First steps to computer-aided decision-making in repair mortar recipes: Working on three fronts

Repair mortars are used for the restoration of natural stone. Such a mortar should be compatible with the stone, i.e. the mortar properties should depend on the stone properties. Each mortar is therefore best tailored on the stone and due to the heterogeneity of natural stone; no general mortar recipe can be used. Currently, repair mortars are used out of experience, because their development is time-consuming and might not lead to good results immediately. Therefore, in order to improve mortar development, a computer-aided decision process is searched for in this study, based on mortar property estimations using the properties of the mortar components (sand, binder). The intention of and approach towards this process is subdivided based on the three main compatibility properties: fluid migration, color and strength. Frequently encountered incompatibilities are described, as well as methods from literature designed to estimate these mortar properties. These methods are then applied on mortar mixes and the estimated values are compared with the measured values. Finally, some suggestions for improvement are made.