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In this paper, the cracking of concrete cover caused by steel bar corrosion was discussed and studied based on the three-period model of steel bar corrosion in concrete. In the analysis, the contour of the corrosion layer was simplified into a semi-ellipse according to the non-uniformity of steel bars in reinforced concrete under a natural environment. The steel bar corrosion was divided into three different periods by two corrosion points, namely, the void to be filled was exactly filled and the concrete cover was exactly cracked. Different assumptions are made for each corrosion period. Before the concrete cover cracks, it is developed into an elastic plate. Based on the theory of elastic mechanics, the maximum corrosion depth of steel bar when concrete cover cracks is predicted. After the concrete cover cracks, a model of the relationship between the crack width of the concrete cover and the maximum corrosion depth of steel bar was established by considering the filling of cracks by corrosion products. The rationality of the model was tested by employing experimental data from the literature, and it was found that the calculated value of the model was in good agreement with the experimental data in the literature. Key words: non-uniform corrosion, three-period of corrosion, concrete cover crack, crack width, corrosion depth. Dans le present document, on a passe en revue et etudie la fissuration de l'enrobage de beton causee par la corrosion des barres d'acier, et ce, sur la base du modele a trois periodes de la corrosion des barres d'acier dans le beton. Dans l'analyse, suivant la non-uniformite des barres d'acier dans le beton arme en milieu naturel, le contour de la couche de corrosion est conceptualise en une semi-ellipse. La corrosion de barres d'acier a ete divisee en trois periodes differentes par deux points de corrosion, a savoir que le vide a remplir etait exactement rempli et que l'enrobage de beton etait absolument fissure. Differentes hypotheses de modele sont faites pour chaque periode de corrosion. Avant que l'enrobage de beton ne fissure, celui-ci est developpe en une plaque elastique. Sur la base de la theorie de la mecanique elastique, on prevoit la profondeur maximale de corrosion d'une barre d'acier au moment de la fissuration de l'enrobage. Apres la fissuration de l'enrobage de beton, un modele de la relation entre la largeur de la fissure d'enrobage et la profondeur maximale de corrosion de la barre d'acier a ete etabli en considerant le remplissage des fissures par des produits de corrosion. La rationalite du modele a ete verifiee en utilisant des donnees experimentales puisees de la litterature, et il a ete constate que la valeur calculee du modele etait en bon accord avec ces donnees experimentales. [Traduit par la Redaction] Mots-cles : corrosion non uniforme, trois periodes de corrosion, fissure de l'enrobage de beton, largeur de la fissure, profondeur de corrosion., 1. Introduction The volume of steel corrosion products in reinforced concrete is 2-6 times that of the original steel (Hansson et al. 2007). The development of volume expansion of steel [...]

This study compared the advantages and disadvantages of various corrosion protection methods for steel rebars and clarified the advantages of the cathodic protection (CP) method in the application of corrosion protection in marine structures. The advantages and disadvantages of sacrificial anodes and impressed current technology for the CP of steel rebars in marine structures were further discussed in detail, and the feasibility of CP applications in practical engineering was evaluated. [ABSTRACT FROM AUTHOR]

This study investigates the enhancement of hydraulic lime mortar (HLM) using varying contents of metakaolin (MK) to improve its application in the restoration of historic buildings. Samples from historic structures were analyzed, and the effects of different MK contents on the physical and mechanical properties of HLM were examined. The reaction mechanism and microstructural changes were evaluated using XRD and SEM analysis. The results indicated that increasing MK levels in HLM led to a decrease in fluidity, with fluidity reducing by 4.8% at 12% MK. The addition of MK increased water consumption for standard consistency by 5.4% and shortened the final setting time by 10.2%. MK consumption promoted secondary hydration, enhancing compressive strength by up to 98.1% and flexural strength by up to 55.1%, and increasing bonding strength by 26.9%. The density of HLM improved with MK addition, slightly reducing moisture content by 4.5% and water absorption by 4.6%, while the water vapor transmission properties decreased by 50.9%, indicating reduced porosity. The elastic modulus of the mortar increased significantly from 2.19 GPa to 7.88 GPa with the addition of MK, enhancing rigidity and crack resistance. The optimal blend for restoration materials was found to be 9.0% MK and 25.0% heavy calcium carbonate and was characterized by moderate mechanical strength, enhanced early strength, commendable permeability, minimal risk of cracking, and ease of application. This blend is highly suitable for the rehabilitation of historic structures. [ABSTRACT FROM AUTHOR]

In order to prepare a green inorganic restoration material that is suitable for the restoration of historical buildings, based on the XRD test results of the bonding materials of several historical brick masonry buildings in Qingdao, an artificial hydraulic lime repair mortar was prepared by mixing metakaolin. The influence of metakaolin on the artificial hydraulic lime mortar was studied by testing the fluidity, setting time, mass loss rate, dring shrinkage rate and mechanical properties. The results show that metakaolin can reduce the fluidity, shorten the setting time, reduce the dring shrinkage rate and improve the compressive strength and bonding strength of artificial hydraulic lime mortar. When the content is 5.0% and 7.5% (mass fraction), the 56 d compressive strength of artificial hydraulic lime mortar increases by 66. 8% and 94.3%, and the bond strength increases by 22.2% and 25.9%. Finally, XRD and SEM were used to test and analyze the microstructure of the materials. The results show that the main reason for the improvement of the performance of the artificial hydraulic lime mortar by metakaolin is that the active SiO2 and Al2 O3 in metakaolin react directly with the lime, and consume Ca(OH)2, which promotes the hydration of cement and enhances the bonding force between the hydrated products and the aggregate. [ABSTRACT FROM AUTHOR]