Several masonry design codes use the unit strength method (USM) to calculate the masonry strength, which uses the compressive strength of blocks and mortar. Some codes and research differ for characterizing the hollow concrete blocks (HCBs) for masonry structures. Some standards establish that the capping in the blocks is in the gross area, and the strength is computed in the net or gross area. Other standards characterize the hollow concrete blocks with capping only in the face-shell, obtaining the strength over the effective areas. These discrepant criteria lead to significant variability in the reported value of compressive strength of blocks and their modulus of elasticity. This study aimed to assess the influence of the capping bedding on the characterization of hollow concrete blocks in uniaxial compressive behavior. The capping on the blocks was evaluated using two experimental variants: (1) over the gross area and (2) over the faces-shell bed. An experimental study was conducted to determine the influence of the maximum strength of blocks from these two different capping methods. Regarding load-displacement behavior, when face-shell capping was used, a decrease in load capacity was obtained. On the other hand, six different values of maximum block strength and modulus of elasticity were obtained.
Álvarez-Pérez et al. (Thu,) studied this question.