Proceedings of the International rilem conference Materials, Systems and Structures in Civil Engineering 2016

96

International RILEM Conference on Materials, Systems and Structures in Civil Engineering 

Conference segment on Service Life of Cement-Based Materials and Structures 

22-24 August 2016, Technical University of Denmark, Lyngby, Denmark 

 

cover [4] [5]. Due to the mechanical deleterious effect of the corrosion phenomenon, it is 

important to develop non-destructive techniques as well as predictive numerical modelling to 

assess the corrosion evolution of RC structures. This could help the structure's end users to 

provide an efficient maintenance policy. The main issue of this paper is to design a specific 

protocol to generate a "controlled" corrosion evolution versus time in order to bring some 

experimental evidences on the concrete cover cracking process due to corrosion and to 

determine relevant input parameters for the numerical modelling.  

 

2.

 

Experimental program 

2.1

 

Materials and specimens  

Twelve single-rebar specimens (500x125x100mm

3

) were casted with a 600mm long and 

20mm diameter steel deformed rebar. The reinforcement was positioned to obtain a 30mm 

concrete cover at two sides of the beam [Figure 1]. The specimens designed with a not 

symmetric location of the rebar aim to get closer to reality, to represent the heterogeneity of 

the mechanical environment of the reinforcement in a structure

. 

A Portland cement and 

siliceous aggregates were used for the concrete composition with a water to cement ratio of 

0.73. This ratio is representative of old reinforced concrete structures. Moreover, it allows the 

penetration of the chloride ions during the accelerated corrosion test.  

 

 

Figure 1. Schematic representation of RC specimens (dimensions in millimeters) 

The cement type used for the concrete composition was CEM I 52.5 CP2 NF according to 

European standards. Concrete was prepared with aggregates having different particle size 

classes ((0/0.315 mm; 0.315/1 mm; 0.5/1 mm; 1/4 mm; 2/4 mm; 4/8 mm; 8/12 mm; 12.5/20 

mm)). Compressive and tensile strengths were measured on concrete cylinders (160mm in 

diameter, 320mm in height) after 28 days according to NF EN 12390-3 [6] and

 

NF EN 12390-

6 [7] standards. The mean compressive strength is 32 MPa ± 2.46, the tensile strength is 2.6 

MPa ± 0.08 and the Young's modulus is 35 GPa ± 1.58. The Poisson's ratio is equal to 0.15. 

2.2

 

Accelerated corrosion tests and monitoring system 

The set-up used for accelerated corrosion test and the monitoring system are illustrated in 

[Figure 2]. RC samples were corroded using a power supply (Agilent 6614C, 100V, 0.5A) 

which delivered an imposed anodic current to the steel rebar. The counter electrode (cathode) 

consisted in an inert platinum titanium mesh (275mm long, 75mm wide) placed into a PVC 

tank containing the

 

alkaline

 

electrolyte (1 g/L of NaOH, 4.65 g/L of KOH, 30 g/L of NaCl) 

which was glued on the top side of the concrete (in the middle of the specimen). All the 

specimens were connected in series and a current density of 100 μA/cm² of steel (0.0172A for 

a steel surface area of 172.8 cm²: diameter 20mm and length 275mm) was applied during the 

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97

International RILEM Conference on Materials, Systems and Structures in Civil Engineering 

Conference segment on Service Life of Cement-Based Materials and Structures 

22-24 August 2016, Technical University of Denmark, Lyngby, Denmark 

 

chosen exposure time (7d, 14d, 21d, 28d and 35d). At the end of each considered exposure 

time, two specimens were disconnected from the electrochemical test set-up. One of the 

specimens was used for the non-destructive electrochemical characterization and the other one 

was dedicated to destructive measurements. The accelerated corrosion test was monitored 

using a data acquisition unit (Keysight 34970A): temperature, delivered constant current, each 

sample voltage and total voltage were recorded every two hours. Moreover, two cameras were 

used for the digital image acquisition of the front side of the two specimens subjected to a 35 

days accelerated corrosion test.  

 

 

 

 

Figure 2. Accelerated corrosion and monitoring system 

2.3

 

Electrochemical characterizations 

In order to determine the corrosion state of the rebar before the accelerated test, half-cell 

potential measurements (E

corr

) linear polarization resistance measurements (LPR) and 

impedance spectroscopy (Re) were carried out, using a potentiostat (Bio-Logic, PARSTAT 

2263) and the usual electrochemical cell with three electrodes. The working electrode was the 

steel rebar, the reference electrode was a KCl saturated calomel electrode (SCE, 242 mV / 

SHE) and the counter electrode was a titanium platinum mesh [Figure 3]. The same 

electrolyte as for the accelerated corrosion test was used. Then the corrosion current density 

J

corr

 (μA/cm²) was calculated based on the following equation:  

J

corr

 =   

                                                                                                                           (1)  

with B a constant (26mV), Rp (ohm) the linear polarization resistance and S (cm²) the steel 

surface (172.78 cm² in this study).  

Data acquisition unit 

Power supply 

Cameras

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