Abstract
Hydrothermal reaction of akermanite at 210°C and 350°C under saturated steam pressure was investigated.
1) The reaction products from akermanite were hillebrandite, illcrystalline magnesium silicate hydrate and kilchoanite at 210°C, and kilchoanite, xonotlite and magnesium silicate hydrate at 350°C. Rate determining process was diffusion process, at first, resulting in slow reaction rate. And reaction became fast, in later stage, because that the interface reaction became the rate determining step.
2) Ca (OH) 2 addition changed the reaction products completely. Mg (OH) 2 was produced instead of magnesium silicate hydrate. Calcium silicate hydrates formed in this system were calcio-chondrodite and γ-Ca2SiO4 hydrate. Reaction rate also changed in a complicated way.
3) Magnesium silicate hydrate was formed when quartz was co-existed. Calcium silicate hydrate were gyrolite, truscottite and xonotlite. Hydrothermal reaction was promoted by quartz, as the rate controlling process was interface reaction from early stage.
