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 transfo rmed to clinoptilolite and mordenite tuffs. The former are porous and relatively soft, whereas the latter are massive and hard. The diagenet ic transformation of volcanic glass to clinoptilolite and mordenite to ok place in an open hydrological system by circulation of alkaline gro und waters. The fluids responsible for mordenite formation had probabl y higher temperature than that of clinoptilolite due to high heat flow rates originating from the emplacement of lavas in their vicinity. Ev en though clinoptilolite and mordenite tuffs have similar chemical ana lyses, the composition of mordenite exhibits lower variability than th at of clinoptilolite. Regarding cement properties, those cements conta ining mordenite tuff have a slightly higher strength than that of ceme nts with either Miles pozzolana or clinoptilolite tuff. The higher str ength of mordenite cement is probably due to the higher zeolite conten t of the mordenite tuff and also its higher reactive silica content. I n 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 tha t a superplasticizer needs to be added in the mixture. In conclusion, the use of zeolitic tuffs as an additive in cement is promising. Howev er, the full evaluation of these materials demands a thorough examinat ion in areas related to their specialised properties and also extended testing on concrete produced with these materials. (C) 1997 Elsevier Science Ltd.