Formation of chemical gardens on granitic rock: a new type of alteration for alkaline systems
Satoh, Hisao; Tsukamoto, Katsuo; Garcia-Ruiz, Juan Manuel
European Journal of Mineralogy Volume 26 Number 3 (2014), p. 415 - 426
published: Jun 1, 2014
ArtNo. ESP147052603005, Price: 29.00 €
In order to understand the groundwater flow at near-underground facilities such as waste repositories, we have studied the effects of flowing an alkaline solution leached from cementitious building materials through the fractures of low-porosity granitic rocks under laboratory conditions. The results show that silica released from the dissolution of sodium-rich plagioclase and quartz reacts with the calcium leached from cementitious buildings to form calcium silicate hydrates (C-S-H) phases in the form of hollow tubular structures. These tubular structures form selectively on the surface of plagioclase in a similar way to reverse silica gardens structures. It was found that the rate of precipitation of C-S-H phases is faster than the rate of dissolution of plagioclase. This self-triggered dissolution/precipitation phenomenon may be an important factor controlling groundwater permeation in natural alkaline underground systems.