Chloride-binding capacity of hydrotalcite in cement pastes containing dolomite and metakaolin

1 Chloride-binding capacity of hydrotalcite in cement pastes 1 containing dolomite and metakaolin 2 3 Alisa Machner 1,2,* , Maciej Zajac 3 , Mohsen Ben Haha 3 , Knut O. Kjellsen 1 , Mette R. Geiker 2 , 4 Klaartje De Weerdt 2 5 1 Norcem AS, R&D, Setreveien 2, P.O. Box 38, 3991 Brevik, Norway 6 2 NTNU Department of Structural Engineering, Richard Birkelandsvei 1A, 7491 Trondheim, 7 Norway 8 3 Heidelberg Technology Center GmbH, Oberklamweg 2-4, 69181 Leimen, Germany 9 10 11 *Corresponding author: [email protected] 12 +47 45394622 13 ORCID-ID: 0000-0002-6334-5116 14 15 ABSTRACT 16 In this study, we investigated well-hydrated cement pastes containing dolomite and metakaolin 17 cured at 38 °C or 60 °C, which were exposed to NaCl or CaCl2 solutions of various concentrations. 18 We determined the chloride-binding capacity, the phase assemblage and the composition of 19 hydration phases formed. The dolomite reaction led to the formation of hydrotalcite, which 20 contributed considerably to the chloride binding of the pastes. When the samples were exposed 21 to CaCl2, significantly more chlorides were bound in the hydrotalcite than when the samples were 22 exposed to NaCl. It was shown that hydrotalcite contained a similar amount of chloride per mol 23 compared to Friedel’s salt when exposed to CaCl2. By mass balance calculations, it was shown that 24 the hydrotalcite formed in the samples containing dolomite can contribute to the chloride binding 25 of the cement pastes to a similar extent as the Friedel’s salt formed in the samples containing 26 limestone. 27 28 29 Keywords: 30 EDX (B), Thermal Analysis (B), X-Ray Diffraction (B), Durability (C), Blended Cement (D) 31 32

Chloride-binding capacity of hydrotalcite in cement pastes containing dolomite and metakaolin

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edx

thermal analysis

xray diffraction

durability

blended cement