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TECHNICAL PAPER

Table 5: Nomenclature assigned to concrete moisture. This was done by keeping the specimen in closed
o
specimens chamber at 30 ± 2 C and RH of 60-70% for 15 days. After
preconditioning, specimens were subjected to total number of
CEMENT TYPE ADMIXED CHEMICAL NOMENCLATURE
8 exposure cycles. Each exposure cycle was consisting of 7-day
OPC - OC
chloride ponding (5% NaCl solution) followed by 2 day of air
OPC 4-Aminobenzoic acid OA drying and7-day carbonation exposure respectively. To ensure
OPC Triethylphosphate OT one dimensional penetration of chlorides, a plexiglass of size
280 × 280 × 70mm was installed on the top [as shown in Figure
Table 6: Mix Proportions
2(a)]. The carbonation chamber which was programmed to a
MATERIAL QUANTITY (kg/m ) CO 2 concentration of 5%, temperature of 28 ± 5 °C, and 70 ± 5%
3
Cement 410 RH [as shown in Figure 2(b)].
Fine Aggregates 572.4
Coarse Aggregate (20mm) 836.34 2.4 Electrochemical measurements
Coarse Aggregate (10mm) 360.4 To monitor the corrosion rate in RC specimens, different
Water 180 non-destructive techniques have been utilised, such as Half
Cell Potential (HCP) and Linear Polarization Resistance (LPR).
carbonation depth and chloride concentration. Former two HCP is one of the most utilised procedures which predicts
properties, indicates their corrosion inhibition efficiency, while the probability of corrosion and is governed by ASTM C876
[33]
later two gives an indication of pore blocking effect. For standards. HCP measurements were performed with ACM field
measurement of first two properties, prism specimens of size
300 × 300 × 150 mm were used. Three Thermo Mechanically
Treated (TMT) bars conforming to IS: 1786-1985 were
[31]
embedded in the specimen and were prepared in accordance
with the ASTM G109 . One rebar was embedded at the top
[32]
with a clear cover of 15mm and other two were placed at
bottom with clear cover of 25mm as shown in Figure 1. For other
two properties, concrete cubes of size 100 mm were used. For
uni-dimensional penetration of carbon dioxide and chloride ion;
only one face of cube remained exposed while other faces were
sealed by applying epoxy on the surfaces of cube. Corrosion (a) Specimen subjected to chloride ponding
inhibitors were added by 1% weight of cement as an admixture
in concrete during casting of specimens. All the specimens were
cast in triplicate in order to ensure precision.

2.3 Exposure Condition

All the specimens were demoulded after 24 hr and water
cured for 7 days at temperature of 27± 2 C and RH of 100%.
o
Subsequently the specimens were kept in the laboratory
environment for next 7 days with RH between 60-80%. Before (b) Specimen exposed to carbonated environment in environment
subjected to combined environment, all the specimens chamber
were preconditioned in order to achieve even distribution of Figure 2: Exposure of RC specimens

Figure 1: Specimen preparation for accelerated corrosion test

THE INDIAN CONCRETE JOURNAL | APRIL 2021 31