Micro-destructive evaluation of the mechanical properties of lime-based mortars

Abstract

In every restoration project, knowledge of the mechanical properties of the original materials is considered essential for engineers, not only for the structural assessment of the monument, but also for the selection of compatible restoration materials. In the case of mortars, however, direct or indirect determination of their mechanical properties is usually challenging, due to the limited size and number of available samples. Hence, alternative non- or micro-destructive techniques need to be exploited for the evaluation of the compressive and flexural strength of historic mortars. In this study, the micro-destructive scratching resistance test is used to assess the compressive and flexural strength of a variety of lime-based mortars, that were either designed and produced in the laboratory using different binders, aggregates and admixtures, or sampled in-situ. Sound linear correlations observed between the intrinsic specific energy, resulting from the scratching resistance test, and the compressive and flexural strength of the laboratory designed and produced mortars validate the potential of the scratch tool in assessing the aforementioned mechanical properties of lime-based mortars. This is further confirmed by results on historic mortar fragments. Therefore, the use of the novel micro-destructive scratch tool is recommended in cases where lime mortar sampling is limited, in order to provide reliable estimates for the mechanical properties of historic mortars.