Compatible Repair Mortars: A New Methodology Based on Digital Image Analysis Applied to the Casemates of Algiers

A methodology based on systematizing information gained from characterization tests on original mortars and quantifying acceptance criteria is proposed to define repair mortars complying with the compatibility principle’s requirements. To this aim, results from physical and mechanical tests combined with optical-microscope Digital Image Analysis (DIA) of thin sections of mortars observed under polarized light are employed to define the original mortar characteristics efficiently and rigorously. Then, compatibility acceptance criteria, including prescriptions on porosity, bulk density, and compressive strength, are defined for the new mortar. The allowable variations of these parameters are quantified to assess to what extent the new mortar is similar to, i.e. compatible with, the original one. An iterative procedure to correct the mix design is proposed based on comparing the new and the original mortar. The mortars sampled from the Ottoman military building Casemates located in the Casbah of Algiers are employed as case study.