Synthesis and Characterization of High-Iron Alite-Calcium Sulfoaluminate-Ferrite Cements Produced from Industrial By-Products

Abstract

Ordinary Portland cement (OPC) and calcium sulfoaluminate cement (CSAC) are well-known and commonly used construction materials. The clinker phases mainly responsible for their strength development are C3S (alite) in OPC, which hydrates to form a calcium silicate gel phase; and C4A3Ś (calcium sulfoaluminate) in CSAC, which hydrates to rapidly form ettringite. The purpose of this work was to produce high-iron alite-calcium sulfoaluminate-ferrite cements, by combining C4AF (ferrite), from 5% to 50% by weight, to the C3S and C4A3Ś clinker phases. Producing this alite-calcium sulfoaluminate-ferrite cement would decrease the requirement of bauxite in the raw materials, which would consequently reduce its cost. The use of industrial by-products would also reduce the CO2 emissions and the firing temperature by 200–250uC compared with OPC. This article presents the synthesis and characterization of five compositions produced from industrial by-products (hydrated lime related to carbide lime, fly ash, slag, and red mud) and bauxite, formulated as follows: C3S from 20% to 50%, C2S from 10% to 20%, C4A3Ś from 10% to 20%, C4AF from 5% to 50%, and CŚ from 4% to 6% by weight. The clinker with the lowest ferrite content required a higher firing temperature (1275uC) than the compositions with high ferrite contents (1250uC). Impurities, such as MgO and TiO2, introduced by the industrial by-products affected the mineralogical compositions. Consequently, some adjustments of the raw mix were necessary to obtain the desired clinker compositions. f 2014 The University of Kentucky Center for Applied Energy Research and the American Coal Ash Association All rights reserved. A R T I C L E I N F O Article history: Received 13 May 2014; Received in revised form 3 June 2014; Accepted 6 June 2014