Influences of high-volume fly ash and bottom ash as feldspar replacements on eco-friendly ceramic building materials

Fly ash and bottom ash in concrete have been extensively studied for decades. Nevertheless, there are few studies on applying fly ash and bottom ash in ceramic building materials, especially in the literature on physical properties and thermal shock resistance. So far, a large amount of bottom ash is buried every year. In this study, the by-products of thermal power plants, which include coal-fired fly ash and bottom ash, are used to replace 10%, 20%, 30%, 40%, 50%, and 60% of the weight of the ceramic raw material (feldspar) to produce ceramic building materials. The sintering temperature ranges from 1100 to 1200°C. Various tests were conducted to determine their performance and thermal shock resistance. According to the test results, the high-volume fly ash and bottom ash samples can be sintered into facing bricks after high-temperature sintering. The shrinkage rate decreases with the amount of addition, reducing volume loss. Warping meets the flatness specification, bending strength far exceeds the standard requirement, and no defects occur after the thermal shock resistance test. The color becomes increasingly saturated in brown with the amount of addition. These results demonstrate that coal ash can be sintered into building ceramics that meet the specification requirements. This suggests that manufacturing fired ceramic building materials using 10% to 60% coal ash is one of the sustainable recycling methods.