Enhancement of fresh properties and performances of the eco-friendly gypsum-cement composite (EGCC)

The area of application of gypsum materials is limited to low values of compressive strength, water resistance and durability. An urgent task is to increase the efficiency of the gypsum composite using Portland cement, as well as natural and industrial waste. In this work, complex studies were carried out, including scanning electron microscopy (SEM) images, differemtial-thermal analysis (DTA) and X-ray diffraction (XRD) patterns, small-angle X-ray diffraction, as well as mechanical and durability tests of hardened composites. The influence of gypsum building materials on the environment and humans throughout the life cycle have been determined. The features of the formation of the structure and hardening of the eco-friendly gypsum-cement composite (EGCC) have been studied taking into account the chemical, structural and morphological features of dihydrate gypsum, Portland cement, opoka, perlite and six different modifiers. The effect of various finenesses of grinding components on the performances of the EGCC has been investigated. It has been revealed that the maximum compressive strength of 18.1 MPa of hardened gypsum cement binder is achieved with a specific surface of 600 m(2)/ kg, a further increase in the specific surface leads to a decrease in compressive strength, which is explained by an increase in water demand. Comprehensive chemical additives have been developed that allow a wider range of setting time, from 35 to 72 min. With the introduction of a complex chemical additive, the volume of micropores decreases, which is due to small-sized new growths located in the pore space of the gypsum matrix. All this leads to improving fresh properties and performances of the EGCC. (C) 2020 Elsevier Ltd. All rights reserved.