Bond strength prediction for reinforced concrete members with highly corroded reinforcing bars

<p>Reinforced concrete structures are subjected to several sources of deterioration that can reduce their load-resisting capacity over time. This has significant consequences for the management of infrastructure, leading to high costs of maintenance, repair, strengthening and premature decommissioning. Assessing the residual capacity of structures is challenging but paramount to manage the infrastructure network effectively. Corrosion of the internal steel reinforcement is among the main causes of deterioration in reinforced concrete bridges. The subsequent reduction in steel-to-concrete bond strength is difficult to evaluate with accuracy. There is no unified theory of general validity. Most existing models adopt measures of the level of corrosion as the key parameter to evaluate the bond reduction. In this paper, a different approach is investigated. Corrosion-induced splitting crack widths are used as the fundamental indicator of bond strength reduction, irrespective of the associated degree of steel corrosion. Available experimental results on deformed steel bars embedded in concrete subjected to either natural or accelerated corrosion, with or without transverse reinforcement, are analysed and compared with a different perspective. The analysis indicates that this new splitting crack-based approach can lead to more accurate predictions. This contributes to a better understanding of the fundamental principles underlying bond of corroded reinforcing bars. Enhanced assessment strategies can lead to a reduction of the safety risks, maintenance costs and environmental footprint of the infrastructure network.</p>

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Bond Strengths of Geopolymer and Cement Concretes

Advances in Science and Technology ◽

10.4028/www.scientific.net/ast.69.143 ◽

2010 ◽

Vol 69 ◽

pp. 143-151 ◽

Cited By ~ 8

Author(s):

Prabir Sarker

Keyword(s):

Reinforced Concrete ◽

Bond Strength ◽

Concrete Cover ◽

Reinforced Concrete Structures ◽

Geopolymer Concrete ◽

Reinforcing Steel ◽

Test Results ◽

Reinforcing Bars ◽

Pull Out ◽

Bar Diameter

Geopolymer is an inorganic alumino-silicate product that shows good bonding properties. Geopolymer binders are used together with aggregates to produce geopolymer concrete which is an ideal building material for infrastructures. A by-product material such as fly ash is mixed together with an alkali to produce geopolymer. Current research on geopolymer concrete has shown potential of the material for construction of reinforced concrete structures. Structural performance of reinforced concrete depends on the bond between concrete and the reinforcing steel. Design provisions of reinforced concrete as a composite material are based on the bond strength between concrete and steel. Since geopolymer binder is chemically different from Ordinary Portland Cement (OPC) binder, it is necessary to understand the bond strength between geopolymer concrete and steel reinforcement for its application to reinforced concrete structures. Pull out test is commonly used to evaluate the bond strength between concrete and reinforcing steel. This paper describes the results of the pull out tests carried out to investigate the bond strength between fly ash based geopolymer concrete and steel reinforcing bars. Beam end specimens in accordance with the ASTM Standard A944 were used for the tests. In the experimental program, 24 geopolymer concrete and 24 OPC concrete specimens were tested for pull out. The concrete compressive strength varied from 25 to 55 MPa. The other test parameters were concrete cover and bar diameter. The reinforcing steel was 500 MPa steel deformed bars of 20 mm and 24 mm diameter. The concrete cover to bar diameter ratio varied from 1.71 to 3.62. It was found from the test results that the failure occurred by splitting of concrete in the region bonded with the steel bar, in both geopolymer and OPC concrete specimens. Comparison of the test results shows that geopolymer concrete has higher bond strength than OPC concrete. This suggests that the existing design equations for bond strength of OPC concrete with steel reinforcing bars can be conservatively used for calculation of bond strength of geopolymer concrete.

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Local bond strength prediction of deformed reinforcing bars in concrete by considering heterogeneity at interface regions

Magazine of Concrete Research ◽

10.1680/jmacr.21.00013 ◽

2021 ◽

pp. 1-62

Author(s):

Shutong Yang ◽

Miao Yu ◽

Kun Dong ◽

Yushan Yang

Keyword(s):

Bond Strength ◽

Strength Prediction ◽

Reinforcing Bars

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