# Some Key Aspects in the Mechanics of Stress Transfer Between SRG and Masony
## 2 Materials and Methods
### Specim Preparation and Application of SRG Reinforcement  
All masonry blocks were constructed with six layers of half-bricks and five 10 mm-thick mortar joints. Nominal dimensions of blocks were 120 mm (length) \(\times\) 120 mm (width) \(\times\) 380 mm (height). In total, thirty-two masonry blocks were prepared: twenty-seven blocks were strengthened with lime-based mortar SRG, and the remaining five blocks were strengthened with cement-based mortar SRG. Before applying the composite, all the masonry blocks were left to soak in a bucket filled with water for at least 20 min (Figure 2). This procedure was necessary to avoid water absorption by the masonry surfaces during the application of the SRG composite \begin{table}
\begin{tabular}{c c c} \hline \hline
**Material** & **Mechanical Property Evaluated** & **Results** \\ \hline \multirow{4}{*}{Brick} & Compressive strength (MPa) & 20.3 \\  & Tensile strength (MPa) & 3.16 \\  & Elastic modulus (GPa) & 7.3 \\  & Fracture energy (N/m) & 29.5 \\  & Flexural strength (MPa) & 5 \\ LM matrix & Compressive strength (MPa) & 12.3 \\  & Fracture energy (N/m) & 30.3 \\  & Flexural strength (MPa) & 7.6 \\ CM matrix & Compressive strength (MPa) & 46.4 \\  & Fracture energy (N/m) & 101 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Mechanical properties of bricks, lime-based mortar (LM) matrix, and cement-based mortar (CM) matrix. Figure 2: Preparation of specimen before the application of the steel-reinforced grout (SRG) composite: (**a**) masonry blocks soak in the water, (**b**) wet specimen removed from the bucket. For all masonry blocks, the width of the steel fiber sheet and the bonded length (\(\ell\)) of the SRG strip was maintained constant and equal to 50 mm and 315 mm, respectively. It should be noted that the mortar was used to embed the fibers only in the bonded area. The fibers were left bare outside the bonded area. The width of the mortar matrix was varied: specimens used as reference [35] had a matrix width equal to the width of the steel fiber sheet, i.e., 50 mm. For the remaining blocks, the width of the mortar was increased to 70 mm and 90 mm, while keeping the width of the fiber sheet constant and equal to 50 mm. To avoid the spalling of the first brick of the masonry block, the bonded area started 35 mm from the top edge of the block itself. In total, three concrete prisms herein reported for the sake of comparison were strengthened with SRG composite [43]. The SRG system bonded to concrete prisms comprised steel fibers embedded in the same cement-based mortar matrix used for masonry. The procedure followed to bond the SRG composite strip to the substrate was the same for all specimens: (1) delimitation of the bonded area using cardboard; (2) application of the first 4 mm-thick layer of mortar matrix; (3) application of steel fibers, which were gently pressed into the mortar using a trovel; (4) application of the second 4 mm-thick layer of mortar matrix to fully cover the steel fibers (Figure 3). All the specimens were left to cure in the laboratory environment under wet cloths for 28 days. Figure 3: Phases of application of SRG reinforcement: (**a**) delimitation of the bonded area; (**b**) application of the first layer of mortar matrix; (**c**) application of steel fiber sheet; (**d**) application of the second layer of mortar matrix. Specimens were named following the notation DS_A_B_C_D_E_Z where A indicates the bonded length, B refers to the matrix width, C indicates the density of steel fiber (LD = 670 g/m\({}^{2}\)), D is the matrix mortar employed (LM = lime-based mortar, CM = cement-based mortar matrix), E when present refers to the test rate, and Z is the number of the specimen (see Tables 3 and 4).