A new predictive 3D FEM model is proposed using the corrosion damage function by measuring the concrete cover crack width, which is a function of the free concrete cover depth, the steel rebar diameter, the mechanical properties of the concrete, and the length of the anodic zone. A significant aspect to evaluate service lifetime conditions in corroded reinforced concrete structures (RCSs) is the concrete cover crack width. Surface cracks originate due to the pressure exerted by the volume expansion of the corrosion products and oxide layer formed on the rebars. In this work, concrete cover crack width on corroded RCS is analyzed by means of finite element method allowing a corrosion damage model to be proposed. The model obtained was used to find a theoretical relationship between the dissolved steel (corrosion process) and the concrete cover crack width. The results were validated using three experimental data sets from the literature: two corrosion case studies in natural environments and one work covering accelerated corrosion in laboratory test conditions. All the beams were exposed to the simultaneous action of flexural stresses and corrosion. A good correlation was observed between the model and the experimental results, thus supporting reliability of the analytical process and validation of the proposed corrosion damage model.

Concrete is a porous material and the ingress of water, oxygen, and aggressive ions, such as chlorides, can cause the passive layer on reinforced steel to break down. Additives, such as fly ash, microsilica, rice husk ash, and cane sugar bagasse ash, have a size breakdown that allows the reduction of concrete pore size and, consequently, may reduce the corrosion process. The objective of this work is to determine the corrosion rate of steel in reinforced concrete by the addition of 20% sugar cane bagasse ash by weight of cement. Six prismatic specimens (7×7×10 cm) with an embedded steel rod were prepared. Three contained 20% sugar cane bagasse ash by weight of cement and the other three did not. All specimens were placed in a 3.5% NaCl solution and the corrosion rate was determined using polarization resistance. The results showed that reinforced concrete containing sugar cane bagasse ash has the lowest corrosion rates in comparison to reinforced concrete without the additive.

A new, sustainable polypropylene terephthalate (PPT) coating was synthesized from recycled polyethylene terephthalate (PET) and applied onto a hydraulic concrete substrate to improve its durability. For the first step, PET bottle wastes were ground and depolymerized by glycolysis using propylene glycol (PG) in a vessel-type reactor (20–180 °C) to synthesize bis(2-hydroxypropyl)-terephthalate (BHPT), which was applied as a coating to one to three layers of hydraulic concrete substrate using the brushing technique and polymerized (150 °C for 15 h) to obtain PPT. PET, BHPT, and PPT were characterized by FT-IR, PET, and PPT using TGA, and the PPT coatings by SEM (thickness), ASTM-D3359-17 (adhesion), and water contact angle (wettability). The durability of hydraulic concrete coated with PPT was studied using resist chloride ion penetration (ASTM-C1202-17), carbonation depth at 28 days (RILEM-CPC-18), and the absorption water ratio (ASTM-C1585-20). The results demonstrated that the BHPT and PPT were synthetized (FT-IR), and PPT had a similar thermal behavior to PET (TGA); the PPT coatings had good adhesion to the substrate, with thicknesses of micrometric units. PPT coatings presented hydrophilic hydrophilic behavior like PET coatings, and the durability of hydraulic concrete coated with PPT (2–3 layers) improved (migration of chloride ions decreased, carbonation depth was negligible, and the absorption water ratio decreased).

Carbonation causes concrete acidification that brings in the loss of the steel rebar's passive layer, which in turn will allow initiation of an active corrosion process. A nondestructive technique to revert this condition is the electrochemical realkalisation (ER) that consists in applying a direct current between the steel bars and an external auxiliary electrode placed on concrete surface with the aim of restoring the alkalinity loss. In the present work is studied the use of a conductive mortar as anode in the electrochemical realkalisation of concrete. Carbonated reinforced concrete specimens with a water/cement ratio of 0.65 were evaluated. ER was applied by 5 days period with a current density of 2 A/m2 and using as anode a layer of modified mortar (add 25% graphite powder by cement weight) saturated with a 1M Na2CO3 solution. The pH in the concrete was determined by the phenolphthalein test and potentiometric titration. After the ER treatment the pH value of the carbonated concrete samples had increased from 8 to 11.95.

In this work the electrochemical behavior of metronidazole is evaluated to inhibit the corrosion process of API 5L X52 steel, in an acidic environment, the active ingredient is obtained by means of purification of a commercial drug, the metallic specimens were immersed in an acid solution (H₂SO₄ 1M), containing the inhibitory substances in concentrations of 0.2, 0.6 and 1.2 mM. The efficiency behavior was determined by the techniques of resistance to polarization and electrochemical impedance. The results show that metronidazole has a corrosion inhibition efficiency of 72% at a concentration of 0.6 mM in an acid medium (H₂SO₄ 1M) for API 5L X-52 steel.