Carbonation Reaction of Calcium Silicate Hydrates by Hydrothermal Synthesis at 150°C in OPC-γ-Ca2SiO4-α-Quartz Systems

In order to develop organic-fiber reinforced building materials with long-term stability and durability, the carbonation of autoclaved calcium silicate hydrate hardening bodies, prepared by low-temperature synthesis (150°C) in Ordinary Portland Cement (OPC)-γ-Ca2SiO4 (γ-C2S)-α-quartz systems, has been investigated. The CO2 absorption decreased remarkably as the water-to-powder ratio (w/p) of the samples decreased, and the carbonation of the samples was inhibited. In addition, this tendency became remarkable by the use of γ-C2S, and carbonation was fully inhibited in the case where the mass ratio of the starting materials OPC, γ-C2S and α-quartz was 1:4:5. It is estimated that only vaterite, which was based on residual γ-C2S after accelerated carbonation and had a lower density than calcite and aragonite, filled the pores and densified the sample.