수산화나트륨 용액에 이 계의 공통이온으로 규산소다를 혼합하여 무기중합반응의 촉진 여부를 구명하고자 하였다. 이를 위하여 할로이사이트를 주광물로 하는 카올린 분말을 몇 가지 다른 온도에서 하소한 후 90℃에서 수산화나트륨-규산소다계 용액과 혼합하여 만든 페이스트의 응결 시간을 측정하는 한편 페이스트 경화체의 광물상과 미세구조를 관찰하였다. 규산 소다의 첨가로 인해 대부분의 페이스트의 응결시간이 단축되었으며 하소온도가 650℃를 넘을 때 응결시간이 다시 지연되는 현상도 사라짐으로서 규산소다가 효과적인 반응 촉진제임이 확인되었다. 응결된 페이스트는 치밀한 비정질 결합상의 생성과 함께 경화하며 결정수가 남은 카올린보다는 모두 탈수된 카올린을 출발 물질로 할 때 바람직한 경화조직을 나타내었다.

Kaolin has been revealed to show an alkali-activation reaction by dehydrating at an adequate temperature and mixing with sodium hydroxide solution at the temperature over 60℃. But the reactivity is not sufficient for the formation of Na-Si-Al geopolymer with a strength of practical use. In this study, sodium silicate was added to the same system as a common ion and its accelerative effect on the geopolymeric reaction was investigated. Setting time of a fresh paste prepared with calcined kaolin powders and sodium hydroxide/silicate solution was measured at 90℃ and then mineralogical and microstructural assessment for the hardened paste were performed. By the addition of sodium silicate, the setting time of most of pastes was reduced and a gradual delaying in setting time occurring at the temperature over 650℃ was eliminated. Hardening of a paste was accomplished with formation of dense and amorphous binding phases from the set paste and more desirable texture of hardened body could be obtained by using a completely dehydrated kaolin rather than an imperfectly dehydrated kaolin as a starting row materials.