PSI - Issue 44

Francesca Ferretti et al. / Procedia Structural Integrity 44 (2023) 2254–2261 Ferretti et al./ Structural Integrity Procedia 00 (2022) 000–000

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2.1.2. Mortars Three different types of mortars were adopted during this experimental campaign based on their usage, as shown in Table 2. Standard prismatic mortar samples of nominal size 40×40×160 mm 3 were casted and cured in laboratory conditions for 28 days; then, three-points bending and compression tests were performed according to EN 1015-11 Standard using a universal testing machine. Average results are reported in Table 2 in terms of compressive strength f c and flexural strength f fl .

Table 2. Average strength values of the mortars Type of mortar Usage

f c (MPa)

f fl (MPa)

Mortar 1 Mortar 2 Mortar 3

Construction of wall panels

5.29 4.63

3.61 2.41 5.26

Reinforced repointing

FRCM and CRM mortar matrix

10.81

2.2. Construction and strengthening procedures Four double-leaf masonry panels, characterized by a Flemish bond, were constructed using solid bricks and lime based mortar. One specimen was unreinforced, while three samples were strengthened according to the retrofitting configurations reported in Table 3. In particular, two samples were strengthened with an asymmetrical configuration, with reinforced repointing on one side and FRCM (CD_2) or CRM (CD_3) on the other side, while one sample was symmetrically reinforced with the FRCM system (CD_4).

Table 3. Masonry specimen size, type and characteristics Specimen Dimensions (mm 3 )

Type of reinforcement

Mechanical anchorage

Symmetrical layout

CD_URM

1300 × 1300 × 250

Unreinforced

-

-

Side A: reinforced repointing

CD_2

1300 × 1290 × 250

Steel anchors

No

Side B: FRCM

Side A: reinforced repointing

CD_3

1290 × 1290 × 250

Steel anchors

No

Side B: CRM

CD_4

1300 × 1290 × 250

Both sides: FRCM

Yes

Glass connectors

To install the reinforced repointing technique on side A of the samples CD_2 and CD_3, the following procedure was adopted (Fig. 1):  Mortar joints on side A of the panel were scratched to a depth of roughly 1 cm (Fig. 1 a );  30 holes were drilled to insert pass-through steel anchors with a diameter of 10 mm (Fig. 1 b );  Galvanized Ultra High Tensile Strength Steel (UHTSS) strands were placed inside horizontal and vertical mortar joints of the specimen, according to the layout reported in Fig. 2, and were tensioned by fixing and screwing to the connectors (Fig 1 c ).  Mortar joints were re-plastered, using Mortar 2 (Fig 1 d ). For the application of FRCM and CRM on side B of the samples CD_2 and CD_3 (Fig. 3), a first mortar matrix layer was casted on the entire surface of the samples (Fig. 3 a ). Then, the glass reinforcing mesh was installed with an overlap of 15-20 cm in the center of the panels (Fig. 3 b for FRCM and Fig. 3 c for CRM). Finally, a second mortar matrix layer was casted above the grid (Fig. 3 d ). The thickness of each mortar matrix layer was equal to 7-8 mm and 10-11 mm for FRCM and CRM systems, respectively. The pass-through steel anchors previously inserted on side A were used as mechanical anchorages for securing the mesh. For the panel CD_4, symmetrically strengthened with FRCM (Fig 3 e-h ), glass connectors were used as mechanical anchorages for securing the mesh.