Near-infrared spectroscopy investigation of the water confined in tricalcium silicate pastes.
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.
Ridi
Francesca
F
Department of Chemistry and CSGI, University of Florence, via della Lastruccia 3, 50019 Sesto Fiorentino, Florence, Italy.
Fratini
Emiliano
E
Milani
Silvia
S
Baglioni
Piero
P
D017610:Calcium Compounds / Q000737:chemistry*; D017640:Silicates / Q000737:chemistry*; D019265:Spectroscopy, Near-Infrared; D014732:Vibration; D014867:Water / Q000737:chemistry*
D017610:Calcium Compounds; D017640:Silicates; D014867:Water; C506393:tricalcium silicate