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Purpose – The purpose of this paper is to determine if a type of cactus mucilage, Opuntia ficus-indica (OFI), may act as a corrosion inhibitor for carbon steel in cement-based materials (mortar) exposed to chloride-laden environment. Design/methodology/approach – Mortar prisms, reinforced with carbon steel rods, were immersed in sodium chloride (NaCl) solution for five wet – dry cycles. The experimentation included electrochemical monitoring (corrosion potential, Ecorr, and polarization resistance, Rp) of carbon steel during the time of exposure until corrosion-induced cracking appeared at the mortar surface. Crack survey on the mortar prisms was performed. Carbon steel rods were retrieved from the mortar after crack survey and steel mass loss at the end of the experimental period was estimated. A comparison between the different mixtures was also performed. Findings – OFI mucilage did perform as a corrosion inhibitor of steel in chloride contaminated mortar. Research limitations/implications – The experimental program needs to be corroborated in concrete specimens with typical dimensions. The surface oxide/hydroxide formation of the carbon steel in contact with the OFI mucilage is still unknown; thus, electrochemical impedance spectroscopy (EIS) and X-ray diffraction (XRD) analyses are needed. Practical implications – OFI mucilage is a suitable natural product that can be used to increase durability of concrete structures not only in countries where OFI cactus is produced, but also in many other countries where this plant is considered a plague. Originality/value – The new information obtained from this paper is the innovative use of a by-product of this cactus plant for construction industry applications.

This paper presents results on the corrosion performance of reinforcing steel in alkaline media when dehydrated Opuntia Ficus Indica (Nopal) was used as an admixture. The dehydrated Nopal material was mixed with saturated calcium hydroxide (SCH) at 0.5, 1.0, and 2.0% by weight. Half cell potentials and Linear Polarization Resistance (LPR) measurements were performed at different time periods to characterize the corrosion inhibiting effect of the admixture. Results showed good corrosion inhibiting effect of dehydrated Nopal on reinforcing steel. The polarization resistance (R P ) value increased from an average of 40 kW cm 2 for regular chloride-contaminated SCH solution, to an average of 150 kW cm 2 for Nopal-added chloride-contaminated SCH solutions. The addition of Nopal led to the formation of a denser and more packed oxide/hydroxide surface layer on the steel surface that decreased corrosion activity. This oxide/hydroxide layer growth was confirmed from microscopic evaluation of the metal surface layer performed at the end of the experiment.

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