Thermal Treatment and Pozzolanic Activity of Calcined Clay and Shale.

TIRONI, ALEJANDRA; CASTELLANO, C. C.; SCIAN, A.N.; IRASSAR, EDGARDO FABIÁN; TREZZA , M.A.; DONZA, H.A.; BONAVETTI,V.L.; RAHHAL, VIVIANA F.

ACI MATERIALS JOURNAL

AMER CONCRETE INST

Lugar: Detroit; Año: 2019 vol. 116 p. 133 - 143

0889-325X

Clay minerals are the most abundant raw materials for calcined pozzolans. Thermal transformation includes: dehydration; dehydroxylation, mineral collapse and neo-formation. Depending on the type and amount of clay mineral, the nature and amount of associated minerals, the thermal treatment determines the pozzolanic activity. In this paper, ten natural shales or clays (6 illite, 2 kaolin and 2 loess) from Buenos Aires Province (Argentine) were identified using XRD, FTIR and TG. The thermal transformation was checked by XRD or FTIR and the electrical conductivity (EC) at the calcination window. The pozzolanic activity was evaluated using the Frattini test and strength activity index (SAI). Frattini test gives positive results after 7 days and SAI is greater than 0.90 at 28 days, but the compressive strength development depends on main clay mineral. The EC was effective to evaluate the Ca(OH)2 fixation during the first time and it is related to the specific surface obtained.