Recycling of washed olive pomace ash for fired clay brick manufacturing

• Pretreated ash from olive pomace is used as raw material for brick manufacturing.
• Pretreating ash by leaching is also useful for obtaining potassium-rich solutions.
• Leached ashes are a pore former in bricks improving thermal conductivity.
• Mechanical properties of resulting bricks fulfill product requirements.

Milled or micronized washed olive pomace ash was used to replace different amounts (5 and 10 wt%) of clay in brick manufacture. The properties of these bricks were compared to conventional products following standard procedures. Bricks formed with ash showed a decrease of 0.13–0.16 W/m K in thermal conductivity. With a minimum bulk density and bending strength of 1790–1810 kg m−3, and 10–12 N mm−2, respectively, fired bricks fulfil standard requirements for clay masonry units. Milled ash performs better than micronized ash. The ash leachate is a valuable source of potassium for the manufacture of fertilizers.