Mixture design applied to the development of composites for steatite historical monuments restoration

Abstract

Abstract 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.