Iranian Eocene Green Tuffs as Natural Pozzolan for Use in Cement Industries

Eocene Green Tuffs are widespread in Central Alborz in the north of Iran. In parts, they are used as natural Pozzolan. In this study, the Pozzolanic activities of tuff samples from Qazvin to Semnan in Alborz Mountain were examined. The Pozzolanic activity patterns vary in different beds and even change laterally. Chemical examination of the samples indicated that they all belong to acidic rock group and were consistent with related standards. Pozolanic activity calculated for samples using hydraulic factor, thermal analysis and ion concentrations. Data obtained based on thermal analysis, presented a range of Pozzolanic activities for tuffs with similar chemistry and appearance. It was found in this research that mineralogy and texture controlled Pozzolan activity. Tuffs with high activity had glass in their matrix, but weathering and recrystallization reduced the activity. Petrographical examinations play an essential role in evaluating the availability of tuffs as natural Pozzolan in Central Alborz.