Abstract
The hydrothermal reaction of silica-lime-water-surface active agent was studied by statistical method. The elements of this system consist of reaction time and temperature, molding pressure and temperature, surface area of silica, kind of surface active agent, ratio of lime/silica and NaOH/lime. The elements of the hydrothermal reaction were analysed by orthogonal array. The main effects, interaction and partition of contribution (%) were corrected and estimated for each element and level. The results were as follows.
1) The molded sample at high temperature (100°C) and high pressure (100kg/cm2) cracked often when seperated from metal mold, and decreased bending strength.
2) Surface area of silica did not affect in the hydrothermal reaction when powder of silica as start material (in hydration system) possessed area over 3500cm2/g.
3) Generally, bending strength and unreacted lime of hydration reaction products were decreased when small amount of surface active agent was initially added to silica-lime-water-system, in spite of resulting surface gloss and smoothness of the products.
4) Especially, the anionic and nonionic surface active agent was absorbed to silanol group of silica and interfered hydration reaction of initial composite. Also, addition of sodium hydroxide to system as catalyst accelerated the reaction, while decreased the bending strength.
5) Estimations of the population mean of bending strength of test pieces were decided as 39.49±1.91 (kg/cm2).
6) The best result was obtained when the initial mixture of C/S 0.51.0 reacted at 200250°C for 2025hrs. The reaction was almost decided through statistical treatment of above mentioned elements. although the existence of several other unknown elements possessing slight effect to the hydration reaction was presumed.
