2.4 Test Results and Discussions
43
Fig. 2.12 Effects of steel fiber content and type on the dynamic compressive properties of UHPCC
a peak stress b peak strain c dynamic elastic modulus, Ren et al. (2018), copyright 2020, with
permission from Elsevier
patterns of UHPCC specimens under static and dynamic loadings lead to
the different effects of steel fiber mixing ratio. Under the static loadings,
the specimen only has one major crack across the weak zone and the fiberbridging effect plays an important role to delay the formation and propagation
of the cracks. Under the dynamic loadings, the specimen is fractured into
fragments and the steel fibers are pulled out from the matrix, which makes the
fiber-bridging effect weakening to some extent.
(iii) The micro-straight steel fiber has slightly better effect on improving the
dynamic compressive strength of UHPCC with the volume fraction of 2.0%
than the hooked steel fiber at a similar strain rate, while these two types of steel
fibers have the similar enhancement effect on that when the steel fiber content
is 1.0%. For example, at the strain rate around 155.7 s
−1 , the dynamic compressive strength of UHPCC with 2.0% micro-straight steel fibers is 226.7 MPa,
which is 7.7% and 4.4% larger than that of the plain UHPCC and UHPCC
with 2.0% hooked steel fibers, respectively.
43
Fig. 2.12 Effects of steel fiber content and type on the dynamic compressive properties of UHPCC
a peak stress b peak strain c dynamic elastic modulus, Ren et al. (2018), copyright 2020, with
permission from Elsevier
patterns of UHPCC specimens under static and dynamic loadings lead to
the different effects of steel fiber mixing ratio. Under the static loadings,
the specimen only has one major crack across the weak zone and the fiberbridging effect plays an important role to delay the formation and propagation
of the cracks. Under the dynamic loadings, the specimen is fractured into
fragments and the steel fibers are pulled out from the matrix, which makes the
fiber-bridging effect weakening to some extent.
(iii) The micro-straight steel fiber has slightly better effect on improving the
dynamic compressive strength of UHPCC with the volume fraction of 2.0%
than the hooked steel fiber at a similar strain rate, while these two types of steel
fibers have the similar enhancement effect on that when the steel fiber content
is 1.0%. For example, at the strain rate around 155.7 s
−1 , the dynamic compressive strength of UHPCC with 2.0% micro-straight steel fibers is 226.7 MPa,
which is 7.7% and 4.4% larger than that of the plain UHPCC and UHPCC
with 2.0% hooked steel fibers, respectively.