Page 4 - Open-Access-Dec-2019

TECHNICAL PAPER

effeCt of passive

ConfineMent proviDeD

froM engineereD

CeMentitious

CoMposites (eCC)

Cover on Corrosion of

steeL reinforCeMent ZhITAO ChEn, XIn QIn,

KhIn Phyu Phyu ThAw, En-huA yAng

Abstract Fundamentally, corrosion-induced cracking and spalling of
concrete cover are attributed to the brittle nature of concrete.
This paper investigates the effect of passive confinement Adding fibres either metallic or polymeric into cement-based
provided from ECC cover on corrosion of steel reinforcing materials (FRCs) can improve their tensile strength, tensile
bars. ECC and fibre-reinforced concrete (FRC) with different ductility, cracking resistance and damage tolerance [10-12] , which
fibre dosage are used as cover materials to provide different can overcome the brittle nature of concrete. Among them, the
levels of passive confinement to the steel reinforcement Engineered Cementitious Composites (ECC) is a new class of
subject to corrosion. Results showed that specimen with ECC high performance fibre-reinforced cementitious composites
cover showed significant performance improvement with featuring high tensile ductility and damage tolerance. Unlike
reduced mass loss and mass loss rate of steel reinforcement conventional FRC which still shows post-peak tension softening,
and increased residual flexural load capacity. The fundamental ECC exhibits tensile strain hardening with the formation of
change of failure mode of cover material from brittle to ductile is multiple micro-cracks after matrix first cracking [13, 14] .
the key to enhance the corrosion resistance in R/C.
It has generally been accepted that addition of fibres in the
Keywords: Corrosion, Engineered Cementitious Composites,
Fibre-reinforced concrete, Steel reinforcement. concrete cover can reduce and prevent corrosion-induced
cracking and spalling, and thus corrosion rate may be slowed
down in the propagation phase after corrosion initiation [15, 16] .
1. INTRoDUCTIoN
Most studies conclude that the fibres could provide a positive
Corrosion of steel reinforcement is one of the leading effect on protection of steel corrosion in cracked concrete due
causes of deterioration of many reinforced concrete (R/C) to superior crack bridging capacity [17, 18] . The fibres can suppress
infrastructures [1-3] . Corrosion of steel reinforcement in concrete the crack growth after cover cracking resulting in the decrease
is an electrochemical process which involves the formation of a of the permeation of harmful substances [19, 20] . However, few
cathode and an anode on steel reinforcement. In the presence studies are carried out to study the effect of passive confinement
of moisture and oxygen, corrosion of reinforcing steel starts and failure mode of concrete cover material on the corrosion of
when the protective passivity layer of oxide on the surface of the steel reinforcement. The transition from brittle to ductile failure
steel is destroyed known as de-passivation due to carbonation mode of cover materials might lead to different response of
of concrete, ingression of chloride ion through concrete cover, steel corrosion.
or both [4-6] . Since the volume of corrosion products, i.e., rust, is
several times larger than that of original steel, strong expansion This paper investigated the effect of passive confinement
force builds up along the rebar and concrete interface which and failure mode of cover material on the corrosion of steel
causes cracking and spalling of concrete cover [7-9] . Cover reinforcement. ECC and FRCs with different fibre were used
cracks allow rapid ingress of aggressive chemicals from the as cover materials to provide different levels of passive
environment and thus further accelerates corrosion. confinement to the steel reinforcement subject to corrosion.

10 The IndIan ConCreTe Journal | deCember 2019