Compatibility assessment for repair mortars: an optimized cement-based mix for Tuffeau de Lincent

Mortars developed for the reconstitution and ‘plastic repair’ of natural stones have become increasingly popular. They are an alternative for the replacement of deteriorated stones, since they are capable of preserving the (memory of) diversity in building materials. This article addresses some key elements for the compatibility between repair mortars and stones. This research accordingly studies the compatibility of a repointing mortar designed for the Tuffeau de Lincent (Belgium), a friable stone in need for restoration and replacement, which was developed using an auto-formulation tool, based on strength and colour compatibility. The selected repointing mortar was further tested in order to assess its use as plastic repair mortar for the Tuffeau de Lincent stone. The developed mortar was considered compatible in colour with the stone and had a strength of 14 MPa, which falls within the strength range of the stone (8–18 MPa). However, porosity and pore size distribution measurements indicated that the stone and the mortar were different. This study compares the first product of the prototype formulation tool and lays the foundations for a more expanded and larger auto-formulation tool for the repair of natural stone.