Mechanical characterization of historical rubble stone masonry and its correlation with the masonry quality assessment

Abstract

The paper presents a study on the mechanical characterization of eight rubble stone masonry walls from different structures of a Portuguese monument and on the assessment of their quality using the Masonry Quality Index (MQI) and the Italian Building Code Commentary (IBCC 2019). Rebound hammer tests were used to evaluate the quality of stone units and mortar joints, and flat-jack tests to assess the mechanical properties of masonry walls. The results allowed to propose new quantitative criteria to rate the quality of mortars and stones in MQI and to support the decision of applying the multiplication factor concerning the quality of mortars in IBCC 2019 methodology.Image processing was used to quantify several features of masonry walls and introduce new quantitative criteria on MQI. The results identified the amount of mortar, the mortar quality, the shape features of stone units and the horizontal alignment of joints as key parameters in the mechanical resistance of rubble masonry made of irregular hard stone and lime-based mortars. The mechanical properties obtained by IBCC 2019, MQI and double flat-jacks tests showed good correlations, highlighting the advantages that come from the quality assessment of masonry to estimate masonry mechanical properties.