Theory

The corrosion of steel reinforcement is one of the main causes of damage and premature failure of reinforced concrete structures, increasing the costs for inspection, maintenance, restoration, and replacement of infrastructure. Recently, Dr. Talakokula and Prof. Bhalla (2015) proposed a new corrosion assessment approach based on the mechanical impedance EMI technique (Refer thesis of Dr. Vislalakshi Talakokula for more information) click here. Figures 1(a) and 1(b) present the experimental setup for the rebar corrosion related laboratory experiments for bare rebar and embedded rebar respectively.

Figure 1: Data acquisition setup for accelerated corrosion in (a) bare rebar (b) embedded rebar

EXPERIMENTAL DETAILS

In the accelerated corrosion experiments of bare rebar, following components are used:

• Copper rod acting as Cathode.

• Bare rebar acting as Anode.

• PZT patches bonded to rebar which is further connected to LCR meter by electrodes.

• Beaker containing brine solution whose salinity is 35 parts per thousand.

For accelerated corrosion experiments in embedded rebars, the components are same except that a 150 x 150 x 150 mm concrete cube with an embedded bar replaces the bare rebar as shown in Figure 2(a) and 2(b) respectively.

EXPERIMENTAL PROCEDURE
The setup for accelerated corrosion for bare rebar and reinforced concrete is shown in Figure 2(a) and 2(b) respectively. Through this animation, the user can visualize the process of accelerated corrosion and can obtain signatures of the PZT patchs bonded to rebar during various stages. Figure 2 shows a screenshot of the animation. The user can visualize the process by plotting in excel and observe the changes in signature with increasing corrosion.

Figure 2: Setup for accelerated corrosion (a) Bare rebar (b) Reinforced Concrete

To statistically quantify damage, compute root mean square deviation (RMSD) in conductance by following equation directly in MS excel:

where

G_i⁰ = Baseline conductance value at i^th frequency.

G_i¹ = Conductance value after a damage at i^th frequency.

n = No. of frequency data points

As an exercise plot a histogram of RMSD for the various damaged states. Note your observations and draw conclusions.