The influence of the addition of calcium carbonate on the energy efficiency of fired clay bricks manufacture

Abstract

The results of a study that assesses the effect of adding small amounts of calcium carbonate as fluxing agent on fired Clay bricks are presented. The paper aims to improve the energy demand of fire clay bricks manufacture through the reduction of firing temperature and process duration. The paper shows that additions in the range of 2-5 % (wt) of clay improves compressive strength of bricks fired at temperature around 900 ºC and sintering times between 1-3 hours. This effect would be caused by modifications of the mineralogical transformations through which clay minerals undergo in the presence of calcite, which reduces sintering temperature in clays containing mainly montmorillonite. This paper presents a broad study of the changes of phisico-chemicalmechanical properties at both macroscale and microscale levels. The results show a consistent increase in compressive strength, associated with the formation of the phase anorthite within the reaction products. These results were tested in real prototypes, where the compressive strength of the manufactured bricks increased by 40-50%, while the energy demand decreased by 30-50%.