Thermal transformation of illitic-chlorite clay and its pozzolanic activity

LEMMA, ROXANA; TREZZA, MONICA A.; BONAVETTI, VIVIANA L.; IRASSAR, EDGARDO F.; CASTELLANO, CRISTINA C.; RAHHAL, VIVIANA F.

RILEM Bookseries

Springer Netherlands

Lugar: La Habana; Año: 2018 vol. 16 p. 266 - 272

2211-0844

Illite-chlorite clay from quarry located at Buenos Aires Province (Argentine) was characterized by XRD, FTIR and TG-DTA. Mineralogical transformations during clay firing under oxidizing conditions were studied from 100 to 1100, °C by XRD and FTIR. From select temperatures, calcined clay was ground (85% passing to 45, µm sieve) and the pozzolanic activity of blended cements (25% w/w) was evaluated by the Frattini test and the strength activity index (SAI). Finally, the hydration phase assemblage of blended cements was studied using XRD analysis. The solid-state phase transformations of clay during thermal treatment involves: water loss at low temperature; the partial dehydroxylation of chlorite resulting in the ?modified chlorite structure? between 500 and 600, °C and its collapse at 800, °C; the dehydroxilation of illite is completed and its structure collapsed up to at 900, °C. Up to 1000, °C, the clay minerals are collapsed thoroughly, with formation of amorphous compounds. Results of Frattini tests indicate that materials present pozzolanic activity after 7 days when they are fired up to 900, °C, however the best SAI (~1.00) at 28, days occurs for clay calcined at 1100, °C. For blended cements, the hydration products assemblage is similar to plain Portland cement used at all ages.