25 years of field exposure of pre-cracked concrete beams; combined impact of spacers and cracks on reinforcement corrosion

We present the preparation and inhibition behavior of rebar in the presence of calcium nitrate (CN)-containing microcapsules with concentrations of 0.50, 2.00, and 5.00 wt.% in concrete. From both open circuit potential (OCP) and electrochemical impedance spectroscopy spectra, it was found that an addition of microcapsules containing CN corrosion inhibitor into concrete beams successfully repassivated or maintained the passivity of the rebar when the concrete was cracked. This corrosion inhibitor repassivated the rebar by forming a passive layer on the rebar surface under the crack. This repassivation process was evident by an increase of OCP values to more positive values or by stable OCP values at around -100 mV vs SCE. An increase in phase angle after corrosion activation for the sample with 2.00 wt.% microcapsule clearly showed this repassivation process. The optimum concentration for maintaining the passivity on rebar in the cracked concrete was found to be 5.00 wt.%.

Download Full-text

Shear behavior degradation and failure pattern of reinforced concrete beam with chloride-induced stirrup corrosion

Advances in Structural Engineering ◽

10.1177/1369433219855917 ◽

2019 ◽

Vol 22 (14) ◽

pp. 2998-3010 ◽

Cited By ~ 1

Author(s):

Zhao-Hui Lu ◽

Hai Li ◽

Wengui Li ◽

Yan-Gang Zhao ◽

Zhuo Tang ◽

...

Keyword(s):

Shear Strength ◽

Reinforced Concrete ◽

Concrete Beams ◽

Concrete Strength ◽

Shear Behavior ◽

Reinforced Concrete Beams ◽

Failure Pattern ◽

Reinforcement Corrosion ◽

Shear Span ◽

Depth Ratio

Reinforcement corrosion exhibits an adverse effect on the shear strength of reinforced concrete structures. In order to investigate the effects of chloride-induced corrosion of reinforcing steel on the shear behavior and failure pattern of reinforced concrete beams, a total of 24 reinforced concrete beams with different concrete strength grades and arrangements of stirrups were fabricated, among which 22 beams were subjected to accelerated corrosion to achieve different degrees of reinforcement corrosion. The failure pattern, crack propagation, load–displacement response, and ultimate strength of these beams were investigated under a standard four-point loading test in this study. Extensive comparative analysis was conducted to investigate the effects of the concrete strength, shear span-to-depth ratio, and stirrup type on the shear behavior of the corroded reinforced concrete beams. The results show that increasing the stirrup yielding strength is more effective in improving the shear strength of corroded reinforced concrete beams than that of concrete compressive strength. In terms of three types of stirrups, the shear strength of the beams with deformed HRB-335 is least sensitive to stirrup corrosion, followed by the beams with smooth HPB-235 and the beams with deformed HRB-400. The effect of the different stirrups on the shear strength depends on the corrosion degree of stirrup and shear span-to-depth ratio of the beam. The predicted results of shear strength of corroded reinforced concrete beams by a proposed analytical model are well consistent with the experimental results.

Download Full-text

Influence of Cracks on the Service Life of Concrete Structures in a Marine Environment

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.399.153 ◽

2008 ◽

Vol 399 ◽

pp. 153-160 ◽

Cited By ~ 10

Author(s):

Katrien Audenaert ◽

Liviu Marsavina ◽

Geert de Schutter

Keyword(s):

Service Life ◽

Marine Environment ◽

Thermal Effects ◽

Influencing Factor ◽

Concrete Structures ◽

Reinforcement Corrosion ◽

The Finite Element Method ◽

Test Program ◽

Cracked Concrete ◽

Set Up

Chloride initiated reinforcement corrosion is the main durability problem for concrete structures in a marine environment. If the chlorides reach the reinforcement steel, it will depassivate and start to corrode in presence of air and water. Since the corrosion products have a larger volume than the initial products, concrete stresses are induced, leading to spalling and degradation of the concrete structures. If cracks, caused by early drying, thermal effects, shrinkage movements or overstress, are present in the concrete, the penetration of chlorides is much faster compared to uncracked concrete. In this way, the corrosion process is initiated earlier and the service life is decreasing drastically. In order to study the influence of existing cracks in concrete structures on the penetration of chlorides a test program was set up at the Magnel Laboratory for Concrete Research of Ghent University, Belgium in cooperation with the “Politehnica” University of Timisoara, Romania. The first part of the test program consists of concrete specimens with artificial cracks. The chloride penetration into the concrete was realised with a non-steady state migration test and modelled with the finite element method COSMOS/FFE Thermal software. Based on the experimental and numerical results, a crack influencing factor was determined. With this factor, the resulting service life of the cracked concrete construction is determined and compared with the original service life.

Download Full-text