The production of porous brick material from diatomaceous earth and Brazil nut shell ash

•Lightweight ceramic from low-cost raw materials were achieved at 850°C.•Diatomaceous earth with 10wt% of BNS ash reduced the sintering temperature 100°C.•Addition of 10wt% ash produces lightweight bricks with 8.5MPa at 850°C.•Porous brick obtained at 850°C and 10wt% ash had thermal conductivity of 0.20W/mK. Diatomaceous earth was mixed with Brazil nut shell ash (BNS ash) in different amounts between 0 and 30wt% and sintered at temperatures between 750 and 950°C. The BNS ash contains 33wt% K2O and 11wt% CaO mainly in carbonate form. The addition of BNS ash into the diatomaceous earth caused significant changes of the microstructure after sintering. The BNS ash addition produces lightweight porous bricks with acceptable strength at lower sintering temperature. The best combination of strength and porosity was achieved for a mixture of 10wt% of BNS ash in the diatomaceous earth sintered at 850°C. The achieved high porosity was 49%, density 1.06g/cm3, thermal conductivity 0.20W/(mK) and the compressive strength was 8.5MPa.