On the production of fired clay bricks from waste materials: A critical update

Recently, the production of bricks from waste materials was reviewed by Zhang in Construction and Building Materials. The main focus was a division into three producing methods: firing, cementing and geopolymerization. Both firing and cementing methods were indicated to consume significant amount of energy and release large quantities of greenhouse gases. Based on these drawbacks and taking into account the need to protect clay resources, it was concluded that geopolymerization seems to be the trend to follow. Most of the reviewed works on the firing method, published since 1987, were related to wastes incorporated into clay ceramics. In the present work, starting from previous review articles, additional information was added to extend the knowledge, not covered by Zhang, on the incorporation of wastes into clay ceramics. The particular case of Brazil, in which large and easy to mine clay deposits support an extensive network of ceramic industries, is surveyed. Fuel containing wastes contribute to save in firing energy, while fluxing wastes improve the ceramic properties. At least for the next decades, clay ceramic incorporation seems to be the most realistic solution for recycling industrial wastes in countries, such as Brazil, with vast clay resources.