Sawdust recycling in the production of lightweight bricks: How the amount of additive and the firing temperature influence the physical properties of the bricks

Abstract

This paper studies the influence of sawdust on the petrophysical properties of solid bricks. Brick samples without additives were handmade using a clayey earth that is rich in quartz and phyllosilicates and has some carbonate content. Similar bricks were made with added sawdust at 2.5%, 5% and 10% weight. The bricks were fired in an electric kiln at 800 °C, 950 °C and 1100 °C. The addition of sawdust did not change the mineralogy of the fired bricks. As the firing temperature increased, the quartz content fell and carbonates and phyllosilicates disappeared causing new silicates (gehlenite, wollastonite, anorthite and diopside) to develop. There was an increase in the vitrification of bricks, which also became more compact. At high firing temperature, the bricks had a higher water absorption capacity and worse interconnection between the pores. The high level of vitrification reached at 1100 °C enabled greater transmission of heat inside the bricks. The most refractory bricks were those fired at 800 °C with a 10% sawdust content. When subjected to the salt crystallization test, the most resistant bricks were those with the lowest sawdust content and the highest firing temperature.