Torque Penetrometric Test for the in-situ characterisation of historical mortars: fracture mechanics interpretation and experimental validation

Abstract

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

Mechanical Behavior of Natural Hydraulic Lime Mortars

“…In total, seven types of mortars were prepared and tested (see Table 2). All of them presented a lime/aggregate volume ratio 1:3 as it is the one commonly used for the historical mortars [22,23]. Volume proportions of compounds were converted to weight to obtain a convenient measurement for the mixing process.…”

In Plane Behaviour of Masonry Walls Reinforced with Mortar Coatings and Fibre Meshes

“…In addition, direct tensile tests of the fibre glass wires were executed in order to examine the nominal properties indicated by the producer. Some non-standard material tests were also carried out by using non-destructive test methods as proposed in Marastoni et al (2016), with a very good agreement with the standardized procedures. In Tables 1 and 2 the nominal and experimental results of the tests carried out on the materials are reported.…”

Non-Invasive Identification of Vulnerability Elements in Existing Buildings and Their Visualization in the BIM Model for Better Project Management: The Case Study of Cuccagna Farmhouse

“…The foundations investigation has also confirmed the probable difference in the construction period of some parts of the building [27,28]; • Sonic investigations on some walls, in those areas where the crack pattern showed fissures of doubtful interpretation, in order to investigate the panel homogeneity and identify possible detachments of internal leaves and/or surface plasters; • Superficial and deep penetrometric tests for mortars characterization; • Bricks characterization based on the behavior detected on bricks preserved on site and probably contemporary to the ones in use. The results obtained were compared with values available in the literature for materials of the same type and period [29][30][31]; • Penetrometric tests (©Resistograph) to characterize the timber floors and roofs [32][33][34].…”