Masonry construction is a favorable alternative because of its robust thermal and acoustic properties, fire resistance, high load-bearing capacity, and minimal maintenance. However, traditional masonry construction requires specific on-site mixed mortar, a long construction time, and skilled masons. Several masonry construction systems, such as mortarless masonry, often called dry-stacked interlocking masonry (DSIM), have recently been introduced; these systems provide timely, efficient, and less costly construction. This paper briefly reviews the structural behavior of DSIM systems developed in different countries. The limitations of these studies, as well as the detailed classification of DSIM systems based on material, interlocking mechanism (i.e., projected nibs, dove-tailed lug, grout cores), alignment (running or stack bond), applicability to accommodate vertical and horizontal reinforcement, and block type (hollow or solid), are presented. In addition, the results of published experimental investigations evaluating the compressive strength and the in-plane and out-of-plane flexural behavior of DSIM walls are summarized. Analyzing the development of DSIM systems reveals the need for more structural efficiency of some types of interlocking masonry blocks due to the complexity of the block shape, which leads to misalignment during construction. The structural performance of all DSIM block types is affected by the block strength and interlocking mechanism in the horizontal and vertical directions. Interconnecting the cells with grout and reinforcement significantly increased the system strength and increased the initial stiffness. To develop design guidelines for DSIM systems for upcoming generations of masonry codes and standards, more comprehensive studies should be conducted to quantify the structural performance of each type of DSIM, especially their out-of-plane behavior and seismic response.
