Near-infrared spectroscopy investigation of the water confined in tricalcium silicate pastes |
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Authors: | Ridi Francesca Fratini Emiliano Milani Silvia Baglioni Piero |
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Affiliation: | Department of Chemistry and CSGI, University of Florence, via della Lastruccia 3, 50019 Sesto Fiorentino, Florence, Italy. |
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Abstract: | Near-infrared (NIR) spectroscopy has been employed to investigate the evolution of the vibrational spectrum of water entrapped in a tricalcium silicate paste. The overall free water, which decreases as a function of time due to the formation of the hydrated phases (portlandite, Ca(OH)(2), and hydrated calcium silicate, C-S-H) during the hydration reaction, is quantified by the decrease in the area of the NIR band at about 5000 cm(-1). The coexistence of two types of water in the hydrated phases (a "surface-interacting water" (type I) and a "bulklike water" (type II)) during the hydration is obtained by the analysis of the band at about 7000 cm(-1). The deconvolution of this band allows the quantification of the two water types. As the reaction advances, part of the "bulklike water" is converted to "surface-interacting water" in direct agreement with the C-S-H surface development. Finally, the Ca(OH)(2) formation can be concurrently monitored by NIR through the increase of a very sharp peak at 7083 cm(-1). Near-infrared spectroscopy allows determination in a very simple way of the most important features of the tricalcium silicate setting process. |
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