PSI - Issue 37

Ghusoon S. Alshami et al. / Procedia Structural Integrity 37 (2022) 367–374 Alshami et al./ Structural Integrity Procedia 00 (2021) 000 – 000

370

4

Table 1: Test matrix

Prism Designation

Number of CFRP layers

CFRP Anchors

h emb (mm)

C

-

- -

- -

L1

1 1 1 1 1

AL1-E50 AL1-E75 AL1-E100 AL1-E125

50 75

✓ ✓ ✓ ✓

100 125

3.2 Material Properties The concrete compressive strength for the prism was measured by crushing 3 cubes after 28 days of curing using a compression-testing machine. The average cylindrical concrete compressive strength ( f’c ) was calculated to be 50.4 MPa. The CFRP sheets were composed of high strength unidirectional carbon-fiber fabrics (MAPEWRAP C UNI AX 300) that will be bonded to concrete surfaces by first using a primer (MapeWrap Primer 1) to set the concrete surface and then impregnated in epoxy adhesive (MapeWrap 31). Table 2 presents the mechanical properties of the dry CFRP sheets, CFRP laminates, primer, and epoxy adhesives. CFRP anchors were ready-made, and their mechanical properties are provided in Table 3. Table 2: Properties of CFRP sheets, laminates (sheets with epoxy), primer, and epoxy adhesive

Material Industrial Name MAPEWRAP C UNI-AX 300

Density/ weight

Thickness (mm)

Elastic Modulus (GPa)

Tensile Strength (MPa)

Elongation at failure (%)

Material

CFRP Sheet

0.164

252

4900 1492

2

300 g/m 2

CFRP laminate

0.5

83.848

1.7

Primer

MapeWrap Primer 1

1.1 Kg/L 1.06 Kg/L

- -

-

-

-

Epoxy Resin

MapeWrap 31

2.6

40

1.6

Table 3: Properties of CFRP anchors

Material Industrial Name MapeWrap C FIOCCO

Density (g/cm 3 )

Diameter (mm)

Surface Area (mm 2 )

Elastic Modulus (GPa)

Tensile strength (MPa)

Elongation at failure (%)

Material

CFRP Anchors

1.8

10

26.79

230

4830

2

3.3 Strengthening Procedure All prisms were grinded at the bottom creating a rough surface to ensure good bonding properties with the CFRP sheet. After cleaning the surface, the locations of the CFRP laminate and anchors were marked, anchor holes were drilled at a diameter of 12 mm, and the notch was grinded. Next, CFRP sheets and anchors were cut to the specified dimensions and quantities to be ready for the strengthening process. Following that, the primer and epoxy were prepared by mixing the provided components A and B for each at a ratio of 3:1, respectively to form a homogenous mixture. The surfaces and holes in the prisms were cleaned then brushed with a primer layer to ensure better bonding with the CFRP laminate. Then, the CFRP sheets were impregnated into the epoxy mixture and placed on the designed locations. A groove roller was used to densify the CFRP laminate and remove all air bubbles. For the anchored specimens, a metallic spatula was used to separate the fibers of the CFRP laminates in the location of anchor holes. Then anchors were impregnated in epoxy and embedded into the predrilled holes from one end and splayed on the CFRP laminate from the other end. The groove roller was used again after installing the anchors. Finally, the strengthened prisms were left to dry for 3-4 days before testing. Figure 3 shows specimen preparation and the strengthening procedure.