Abstract
Complex additives based on combinations of calcined clays, including kaolinite with limestone, due to the synergetic effect play a major role in the creation of blended cements. Usually carbonate rocks contain clay impurities with adverse effects on the properties of the resultant cements and concretes. At the same time calcium carbonate contained in marl clays during calcination allows getting high-quality pozzolanic material. The effective complex additive based on the calcined mixture of clay and limestone was created. The aim of the study is to determine the effect of fast and slow cooling methods of the artificial mixture after calcination on the hydration products composition of blended cement stone with complex additives of calcined mixtures of clays and carbonates. Obtained results allow determining the conditions for obtaining effective complex additives based on calcined mixtures of ubiquitous clays and carbonate rocks for their application in blended Portland cement, and thus to expand the range of the latter. It is found that the preferred method is the fast cooling of the resulting mixture, which contributes to obtaining a complex additive with higher pozzolanic properties, compared with the additive obtained by the slow cooling method.
Highlights
Complex additives differing by the synergetic effect presence in the co-introduction of multiple mineral additives play a major role in the blended cements creation [1,2,3,4,5]
The blended cement with 20 % of complex additive based on calcined mixture of kaolinitic clay and limestone L1; 3
The blended cement with 20 % of complex additive based on calcined mixture of polimineral clay and limestone L2; In Fig. 3 simultaneous TG-DTA of control sample OPC cement stone is submitted
Summary
Complex additives differing by the synergetic effect presence in the co-introduction of multiple mineral additives play a major role in the blended cements creation [1,2,3,4,5]. Carbonate rocks contain clay impurities with adverse effects on the properties of the resultant cements and concretes. At the same time calcium carbonate contained in marl clays during calcination allows getting high quality pozzolanic material. The main products formed during low-temperature solid-phase synthesis are: onecalcium aluminate, which is formed at a temperature of 500 oС [6] and dicalcium silicate, which is formed at 700-800 oС [6, 7]. Dicalcium silicate according to N.A. Toropov [8] can exist in five modifications; three of them are formed only as a result of sintering. For lowtemperature solid-phase synthesis, βС2S and γС2S are characteristic. The first one is active, but unstable and, upon slow cooling, is capable of transforming into the second, which is extremely undesirable, due to the fact that γС2S does not possess hydraulic properties under normal conditions
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