PSI - Issue 54

Jamal A. Abdalla et al. / Procedia Structural Integrity 54 (2024) 609–616 Abdalla et al./ Structural Integrity Procedia 00 (2019) 000 – 000

612

4

(d)

(e)

Fig. 1. Geometrical configuration of the tested beams (a) CN and CR; (b) NU-90 and RU-90; (c) NS-90 and RS-90; (d) NCU and RCU; (e) NU 45 and RU-45

2.2. Material properties Two different self-consolidating concrete (SCC) mixes were prepared at a ready-mix plant. One mix consisted of 100% natural aggregates, while the other mix utilized 100% recycled aggregates. The physical and mechanical properties of the recycled aggregates used in the study are mentioned in (Abdalla, et al., (2022)). It is worth mentioning that all tested properties met the required standards. The desired compressive strength for both concrete mixtures was set at 30 MPa. The proportions of the fresh concrete mixes can be found in (Abdalla, et al., (2022)). For testing the compressive strength of the concrete, cylinders measuring 300 mm in height and 150 mm in diameter were cast and cured alongside beams. After 28 days, the average compressive strength obtained for the concrete with natural aggregates was 37 MPa, while the mix containing recycled aggregates yielded an average strength of 36 MPa. As for the steel reinforcement, tensile tests were performed on rebars with diameters of 8 mm and 12 mm. The average yield strength obtained was 550 MPa, with an elastic modulus of 200 GPa. Carbon Fiber Reinforced Polymer (CFRP) laminates were utilized and a two-part epoxy adhesive was used to bond the CFRP sheets to the concrete. The manufacturer-specified design thickness, tensile strength, elastic modulus, and rupture strain are listed in Table 1. Table 1: Mechanical properties of CFRP sheets and laminates Material Material Density/ weight Thickness (mm) Elastic Modulus (MPa) Ultimate tensile strength (MPa) Elongation at failure (%)

MapeWrap C UNI-AX 300 MapeWrap C UNI-AX 300 MapeWrap 31 SP

CFRP sheets

1800 kg/m 3

0.164

252,000

4,900

2

CFRP Laminates Epoxy Adhesive

-

0.5

83,848

1,492

1.7

1.14 kg/dm 3

-

1000

28

3.4

2.3. Test setup

The beams were subjected to a four-point bending test as depicted in Fig. 3. A universal testing machine with a capacity of 2000 kN was utilized to apply the load at a controlled rate of 1 mm/min. The shear span and overhang lengths measured 615 mm and 75 mm, respectively. For measuring the mid-span deflection, a linear differential variable transducer (LVDT) was positioned at the bottom of the beam specimens, precisely at the mid-span, as