PSI - Issue 64

Paula Folino et al. / Procedia Structural Integrity 64 (2024) 1452–1459 Folino et al. / Structural Integrity Procedia 00 (2019) 000 – 000

1455

4

2.2. Details of concrete specimens The unjacketed reference beams had a cross-section of 150x200mm and a total length of 1200mm, a bottom reinforcement of 2Ф12, top reinforcement of 2Ф6, and only three constructive stirrups Ф6 located at the ends and the center of the beam, as shown in Fig. 1a. Three concrete jacket types were designed as follows - 60mm thick jackets of SCHSC with 8 stirrups Ф8 and 4 Ф6 reinforcement bars (See Fig. 1b). Moreover, two types of the reference beams surface condition were considered. In one case, the exterior layer of concrete was removed until coarse aggregates were exposed, achieving a rough surface (RS), while in the other case, no treatment was applied maintaining the original smooth surface. Before pouring concrete, the beam faces were cleaned using a wire brush and compressed air; then moistened until saturation without pooling. Concrete was poured from the top. It is worth noting that, regarding the dimensions of the used fibers, the nominal maximum size of the fibers should be less than half of the spacing between reinforcements or lateral obstructions. However, for the selection of fibers, priority was given to maintain a high aspect ratio l f / D , where l f is the effective length and D is the effective diameter, respectively, to ensure the bridging effect of the matrix (Bayraktar et al., 2023). In addition to the beams and their jackets, cylindrical specimens of 100mm diameter and 200mm height were molded with each of the concretes used to undergo uniaxial compression (UC) and splitting tensile (ST) tests, as well as prisms of 550mm length and 150x150mm cross-section with a 25mm notch in the middle, tested under three-point bending (TPB). A summary of the experimental samples and test types and layouts can be seen in Table 3. - 60mm thick jackets of SCFRHSC (See Fig. 1d), - 30mm thick jackets of SCFRHSC (See Fig. 1c),

Table 3. Tested specimens. Specimen

Qty

Test

Test Layout

Beam 150x150x1200 NSC

3 3 3 2 2 2

Beam 150x150x1200 U30 SCFRHSC Beam 150x150x1200 U30 SCFRHSC RS Beam 150x150x1200 U60 SCFRHSC Beam 150x150x1200 U60 SCFRHSC RS Beam 150x150x1200 U60 SCHSC RS

TPB

Cylinder 100x200 NSC

3

UC

Cylinder 100x200 SCFRHSC

3

Cylinder 100x200 NSC

3

ST

Cylinder 100x200 SCFRHSC

3

Prism 150x150x550 SCFRHSC

2

TPB

2.3. Equipment and measurement devices A closed loop servo-hydraulic GCTS brand testing machine of 2000 kN capacity was used for performing Uniaxial Compression (UC), Splitting Tensile (ST) and Three-Points Bending (TPB) tests on small samples. Uniaxial compression tests were conducted according to ASTM C39-05, measuring axial deformations using two variable linear