resumo
This paper describes a study of the hydraulic reactions between metakaolin (MK) and air lime using electrochemical impedance spectroscopy (EIS) and nuclear magnetic resonance spectroscopy (NMR). Tests were carried out at 20, 25 and 30 degrees C on lime-MK pastes with 10:1 w/w ratio. Tests over 28 days allowed identification of relevant changes in the EIS signals and characterization of pastes using thermal analysis (TGA/DSC), scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP) and uni-axial compressive tests. Tests over shorter periods of time (up to 42 h) allowed more detailed studies of the hydraulic phases formed at the very beginning of the reactions. Results of thermal analyses demonstrate formation of hydraulic compounds such as CSH, C(4)AH(13) and C(3)ASH(6) and show their evolution over time. MIP analysis demonstrates changes in pore size distribution related to the formation and trasformation of hydraulic phases. Variations of impedance response with time are shown to be associated with reaction kinetics. Changes in the NMR signal within the first 42 h of reaction are shown to be associated with the dissolution of calcium hydroxide in the pore solution. Overall, this paper demonstrates the importance of NMR in the study of hydraulic reactions in lime based materials and the ability of EIS to detect the formation of hydraulic compounds and the end of the calcium hydroxide dissolution process.
palavras-chave
PORE-SIZE DISTRIBUTION; MAS NMR; POZZOLANIC ACTIVITY; SI-29; CEMENT; SYSTEM; AL-27; 60-DEGREES-C; KAOLINITE; MORTARS
categoria
Chemistry; Geology; Mineralogy
autores
Pesce, GL; Bowen, CR; Rocha, J; Sardo, M; Allen, GC; Walker, PJ; Denuault, G; Serrapede, M; Ball, RJ
nossos autores
João Rocha
Prof. Catedrático
Mariana Coutinho Sardo
Investigador Auxiliaragradecimentos
The authors would like to thank Singleton Birch Ltd and Imerys Minerals Ltd. for providing the materials used in the tests. Thanks are also due to the Engineering and Physical Sciences Research Council (EPSRC), for projects EP/I001204/1 and EP/J004219/1 and the UK India Education and Research Initiative (UKIERI II) coordinated by the British Council, New Delhi, India, for financial support through a thematic partnership.