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Calcium silicate hydrate characterization by spectroscopic techniques

AuthorsMartin-Garrido, Moisés; Martínez-Ramírez, S. CSIC ORCID ; Pérez, Gloria; Guerrero Bustos, Ana María
Issue Date21-Sep-2016
CitationYOCOCU (2016)
AbstractCalcium silicate are present in the binder of many mortars used in the Cultural Heritage, such as lime-pozzolan mortars or hydraulic mortars. After hydration the calcium silicate give rise to an amorphous hydrated calcium silicate (called C-S-H† gel) whose structure resembles that of the tobermorite and jenite minerals. However, while the C-S-H gel has no well-defined stoichiometry, the other two minerals are crystalline with a well-established chemical formula, Ca5Si6O16(OH)2·4H2O for tobermorite and Ca9Si6O18(OH)6·8H2O for jenite. Both minerals have a Ca/Si ratio of 0.83 and 1.5 respectively, while the C-S-H gel has a variable stoichiometry, presenting Ca/Si relations ranging from 0.5 to 2.1. C-S-H gel can be prepared by different methods, including i) hydrothermal reaction1 of CaO and SiO2, ii) aqueous reaction of CaO and SiO2, iii) aqueous reaction of Ca(NO3)2·4H2O and Na2SiO3∙5H2O (double decomposition method2), and iv) mechanochemical reaction3 of CaO and SiO2. Different preparation methods lead to variations in structure of C-S-H. Some disadvantages come from hydrothermal and mechanochemical synthesis since they need a long time to assess the complete hydration of the SiO2 and CaO compounds; furthermore, portlandite is formed as a secondary reaction product. Due to the low crystallinity of C-S-H gel, spectroscopic techniques such as Micro-Raman; Fourier Transformed Infrared (FT-IR) and Nuclear magnetic Resonance (NMR) are the most suitable methods to characterize the structure of the compound. The synthesis of the C-S-H gel was done in different ways: a) the double decomposition and b) hydrothermal, using aqueous solutions of Ca(NO3)2·4H2O and Na2SiO3·5H2O. The formation of the amorphous compound was monitored by Raman and Infrared Spectroscopy. X-Ray Diffraction (XRD) analysis was done in order to follow the crystalline calcium silicate phases formed under hydrothermal synthesis.
DescriptionV Conferencia Internacional YOCOCU (YOuth in COnservation of CUltural Heritage); Madrid, 21 al 23 de septiembre de 2016; salón de actos del Museo Nacional de Arte Reina Sofía
Appears in Collections:(CFMAC-IEM) Comunicaciones congresos
(IETCC) Comunicaciones congresos
(VATC) Comunicaciones congresos

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