Page 5 - Open-Access-June-2020

TECHNICAL PAPER

2. FLEXURAL BEHAVIOR OF ECC ELEMENTS

In general, it is expected that plain and reinforced ECC
(RECC) elements exhibit significant changes in the flexural
characteristics such as (1) load carrying capacity, (2) deformation
and ductility, (3) energy dissipation and damage tolerance owing
to tensile strain-hardening and load carrying property of ECC.
Hence, many research studies (see Table 1) have investigated
the flexural behavior and response of plain and RECC elements
such as beams, composite slab systems and plates.

2.1 Flexural Behavior of Reinforced ECC Beams

While understanding the flexural behavior of ECC beams,
the following parameters such as load carrying capacity and
Figure 2: Compressive Stress-strain response of eCC [12] influence of longitudinal reinforcement, stiffness and ductility,
cracking behavior and failure modes and size effect are to be
explored. Upon considering the above-mentioned parameters,
specimen is shown in Fig. 2. Unlike high strength concrete, some of the notable studies available in literature are presented
the post cracking behavior of ECC is gentle strain-softening, in the following section for better understanding.
accompanied by gradual bulging of the specimen .
[11]
2.1.1 Load carrying capacity and Influence of
Usage of ECC materials in civil engineering infrastructures
is increasing remarkably. ECC can be used for construction Longitudinal Reinforcement
of new seismic resistant structures, more specifically beam- In general, ECC beams with longitudinal reinforcement have
column joints , seismic dampers , seismic resistant wall shown higher load carrying capacity than unreinforced ECC
[13]
[14]
panels , bridge decks and other energy absorbing structures. beams for obvious reasons . For a particular percent of
[16]
[15]
[22]
In addition, ECC can also be applied to all kinds of repair, any (i.e. steel / Fiber Reinforced Polymer (FRP)) longitudinal
retrofitting, and rehabilitation works such as patching repair, reinforcement, ECC beams have shown higher load carrying
overlay repair, etc. of deficient concrete structures to increase capacity than reinforced concrete (RC) beams due to tensile
their inherent ductility and load carrying capacity [17, 18] . Ability of load carrying capacity of ECC [22,12] . The contribution of ECC on
precasting of ECC further contributes to various applications load carrying capacity is found to be higher in balanced, under-
such as floor, plates and infill wall panels [19-21] . By accounting reinforced and significantly under-reinforced ECC beams than
for higher durability of ECC, this material can also be applied over-reinforced beams due to tensile strain-hardening behavior
to all kinds of surface coating to reduce and arrest the cracks of ECC .
[23]
triggered by environmental effects.
ECC exhibits higher load carrying capacity, shear resistance and 2.1.2 Stiffness, Deflection and Ductility
ultra-high ductility. Structural applications of ECC and related
research investigations have come to practice in the year 2000. In general, ECC beams with longitudinal reinforcement have
Over past two decades, several research studies have been shown higher stiffness than unreinforced ECC beams due to
[22]
conducted on the behavior of ECC structural elements and the presence of reinforcement . In the case of steel reinforced
demonstrated its potential. It is worth noting that, no review ECC beams, the initial and post cracking stiffness was less than
[22]
on structural behavior of ECC elements is available at present. that of steel reinforced concrete beams . On contrary, the FRP
Hence, it is necessary to review, discuss and summarize all those reinforced ECC beams had identical initial stiffness but higher
research studies towards successful utilization. In this paper, all post-cracking stiffness than that of FRP reinforced concrete
[24]
the notable research studies related to the behaviors of ECC beams .
structural elements are discussed. At first the flexural, shear, RECC beams with steel/FRP reinforcement have shown higher
axial, and impact behavior of ECC elements are presented. deflection/deformation capacity than RC beams due to multiple
Further, the structural behavior of ECC strengthened elements cracking behavior of ECC [22,24] .
are presented. Furthermore, the behavior of RC elements
repaired/retrofitted using ECC are presented. Finally, the Irrespective of failure modes (i.e. flexural-tension and flexural-
response of ECC members against time dependent seismic compression) steel/FRP reinforced ECC beams showed higher
loadings are discussed. ductility/energy dissipation than RC beams. This is achieved due

6 The IndIan ConCreTe Journal | June 2020