Gypsum plaster using rock waste: A proposal to repair the renderings of historical buildings in Brazil

Abstract

Most of the historical buildings around the world have been suffering from wear of their external coatings, which require constant repair to maintain the aesthetic and cultural characteristics of these buildings. This exploratory research evaluated the rendering plasters of four historical buildings located in Campos dos Goytacazes, in the interior of the state of Rio de Janeiro, Brazil, by consulting historical data, architecture analysis and characterization of the external coatings, which were identified as gypsum plasters. Thus, a methodology was proposed to evaluate the feasibility of using a new gypsum plaster, with the use of rock waste, to repair these valuable coatings. 1:3:0.8 plasters (gypsum:sand:water) were used, using waste to replace sand and gypsum, performing the analysis of the main parameters in the fresh (consistency, incorporated air content, mass density, water retention and squeeze-flow) and hardened state (density, mechanical strength, water absorption and adhesion). The results proved the feasibility of using the waste in renderings to repair the studied buildings, namely when 25% of sand was replaced with waste. With this composition, flexural strength increased from 0.91 MPa to 1.33 MPa and compressive strength from 1.89 MPa to 3.18 MPa.