Determination of Masonry Compressive Strength Properties by Testing Cores

Dealing with the seismic vulnerability assessment of existing masonry constructions is not an easy task, especially concerning the difficulties in determining the masonry mechanical properties. Experimental tests, classifiable, depending on their invasiveness, as non-destructive, slightly-destructive or destructive, may be performed directly on-site or in laboratory on materials extracted on-site. Existing buildings with an historical, architectural or artistic value cannot be severely damaged by testing; therefore, there is the need of assessing the reliability of non-destructive and slightly-destructive testing methodologies for the determination of the material parameters. The goal of the present research is to evaluate the suitability of testing cores for the determination of the masonry compressive strength. Testing a masonry core in compression is not a standardized procedure and it implies the casting of high-strength mortar caps at the top and at the bottom of the samples to obtain regular surfaces on which applying the compressive load and to simulate the confinement given, on site, by the surrounding masonry. In this research, a solid clay brick masonry typology is considered, for which the compressive strength is estimated by testing cores and standard wallets. To investigate the reliability of the testing method, both single-wythe and double-wythe cores are subject to uniaxial compression tests, also considering variations in the dimensions of the high-strength mortar cap. Correlations between the results obtained by testing cores and wallets are presented in the paper, in terms of compressive strength and evolution of the crack pattern.