Experimental analysis of the bonding strength between textile reinforced mortars and rammed earth structures

In recent decades, there has been an increased interest in the field of rammed earth (RE) structures, largely driven by concerns regarding sustainability. However, the structural integrity of these systems may be jeopardized by lateral forces, including seismic forces. Among the various seismic retrofitting techniques, textile-reinforced mortars (TRM) have demonstrated efficacy in enhancing the seismic response of masonry structures. In order to apply the TRM to RE walls, it is necessary to study the bonding between the two materials to ensure proper load transfer. In this study, three primers (synthetic resin, acrylic polymer, and lime-based mortar) were utilized to prepare the rammed earth (RE) surface prior to casting the textile-reinforced mortar (TRM). Two distinct mortars were evaluated for integration within the TRM system's matrix. The mechanical strength of the RE-TRM interface was assessed through a series of rigorous testing procedures, including pull-off, double shear, and single-lap shear tests. As anticipated, in the absence of treatment on the RE surface, the interface between the two materials exhibited inadequate strength, resulting in delamination failures. The primers were capable of modifying the failure mode of the specimens; in these cases, the properties of the mortar gained importance. The mortar, which demonstrated inferior mechanical performance, exhibited signs of tensile failure or fiber pullout. The acrylic polymer primer enhanced the shear strength of the RE-TRM system by 14.5–46.3%. In single-lap shear tests, delamination of the TRM at the RE interface was observed to occur exclusively in instances where the RE surface was not treated with primers or when the specimen's anchorage length was found to be inadequate. In more favorable conditions, the system exhibits a capacity to resist a tensile load that is equivalent to the tensile strength of the fibers.