Effect of Temperature on C3S and C3S + Nanosilica Hydration and C–S–H Structure |
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Authors: | Isabel F. Sáez del Bosque Manuel Martín‐Pastor Sagrario Martínez‐Ramírez María Teresa Blanco‐Varela |
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Affiliation: | 1. Instituto de Ciencias de la Construcción Eduardo Torroja (IETcc‐CSIC), , Madrid, 28033 Spain;2. Unidad de Resonancia Magnética, RIAIDT, de la Universidad de Santiago de Compostela, , Santiago de Compostela, 15782 Spain;3. Instituto de Estructura de la Materia (IEM‐CSIC), , Madrid, 28017 Spain |
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Abstract: | This study aimed to monitor the effect of temperature and the addition of nanosilica on the nanostructure of the C–S–H gel forming during tricalcium silicate (C3S) hydration. Two types of paste were prepared from a synthesized T1 C3S. The first consisted of a blend of deionized water and C3S at a water/solid ratio of 0.425. In the second, a 90 wt% C3S + 10 wt% of nanosilica blend was mixed with water at a water/solid ratio of 0.7. The pastes were stored in closed containers at 100% RH and 25°C, 40°C, or 65°C. The hydration reaction was detained after 1, 14, 28, or 62 d with acetone, and then pastes were studied by 29Si magic angle spinning nuclear magnetic resonance (29Si MAS NMR).The main conclusion was that adding nSA expedites C3S hydration at any age or temperature and modifies the structure of the C–S–H gel formed, two types of C–S–H gel appear. At 25°C and 40°C, more orderly, longer chain gels are initially (1 d) obtained as a result of the pozzolanic reaction between nSA and portlandite (CH) (C–S–HII gel formation). Subsequently, ongoing C3S hydration and the concomitant flow of dimers shorten the mean chain length in the gel. |
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