The Role of Top Matrix Layer on the GTRM-To-Masonry Bond

This study aims to shed light on the role of a bond-related parameter that has received very little attention by the academia, namely that of individual mortar layers (bottom and top mortar layer in single-textile layer TRM configurations). To this purpose, single-lap/single-prim shear bond tests were carried out on masonry wallettes furnished with: (i) "conventional" TRM strips (the term "conventional" accounting for a single dry AR glass fiber textile strip sandwiched between two mortar layers, the bottom one bonded on the masonry and the top one); and (ii) "top mortar-less" TRM strips (that is, same as "conventional" ones but lacking their top mortar layer). Masonry comprised fair-faced solid clay bricks stack-bonded with a cement/lime general purpose mortar. The TRM strips were constructed using a cementitious mortar (based on Ordinary Portland Cement-OPC) and had a bond length equal to 250 mm which was larger than the effective one. Strains were measured along the central longitudinal fiber yarn by means of strain gauges. Digital Image Correlation (DIC) analysis was also conducted for some of the `top mortar-less' specimens. The comparison of fracture energies of the two TRM configurations reveals that (for this type of TRM/substrate combination) the effect of the top mortar layer on the TRM-to-matrix bond characteristics is appreciable. Additionally, from the DIC analysis it is concluded that each load-aligned fiber yarn is activated along a length that varies among different yarns.