Reinforcement of the microstructure of gypsum board composite with modified calcium carbonate, sulfonate, and starch to reduce water absorption and increase mechanical strength

This research was conducted to enhance the strength and reduce the water absorption of gypsum board. Initially, the effect of unbleached fiber was examined, followed by an investigation into the impact of calcium carbonate modified with stearic acid, lignosulfonate, polyvinyl alcohol, corn starch, and tapioca on the flexural strength of the samples. These additives were incorporated into the plaster at varying levels to determine the most effective amount for improving the properties of the gypsum board, including bending strength, through trial and error. The compressive strength, water absorption, density, and microstructure of samples from optimal treatments were analyzed. The results revealed that stearic acid formed a coating layer on the calcium carbonate particles, reducing moisture absorption to approximately 1.1 times that of untreated fibers compared to the control samples. Furthermore, the compressive strength increased in all treatments with unbleached pulp compared to the control samples, with tapioca starch showing the most significant increase at 2.3 times that of the control samples. Electron microscope images displayed a uniform distribution of gypsum fibers and crystals, resulting in a homogeneous texture and proper connection between them. Despite falling into the low-density category (0.74 g/cm3), the optimal treatment samples exhibited higher compressive strength than the minimum standard value. The produced gypsum boards demonstrated standard resistance and appropriate water absorption.