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Se presentan las nuevas expresiones para calcular la resistencia a corte de muros diafragma de mampostería incluida en el Capítulo 4 de las Normas Técnicas Complementarias para el Diseño y Construcción de Estructuras de Mampostería 2017 del Gobierno de la Ciudad de México. Se consideran tres modos de falla: por aplastamiento, por deslizamiento y por tensión diagonal. Las expresiones se adaptaron de las especificadas en el código canadiense, utilizando los parámetros de resistencia usados en la norma mexicana, y se refiere a una resistencia a corte en los tres modos de falla. Se verificó que los resultados de resistencia calculados con estas expresiones dan resultados satisfactorios, al compararlos con resultados de una campaña experimental que también se presentan aquí. La campaña experimental incluyó seis especímenes, escala 1:2, en los que las variables de estudio fueron la rigidez relativa muro/marco, el uso de elementos de confinamiento y el refuerzo horizontal. Los resultados indican que la rigidez relativa muro/marco tiene un efecto relevante en la resistencia al agrietamiento del muro y la resistencia máxima del sistema. Adicionalmente, la contribución del refuerzo horizontal a la resistencia lateral depende de la rigidez relativa muro/marco, un fenómeno que las expresiones de diseño no toman en cuenta. Los elementos de confinamiento no incrementan la resistencia lateral ni la capacidad de desplazamiento del sistema; sin embargo, las dalas y castillos mejoran la estabilidad fuera del plano del muro y el contacto entre el muro y el marco.

A finite element (FE) method was proposed to calculate the corrosion penetration depth (rcrit) on steel reinforcement necessary for the first visible crack to appear on the concrete cover. The FE analysis was carried out using the commercial software from ANSYS. The obtained FE method is a function of free concrete cover depth (C), reinforcement diameter (D), length of the anodic zone (L), and concrete type. The results show a strong influence of localized corrosion (small-size anode versus large-size cathode) on the prediction of the rcrit value. This influence can only be analysed three-dimensionally. The proposed FE method is validated with experimental results from literature. This approach is a novelty in considering the longitudinal direction in the analysis to account for the extension of the anodic cell. Corrosion type strongly depends on the C/L ratio, this leads to uniform corrosion for values between 0.02 < C/L1 < 0.1 and localized corrosion for values between 0.5 < C/L < 4.0.

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.

Reinforced concrete was fabricated using recycled concrete coarse aggregate and replacing partially Portland cement with supplementary materials as fly ash, ground granulated blast furnace slag and silica fume. On test specimens, partially immersed in 3.5% Na2SO4 aqueous solution, the efficiency of the supplementary materials against corrosion was evaluated. For such aim, corrosion potentials and corrosion current density of reinforcement were determined by means of electrochemical techniques as Open Circuit Potential (OCP) and Linear Polarization Resistance (LPR), respectively. The results show that the silica fume addition was the best efficiency against steel corrosion.

The kinetics of corrosion was evaluated and the deterioration of the reinforced concrete made with recycled aggregate and pozzolanic materials was inferred. Four series of cylindrical specimens were made with water-binder ratio of 0.48; the reference series was made with natural aggregate and 100% Compound Portland Cement, the second series was with recycled coarse aggregate (RA) and a 100% CPC, a third series was made with RA, 30% fly ash and 70% CPC and the fourth series was made with RA, 10% silica fume and 90% CPC. Test specimens of each mixture were exposed to a 3.5% NaCl aqueous solution and the corrosion current density was obtained using Electrochemical Impedance Spectroscopy (EIS). The results show that the system of concrete with recycled aggregate and with silica fume addition has more corrosion resistance, because it presented the highest values of Resistance of charge transfer of reinforcement