An investigation of bond behavior between composite materials (CFRP, GWMM, KPGC) and substrates (Brick and Concrete) for strengthening existing masonry structures

Abstract

The use of novel composite materials to repair and upgrade existing masonry structures is a major research topic. The Rilem Technical Committee 250-CSM (Composites for the Sustainable Strengthening of Masonry) and Assocompositi (Italian Industry Association for Composite Materials) conducted a round robin test to study the properties of up to 25 types of composite materials in terms of direct tension and bonding behavior. These research results provide a more comprehensive understanding of the mechanical properties of fabric reinforced cementitious matrix (FRCM) reinforcement systems and further improve the standardization of testing procedures. However, owing to the diversity of composite materials and substrates, these results cannot be directly applied to strengthening existing masonry structures in China.In this study, we aimed to comprehensively investigate the bonding behavior between various commonly used composite materials and substrates. Three brick types commonly used in rural areas of China were selected as substrates, namely clay solid brick, shale perforated brick, and concrete hollow block, and three mainstream composite materials were selected as reinforcement materials, namely carbon fiber-reinforced polymer (CFRP), galvanized wire mesh mortar matrix (GWMM), and knitted polyester geogrid cementitious matrix (KPGC). It should be noted that both GWMM and KPGC can be viewed as FRCMs, because they comprise both a fabric and matrix. First, the mechanical properties of the composites were determined by unidirectional tensile tests. Second, single- and double-lap tests were conducted using a specially designed test setup. A comprehensive analysis of the experimental results was conducted, including failure modes, load-global slip curves, failure loads, peak stresses, and exploitation ratios. Finally, the prediction formula for the bonding load capacity of the composite materials mentioned above was explored using the experimental results recorded in this study and relevant literature. The results not only explain the bonding behavior among CFRP, GWMM, PGCM and different substrates, but also broaden the material selection scopes in the repair process of existing masonry structures in a large number of villages and towns in China.