Change of Structure of Porous Hydrated Calcium Silicate by Dissolution in Paddy Soil

概要

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Change of the structure of porous hydrated calcium silicate material (PS) by dissolution both in paddy soil and under laboratory conditions was studied using a X-ray diffractometer and a scanning electron microscope. The main crystalline minerals of PS were 11 Å tobermorite and quartz. The X-ray diffraction peaks of calcite (CaCO_3) appeared at 14 d after transplanting (DAT) in paddy soil and their area increased with increase of the incubation time, whereas the area of the peaks of tobermorite decreased. The peaks of tobermorite disappeared at 53 DAT. The shape of PS, however, remained even at 120 DAT. It was suggested that the original shape of tobermorite was replaced by that of the silica skeleton. This silica skeleton with a large surface area was assumed to lead to a continuous supply of silicon to rice plants throughout the growing period. X-ray diffraction patterns of PS after incubation under laboratory conditions indicated that CO_2 and moisture are required for the dissolution of tobermorite. Tobermorite reacts with H_2CO_3 to produce calcium carbonate and silica gel.
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