Treatment of the Local Construction Gypsum Weak Points by the Addition of 4% w/w White Portland Cement

The amazing properties of structural gypsum make it as a miracle material for finishing construction processes, especially from the health and the environmental point of view. Chemically, the binding forces between gypsum molecules are limited to dipole-dipole interactions (hydrogen bonding) rather than that of fixed conventional bonds. Such relatively weak bonds are responsible for the two common weak points including the water solubility and the relatively low hardness. Therefore, white Portland cement was suggested as an additive for treating those essential disadvantages of construction gypsum. Samples of different ratios at 0.0%, 0.5%, 1.0%, 2.0%, 3.0%, 4.0%, 5.0%, 6.0% and 8.0% w/w of white cement to gypsum were made using 0.07x0.07x0.07m and 0.05x0.05x0.05m test cubes. The standard tests of physical and mechanical properties including hardness, compressive strength, setting time, and water resistance were measured. The results indicate that the presence of cement as an additive could eliminate the weak points of construction gypsum without any negative side effects. The study was supported by an aging investigation using thermodynamic and kinetic analyses. In conclusion, it was strongly recommended to exploit the white cement as an additive at a ratio of 4% w/w or 4.5% v/v to improve the physical properties of building gypsum. It was found that the presence of white cement at the optimum ratio of 4.0% w/w is not limited to eliminating the weak points of gypsum including the relatively low hardness and water solubility, but it extends in supporting other important properties including both the compressive strength and setting time. The suggested additive has many desirable characteristics such as availability, healthy, economical, odorless, no coloring, used in few ratios, easy to deal with, and no volatile organic compounds (VOCs). The presented success can be applied by the construction industry to produce improved gypsum with no weak points.