Investigation of Interfacial Interaction of Concrete Masonry Assembly Subjected to Monotonic Loading

Concrete masonry prisms are composed of various materials, and the properties of and interaction among these materials play a crucial role in the overall performance of masonry structure. Previous studies considered testing complete prisms, which provide the strength of the masonry and strains measured from the outer surface. However, testing full prisms fails to provide information about the interactions among the materials used in the prism. Hence, an innovative approach was designed in which cut prisms were tested to understand the interactions among grout, mortar, and concrete blocks in masonry assemblages under monotonic compression loading. Eighteen three-course-high grouted concrete masonry prisms were constructed using 20-cm normal-strength (NS), 20-cm high-strength (HS), and 25-cm HS concrete blocks. Prisms were cut along their length (CL) or width (CW) to observe and determine the interactions among various masonry materials. Digital image correlation (DIC) was employed to measure strain, strain contours, crack initiations, and crack growths throughout the loading process. The study also investigated the effects of block strength and geometry on prism compressive strength. The study found that the analysis of cut surfaces provides a comprehensive understanding of block–mortar–grout interactions compared with traditional face shell observations. The lateral strain was observed to induce grout–block separation, and the longitudinal strain generated significant concentrations at the block–mortar interfaces. The study found that the prisms of high-strength blocks significantly outperformed their counterpart prisms of normal-strength blocks; HS20 prisms exhibited 17%–18% higher strength than NS20 prisms. Furthermore, block size was critical, because HS25 prisms demonstrated 13%–21% higher strength than HS20 prisms due to larger bearing areas and improved load distribution. The study concludes that the DIC technique can effectively monitor crack propagation, patterns, and widths within the respective cut directions (length and width) of the masonry prisms.