Experimental study effect of bottom ash and temperature of firing on the properties, microstructure and pore size distribution of clay bricks: A Lithuania point of view

The paper studied the feasibility of reusing the bottom ash (BA) in clay bricks production. The study has researched the influence of BA on clay bricks' physical and mechanical properties, the micro-and structure of samples, resistance to freezing and thawing porosity, average pore size and pore size distribution. Clay bricks were made from BA from 10% to 40% and clay (with CaO less than 1%), fired at 900 and 1000 °C. The open porosity of clay bricks developed when a BA was added due to burning a small amount of organic part of clay, decarbonising calcite, and the release of gaseous substances and crystalline moisture. The infrared spectra of clay brick samples fired at 900 and 1000 °C showed the presence of Si-O, Si-O-Mg, and Si-O-Al bond. These results are consistent with the XRD patterns. Clay bricks' physical and mechanical properties changed with the presence of BA: shrinkage, density and compressive strength decreased, water absorption and open porosity increased. It is recommended to add 10% and 20% BA to the clay body and fire at 900 °C, or 10–30% BA and fire at 1000 °C. In freezing and thawing resistance, clay bricks containing BA10 and BA20 fired at 900 and 1000 °C can be utilized in moderately aggressive environments. Samples containing BA30 and fired at 1000 °C can be used in passively aggressive environments. Micropores predominate in clay bricks; however, with an increase in BA, micropores turn into mesopores. The pore diameter of samples changes with BA and the firing temperature. The specific surface area is directly proportional to the amount of added BA. The use of bottom ash in the production of clay bricks will allow producing clay brick without deteriorating its quality and reduce the consumption of natural resources by up to 30%.