PSI - Issue 64

Maher AL-Hawarneh et al. / Procedia Structural Integrity 64 (2024) 1103–1110 Maher / Structural Integrity Procedia 00 (2019) 000 – 000

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system has its fibres aligned in one direction only and the bi-directional system has its fibres in two orthogonal directions. The details of these two fabrics were provided by the manufacturer as shown in Table 2. The mortar is a one-component, shrinkage compensated, polypropylene-fibre reinforced cementitious matrix design to be used with the fibres. It has a 28 days compressive strength of 50 MPa.

Table 2: Fabric properties Fabric properties

Uni-directional Carbon

Bi-directional Carbon

Warp Spacing Weft Spacing

15 mm 30 mm

20 mm 20 mm

Equivalent Dry Fabric Thickness

0.157 mm 280 g/m 2 450 kN/m

0.044 mm

Density

80 g/m 2

Ultimate Tensile Strength Axial Stiffness by width unit

138 kN/m 9,200 kN/m 46 mm 2 /m

30,000 kN/m 162 mm 2 /m

Area by width unit

2.3 FRCM application Surface roughening was completed using a pressurized abrasive blaster with crushed glass abrasive media. The process created a roughened surface equivalent to a concrete surface profile (CSP) of 6 on the scale used by ICRI (2013). Each sample was carefully examined and compared with the respective ICRI scale to ensure conformity among all the samples. One bi-axial foil strain gauge was attached at the mid-height on the cylinder face. The strain gauge used is type PFLC-30-11, which had a strain gauge length of 60 mm, and manufactured by Tokyo Measuring Instruments Laboratory Co., Ltd. (TMIL). This type of strain gauge can read both axial and lateral components of strain. To protect the strain gauge from contacting wet mortar during jacket casting, the foil strain gauge and electrical bases of each cylinder was covered with layer of wax. For preparing the carbon fibre mesh, a strip of 180 mm wide was cut. This width is less than the height of a standard concrete cylinder by 20 mm, to ensure a 10 mm clear space between the top and bottom of the cylinder and the FRCM layer. This spacing is provided to ensure that FRCM layer would not be subjected to axial compression during the compressive axial loading. An overlapping length of 75 mm was provided to ensure adequate anchorage for the carbon mech. This overlap length is common in such types of jacketing as it minimizes de-bonding and premature splitting or slipping failure of the FRCM (Wan et al. 2022). The strong axis of the uni-directional fibre mesh was applied in the transverse direction of the cylinder. For the two-layer configuration, the second fibre mesh layer was continuously wrapped on top of the first layer To apply the mortar, a cast-in-place method was used, as this method would be much more efficient, and would also maintain consistency of the fabric thickness across all samples. The jacket moulds were fabricated by forming cylinders out of aluminum sheets, cut to the height of the cylinders. These are then secured to wooden bases using strong adhesive and caulk to ensure there are no leaks. The inside of each mould is coated with lubricating oil, and the wrapped cylinders are dampened with water, before being placed inside the moulds, to increase the bond effectiveness of the FRCM and concrete interface. At the same time as the mould preparation, the mortar component of the FRCM was being mixed. After the mixing was completed, the mortar was immediately poured into the gap between the cylinder and the mould, ensuring total encasing of the carbon mesh. This method also resulted in the FRCM layer being cast along with the exact spacing from the top and the bottom of the cylinder. The mould was then tampered using thin steel rods, and the wooden bases were lightly tamped and vibrated. This is done to ensure a minimal formation of honeycombs and air voids within the FRCM layer. The jacket thickness for all specimens was 13 mm for both one-layer and two-layer configurations. The thickness of the jacket was kept as uniform as possible across all samples ensuring equal thickness of mortar layers enclosing the textile. The second fibre layer was a continuation of the first fibre layer and was warped directly on the top of the first fiber layer with no interlayer between them. After the FRCM layer hardened for 24 hours, the specimens were de-moulded and placed in a moist curing room for the remainder of the 28-day curing time.