INFLUENCE OF REDISPERSIBLE POLYMER POWDER ON THE MICROSTRUCTURE AND PHASE COMPOSITION OF GYPSUM CONCRETE CONTAINING LIME WASTE

The study investigates the structural and physicochemical characteristics of gypsum concrete containing lime waste and Redispersible Polymer Powder (RPP). The composition selected for the investigations consisted of 75% G-6 gypsum, 25% lime waste and 0.10% RPP relative to the mass of dry components. The physicochemical characteristics of the modified gypsum concrete were studied using thermogravimetric and differential thermal analysis, X-ray diffraction, infrared spectroscopy and scanning electron microscopy. Thermal analysis of gypsum concrete containing 0.10% RPP showed that the principal mass loss occurred in the temperature range of 301.08–601.24 °C, while a pronounced thermal effect was recorded at approximately 414.49 °C. X-ray diffraction analysis identified gypsum (CaSO₄·2H₂O) as the main crystalline phase and quartz (SiO₂) as a secondary phase. The crystallite size of gypsum in the (020) direction was calculated to be approximately 100 nm. Comparative scanning electron microscopy of samples with and without RPP showed denser intercrystalline contacts and a decrease in structural voids in the modified material. Infrared spectra of the samples also demonstrated differences in characteristic absorption regions, indicating changes in the physicochemical structure of the gypsum matrix after the addition of RPP.