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.