Preparation and Application of CSA Expansive Additives Using Industrial Wastes

Calcium sulfoalumiante(CSA) was prepared for using natural calcite($CaCO_3$) and industrial by-products and wastes, such as $Al(OH)_3,\;CaSO_4{\cdot}2H_2O$. The mixture of raw materials was fired at 20, 400, 600, $1200^{\circ}C$ for 1h and cooled rapidly in air. The cement replaced by 10 wt% $C_4A_3S$ expansive additives was investigated by the measurement of the hydration products and compressive strength, setting time, expansion at wet curing condition. $C_4A_3S$ was found in x-ray diffraction pattern over the temperature $1200^{\circ}C$. The setting time or the cement pastes added clinkers fired at different temperature was shorter than ordinary portland cement. The compressive strength was higher than the ordinary portland cement about 20~30%. The mainly hydration products were ettringite, and $Ca(OH)_2$. The expansion due to the formation of ettringite during hydration decreased the drying shrinkage of hardened cement rather than the ordinary portland cement.

산업폐기물을 이용한 CSA계 팽창재 제조 및 응용

$C_4A_3S$ 합성은 천연원료인 석회석과 산업폐기물 및 부산물인 수산화알루미늄, 이수석고를 일정혼합비로 균일하게 혼합하여 20, 400, 600, $1200^{\circ}C$에서 1시간 소성 후 급냉하여 $C_4A_3S$ 클링커를 합성하였다. 합성한 클링커를 보통 포틀랜드 시멘트에 10 wt%치환하여 수중 양생하에서 수화반응 및 물성특성을 조사하였다. $1200^{\circ}C$에서 $C_4A_3S$ 클링커가 합성됨을 X-Ray diffraction pattern으로 관찰할 수 있었다 $1200^{\circ}C$에서 소성된 시료는 급결성을 띠었으며, 압축강도는 보통 포틀랜드 시멘트보다 20~30% 정도 높게 나타났다. 주요 수화생성물은 ettringite, 수산화 칼슘이며, ettringite의 팽창으로 인하여 모르타르의 건조수축이 보통 포틀랜드 시멘트보다는 낮게 나타났다.