Compressive strength of solid clay brickwork of masonry bridges: Estimate through Schmidt Hammer tests

Theoretical approaches and code formulas assume the compressive strength of solid clay brickwork as a function of the compressive strength of bricks and mortar. Such an approach is not so easy to be applied in practice since the strength of the components may be identified only by means of indirect testing through rebound hammers or penetrometers. Since brickwork strength largely depends on the brick properties, the mortar playing a minor role, a low detailed and fast estimate of brickwork strength may be deduced from the bricks only. In this paper, the type-N Schmidt rebound hammer, i.e. the standard one for concrete, is applied to the solid clay brickwork of arch bridges and industrial facilities. Due to the higher quality of the materials used in these cases, on the basis of a specific calibration curve, the rebound hammer is demonstrated to provide an estimate of the compressive strength affected by a +/- 25% error. Relying on a large data base, it is showed that in other cases, mainly residential buildings, such an approach is not applicable due to the lower quality of materials and larger scattering of the mechanical properties.