Determination of the initial shear strength of AAC masonry with and without pre-compression according to EN 1052-3

Aim: In this paper, a comparative study on the initial shear strength of aerated autoclaved concrete (AAC) masonry is presented. Shear tests were carried out according to EN 1052–3 to characterize the shear-bond behavior of masonry assemblages constructed with AAC blocks with different compressive strengths. Method: To assess the influence of the axial pre-compression on shear strength, the two different testing procedures suggested in EN 1052–3 were followed and compared. The first procedure (called A) imposes three levels of axial pre-compression, in the second procedure (called B) shear tests are carried out without axial pre-compression. Results: For tests performed according to the procedure A, the dispersion of values of the shear strength increases as the pre-compression level decreases. The so obtained mean values of the initial shear strength are close to the characteristic value suggested by Eurocode 6 (EN 1996–1–1). For tests performed according to the procedure B. often the mean value of the initial shear strength is higher than the value obtained for the procedure A. However, in this case most of the specimens were characterized by crushing or by a splitting failure in the units. Conclusions: According to the authors' opinion, the higher values of initial shear strength obtained with the procedure B can be justified in view of some criticisms probably caused by the rotation of the blocks in the test setup.