The impact of substitution of cement paste with uncalcined clay (bentonite and kaolinite) in the range of 5% by volume of paste on the development of hydration and properties of mortar was investigated. Two issues were addressed, the expected filler effect of the dispersed sub-micron clay particles, and the possible chemical reactivity of the clay.
The study indicated that Portland cement paste may be modified by addition of well dispersed clay and that the impact includes accelerated cement hydration as well as altered distribution of products. Compressive strength development was accelerated, but later age strength was reduced, especially for the bentonite mixes. In contrast, microscopic porosity measurements indicated no detrimental impact on the coarse capillary porosity.
The investigation indicates that for durability related engineering properties, the application of uncalcined clay might be a potential means for reduction of the clinker factor in concrete in support of sustainability.
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1. Scrivener KL John VM Gartner EM: “Eco-efficient cements. Potential economically viable solutions for a low-CO2 cement-based materials industry.” In United Nations Environment Program Paris France 2016 64 pp.
2. Damtoft JS Lukasik J Herfort D Sorrentino D Gartner EM: ”Sustainable development and climate change initiatives”. Cement and Concrete Research Vol. 38 No. 2 2008 pp. 115-127.
3. Lothenbach B Scrivener K and Hooton RD: “Supplementary cementitious materials”. Cement and Concrete Research Vol. 41 No. 12 2011 pp. 1244-1256.
4. Kocaba V: “Development and evaluation of methods to follow microstructural development of cementitious systems including slags” PhD thesis EPFL-TH4523 EPFL Laboratoire des Matériaux de Construction Lausanne Switzerland 2009 263 pp.
5. Fernandez Lopez R: “Calcined clayey soils as a potential replacement for cement in developing countries”. PhD thesis EPFL-TH4302 EPFL Laboratoire des Matériaux de Construction Lausanne Switzerland 2009 178 pp. 29
6. Krøyer H Lindgreen H Jakobsen HJ Skibsted J: “Hydration of Portland cement in the presence of clay minerals studied by 29Si and 27Al MAS NMR spectroscopy”. Advances in Cement Research Vol. 15 No. 3 2003 pp. 103-112.
7. Lindgreen H Geiker M Krøyer H Springer N Skibsted J H: “Microstructure engineering of Portland cement pastes and mortars through addition of ultrafine layer silicates”. Cement and Concrete Composites Vol. 30 No. 8 2008 pp. 686-699.
8. Kjeldsen AM: “New Concretes through addition of layer silicates. Bentonite clay soprtion.” Personal communication 2003.
9. Lindgreen HB Jakobsen HJ Geiker MR Stang H Krøyer H Skibsted JB: “Suspension of clays in water for addition to e.g. concrete”. Patent WO2008052554A1 2008-05-08.
10. EN 196-1. Methods of testing cement - Part 1: Determination of strength 2005.
11. EN 1015-03. Determination of consistence of fresh mortar (by flow table) 2004
12. NordTest NT Build 492 “Concrete mortar and cement-based repair materials: chloride migration coefficient from non-steady-state migration experiments” approved 1999-11.
13. Fontenay le Sage de C Sellevold EJ: “Ice formation in hardened cement pastes – I. Mature water-saturated pastes” Durability of building materials and components ASTM STP 691 1980.
14. Bager D & Sellevold EJ: “Ice formation in hardened cement paste Part I – Room temperature cured pastes” Cement and Concrete Research Vol. 16 1986 pp. 709–20.
15. Sellevold EJ & Bager D: “Low temperature calorimetry as a pore structure probe” Proceedings 7th International Congress on the Chemistry of Cement Paris vol. 4; 1981.
16. Osbæck B: “The influence of air content by assessing the pozzolanic activity of fly ash by strength testing”. Cement and Concrete Research Vol. 15 No. 1 1985. pp. 53-64.
17. Wu M Fridh K Johannesson B & Geiker M: “Impact of sample crushing on porosity characterization of hardened cement pastes by low temperature calorimetry: Comparison of powder and cylinder samples.” Thermochimica Acta Vol. 665 2018 pp. 11-19.