A Comparison of Thermal and Mechanical Properties of Clay Bricks Prepared with Three Different Pore-Forming Additives: Vermiculite, Wood Ash, and Sawdust

The thermal and mechanical properties of fired clay bricks containing three different pore-forming additives at comparable concentrations (~25 wt %) were investigated. The additives included three types: inorganic (vermiculite), organic (sawdust), and ash (wood ash). These additives have very different pore-forming mechanisms during the firing process and leave very different residuals in the fired brick. Brick properties are affected by the brick forming process (e.g., the raw materials, forming, drying, and firing processes), and so there is wide variation in the effects of additives on brick properties in the published literature. Therefore, the objective of this effort was to compare selected properties of fired clay bricks with different types of additives, while keeping the brick forming process the same. In this study, the trends in bulk density, porosity, water absorption, compressive strength, and thermal conductivity with incorporation of additives in clay bricks support those that have been published. However, the thermal conductivity of the brick with 25 wt % wood ash was comparable to that for the brick without additives, despite having greater porosity and lower bulk density. This supports that both the pores formed during the firing process and the residuals of the additives significantly impact the brick properties. (c) 2019 American Institute of Chemical Engineers Environ Prog, 38: e13150, 2019