This research presents a novel integrated methodology for the experimental characterization of historical mortars, including different types of laboratory tests. Different experimental tests on lime mortar brickwork were carried out, including Brazilian tests on core drilled masonry samples with one diametral mortar joint and double punch tests on extracted mortar joints. By representing the mortar’s state of failure on the Mohr’s plane for the different tests, it is possible to estimate the material’s strength envelope through a least square minimization method. The proposed approach can be useful to evaluate the compressive, tensile and shear behaviour of mortar in existing structures.Peer ReviewedPostprint (author's final draft

The assessment of historical structures requires appropriate knowledge of the behaviour of the investigated materials. Concerning masonry, its mechanical characterisation is a challenging task, since its composite nature requires the careful evaluation of the behaviour of its material components. In particular, the experimental assessment of the strength of existing mortar in historical structures still encounters several difficulties. This study investigates a novel Minor Destructive Testing (MDT) technique virtually equivalent to the vane test used for soils. The instrumentation, called herein Torque Penetrometric Test (TPT), is composed of a steel nail with four protruding teeth and a torque wrench. The test consists in inserting the toothed nail into a mortar joint and then applying a torque by means of a dynamometric key, until reaching the failure of the material. This work presents a novel interpretation theory based on basic concepts of fracture mechanics and applied to the micro-mechanical analysis of the stress state induced by the instrument on the investigated mortar. The proposed interpretative theory is validated through the execution of experimental tests in the laboratory and in a historical masonry building. The test proves to be effective for a quick in-situ MDT evaluation of the strength of existing mortars.Peer ReviewedPostprint (author's final draft

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