Evaluation of spent diatomite incorporation in clay based materials for lightweight bricks processing

Highlight
- The use of diatomaceous earth residues in the ceramic industry is a sustainable alternative.

In this study, diatomaceous earth residues from two industrial processes, refining of vegetable oils and brewing, have been used as raw materials for brick making. The aim has been to substitute part of the clay traditionally used for the manufacturing of bricks, between 3 and 10 wt.%, with the aforementioned residues, so obtaining ceramic pieces at three firing temperatures: 850, 950 and 1050 °C. The studied properties were compared with those of conventional materials (100% clay), and the results show that these alternative raw materials can be considered technological “nutrients” whose addition improves the behaviour of the materials in the drying process. The incorporation of these materials also increases the open porosity of the fired pieces and reduces the bulk density by up to 10%. The increase in porosity is greater in materials that incorporate diatomites from oil filtration, reaching the maximum value (37 vol.%). These results are confirmed from the microstructure observed by SEM. With regard to mechanical properties, increasing the content of both residues generally decreases the bending strength to values exceeding 10 MPa, thus resulting admissible for use in construction. Moreover, the energy release from the residues during the firing stage is greater than the energy demand required for drying, while the thermal conductivity values of the final materials decreases with the amount of residue, which confers thermal insulating properties to the ceramic pieces and thus can reduce the energy consumption of buildings.