.

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