Technical feasibility of reusing coal combustion by-products from a thermoelectric power plant in the manufacture of fired clay bricks

• Thermoelectric power plants produce tonnes of residues that have not been reused.
• Bottom ash was incorporated in clay to produce fired ceramics.
• Bottom ash reduces the melting point of liquid phase during the firing process.
• The incorporation of bottom ash up to 20 wt.% generates ceramics with proper properties.
• The resistance against salt fog increases with the addition of 15 wt.% of bottom ash.

This paper intends to study the suitability of reuse a waste produced by thermoelectric power plants in the clay bricks industry. One of the main by-products is bottom ash and currently only half of these residues are reused; therefore a new environmentally-friendly solution is researched.Besides a chemical and mineralogical characterization of bottom ash, clay bodies were moulded by using clay pastes with 2.5, 5, 10, 15 and 20 wt.% of bottom ash. Then the green bodies were fired at 900, 1000 and 1100 °C and thereafter studied.This bottom ash shows particular features of a fluxing agent which reduces the melting point of the liquid phase, and so the water absorption and open porosity tend to decrease with the increasing amount of waste, while the bulk density increases. Improvements were found; some regarding the mechanical strength and salt fog resistance due to bottom ash incorporation, especially in the case of samples fired at 900 °C with 20% of bottom ash. Since ceramics made from these mixtures reveal good performance at all levels, the bottom ash shows high potential to be used in the ceramic industry.