Effect of relative humidity on the carbonation rate of portlandite, calcium silicate hydrates and ettringite

By Sarah Steiner, B. Lothenbach, T. Proske, A. Borgschulte, F. Winnefeld. Cement and Concrete Research, 2020

284 citations recorded by the source corpus.

Abstract The carbonation of portlandite, calcium silicate hydrate (C-S-H), and ettringite was investigated at 57% RH and 91% RH using X-ray diffraction, thermogravimetric analysis, infrared spectroscopy, and the phenolphthalein spray test. The experiments show that the carbonation of portlandite, ettringite, and C-S-H with Ca/Si = 0.7 is significantly faster at 91% RH than at 57% RH. Little effect of RH is observed for C-S-H with higher Ca/Si. Portlandite and C-S-H with Ca/Si = 0.7 carbonate only partially at 57% RH; complete carbonation is observed if the relative humidity is increased to 91% RH. In contrast, the carbonation of C-S-H with Ca/Si = 1.2 and 1.5 is complete at both relative humidities. The carbonation rate of C-S-H decreases with decreasing Ca/Si ratio, both at 57% and 91%RH. Carbonation at 57% RH promotes the formation of vaterite and aragonite over calcite; the precipitation of amorphous calcium carbonate is observed for C-S-H with Ca/Si = 0.7.

Subfields: Biomaterials, Civil and Structural Engineering, Environmental Engineering

View Paper: https://www.semanticscholar.org/paper/123e8360e1a4ee1b1dcb6dd1fc8ab8fb16f390b5

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Citations in the corpus

Understanding the carbonation of concrete with supplementary cementitious materials: a critical review by RILEM TC 281-CCC (2020, background): “The destabilisation of C–S–H to silica gel, however, often remains incomplete, particularly at lower relative humidity [27, 30].”