Effect of the degree of corrosion on bond performance of Cement Polymer Composite (CPC) Coated steel rebars

Deepak K Kamde,Radhakrishna G Pillai,M.G Alexander,H Beushausen,P Moyo,F Dehn

doi:10.1051/matecconf/201819904010

Deepak K Kamde, Radhakrishna G Pillai + Show 4 more

Open Access

https://doi.org/10.1051/matecconf/201819904010

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Abstract

Currently, large infrastructures (bridges, highways, etc.) are designed for more than 100 years. To achieve long service life, coated rebars (mostly, cement polymer composite (CPC) coated rebars) are being used to enhance the corrosion resistance. However, inadequately coated rebars can lead to premature corrosion. This can also affect the bond between the rebar and the concrete. To assess the effect of CPC coating on bond strength, pull-out specimens of (150×150×100) mm with 12 mm diameter rebar with 100 mm embedded length were cast and tested. For this, three replica specimens with two types of reinforcement namely, i) Uncoated steel ii) CPC coated steel were cast. To induce corrosion, additional five specimens with CPC coated steel rebars were cast with premixed chloride and cured for 28 days. During the curing period, continuous monitoring of corrosion potential and rate was done and degree of corrosion was assessed. The effect of degree of corrosion on bond of steel-concrete-coating interface was quantified. The CPC coated rebars without corrosion exhibited 10% bond reduction. CPC coated rebars with corrosion exhibited 30-70% reduction in bond strength. Also, the corrosion is found to adversely influence the stiffness of the bond.

Highlights

The service life of RC structures is defined as the duration for which structure is able to safely meet the performance requirements
This paper presents the influence of Cement Polymer Composite (CPC) coating and corrosion on the bond strength between the rebar and concrete
In uncoated steel-concrete systems, the bond stress-slip behaviour is dependent on the adhesion, friction, and mechanical interlocking between steel and concrete

Summary

Introduction

The service life of RC structures is defined as the duration for which structure is able to safely meet the performance requirements. In the case of uncoated rebars, corrosion can result in reduction of bond between steel and concrete. A recent study showed that a mass loss less than 2.5% does not influence the bond behaviour of uncoated steel [4]. It was reported that the initial corrosion products (say, up to 3% mass loss) can result in reactionary confinement and mechanical interlocking, leading to increased frictional force between uncoated rebar and concrete [5]. This paper presents the influence of CPC coating and corrosion on the bond strength between the rebar and concrete. To investigate the effect of coating on the bond between the rebar and concrete, pull-out specimens (as per IS 2770 – Part 1 (2007)) with following reinforcements were cast: 1) uncoated, 2) cement polymer composite (CPC) coated steel rebars. To evaluate the effect of corrosion, the specimens with CPC coated steel rebars were embedded in concrete with premixed chlorides (2% NaCl by weight of cement)

Specimen preparation

Exposure and pull-out test

Results and discussion

Conclusions