Assessment of pozzolanic activity of different calcined clays

ALEJANDRA TIRONI; MÓNICA ADRIANA TREZZA; ALBERTO NESTOR SCIAN; EDGARDO FABIÁN IRASSAR

CEMENT & CONCRETE COMPOSITES

ELSEVIER SCI LTD

Lugar: Amsterdam; Año: 2013 vol. 37 p. 319 - 327

0958-9465

The pozzolanic activity of calcined clays depends on the type and amount of clayed minerals, the nature and amount of impurities, the thermal treatment used for its activation and the specific surface obtained after calcination. In this paper, four test methods for assessment the pozzolanic activity on seven calcined clays (five kaolinites and two bentonites) were analyzed. Natural clays were calcined and investigated by two direct tests (Frattini and saturated lime) and two indirect tests (strength activity index and electrical conductivity). Frattini test and the strength activity index (SAI) were found to be the most accurate and reliable methods to assess pozzolanic activity over time. Frattini test evaluates accurately the calcium hydroxide (CH) consumption by pozzolanic reaction, and SAI test discriminates the real contribution of pozzolanic reaction to densification of microstructure. The electrical conductivity (EC) and the lime consumption (LC) tests evaluate the ability of pozzolanic material to fix CH during the first time of contact and their results are correlated with the specific surface of calcined clay.