Page 12 - Open-Access-June-2020

TECHNICAL PAPER

6. IMPACT & BLAST LOADING BEHAVIOR the cracks observed were oriented in both the perpendicular
and longitudinal to the direction of loading in dynamic tests.
Infrastructure is subjected to different types of loadings and However, in the case of quasi-static tests, the longitudinal cracks
one of them is impact and blast for which the materials have to were not observed.
withstand. The high-energy dissipation and damage tolerance
[55]
property of ECC compared to conventional concrete makes it Yang and Li developed two impact resistant ECC mixtures by
suitable to use for impact and blast resistant structures. tailoring micromechanical properties and demonstrated their
impact behavior at high strain rates of magnitude ranging from
−5
6.1 Impact and Blast Behavior of ECC Elements 10 to 10 s . Finally, the study concluded that the impact load
−1
−1
carrying capacity and energy dissipation of RECC beams were
Generally, ECC elements such as beams and panels showed enhanced significantly compared to that of RC beams.
improved impact and blast load carrying capacity, ductility and
[56]
cracking behavior than concrete elements. Few studies (see Zhang et al. evaluated the response of impact loading on
Table 5) have investigated the impact and blast response of ECC ECC blast panels with different thickness and compared with
against concrete as their major interest. RC panels of constant thickness. The study concluded that
the presence of ECC enhances the cracking behavior, impact
Maalej et al. investigated the ballistic impact resistance of resistance and energy absorbing capacity against multiple
[53]
ECC by conducting pneumatic gun tests with prismatic panels. impacts compared to the RC panels.
The study concluded that very little spalling, no fragmentation,
[57]
very small crater size, no scabbing and significant enhancement Nam et al. investigated the impact resistance of ECC
in cracking behavior of ECC specimen were observed. specimens against plain concrete specimens under high
impact velocity and reported that the failure such as scabbing,
Michtcherine et al. investigated the dynamic properties of a perforation and formation of radial cracks was eliminated due to
[54]
Hopkinson bar at high strain rates and compared them against the multiple cracking property of ECC more than plain concrete
the quasi-static uniaxial tensile tests. The study reported that specimen.

Table 5: Impact and Blast Behavior of ECC Elements
sl. type of dimensions loading
no. referenCes speCimen (mm) rate oBjeCtive oBservations
1. Maalej et al. [53] Prismatic c/s - 300×170 300-700 m/s To investigate ECC for its It exhibits a higher strain capacity of 4%.
*
panels t -55, 75, 100, potential as impact and blast
*
resistant material.
120&150
2. Mechtcherine et al. [54] Cylinder with D - 75 140-180 s -1 To investigate the mechanical The specific fracture energy obtained
*
and without l - 250 behavior of ECC using dynamic for notched specimens was 5500 N/m,
*
notch loading and compared with which is 50 times higher than that of
quasi-static loading method. conventional concrete.
3. Yang and Li [55] Beams l - 305 10 to To investigate the impact i) The load carrying capacity and
−5
*
−1
d - 51 10 s −1 resistance of ECC under high energy dissipation of RECC beams
*
loading rate. increased by 32% and 500%,
h - 76
*
respectively compared to RC beams.
ii) The structural load and energy
capacities enhanced by the addition
of steel reinforcement in RECC
beams more than RC beams.
4. Zhang et al. [56] Panels h -2000 - To evaluate the damage and ECC exhibits smaller indentation depth
*
w - 1000 failure response of ECC blast and crater size on the impact face and
*
panels and compared with smaller exit crater on the distal face.
t - 100
*
conventional RC blast panels.
5. Nam et al. [57] Beams h*-300 450 to To investigate the impact The ratio of mass loss of ECC specimen
w*- 300 750 m/s resistance of ECC specimens. decreased with increase in impact
velocity unlike plain specimens. ECC
t*- 100
specimens with more fibers showed
reduced penetration depth due to the
controlled scattered cracking.
* (c/s-cross section, t-thickness, l-length, D-diameter, d-depth, h-height & w-width)
The IndIan ConCreTe Journal | June 2020 13