Evaluation of organic based corrosion inhibiting admixtures for reinforced concrete: Fid-Bau Portal

Evaluation of organic based corrosion inhibiting admixtures for reinforced concrete

Vishnudevan, M. / Thangavel, K.

Purpose - Admixtures are materials that are added to concrete at some stage in its production to give concrete new properties whether in fluid or plastic conditions. The admixtures used in the construction industry are broadly classified into Mineral and Chemical admixtures. In recent years, the use of mineral and chemical admixtures in producing high performance concrete has increased significantly. The chemical reaction of cement with admixtures differs from material to material. Calcium nitrite based corrosion inhibiting admixtures have gained popularity for protection of reinforced and pre-stressed concrete structures but calcium nitrite is not commercialized indigenously in India due to manufacturing difficulties. Hence, the objective of the present investigation was to study a novel corrosion inhibiting admixture system and to compare its effectiveness with sodium nitrite. Design/methodology/approach - Di-sodium phthalate, sodium orthophosphate and sodium nitrite-based corrosion inhibiting admixtures were selected for the present investigation. The critical quantities of corrosion inhibiting additives were determined by accelerated laboratory tests. The following types of tests were conducted to evaluate the efficiency of the corrosion inhibiting admixtures: compressive strength of 100 x 100 x 100 mm concrete cubes after 3,7,14 and 28 days of curing, linear polarization resistance measurements, electrochemical impedance spectroscopy measurements, an accelerated 12 V controlled potential test. Findings - From the above tests, the inhibitor admixtured concrete not only improved in compressive strength but also increased its corrosion resistance properties. Of the inhibitors studied, di-sodium phthalate showed superior corrosion resistance properties, compared to sodium nitrite. Originality/value - Di-sodium phthalate may be considered a better substitute for calcium nitrite-based corrosion inhibiting admixtures for durable concrete structures. This fulfils the objective of the investigation.