Synergistic effect of fly ash and glass cullet additive on properties of fire clay bricks

Abstract

In this paper, the physical property and compressive strength of fire clay bricks incorporating combined fly ash (FA) and glass cullet (GC) were studied. Clay bricks were fabricated with the incorporation of FA-GC powder (FA: GC = 1:1) at 0, 2, 4, 6, and 8% by weight of clay and fired at 950, 1050, and 1100 °C. The physical properties viz., firing shrinkage, porosity, density, and compressive strength were tested. The results showed that the increase in FA-GC content decreased the porosity and water absorption; and increased the firing shrinkage, bulk density, and strength of the fire clay bricks. The fire clay brick with a required compressive strength of over 17.2 MPa per ASTM C62-13a could be obtained with 4% FA-GC and a low firing temperature of 950 °C. The linear firing shrinkage of this brick was 3.9%, which was slightly higher than that without additive. The incorporation of FA increased the strength through the increased SiO2, Al2O3, and MgO from the ash. Whereas the GC acted as a flux and helped the fused-bonding of glass phase with clay, facilitated the crystalline quartz fusion, and enabled sintering at reduced temperature. As a combined additive, the GC-FA imparted a synergistic effect in producing fired clay brick at lower firing temperature and maintaining sufficiently high strength.