Characterization of mortar and stone masonry quality in Amatrice historical buildings hit by the 2016 central Italy earthquake

The 2016 Central Italy seismic swarm, and in particular the first stroke on 24th of August in Amatrice, hit a rural zone on Apennine composed by a typical masonry made of rubble stone, arranged in two leaves with weak mortar. The first weakness of rubble masonry is related to masonry disaggregation, which does not allow a macro-element activation.The paper presents the research carried mainly in the Amatrice region to characterize the masonry quality and its properties. Firstly, physical and chemical characterization of the constituting mortars was performed analysing 33 mortar specimens. The bulk characterization was performed through X-ray powder diffraction (XRPD) coupled with scanning electron microscopy and X-ray microanalysis (SEM-EDS). Those analyses, compared with the analysis of the masonry quality looking at the arrangement of the entire panel, provided an evaluation of the quality and gave an insight of the main issues of the materials, defining three different mortar groups summarized in two masonry typologies. A case study is presented to focus on the accelerations which lead to the masonry disaggregation compared to those associated with the mechanism activation.The paper aims at characterizing the masonry pointing out the weaknesses which led to the building collapse, with the goal to propose data and information crucial to design efficient and effective strengthening interventions which can avoid the dramatic effects observed.