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 mathematical model to predict the time to the initiation of corrosion-induced cracking of reinforced concrete structures was developed. To determine the corrosion penetration in reinforcement steel, a three-dimensional finite element model was developed. Modeling was based on geometric parameters such as the free concrete covering, reinforcement bar diameter, type of concrete, and the corroded length. Using finite element and statistical analyses, mathematical expressions were calculated to obtain time-to-corrosion cracking. Calculated cracking times were compared to published experimental data. The parametric sensitivity of the model is established with reference to published experimental evidence, and the role of the important design variables in the evolution of this mechanical problem is identified and discussed.

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.

The main cause of deterioration of concrete structures is due to the penetration of aggressive ions such as chloride ion. Concrete is considered as a material formed by several phases such as paste and aggregate; therefore, obtaining an analytical solution to the problem of ionic transport becomes very complex. In this work the mechanism of ionic transport of diffusion and migration of these ions is investigated using a mesh free method, which does not need to generate a mesh to obtain an approximate solution of the problem. The method of Radial Basis Functions with multiquadric core is used to simulate the transport of ions and obtain profiles of concentration of chlorides at different times of a concrete sample subject to an externally applied electrical potential.