3.3 Dynamic Spalling Test
61
Fig. 3.6 Determination of the dynamic spalling strength (Rong and Sun 2012)
where τ t is the time required from the tensile stress of the specimen reaching the
rupture, which is obtained by multiplying the number of stress waves (the peak stress
of which is lower than the dynamic spalling strength) and the time interval 1.0 μs,
as shown in Fig. 3.6. E S is the approximate tensile elastic modulus. Hao et al. (2016)
has formulated the dynamic compressive/tensile elastic modulus of concrete, which
is dependent on the strain rate and could not directly applied at present. In Ref. (Ren
et al. 2018), we have experimentally studied the dynamic compressive mechanical
behavior of UHPCC, by assuming the tension–compression symmetry of UHPCC,
the E S of the N-0, S-1, S-2, H-1 and H-2 UHPCC specimens are adopted as 46.0 GPa,
47.3 GPa and 48.1 GPa, 46.4 GPa and 48.2 GPa, respectively.
3.4 Test Results and Discussions
3.4.1 Dynamic Failure Patterns
The typical dynamic failure patterns of UHPCC specimens with different steel fiber
contents and types are shown in Fig. 3.7. In which the white numbers represent the
distance “l” between the first fractured section and the free end of specimens, and
the corresponding tensile strain rates are given under the photos. Besides, the tiny
cracks are highlightened by the solid red lines in Fig. 3.7(b–e).
It can be observed that the fractured sections of all specimens are relatively flat
and perpendicular to the longitudinal axes of specimens, and the damage degree of
UHPCC specimens without mixing fibers (N-0) is more severe than that of steel
61
Fig. 3.6 Determination of the dynamic spalling strength (Rong and Sun 2012)
where τ t is the time required from the tensile stress of the specimen reaching the
rupture, which is obtained by multiplying the number of stress waves (the peak stress
of which is lower than the dynamic spalling strength) and the time interval 1.0 μs,
as shown in Fig. 3.6. E S is the approximate tensile elastic modulus. Hao et al. (2016)
has formulated the dynamic compressive/tensile elastic modulus of concrete, which
is dependent on the strain rate and could not directly applied at present. In Ref. (Ren
et al. 2018), we have experimentally studied the dynamic compressive mechanical
behavior of UHPCC, by assuming the tension–compression symmetry of UHPCC,
the E S of the N-0, S-1, S-2, H-1 and H-2 UHPCC specimens are adopted as 46.0 GPa,
47.3 GPa and 48.1 GPa, 46.4 GPa and 48.2 GPa, respectively.
3.4 Test Results and Discussions
3.4.1 Dynamic Failure Patterns
The typical dynamic failure patterns of UHPCC specimens with different steel fiber
contents and types are shown in Fig. 3.7. In which the white numbers represent the
distance “l” between the first fractured section and the free end of specimens, and
the corresponding tensile strain rates are given under the photos. Besides, the tiny
cracks are highlightened by the solid red lines in Fig. 3.7(b–e).
It can be observed that the fractured sections of all specimens are relatively flat
and perpendicular to the longitudinal axes of specimens, and the damage degree of
UHPCC specimens without mixing fibers (N-0) is more severe than that of steel