Please cite this article in press as: R.A.A. Alves, et al., Mixture design applied to the development of composites for steatite historical monuments restoration, Journal of Cultural Heritage (2020), https://doi.org/10.1016/j.culher.2020.06.001 ARTICLE IN PRESS G Model CULHER-3785; No. of Pages 8 Journal of Cultural Heritage xxx (2020) xxx–xxx Available online at ScienceDirect www.sciencedirect.com Original article Mixture design applied to the development of composites for steatite historical monuments restoration Robinson A.A. Alves , Kurt Strecker , Robson B.D. Pereira , Túlio H. Panzera ∗ Centre for Innovation and Technology in Composite Materials – CIT e C, Department of Mechanical Engineering - PPMEC, Federal University of São João del Rei-UFSJ, São João del Rei, Brazil a r t i c l e i n f o Article history: Received 5 April 2020 Accepted 1 st June 2020 Available online xxx Keywords: Composite materials Restoration Soapstone Characterisation Mixture design a b s t r a c t Natural rocks, as well as artificial man-made materials, undergo degradation caused by natural and man- made agents. Many pieces made of steatite that are part of magnificent monuments, listed as World Heritage Sites, are currently at an advanced level of degradation. Therefore, alternatives and actions are needed to interrupt this process and recover the deteriorated artefacts. In this context, this work aims to develop and characterise composite materials with the potential to repair surface wear, replace damaged parts and produce copies of sculptures made of soapstone. In order to produce materials with colour and texture similar to rocks, the powder residues of soapstone are used as a dispersed phase in the composites. Three different types of matrix materials (epoxy polymer, white Portland cement and pozzolanic Portland cement) are used in composites in order to identify the most suitable composition for restoration works. A statistical methodology based on the design of mixture is applied to identify the best matrix composition. Through this methodology, it is possible to investigate not only the behaviour of the different matrices that act independently but also the effect of the combination of these materials in several proportions. The physical and mechanical properties such as bulk density, apparent porosity, water absorption, compressive strength and elastic modulus are investigated. Composites made with 30% epoxy polymer and 70% steatite particles reach the greatest potential to be applied in restorations of historic monuments made of soapstone. These composites have properties superior to rocks and other composites, in addition to exhibiting texture and colouring similar to natural soapstone. © 2020 Elsevier Masson SAS. All rights reserved. 1. Introduction Many cities were founded in Brazil during the 18th century due to the discovery of large gold deposits, mainly in the state of Minas Gerais. The discovery of gold in Minas Gerais generated a great migratory movement to the region, due to the expectation of rapid enrichment, attracting many people to the villages and cities of the state. Therefore, there was a high population growth and significant economic development in many cities in the interior of the state. The economic factor combined with the strong Christian tradition in Brazil at the time culminated in the construction of magnifi- cent churches richly ornamented with works of art in the “barroco mineiro” style (baroque from Minas Gerais). The great demand for sacred artwork boosted the appearance of talented sculptors of the Baroque (barroco) style of Minas Gerais, the most prominent being that of Antônio Francisco Lisboa, popu- larly known as Aleijadinho [1]. These artists transformed blocks of ∗ Corresponding author. E-mail address: panzera@ufsj.edu.br (T.H. Panzera). wood and rough stone blocks into works of art that commissioned to compose the ornamentation of the churches. Among the main types of rocks used by sculptors of the time, steatite stands out, popularly known as soapstone due to its low hardness. This char- acteristic of the soapstone makes it ideal for obtaining precise and delicate details when carving. However, this feature also makes it very susceptible to vandalism and it is easily worn out. Today, many pieces of soapstone that make up magnificent monuments listed as World Heritage Sites are at an advanced level of degradation [2]. Thus, we need studies and measures whose objectives are to delay this process and restore the damaged parts. Currently, Portland cement mortars are the most common materials used to restore cracks and rebuild soapstone pieces in Brazil. However, the physical characteristics of cementitious mate- rials provide imperfect adhesion to steatite. Additionally, Portland cement mortars have a different texture and colour than rocks [3]. Some researchers have been working on the development of materials to restore soapstone artefacts using waste originating during the manufacture of other products, such as soapstone vases and pans. Composites made with Portland cement and steatite particles were studied to obtain a resistant material with physi- https://doi.org/10.1016/j.culher.2020.06.001 1296-2074/© 2020 Elsevier Masson SAS. All rights reserved.