Recent German paper (with deceptive title) on sustainable concrete design

https://19-pacheco-torgal-19.blogspot.com/2022/07/geopolimeros-rigor-cientifico-e.html

Building on the insights shared in my earlier post (link above) titled 'Geopolymers - Scientific Rigor, Marketing, and False Advertising,' I seize the chance to present a new article authored by four German researchers. This piece, published online in early February, enters the realm of these materials with a distinctive title "LLMs can Design Sustainable Concrete – a Systematic Benchmark".  https://www.researchsquare.com/article/rs-3913272/v1  

Upon thorough examination of the article, it is established that GPT Turbo falls short in designing sustainable concrete. The authors' efforts primarily centered around optimizing resistance, drawing from a pool of 240 alkaline-activated mixtures based on fly ash and GGBS. It's crucial to note that these mixtures were originally sourced from a publication by Indian authors. However, these compositions, inherently unsustainable, employ sodium silicate, as detailed in the related study: Ouellet-Plamondon, C. ; Habert, G. (2014) Life cycle analysis (LCA) of alkali-activated cements and concretes. In Handbook of Alkali-Activated Cements, Mortars and Concretes, 663-686 (Eds) WoodHead Publishing-Elsevier, Cambridge

I would like to take this opportunity to share the contents of an email I sent to researcher Christoph Völker, the primary author of the mentioned article. In the email, I refrained from critiquing a title that veers into misleading advertising, given its inadequate reflection of the article's content. Instead, I focused on expressing my concern about the article's limited contribution to the genuine research needs in this field, as clearly outlined in the work by Palomo et al. (2021), referenced at the end of the email:

"Portland Versus Alkaline Cement: Continuity or Clean Break: “A Key Decision for Global Sustainability” https://www.frontiersin.org/articles/10.3389/fchem.2021.705475/full

PS - The photograph initiating this post depicts an (exposed concrete) art center conceived by the acclaimed Japanese Tadao Ando, a former boxer who redirected his passion toward the field of architecture.

Dear Christoph Völker

Firstly, congratulations on your thought-provoking paper. I am reaching out to provide a minor comment regarding a statement in the introduction of your recent work:  “The development of new cementitious binders low in calcium offers a promising solution, potentially reducing carbon dioxide emissions by 40- 80 percent while retaining structural properties comparable to conventional cement [2] “

I'd like to draw your attention to the Reference 2 you cited, which may include publications asserting that AAC is linked to substantial carbon emission reductions, up to 80%. However, it is crucial to note that such claims lack concrete evidence and are essentially tantamount to non-existence. Ouellet-Plamondon and Habert (2014) demonstrated that only a specific type of AAC, those without sodium silicate, exhibit significantly lower carbon footprints than Portland cement-based mixtures.

Ouellet-Plamondon, C. ; Habert, G. (2014) Life cycle analysis (LCA) of alkali-activated cements and concretes. In Handbook of Alkali-Activated Cements, Mortars and Concretes, 663-686 (Eds) WoodHead Publishing-Elsevier, Cambridge

However, it is crucial to acknowledge that achieving high-strength AAC is contingent upon the use of sodium silicate. Consequently, realizing high-strength AAC with substantial carbon emissions reductions necessitates the utilization of waste-derived activators, an area still in its early stages of development. In this context, it is crucial to consider the insights provided by Van Deventer et al. (2012), who underscore the pivotal role of calcium in attaining elevated strength and durability in AAC. Paradoxically, Fernandez-Jimenez and Palomo (2009) have highlighted that the absence of expansive products resulting from alkali-silica reaction (ASR) is directly associated with low calcium content, implying that AAC with high calcium levels may be more susceptible to ASR.

Van Deventer, J.S.J.; Provis, J.; Duxson, P. (2012) Technical and commercial progress in the adoption of geopolymer cement”, Minerals Engineering Vol. 29, pp.89-104.

Fernandez-Jimenez, A.; Palomo, A., Chemical durability of geopolymers, In Geopolymers, Structure, Processing, Properties and Applications, Ed. J. Provis & J. Van Deventer, pp.167-193, 2009, Woodhead Publishing Limited Abington Hall, Cambridge, UK

PS – In reference to the three distinct families of AAC, namely A) high calcium, B) low calcium, and C) hybrid cements, which comprise various combinations of A) and B), please check the comprehensive study authored by Palomo et al. (2021):

"Portland Versus Alkaline Cement: Continuity or Clean Break: “A Key Decision for Global Sustainability” https://www.frontiersin.org/articles/10.3389/fchem.2021.705475/full