Recycling of sawdust, spent earth from oil filtration, compost and marble residues for brick manufacturing

This paper studies the application of a variety of waste materials in the production of lightweight bricks: sawdust, spent earth from oil filtration, compost and marble. First, the mineralogical and chemical composition and thermal behaviour of the wastes and clay were determined. Next, ceramic bricks were fabricated with different quantities of waste (0–10 wt.% for sawdust, 0–20 wt.% for marble, and 0–30 wt.% for compost and spent earth from oil filtration). These bricks were fired at 950 and 1050 °C. The effect of adding these wastes on the technological behaviour of the brick was assessed by linear shrinkage, water absorption, bulk density, suction absorption, compressive strength and scanning electron microscopy (SEM). The results have shown that the optimum sintering temperature is 1050 °C. Below this temperature, at 950 °C, increased open porosity was observed, which decreased the compressive strength of the bricks. Based on the results obtained, the optimum amounts of waste were 5 wt.% sawdust, 10 wt.% compost and 15 wt.% spent earth from oil filtration and marble. These percentages produced bricks whose mechanical properties were suitable for use as secondary raw materials in ceramic brick production.

► The incorporation of wastes increased the total porosity of the bricks. ► The firing temperature has an effect in the type of porosity. ► At 950 °C, the porosity is mainly open while at 1050 °C the porosity is closed. ► The higher temperature increased the compressive strength of the samples. ► All bricks met the UNE standards and can be used as green construction materials.