Sulfate and Alkali-Silica Performance of Blended Cements Containing Illitic Calcined Clays

FALCONE, DARÍO; CORDOBA, GISELA P.; IRASSAR, EDGARDO F.; ROSSETTI, AGUSTIN

La Habana

Congreso; 2nd International Conference on Calcined Clays for Sustainable Concrete; 2017

Studies of illitic calcined clays are less developed than that corre-sponding to kaolinitic clays, but illite is one of the more abundant clayedminerals of the earth?s crust, as occurs in the Center of the Buenos AiresProvince (Argentina) where the largest cement factories are located. Illite claysdevelop pozzolanic properties when they are thermally treated at 950 °C,causing dehydroxilation and collapse of structure to form a metastable oramorphous aluminosilicate. Illitic calcined clays don?t present a significantwater demand and the compressive strength of blended cements attains to thecorresponding to portland cement at 90 days. It is characterized as slow poz-zolana. Illite incorporates certain proportion of reactive alumina and high pro-portion of alkalis, modifying the pore structure. From durability point of view,the incorporation of illite can affect the sulfate resistance of portland cements orthe alkali-silica reaction (ASR).The aim of this paper is to study the behavior of two different illite calcinedclay blended cements against chemical attack, like sulfate attack and harmfulalkali silica reaction, using the test based on the ASTM C 1012 and ASTM C441, respectively. For sulfate performance, illite calcined clays was blended witha low C3A in 20% and 40% of weight replacement and a very high C3A cement(white), using a 30% of weight replacement; while a low (Na2Oeq < 0.5) andhigh alkali (Na2Oeq = 1.03) cements were used in the ASR-test.After six months, the low and very high C3A cements of both illitic claysshows low expansion in sulfate media (