Thermal Activation of Two Complex Clays (Kaolinite-Pyrophillite-Illite) from Tandilia System, Buenos Aires, Argentina

E.F. IRASSAR; A. TIRONI; TREZZA M.A.

La Habana

Congreso; 2º International Calcined Clays for Sustainable Concrete; 2017

EPA, RILEM

Abstract. The aim of this work is focused to identify natural resources withindustrial potential to be used as supplementary cementitious materials (SCMs)in Portland blended cements. Two clays obtained from the quarries near to Barkerin Tandilia System (Buenos Aires- Argentina) were studied. The geneses of theserocks are by a hydrothermal alteration and include the presence of pyrophillite.Whole-rock were characterized by XRD and FTIR spectroscopy indicating thatmain clayed minerals are kaolinite (Si2Al2O5(OH)4), illite (K0.66Si3.33Al2.66O10(OH)2) and pyrophillite (Si4Al2O10(OH)2) associated with feldspar. Thethermal transformation was studied by differential thermal analysis and the phasechanges were confirmed by XRD and FTIR. Samples of clays were calcined atdifferent temperature (550 to 1050 °C), the electrical conductivity was measuredand the dissolved silica in simulated pore water solution was quantified. Thepozzolanic activity was measured by the compressive strength activity index, onblended cement mortars containing 25% by weight of calcined clays.Results showed pozzolanic activity after 7 days and the compressive strengthvalues exceed the rate of replacement for both clays. The high water demand ofsample containing pyrophillite can be attributed to the exfoliation that occursduring the water loss process.