2.2 Specimen Preparation
33
48mm
35mm
(a) Specimen size
(b) Vertical cross-section of specimen (2% hooked steel fiber)
Fig. 2.1 SHPB specimen, Ren et al. (2018), copyright 2020, with permission from Elsevier
Table 2.1 Quasi-static cubic compressive strengths of UHPCC
Test No.
N-0
S-1
S-2
H-1
H-2
Quasi-static compressive strength (MPa)
116.8
142.7
160.6
126.6
141.7
(25 mm), which guarantees the random fiber orientation and distribution. Also, the
vertical cross-section of UHPCC specimen with 2.0% hooked steel fiber is given
in Fig. 2.1b, which indicates that the steel fibers were uniformly distributed in the
matrix. In order to make the specimen-bar contact as perfect as possible, the end
surfaces of these cylinders were polished, which were flattened to less than 0.1 mm,
and the roughness on the surfaces was less than 0.05 mm. Besides, 15 cubic control
specimens with the size of 100 mm × 100 mm × 100 mm were cast. Three specimens were tested for each batch and the average quasi-static compressive strengths
are listed in Table 2.1. In which the capitals “N”, “S” and “H” represent no mixing
fiber, micro-straight steel fiber and hooked steel fiber, respectively. “0”, “1” and “2”
represent the volume fractions of steel fibers are 0%, 1.0% and 2.0%, respectively.
The similar designation way is used in the following test.
2.3 SHPB Test
2.3.1 Test Device
The SHPB test was conducted on a 50-mm-diameter conic variable cross-sectional
Hopkinson pressure bar, as shown in Fig. 2.2. The lengths of the striker bar, incident
bar and transmitted bar are 400 mm, 2400 mm and 1400 mm, respectively. The
smaller cross-sectional diameter of the incident bar is 37 mm, which is coincident
with that of the striker bar. The specimens were grease-lubricated on both surfaces
to minimize the effect of end friction confinement and then placed between the
incident bar and transmitted bar. In order to eliminate the high-frequency oscillation
and achieve equal stress distribution in the specimen before it was damaged, the pulse
33
48mm
35mm
(a) Specimen size
(b) Vertical cross-section of specimen (2% hooked steel fiber)
Fig. 2.1 SHPB specimen, Ren et al. (2018), copyright 2020, with permission from Elsevier
Table 2.1 Quasi-static cubic compressive strengths of UHPCC
Test No.
N-0
S-1
S-2
H-1
H-2
Quasi-static compressive strength (MPa)
116.8
142.7
160.6
126.6
141.7
(25 mm), which guarantees the random fiber orientation and distribution. Also, the
vertical cross-section of UHPCC specimen with 2.0% hooked steel fiber is given
in Fig. 2.1b, which indicates that the steel fibers were uniformly distributed in the
matrix. In order to make the specimen-bar contact as perfect as possible, the end
surfaces of these cylinders were polished, which were flattened to less than 0.1 mm,
and the roughness on the surfaces was less than 0.05 mm. Besides, 15 cubic control
specimens with the size of 100 mm × 100 mm × 100 mm were cast. Three specimens were tested for each batch and the average quasi-static compressive strengths
are listed in Table 2.1. In which the capitals “N”, “S” and “H” represent no mixing
fiber, micro-straight steel fiber and hooked steel fiber, respectively. “0”, “1” and “2”
represent the volume fractions of steel fibers are 0%, 1.0% and 2.0%, respectively.
The similar designation way is used in the following test.
2.3 SHPB Test
2.3.1 Test Device
The SHPB test was conducted on a 50-mm-diameter conic variable cross-sectional
Hopkinson pressure bar, as shown in Fig. 2.2. The lengths of the striker bar, incident
bar and transmitted bar are 400 mm, 2400 mm and 1400 mm, respectively. The
smaller cross-sectional diameter of the incident bar is 37 mm, which is coincident
with that of the striker bar. The specimens were grease-lubricated on both surfaces
to minimize the effect of end friction confinement and then placed between the
incident bar and transmitted bar. In order to eliminate the high-frequency oscillation
and achieve equal stress distribution in the specimen before it was damaged, the pulse