Effect of citric acid on properties of recycled gypsum plaster to building components

Gypsum plaster recycling shortens the setting times, changing the workability and becomes difficult to work with it. The works found in literature studied the a-hemi-hydrate. Few works studied the gypsum plaster recycling with beta-hemihydrate. This experimental work evaluates the performance of recycled gypsum plaster with citric acid to improve the setting times and workability to building components. Recycled gypsum plaster with five admixture contents was used: 0%; 0.025%; 0.05%; 0.1% and 0.25%. The water/plaster ratio was kept constant (1.0) for all the mixtures. The results showed that the citric acid decreases the recycled gypsum plaster consistency, increasing the fluidity. The setting times were increased, but the compressive strength and hardness were diminished. The microstructure also changed with the admixture addition. Even with these changes in gypsum plaster properties, the recycled material can be used to make components because it reaches the minimum values required by the component standards. (C) 2016 Elsevier Ltd. All rights reserved.