Appendix 1: Table of Subcategory Definitions
Table 7: Low-carbon innovations in clinker substitution and binders
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Categories |
Subcategories |
Description |
|---|---|---|
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Clinker-lowering technologies |
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Supplementary cementitious materials (SCMs) |
Gypsum (calcium sulphate) |
Gypsum is a soft sulphate material required to control how cement hardens. Gypsum is added to clinker, totalling 3–5 per cent of the mix, to form OPC. |
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Limestone |
Ground limestone can be blended with clinker to reduce the final clinker content of cement. Although it is usually regarded as a filler, it is also reactive. |
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Calcined shale |
Clay shale, a fine-grained sedimentary rock formed of clay minerals, can be used as an SCM when calcined. (i) |
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Calcined clay/metakaolin |
Clays, in particular those containing kaolinite, can be used as an SCM when calcined. (ii) Metakaolin is a type of calcined clay. (iii) |
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Volcanic rocks |
Rocks of volcanic origin, particularly pyroclastic materials resulting from explosive eruptions, exhibit pozzolanic behaviour with minimal processing.(iv) |
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Fly ash |
A coal combustion product composed of fine particles that are carried out of the boiler by flue gases in power plants. (v) |
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Granulated blast furnace slag (GBFS) |
Molten iron slags are by-products of iron- and steel-making that have been quenched in water or steam to produce a sand-like granular product. This is then ground for mixing into cement. (vi) |
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Silica fume |
An ultrafine powder collected from the production of silicon and ferrosilicon alloy. Due to its expense, it is mostly used in high-performance concrete. |
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Rice hull/husk ash |
Rice husk is a waste product from rice production, which, if burnt under controlled conditions, can result in a highly reactive pozzolan. (vii) |
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Waste glass |
Recycled glass ground into a fine powder. (viii) |
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Waste |
Any form of waste products (agricultural or industrial waste). |
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Industrial sludge |
A semi-solid slurry produced from waste water from industrial processes. |
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Chemical admixtures |
Materials and chemicals mixed into cement and concrete to alter their performance. (ix) |
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Alternative-clinker technologies |
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Activated binders |
Geopolymers |
Geopolymers typically require an alkaline activation and networking element to bind pozzolanic materials in a polymer formation. This does not include alkali-activated binders, which do not form polymeric connected structures. |
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Alkali-activated binders |
Synthetic alkali aluminosilicate materials produced from the reaction of a solid aluminosilicate (e.g. natural pozzolans, including clays and volcanic rock; or artificial pozzolans, including fly ash and GBFS) with a highly concentrated aqueous alkali hydroxide or silicate solution. (x) This category also encompasses many of the geopolymer-classified patents, as geopolymer cements require alkali activation at the start of the process. |
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Alkali-activated calcined clays |
Geopolymers based on calcined clays as the solid aluminosilicate. This category covers patents in the dataset that use alkali-activated clays to activate non-traditional binders within cement composition. |
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Alternative-clinker cements |
Belite-rich Portland cement clinkers |
Clinkers based on belite rather than alite, produced with the same process as OPC but with lower limestone content and lower calcination temperature. Less fuel for heating is needed, and CO2 emissions from calcination are reduced. (xi) |
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Belitic clinkers containing ye’elimite or calcium sulphoaluminate (CSA) |
Clinkers based on belite containing ye’elimite or calcium sulphoaluminate, produced with the same process as OPC but with less limestone and more aluminum as raw materials. This lowers the sintering temperatures required and the energy requirements for grinding. |
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Belite ye’elimite-ferrite (BYF or BCSA) clinker |
Clinkers based on belite, ye’elimite and ferrite. These are produced with the same process as OPC and lower the sintering temperature and energy requirements for grinding. BYF clinkers are a subset of CSA clinkers, the main distinction being the ferrite element. |
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Low-carbonate clinkers with pre-hydrated calcium silicates |
Binders based on hydraulic calcium hydro silicates with a low calcium share. Carbonates are calcined before processing. Raw materials include marl, limestone, natural sand, slags, glass and fly ash. (xii) |
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Carbonatable calcium silicate clinkers (CCSC) |
Low-lime calcium silicates (e.g. wollastonite) made for carbonation curing instead of hydration. These can be made in the same kilns as OPC using practically the same raw materials as OPC. A lower burning temperature is required. This category includes cements containing formed Ca-silicates before the final hardening step, with the Ca-silicates present in the starting mixture. It also includes cements based on calcium silicate-forming mixtures not containing lime or lime-producing ingredients (e.g. waterglass-based mixtures heated with a calcium salt). |
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Magnesium-based clinkers |
Clinkers based on magnesium oxide, generally produced by calcinating natural magnesite, a process that is highly carbon-intensive. These clinkers could potentially be made using ultramafic rocks instead of limestone, which could result in a truly carbon-negative solution. (xiii) |
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Notes:
(i) Seraj, S., Cano, R., Ferron, R. P. and Juenger, M. C. G. (2015), ‘Calcined Shale as Low Cost Supplementary Cementitious Material’, in Scrivener, K. and Favier, A. (eds) (2015), Calcined Clays for Sustainable Concrete, Dordrecht: Springer, https://link.springer.com/chapter/10.1007/978-94-017-9939-3_66 (accessed 11 Mar. 2017).
(ii) Scrivener, John and Gartner (2016), Eco-efficient cements; Sakai and Noguchi (2012), The Sustainable Use of Concrete.
(iii) National Precast Concrete Association (2017), ‘SCMs in Concrete: Natural Pozzolans’, 22 September 2017, http://precast.org/2017/09/scms-concrete-natural-pozzolans/ (accessed 20 Oct. 2017).
(iv) Snellings, R., Mertens, G. and Elsen, J. (2012), ‘Supplementary Cementitious Materials’, Reviews in Mineralogy and Geochemistry, May 2012, https://www.researchgate.net/figure/259357577_fig4_Figure-4-Global-distribution-of-volcanic-rocks-grey-areas-and-deposits-of-reported (accessed 3 Jul. 2017).
(v) Thomas, M. (2007), Optimizing the Use of Fly Ash in Concrete, Portland Cement Association, http://www.cement.org/docs/default-source/fc_concrete_technology/is548-optimizing-the-use-of-fly-ash-concrete.pdf (accessed 3 Jul. 2017).
(vi) National Slag Association (2013), ‘Blast Furnace Slag’, http://www.nationalslag.org/blast-furnace-slag (accessed 3 Jul. 2017).
(vii) Abood Habeeb, G. and Bin Mahmud, H. (2010), ‘Study on properties of rice husk ash and its use as cement replacement material’, Materials Research, 13(2): pp. 185–190, doi: 10.1590/S1516-14392010000200011 (accessed 3 Jul. 2017).
(viii) Federico, L. (2013), Waste Glass - A Supplementary Cementitious Material, https://macsphere.mcmaster.ca/bitstream/11375/13455/1/fulltext.pdf (accessed 3 Jul. 2017); Ellen MacArthur Foundation (2016), The Circular Economy and the Promise of Glass in Concrete, Case Study, October 2016, https://www.ellenmacarthurfoundation.org/assets/downloads/circular-economy/The-Circular-Economy-and-the-Promise-of-Glass-in-Concrete.pdf (accessed 28 Feb. 2018).
(ix) Portland Cement Association (2017), ‘Chemical Admixtures’.
(x) Duxson, P., Fernandez-Jimenez, A., Provis, J. L., Lukey, G. C., Palomo, A. and van Devener, J. S. J. (2007), ‘Geopolymer technology: the current state of the art’, Journal of Material Science, 42: pp. 2917–2933, doi: 10.1007/s10853-006-0637-z (accessed 3 Jul. 2017).
(xi) Scrivener, John and Gartner (2016), Eco-efficient cements.
(xii) Stemmermann, P., Beuchle, G., Garbev, K. and Schweike, U. (2010), Celitement – A new sustainable hydraulic binder based on calcium hydrosilicates, http://www.celitement.de/fileadmin/user_upload/Downloads/2010-11-16_Celitement_a_new_sustainable_hydraulic_binder_based_on_calciumhydrosilicates.pdf (accessed 26 Apr. 2018).
(xiii) Scrivener, John and Gartner (2016), Eco-efficient cements.