Zeolitic tuffs of Kimolos island, Aegean sea, Greece and their industrial potential

Tuffaceous rocks and lavas of the Pliocene age exist on Kimolos Island, Aegean Sea, Greece. These tuffaceous rocks have been locally transformed to clinoptilolite and mordenite tuffs. The former are porous and relatively soft, whereas the latter are massive and hard. The diagenetic transformation of volcanic glass to clinoptilolite and mordenite took place in an open hydrological system by circulation of alkaline ground waters. The fluids responsible for mordenite formation had probably higher temperature than that of clinoptilolite due to high heat flow rates originating from the emplacement of lavas in their vicinity. Even though clinoptilolite and mordenite tuffs have similar chemical analyses, the composition of mordenite exhibits lower variability than that of clinoptilolite. Regarding cement properties, those cements containing mordenite tuff have a slightly higher strength than that of cements with either Miles pozzolana or clinoptilolite tuff. The higher strength of mordenite cement is probably due to the higher zeolite content of the mordenite tuff and also its higher reactive silica content. In addition, when compared to Miles pozzolana, the zeolite tuffs demand more water to produce paste of the same consistency. This means that when zeolitic cement is used for concrete production, it is likely that a superplasticizer needs to be added in the mixture. In conclusion, the use of zeolitic tuffs as an additive in cement is promising. However, the full evaluation of these materials demands a thorough examination in areas related to their specialised properties and also extended testing on concrete produced with these materials. (C) 1997 Elsevier Science Ltd.