Change in Microstructure, Mechanical Strength, Fire Resistance, and Radiation Attenuation Properties of Gypsum Plaster with Boric Acid

Abstract

In this study, the effect of boric acid addition on the microstructure of gypsum plaster was investigated to determine an environmentally friendly gypsum additive that may enhance mechanical strength, fire resistance, and X-ray radiation attenuation properties. The mechanical strengths of bare gypsum and boric acid-added (0–0.5% by weight with respect to gypsum amount) gypsum plasters were evaluated in terms of compressive and bending strengths. The effects of the different addition procedures of boric acid (0.1% by wt.) on the fire resistance of the gypsum plasterboard were also evaluated. X-ray radiation attenuation properties of boric acid-added (0.1% by wt.) gypsum plasterboard were investigated as well. XRD, ATR-FTIR, Helium pycnometer, N2 adsorption–desorption, and SEM analysis were performed to determine the microstructural properties of gypsum plaster. XRD and ATR-FTIR analysis revealed that boric acid did not change the calcium sulfate dihydrate structure of gypsum plaster. Whereas, Helium pycnometer, N2 adsorption–desorption, and SEM analysis showed that the physical properties of gypsum changed with an increase in pore volume, skeletal density, and particle size after boric acid addition. The increase in the pore volume and particle size decreased the mechanical strength of gypsum. However, boric acid addition on the gypsum plaster plate, especially using the spraying method, enhanced the fire resistance of gypsum. Additionally, boric acid slightly enhanced the X-ray radiation attenuation properties (0.7%) of the gypsum plasterboard.