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TECHNICAL PAPER

machine (serial 1463) using saturated calomel electrode as
reference electrode. The measurements were taken parallel to
the rebar at five points and the average value was considered
Step 1:
as the final HCP value of the specimens. The LPR measurement Filtration
of
was done using ACM field machine provided with guard ring for drilled
restraint current on prismatic specimens. Guard ring was placed samples
over the concrete top face parallel to the rebar line as shown in
Step :2
Figure 3. Adding potassium
chromate indicator
The LPR test (non destructive type) was performed on RC
specimen by applying over potential of ±25mV at a sweep
rate of 0.167mV/sec in order to avoid the casting of multiple Step :3
specimens. However, potentio-dynamic scan (PDP) is preferred Titration
by
over LPR in order to obtain the passivating current density, AgNO 3
especially in case of organic inhibitors. The HCP and LPR tests
were performed after completion of each exposure cycle.
Figure 4: Chloride concentration determination by titration method
2.5 Free chloride Content
The carbonation depth in concrete was measured for each
th
th
The chloride concentration in concrete was measured at the end sample (i.e., control and inhibitor admixed) after 4 and 8
of 4 and 8 exposurecycle. The steps involved for determining cycle. The depth of carbonation was determined by spraying
th
th
chloride concentration are shown in Figure 4. For finding phenolphthalein solution on freshly broken specimen. Given
out chloride concentration the powdered sample powder non-carbonated portion indicated by purple colour and
from cubes were obtained by drilling the cubes at 10 mm, carbonated zone is uncoloured. Depth of carbonated part was
20 mm, 30 mm, 40 mm and 50 mm depth from the exposed measured using vernier calliper of least count 0.01mm from
surface. Samples from six different locations were collected the exposed side of the cube by averaging 10 different points
from each concrete cube and kept in air tight packets. For along the edge of broken surface. The procedure for measuring
the determination of free chloride content, 3 g of concrete carbonation depth is shown in Figure 5.
powder was transferred to a 100-mL beaker and 50 mL of
distilled water was added. The sample was heated gently and 3. RESULTS
thoroughly mixed by a stirrer. The solution was then cooled and
filtered using Whatman No. 1 filter paper and the free chloride 3.1 Half-cell potential measurement
content was then determined by titrating against 0.1M AgNO3 Figure 6 reveals the HCP values for OPC control as well as
solution [34-35] . The steps involved in determination of chloride inhibitor admixed specimens exposed to combined aggressive
concentration are shown in Figure 4. environment. HCP values were measured after every exposure
cycle.
2.6 Carbonation depth

Linear polarization
Step 1: Splitting specimen
Half Cell measurement in to halves

Aggregate

Step 2: Application of
phenolphthalein solution

Step 3: Measure depth
by vernier calliper

Figure 3: Test setup for electrochemical corrosion measurement Figure 5: Carbonation depth measurement

32 THE INDIAN CONCRETE JOURNAL | APRIL 2021