フライアッシュと石灰, セッコウとの水熱反応性

II. 反応性におよぼす微量鉱物成分の影響

抄録

In order to clarify effects of mineral components of fly ash on hydrothermal reactivity of fly ash at 80°C, solubilities of SiO₂, Al₂O₃ and Fe₂O₃ from fly ash were investigated by treating fly ash in HCl and NaOH solutions. Treated and untreated fly ashes were reacted with lime and gypsum in water or in NaOH solution at 80°C.
From these experiments, the following results were obtained :
(1) Among minor components of fly ash, most of CaO and SO₃ were not contained in the glass phase of fly ash, but present as calcite and anhydrite on the surface of fly ash particles. These CaO rich phases hindered the dissolution of SiO₂ and Al₂O₃ and deteriorated the reactivity of fly ash in water with lime and gypsum at 80 °C.
(2) In NaOH solution, SiO₂ and Al₂O₃ were well dissolved even from the fly ash with low reactivity in water.
(3) When fly ash was reacted with lime and gypsum in NaOH solution at 80°C, monosulphate and C-S-H were formed. Reactivity of fly ash rich in CaO content was improved sufficiently in case that it was reacted in NaOH solution.
(4) By removing CaO rich phase from the surface of fly ash particles by dissolving in HCl solution, the reactivity was well improved to form monosulphate, ettringite and C-S-H. It was observed by SEM that the surface of fly ash particles was covered with C-S-H.