Properties of recycled gypsum plaster with additives

• Grant number: 13/12145-3
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: September 01, 2013
• End date: September 01, 2015
• Field of knowledge: Engineering - Civil Engineering - Construction Industry
• Principal Investigator: Gladis Camarini
• Grantee: Natalia Reggiani Manzo
• Host Institution: Faculdade de Engenharia Civil, Arquitetura e Urbanismo (FEC). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil

Abstract

Gypsum has the property to lose ¾ of water molecules, during calcination, turning into hemihydrate (gypsum) which, in contact with water, rehydrates up recovering the original form of the dihydrate. The plaster in contact with the water passes through stages of dissolution, nucleation, and recrystallization. After a certain time (setting time) the paste hardens and gains strength. The physical characteristics of the hardened product depend on the crystalline structure formed during contact with water. This allows the use of additives to modify the plaster properties, enabling it to obtain a product with the desired characteristics for its industrial use. This study aims to investigate the influence of the addition of different organic acids on the properties of recycled gypsum from construction. It will be tested in this study, citric acid, tartaric acid, and tannic acid also. Tests are performed: setting times, consistency and heat of hydration, compressive strength, hardness, and air permeability of recycled gypsum binders. The study will assess if the additive influences the properties in the fresh state, especially the fluidity of the paste, without interfering with their performance in the hardened state. (AU)