Earlier work at Staffordshire University revealed encouraging results when sewage sludge ash from a fluidized bed incinerator was added to a series of common commercial brickclays used in the United Kingdom. The results of this work led a United Kingdom brick manufacturer to the identification of this material as a possible replacement for the sand addition to the bricks produced at one of their factories. As a result, an experimental programme was formulated at Staffordshire University's Ceramic Technology Laboratory which used the factory's current mix-design as a control standard against a mix-design in which the sand component was replaced weight-for-weight with sewage sludge ash. Comparative bodies were fabricated and both laboratory and factory firings undertaken. Physical testing results have revealed that the experimental mix-design containing the sewage sludge ash contributes positively to the ceramic properties of the control product in both the unfired and fired condition. Moreover, the fired colour of this experimental product has also been found to be indistinguishable from the control.
Anderson, M., Skerratt, R. G., Thomas, J. P., & Clay, S. D. (1996). Case study involving using fluidised bed incinerator sludge ash as a partial clay substitute in brick manufacture. Water Science and Technology, 34(3-4–4 pt 2), 507–515. https://doi.org/10.1016/0273-1223(96)00618-X