Concrete block masonry stands as one of the most prevalent structural materials in both Quebec and across Canada with many applications to loadbearing elements in residential, commercial, and industry low-to-mid-rise buildings. In this paper, mechanical testing done at McGill University investigates some critical aspects related to the compressive behavior of concrete block masonry that are still under-researched, specifically the bond pattern and size effects, as well as their combination, leveraging modern field deformation measurements applied to experimental tests. In current construction, stack bond emerges as the second most popular choice after the running bond for concrete masonry units. Despite the behaviors and deformations of assemblies built with either stack or running bond patterns tend to differ when subjected to uniaxial compression loading, limited data is presently available on this aspect and the combined aspect ratio effects. With respect to size effect, limited data exists on the impact of the height-to-width ratio on compressive strength, albeit CSA-S304-14, Table D.1 provides some guidance, offering universal correction factors for same-bond masonry specimens. Secondly, the CSA mandates the use of running bond prisms to represent characteristics under uniaxial compression testing, a practice seldom implemented in labs. This research addresses the knowledge gaps mentioned above through laboratory experiments, testing a total of 56 different assemblies under uniaxial monotonic compression loading, with unit and mortar testing to enhance data correlation. Preliminary findings suggest that stack bond assemblies, on average, demonstrated a compressive strength up to 15% greater than their running bond counterparts. Additionally, concerning the size effect, results for stack bond assemblies align with CSA standards, while for running bond assemblies, our tests indicate the need for a smaller correction factor.
