The effect of a mechano-chemical treatment was investigated on the consolidation of calcium-silicate by carbonation. Amorphous CaSiO3 powder was used as a starting powder and vibration ball-milled for 24h in air. In order to obtain CaSiO3 powders with different degree of milling a powder filling in a pot for vibro-milling was varied from 10 to 50g. The wet body of each milled powder was carbonated in 0.33MPa CO2 atmosphere at 80°C for 6h.
The obtained results are the following:
(1) The starting CaSiO3 powder had the chain structure of SiO4 tetrahedron similar to wollastonite and the deviations from structural regularity increased with decreasing powder filling in the pot for milling. The CaSiO3 powder with larger structural disturbance showed higher solubility in water.
(2) When the fully ground CaSiO3 was used, a dense consolidated body with high compressive strength was obtained. The compressive strength (σ) of the consolidated body largely depended on porosity, and was showed by the following equation at the porosity of ε.
σ=344exp(-0.56ε)
(3) After carbonation, pores in the consolidated bodies were filled with needle-like crystals. The precipitated crystalline phase was composed of a large amount of aragonite and a slight amount of calcite. The needle-like crystals were aragonite and seemed to play an important role to improve the mechanical strength of the consolidated bodies.
(4) During carbonation, the poly-condensation of SiO4 tetrahedron occurred as well as the precipitation of CaCO3 to form three-dimensional networks, and thus the consolidation proceeded.
