Cymbopogon citratusand NaNO₂Behaviours in 3.5% NaCl-Immersed Steel-Reinforced Concrete: Implications for Eco-Friendly Corrosion Inhibitor Applications for Steel in Concrete

Abstract

This paper studies behaviours of Cymbopogon citratus leaf-extract and NaNO 2 , used as equal-mass admixture models, in 3.5% NaCl-immersed steel-reinforced concrete by nondestructive electrochemical methods and by compressive-strength improvement/reduction effects. Corrosion-rate, corrosion-current, and corrosion-potential constitute electrochemical test-techniques while compressive-strength effect investigations followed ASTM C29 and ASTM C33, in experiments using positive-controls for the electrochemical and compressive-strength studies. Analyses of the different electrochemical test-results mostly portrayed agreements on reinforcing-steel anticorrosion effects by the concentrations of natural plant and of chemical admixtures in the saline/marine simulating-environment and in the distilled H 2 O (electrochemical positive control) of steel-reinforced concrete immersions. These indicated that little amount (0.0833% cement for concrete-mixing) of Cymbopogon citratus leaf-extract was required for optimal inhibition efficiency, = 99.35%, on reinforcing-steel corrosion, in the study. Results of compressive-strength change factor also indicated that the 0.0833% Cymbopogon citratus concentration outperformed NaNO 2 admixture concentrations also in compressive-strength improvement effects on the NaCl-immersed steel-reinforced concrete. These established implications, from the study, on the suitability of the eco-friendly Cymbopogon citratus leaf-extract for replacing the also highly effective NaNO 2 inhibitor of steel-in-concrete corrosion in concrete designed for the saline/marine service-environment.

Recent Advances in the Use of Green Corrosion Inhibitors to Prevent Chloride-Induced Corrosion in Reinforced Concrete

“…Cymbopogon citratus leaf extract inhibition efficiency is verified by Okeniyi et al [54] on NaCl-immersed concrete reinforced with carbon steel rebars. It is found that a leaf extract concentration of 0.083% vs. cement weight is sufficient to guarantee an IE% equal to 99.35%.…”

“…Another plant extract of interest is the one obtained from Cymbopogon citratus, a grass widely known and cultivated in Asia and India. A content of 0.083% vs. cement weight inside mortars gives an efficiency of 99.35%-beyond the inhibitive properties obtained by using 0.417% of NaNO 2 -also having beneficial effects on the mechanical properties of the tested concrete samples [54]. An interesting comparison between a green inhibitor and nitrites was offered by [46], who evaluated the effectiveness of licorice.…”

Biological Corrosion Inhibitors for Concrete

“…h) Fresh leaves of Bambusa Arundinacea are used as corrosion mitigators in reinforced concrete when its ecofriendly, non-toxic and hydrophobic extract is added in concrete during casting [29]. i) A tropical plant, Cymbopogon citratus or lemon grass extract is superior than sodium nitrite in inhibiting corrosion [30]. A minor quantity of its extract is enough to add compressive strength and corrosion inhibition efficiency of RC.…”

Use of Lawsonia Inermis and Sodium Nitrite as Surface Applied Corrosion Inhibitors

“…Due to the chloride attack, acid or sulphate attack, degradation of reinforcement in concrete occur which leads to the breakdown of the passivation film surrounding the reinforcement and makes the steel vulnerable to corrosion. Corrosion due to chloride attack on steel reinforcement bars in concrete is more dangerous because chloride ion promotes and accelerates the corrosion reaction by forming an intermediate product but without the chloride ion being consumed through the reaction process (Okeniyi et al 2018). Contaminated water, aggregate and admixtures containing chlorides are some of the ways the chlorides get into the fresh concrete.…”