Serra Geral Formation—São Paulo State, Brazil: a potential source for natural pozzolans

The Serra Geral flood basalts cover an area of approximately 1.2×10 6 km 2, which corresponds to 75% of the Parana Basin. The Serra Geral flood basalt province is one of the largest of the world with a total volume of lava flows exceeding 1.0×10 6 km 3. The Serra Geral Formation comprises a variety of basic (90% of total volume), intermediate (7%) and acid rocks (3%). Intermediate and acid rocks were focused as targets of an exploration program carried out for natural pozzolans. In Sao Paulo State, these rocks crop out in the western portion. This paper presents results of a detailed sampling program and laboratory work which led to the identification of potentially pozzolanic rocks. Some of these rocks gave compressive strengths at 7 days between 3 and 6.4 MPa. Besides, for rocks with compressive strengths under 6.0 MPa, the thermal activation was effective improving their pozzolanic properties. Considering these results as well as the area of occurrence, we conclude that intermediate and acid rocks of the Serra Geral Formation in the western portion of Sao Paulo State represent a potential source for natural pozzolans.