Synergistic effect of mineral admixture and bio-carbonate fillers on the physico-mechanical properties of gypsum plaster

The present study proposes a new strategy to develop a composite gypsum binder with enhanced strength and stability using mineral admixture (zeolite) and bio-carbonate fillers (waste shell powders). The produced gypsum composites were experimentally investigated to study the synergistic effect of zeolite (natural and calcined) and shell powders (egg, conch, cuttlebone and scallop) on the physical and mechanical properties of gypsum composites. The mechanical strength evaluation showed desirable results due to the filling ability as well as reinforcing property of the shell powders when used in combination with zeolite. In addition the natural zeolite acted as internal curing agent and enhanced the gypsum hydration due to their water imbibing quality thus providing high water of crystallization for gypsum formation. The calcined zeolite acted as densifying agent and improved the water stability and reduced the total porosity of the gypsum matrix. The X-ray diffraction studies and IR spectroscopic results showed well hydrated crystalline gypsum dihydrate phases and the SEM images showed significant improvement in the morphology of the plaster leading to enhanced water and thermal stability. Thus the proposed design strategy proves to be a technical solution for the production of high performance gypsum composites utilising the binding capacity of zeolite and filling ability of waste shell powders. (C) 2019 Elsevier Ltd. All rights reserved.