Granite processing waste as a source of flux for the production of acid resistant sewage bricks

Local Egyptian siliceous plastic clay together with granite processing waste was used in batch formulations for the production of acid resistant sewage bricks. 40-50 % granite waste was added with or without the incorporation of 5 or 10 % of local potash feldspar as a co-flux. Two groups of batches comprising eight mixes were formulated. The processed cylinders were fired between 1000 and 1200 °C. Densification took place between 1100 and 1175 °C. The bodies showed relatively high cold crushing strength between 74 and 127 MPa and high resistance to attack by acids between 0.22 and 0.64 %. These values are better than those required by the Egyptian specifications, i.e. 30 MPa and 3.5 % respectively. The application of granite waste as a source of quartz and feldspar eliminated the grinding step in processing the raw materials. The fine granite waste lowered the temperature of liquid phase formation and its viscosity, leading to the crystallization of neogenic feldspar minerals and thereby incorporating part of the Na + and Ca 2+ ions in their structure. This improved the resistance to acid attack. The application of a co-flux (5 to 10 %) increased the strength and acid resistance of the produced bricks.