Effect of wetting-drying cycles on gypsum plasters containing ground basaltic pumice and polypropylene fibers

Abstract

Gypsum plaster is a widely used construction material. It is preferred because it is lightweight, fire-resistant and has good thermal properties. This study demonstrated the use of ground basaltic pumice in polypropylene fiber reinforced gypsum plasters. Twelve different series of 40 x 40 x 160 mm size gypsum plaster samples were produced. Ground basaltic pumice (GBP) was used at 10%, 20%, and 30% while polypropylene fibers (PP) at 0.5% and 1%, by weight. In addition, class F fly ash was used in the series at a constant amount. The unit weight, ultrasonic pulse velocity, apparent porosity, and water absorption values of the samples were obtained. In order to determine the mechanical properties of the samples, compressive and bending strength values were performed. Furthermore, the thermal conductivity coefficients of the samples were measured. Twenty five wetting-drying cycles were applied to the samples to perform accelerated aging. After the application of the wetting-drying cycles the mass changes, apparent porosity values, thermal conductivity coefficients, and compressive strengths of the samples were determined. Additionally, scanning electron microscope tests were used in order to examine the microstructure. The results showed that, while GBP had negative effects on the mechanical properties of the samples. The samples had a compressive strength loss of up to 7 MPa, which varied depending on their GPB content. On the other hand, GBP addition improved the thermal insulation properties. The thermal conductivity coefficients decreased from 0.580 W/mK to 0.406 W/mK. PP fiber addition increased the bending strength of the reference sample up to approximately 21.5% and the bending strength of the GBP containing samples up to 14%. In addition, PP addition also reduced the negative effects of the wetting-drying cycles which in turn decreased the strength loss between 5.5%-7%.