Abstract
When $Al_2(SO_4)_3$ as an accelerator was added to $\beta$-hemihydrate gypsum, the setting time, mobility and compressive strength properties of $\beta$-hemihydrate gypsum were examined with the adding of two types grounded gypsum crushed by ball mill. By 15wt% adding of 7% $Al_2(SO_4)_3$ dilute solution, the setting time of $\beta$-hemihydrate gypsum was sharply accelerated than that of non-added $\beta$-hemihydrate gypsum. When ground phospho gypsum(PG) and chemical gypsum(CG) were added to $\beta$-hemihydrate gypsum, the initial and final setting time of $\beta$-hemihydrate gypsum were accelerated markedly with the increasing of grinding time and added amount of ground phospho gypsum. Especially, this trend largely presented when ground phospho gypsum was added to $\beta$-hemihydrate gypsum. The compressive strength of $\beta$-hemihydrate gypsum added by ground phospho and chemical gypsum was largely increased at initial curing time such as 1, 3 days. Particularly, the compressive strength of $\beta$-hemihydrate gypsum added by ground phospho gypsum was increased by 15~20% than that of ground chemical gypsum.
석고의 경화촉진제로 $Al_2(SO_4)_3$을 첨가하고 ball mill로 분쇄한 2종류의 이수석고(인산 이수석고, 화학이수석고)의 첨가량에 따른 $\beta$-반수석고의 수화응결 및 유동성, 압축강도, 수화상태등에 미치는 영향을 파악하였다. 7%로 희석한 $Al_2(SO_4)_3$를 $\beta$-반수석고에 15wt% 첨가시 수화응결은 무첨가시보다 초결 및 종결시간이 크게 단축되었다. 마쇄인산 이수석고 및 화학이수석고의 첨가시 수화응결은 인산 이수석고의 분쇄시간 및 첨가량 증가에 따라 초결 및 종결시간이 현저히 단축되었으며 특히, 마쇄 인산이수석고의 첨가에 의한 효과가 더 크게 나타났다. 마쇄인산 이수석고와 화학 이수석고가 첨가된 $\beta$-반수석고의 압축강도는 1, 3일의 초기 재령에서 크게 증진되었고 특히, 화학 이수석고에 비하여 마쇄인산 이수석고의 첨가로 $\beta$-반수석고 경화체의 초기 압축강도가 15~20% 증가되었다.
