The Reuse of Plasterboard as an Additive in the Manufacture of Bricks as an Effective Way of Improving Their Durability

This paper investigates the feasibility of recycling plasterboard from suspended ceilings as an additive in brick production. To this end, five types of bricks were manufactured by hand, using a clayey soil from Guadix (Granada, Spain) to which either 10% or 20% by weight of plasterboard was added with two different particle sizes (fine and coarse). A control brick made without additives was also prepared. The samples were fired at 950 °C and then analyzed using X-ray diffraction, polarized optical microscopy, scanning electron microscopy, hydric tests, ultrasound, colorimetry, and salt crystallization tests, so as to assess the effects of the additive on the properties of the bricks. The results revealed that in the bricks made with added plasterboard, anhydrite was formed after firing, along with other characteristic phases of bricks (quartz, illite/muscovite, feldspars and hematite). Anhydrite crystals sintered during the firing process. Use of the additive produced low-to-moderate chromatic changes and created a good bond with the clay matrix. Hydric tests and ultrasound demonstrated that the addition of plasterboard decreased compactness and increased water absorption and open porosity, particularly at 20% by weight. By contrast, the salt crystallization test showed that the samples containing plasterboard, especially those with 20% by weight, were more resistant to decay than the control bricks. Overall, the results show that plasterboard could be a viable additive in brick manufacturing.