土木工程外文文献及翻译

Original Article

Impact of crack width on bond: confined and unconfine

d rebar

David w1, Denglei Tang2, Thoma

s K. C.Molyneaux3 and Rebecca Gravina3

(1)School of the Built Environment, Heriot Watt University, Edinburgh, EH14

4AS, UK

(2)VicRoads, Melbourne, VIC,

Australia

(3)School of Civil, Environmental and Chemical Engineering, RMIT

University, Melbourne, VIC, 3000, Australia

David W. Law

Email:

*************.uk

Received: 14January2010Accepted: 14Decemb er2010Published online: 23December2010 Abstract

This paper reports the results of a research project comp aring the effect of surface crack width and degree of corrosi on on the bond strength of confined and unconfined deforme d 12 and 16mm mild steel reinforcing bars. The corrosion was induced by chloride contamination of the concrete and

an applied DC current. The principal parameters investigated were confinement of the reinforcement, the cover depth, bar diameter, degree of corrosion and the surface crack width. T he results indicated that potential relationship between the cra ck width and the bond strength. The results also showed an increase in bond strength at the point where initial surface cr acking was observed for bars with confining stirrups. No suc h increase was observed with unconfined specimens.

Keywords:bond;corrosion;rebar;cove

r;crack width;concrete

1 Introduction

The corrosion of steel reinforcement is a major cause of the deterioration of reinforced concrete structures throughout

the world. In uncorroded structures the bond between the st eel reinforcement and the concrete ensures that reinforced co ncrete acts in a composite manner. However, when corrosion of the steel occurs this composite performance is adversely affected. This is due to the formation of corrosion products on the steel surface, which affect the bond between the steel and the concrete.

2 Experimental investigation

2.1 Specimens

Fig.1Beam end specimen

Deformed rebar of 12 and 16mm diameter with cover of three times bar diameter were investigated. Duplicate sets of confined and unconfined specimens were tested. The con fined specimens had three sets of 6mm stainless steel stirr ups equally spaced from the plastic tube, at 75mm centres.

This represents four groups of specimens with a combin ation of different bar diameter and with/without confinement. The specimens were selected in order to investigate the infl uence of bar size, confinement and crack width on bond stre ngth.

2.2 Materials

Table1Concrete mix design

Materi al Cement w/c Sand

10 mm

washed

aggrega

te

7 mm

washed

aggrega

te

Salt Slump

Quantit y 381 kg/

m3

0.4

9

517 kg/

m3

463 kg/

m3

463 kg/

m3

18.84 kg/

m3

140 ± 25 mm

(1)

where is the bond strength for grade 40 concrete, τexptl is the experimental bond strength and f c is the experi mental compressive strength.

The tensile strength of the Φ12 and Φ16mm steel ba rs was nominally 500MPa, which equates to a failure load of 56.5 and 100.5kN, respectively.

2.3 Experiment methodology

Fig.2Accelerated corrosion system

When the required crack width was achieved for a parti cular bar, the impressed current was discontinued for that ba