Abstract
Calcium monosulfate hydrates, Ca4[Al2(OH)12][(1-x)SO4⋅x(OH)2]⋅6H2O were synthesized at 20°C from aluminate haüyne, Ca8Al12O24(SO4)2 by hydration under the presence of gypsum and portlandite. The experimental water/solid ratio was 0.80. Quantitative analysis by EPMA revealed that the x reaches up to 0.16 under the present synthetic conditions where ettringites are considered to be stable at lower water/solid ratios. Stabilities of accompanied phases were discussed in terms of phase assemblage.
