5.2 Basalt Aggregated UHPCC Target
119
the fiber mixing ratio from 0% to 1.5% makes the corresponding averaging cratering
diameter decrease from 457.5 mm to 267.5 mm (decreases by nearly 42%) and
488 mm to 267.5 mm (decreases by nearly 45%), respectively. In comparison, when
the compressive strength of the target varied from 87.3 MPa to 114 MPa, increasing
the fiber mixing ratio from 0% to 3% makes the corresponding averaging cratering
diameter decrease from 457.5 mm to 141.5 mm (decreases by nearly 70%) and
488 mm to 166.5 mm (decreases by nearly 66%), respectively.
The above comparison indicates that the larger reduction of the cratering diameter
is when the fiber mixing ratio increases from 0 to 1.5%. Furthermore, the cost of
every cubic meter UHPCC (about 2.5t) with 3% steel fibers volumetric ratio is about
35% higher than that of UHPCC (about 2.5t) with 1.5% steel fibers volumetric
ratio. By comprehensively considering the crack-prohibiting efficiency, costs and
the workability of the composites, 1.5% of the fiber mixing ratio is the most efficient
and economical for UHPCC in the construction of protective structures.
(3) The influence of projectile striking kinetic energy
By comparing with the tests 1 and 2, when the striking velocity of the projectile
increases from 510 to 850 m/s, which means the impact kinetic energy increases about
2.7 times, for various compressive strength and fiber addition fractions, the corresponding average impact cratering diameters d c increases about 6.7% (87.3 MPa),
0% (99.3 MPa), 25% (67.5 MPa), 12% (125.2 MPa) and 17.7% (114 MPa), respectively. Comparably, the cratering depths h c increases about 60% (87.3 MPa), −16%
(99.3 MPa), 30% (67.5 MPa), 21% (125.2 MPa) and 2% (114 MPa), respectively.
It indicates that, under the same compressive strength and fiber mixing fraction, the
impact cratering dimensions enlarges with rising the striking velocities.
Besides, taking tests 3–5 for considerations, for shots A-4-1 and A-4-3 (2% fiber
addition) in test 1, shots A-4-2 and A-4-4 (2% fiber addition) in test 2, shot B-3-1
(3% fiber addition) in test 3, shot B-3-2 (3% fiber addition) in test 4, shot B-3-3 (3%
fiber addition) in test 5, the compressive strengths of the targets are nearly equal
(125.2 and 128 MPa, 2% deviation). Figure 5.13a shows the variations of impact
crater dimensions with the impact energy of the projectiles under above shots.
Additionally, for shots A-2-1 and A-2-3 (no fiber addition) in test 1, shots A-2-2
and A-2-4 (no fiber addition) in test 2, shot B-2-1 (2% fiber addition) in test 3, shot B2-2 (2% fiber addition) in test 4, shot B-2-3 (2% fiber addition) in test 5, compressive
strengths (87.3 and 88 MPa, 1% deviation) are almost the same. Figure 5.13b shows
the variations of impact crater dimensions with the impact energy of the projectiles
under above shots.
From Fig. 5.13a, we can find that, under the same compressive strength, the
dimensions of the impact crater increases with rising the impact kinetic energies of
the projectile while the fiber addition ratio increases from 2 to 3%. As in Fig. 5.13b,
the dimensions of the impact crater decreases with the rising of the impact kinetic
energies of the projectile while the fiber addition ratio increases from 0 to 2%. Thus,
we may draw a conclusion that, the influential degrees of the opposite contributions
of the impact kinetic energy in enlarging the crater dimensions as well as the fibers in
reducing the crater dimensions are difficult to determine. This is because the eventual
119
the fiber mixing ratio from 0% to 1.5% makes the corresponding averaging cratering
diameter decrease from 457.5 mm to 267.5 mm (decreases by nearly 42%) and
488 mm to 267.5 mm (decreases by nearly 45%), respectively. In comparison, when
the compressive strength of the target varied from 87.3 MPa to 114 MPa, increasing
the fiber mixing ratio from 0% to 3% makes the corresponding averaging cratering
diameter decrease from 457.5 mm to 141.5 mm (decreases by nearly 70%) and
488 mm to 166.5 mm (decreases by nearly 66%), respectively.
The above comparison indicates that the larger reduction of the cratering diameter
is when the fiber mixing ratio increases from 0 to 1.5%. Furthermore, the cost of
every cubic meter UHPCC (about 2.5t) with 3% steel fibers volumetric ratio is about
35% higher than that of UHPCC (about 2.5t) with 1.5% steel fibers volumetric
ratio. By comprehensively considering the crack-prohibiting efficiency, costs and
the workability of the composites, 1.5% of the fiber mixing ratio is the most efficient
and economical for UHPCC in the construction of protective structures.
(3) The influence of projectile striking kinetic energy
By comparing with the tests 1 and 2, when the striking velocity of the projectile
increases from 510 to 850 m/s, which means the impact kinetic energy increases about
2.7 times, for various compressive strength and fiber addition fractions, the corresponding average impact cratering diameters d c increases about 6.7% (87.3 MPa),
0% (99.3 MPa), 25% (67.5 MPa), 12% (125.2 MPa) and 17.7% (114 MPa), respectively. Comparably, the cratering depths h c increases about 60% (87.3 MPa), −16%
(99.3 MPa), 30% (67.5 MPa), 21% (125.2 MPa) and 2% (114 MPa), respectively.
It indicates that, under the same compressive strength and fiber mixing fraction, the
impact cratering dimensions enlarges with rising the striking velocities.
Besides, taking tests 3–5 for considerations, for shots A-4-1 and A-4-3 (2% fiber
addition) in test 1, shots A-4-2 and A-4-4 (2% fiber addition) in test 2, shot B-3-1
(3% fiber addition) in test 3, shot B-3-2 (3% fiber addition) in test 4, shot B-3-3 (3%
fiber addition) in test 5, the compressive strengths of the targets are nearly equal
(125.2 and 128 MPa, 2% deviation). Figure 5.13a shows the variations of impact
crater dimensions with the impact energy of the projectiles under above shots.
Additionally, for shots A-2-1 and A-2-3 (no fiber addition) in test 1, shots A-2-2
and A-2-4 (no fiber addition) in test 2, shot B-2-1 (2% fiber addition) in test 3, shot B2-2 (2% fiber addition) in test 4, shot B-2-3 (2% fiber addition) in test 5, compressive
strengths (87.3 and 88 MPa, 1% deviation) are almost the same. Figure 5.13b shows
the variations of impact crater dimensions with the impact energy of the projectiles
under above shots.
From Fig. 5.13a, we can find that, under the same compressive strength, the
dimensions of the impact crater increases with rising the impact kinetic energies of
the projectile while the fiber addition ratio increases from 2 to 3%. As in Fig. 5.13b,
the dimensions of the impact crater decreases with the rising of the impact kinetic
energies of the projectile while the fiber addition ratio increases from 0 to 2%. Thus,
we may draw a conclusion that, the influential degrees of the opposite contributions
of the impact kinetic energy in enlarging the crater dimensions as well as the fibers in
reducing the crater dimensions are difficult to determine. This is because the eventual