Plaster composites modified morphology with enhanced compressive strength and water resistance characteristics

Abstract

Due increasing attention for non-conventional building materials, modified gypsum plaster composites were studied to assess their water resistance when blended with different additives and their effect on the strength properties. The plaster-composites were formed by dry mixing of fine or ultrafine sand, silica fume, silica gel, rice husk, slag, calcium carbonate or polyvinyl acetate (PVA). Their phase composition was investigated using FTIR and XRD with crystallite size data to be correlated with their microstructure morphologies as elucidated by SEM for the air- and water-cured samples.Results clarified that the morphology and some grain dimensions of set plaster composites have changed leading to improve their compressive strength and water resistance. The set plaster grain dimensions altered from long acicular crystals to short compact thin one. Composites with almost all additives reveal resistance to water whereas silica gel showed lower effect, due to its higher affinity to humidity. The compressive strength and softening coefficient of the water-cured plaster-slag composite increased by about 30% compared with air-cured blank sample due to the hydration of slag in gypsum composite matrix. Either calcium carbonate or PVA usage (3 wt%) in gypsum composites improved the compressive strength by about 14 and 19% of water cured samples, respectively. The synthesized plaster composites are promising building units for various applications when lightweight, high porosity, water resistant building units are needed.