Evaluation of Technological Properties of Mortars with the Addition of Plaster Byproduct

The incorporation of waste into construction materials is a potential topic for study and is seen as a solution for many industries that face the following impasse: the risk to the environment due to the accumulation of waste in yards. In view of this, during the production of lactic acid, which is widely used in industries, gypsum is produced as a byproduct, yielding one ton for each ton of lactic acid. Aiming at a functional destination for this byproduct, this study proposes its addition in mortars for covering walls and ceilings. The research proposal was a mortar in a 1:6 ratio (cement:sand) with the addition of 0, 3, 6 and 10% of industrial plaster byproduct. The cement used to prepare the mortar was CPII-E32. To characterize the raw materials, scanning electron microscopy, X-ray fluorescence and X-ray diffraction analysis were carried out. To evaluate the properties in the fresh state, a consistency index and mass density and entrained air tests were carried out. In the hardened state, mass density, axial compression strength, flexural tensile strength and water absorption via capillarity were evaluated after 28 days of age. Microstructural characterization techniques were also carried out on the reference mixtures and with 3% addition of the byproduct gypsum, such as scanning electron microscopy and X-ray diffraction. The results showed that the byproduct is hemihydrate and its addition improved the workability of the mortar. Mortars with the addition of byproduct gypsum showed a reduction in mechanical resistance. The most satisfactory results were for the mixes with a 3% addition, indicating greater resistance to axial compression and flexural traction, with 3.90 MPa and 1.14 MPa, respectively.