Preparation of eco-friendly lightweight gypsum: Use of beta-hemihydrate phosphogypsum and expanded polystyrene particles

Abstract

Beta-hemihydrate phosphogypsum (β-HPG) as a cementitious material can be used for the preparation of lightweight gypsum to facilitate the utilization of phosphogypsum (PG) and reduce the energy consumption of buildings. In this work, expanded polystyrene (EPS) particles as lightweight aggregates were mixed with β-HPG during the preparation process. In order to improve the hydrophilicity of EPS particles, core–shell EPS particles were obtained by the modification of ethylene–vinyl acetate copolymers (EVA), triethanolamine (TEA) and the coatings of SAC paste. Effects of core–shell EPS particles and calcium sulphoaluminate cement (SAC) on the performance of lightweight gypsum were evaluated by compressive strength, bulk density, thermal conductivity and microstructure. The results show that lightweight gypsum with core–shell EPS particles has better interface and higher compressive strength compared to that produced with unmodified EPS particles. Moreover, SAC can further increase the compressive strength of lightweight gypsum. Ettringite, aluminate hydroxide and C-S-H gels are formed to optimize the microstructure and increase the compressive strength of lightweight gypsum through the addition of SAC. Eco-friendly lightweight gypsum with high compressive strength, adjustable bulk density and low thermal conductivity can be prepared. In general, this study provides a high value-added product for the utilization of PG and the improvement of building energy efficiency.