Studies on the feasibility of using certain admixtures for enhancing the performance of gypsum plaster

Abstract

Gypsum plaster has been utilized by mankind for construction purposes since time immemorial and is still being in use for several structural applications. Last few decades is accompanied by a tremendous growth in the usage of gypsum plaster for internal plastering and several other structural applications. The negative impacts associated with the production of cement contributes significantly towards the increase of global warming by releasing of large amounts of CO2 therebymaking gypsum plaster as a material of choice over the conventional cement plaster. Though the usage of gypsum plasters is widespreaddue to their several advantages their brittleness and poor water resistance poses a serious setback for use of gypsum plaster in exterior applications. To delimit the boundaries of usage of gypsum plaster beyond certain interior applications, more significant and advanced modifications in the gypsum plaster is required without causing any negative impact on the environment and social health. The research works explained in the dissertation details the methodologies adopted to improve the strength and stability of the gypsum plaster through the incorporation of certain admixtures. The adopted research methodology is multidisciplinary in nature which involves a detailed investigation on the physical, mechanical, durability, thermal and micro structural properties of gypsum plaster due to the additions of chemical admixtures (superplasticizer and SBR latex), bio based fillers (shell powders) and mineral admixture (zeolite). Strength improvement, pore structure refinement, water stabilization and microstructure enhancement are the four key research areas focussed in the present study. Investigations were done through a series of scientific papers which centred on the key research disciplines thereby achieving the objective of the research work The first study aims at analyzing the combined effects of individual additions of different active water reducing agents (superplasticizers) with polymer bonding agent (SBR latex) on the properties of gypsum plaster. Three commercially available superplasticizers were added to the latexgypsum blends at various percentage increments of 0.2% to 1%. The characterization of superplasticized latex plaster blends was done by measuring the wide range of properties of latex-gypsum plaster. Initially the combined effects of latex and super plasticizer concentration on the fresh state properties of the plaster were analyzed. The fresh state results showed that the water demand was much reduced without affecting the workability. The mechanical properties investigation proved that the properties of the plaster were much enhanced with improved water resistance behaviour. The microstructure studies using Scanning Electron Microscopy confirmed the denser and compact gypsum grains with mass reduction in porosity. A significant improvement in thermal stability and electrical conductivity of the plaster was also observed in the superplasticizers-latex blended gypsum plaster newline