Investigation of using bottom or fly pine-olive pruning ash to produce environmental friendly ceramic materials

The present study investigates the feasibility of using fly or bottom biomass ash as a partial replacement in the production of eco-friendly construction materials. The fly and bottom ashes from combustion of biomass (olive pruning and pine pruning) generated in a Spanish Power Plant were used as raw materials to replace clay for the production of fired bricks. First, the mineralogical and chemical composition and thermal behavior of the ashes and clay were determined. Next, ceramic bricks were manufactured by compressing clay and different quantities of fly or bottom biomass (0-30 wt%). Different firing temperatures, 900 and 1000 °C, were studied. The effect of adding fly or bottom biomass ash on the technological behavior of the brick was assessed by studying linear shrinkage, water absorption, bulk density, compressive strength, thermal conductivity and the morphology. The results have shown that the optimum sintering temperature was 1000 °C. The increase in the firing temperature from 900 to 1000 °C, raised the compressive strength and decreased the water absorption. The addition of 30 wt% of bottom or fly biomass ash produced bricks with very high water absorption values and low mechanical properties. Based on the results obtained, the optimum amounts of bottom or fly ash were 20 wt%. These percentages produced bricks whose mechanical properties were suitable and thermal conductivity decreased by 21% respect to the standard bricks. The addition of bottom biomass ash produced bricks with slightly better properties, due to the most appropriate composition of these ashes. The bricks do not present environmental problems according to the leaching study. Therefore, fly and bottom biomass ash from the combustion of olive-pine pruning could be used as secondary raw materials in ceramic brick production.