This study evaluates the stability and transport behaviors of hazardous nanoparticles into soil landfills using experimental procedures to simulate the effects of natural silica nanoparticle suspensions during their percolation into the soil layers of municipal waste landfills. For this, we prepared stabilized suspensions of nanoparticle oxides containing silicon (NPSiO 2 ), titanium (NPTiO 2 ), copper (NPCuO) and zinc (NPZnO), which are recognized as hazardous to the environment, and we conducted leaching experiments within the soil column by simulating landfills layers and simulating the capture and attenuation of nanomaterials into municipal waste landfills. The results demonstrated that the presence of NPSiO 2 in suspensions increases the stable concentrations of copper, zinc and titanium oxides and strongly decreases soil layer effectiveness. In contrast, NPZnO improves effectiveness due to its ability to promote agglomeration and setting conditions, allowing further complexation.
Protection techniques against corrosion for concrete structures are required when there is concern about the possibility of corrosion of steel reinforcement. Among the techniques available as corrosion protection techniques, cathodic protection is outstanding for both preventing premature corrosion as well as reducing an ongoing corrosion process. Abroad, the cathodic protection technique has been applied to several types of concrete structures, especially those subject to corrosion attack by chloride ions. In Brazil, this technique is hardly used regarding concrete structures which is partially due to the lack of knowledge of cathodic protection techniques and the lack of commercially available systems for application for concrete structures (reinforced or prestressed). The objective of this paper is to present the principle of cathodic protection both for new concrete structures as well as for those in the process of steel reinforcement corrosion. Cathodic protection methods with impressed current and with sacrificial anodes are discussed. A case study with the use of impressed current cathodic protection is also presented.A adoção de técnicas de proteção às estruturas do concreto é recomendada quando há preocupação com a corrosão das armaduras de aço--carbono. Dentre as principais técnicas, destaque-se a proteção catódica que pode tanto evitar a corrosão prematura como diminuir um processo corrosivo em curso. No exterior, a técnica de proteção catódica tem sido aplicada em vários tipos de estruturas de concreto, especialmente nas sujeitas à corrosão pelo ataque de íons cloreto. No Brasil, essa técnica é pouco usada em estruturas de concreto, o que decorre, em parte, do desconhecimento sobre o seu princípio de funcionamento e da ausência de sistemas disponíveis para aplicação ao concreto (armado ou protendido). O objetivo deste trabalho é apresentar o princípio da proteção catódica para estruturas com armaduras de aço-carbono novas ou já em processo de corrosão. Os métodos de proteção catódica por corrente impressa e por anodo de sacrifício são discutidos. Um caso prático com uso de proteção catódica por corrente impressa, também, é apresentado.Palavras-chave: concreto, proteção catódica, corrente impressa, proteção galvânica. AbstractResumo
The heritage of modern architecture in exposed reinforced concrete has been shown pathological manifestations affecting the structural safety and functionality of the buildings. The manifestations are, primarily, associated with the steel corrosion; however published data obtained from site surveys, on the Brazilian architectural heritage and related to the issue, are still scarce in the literature. Thus, the aim of the study is to assess the current condition of the exposed concrete façades reinforcement of the Vilanova Artigas building, a Brazilian architectural heritage, opened in 1969. Legal restrictions limited the destructive tests and sampling areas. The history of the interventions, environmental aggressiveness and preliminary inspection (in the parent concrete and patch repairs) provided qualified information for analyzing in situ testing results. In the sampling areas physical, chemical and electrochemical tests were carried out. The façades surfaces are naturally porous, irregular, with concrete segregation and corrosion products stains; 24% of the concrete was replaced with proprietary mortar repair. In patch repairs, the average carbonation depth ranged from 3 to 29 mm, in concrete it ranged from 15 to 30 mm. The reinforcement cover ranged from 8 to 33 mm. Corrosion potential maps, with equipotential lines drawn at 50 mV intervals, indicated the corrosion-prone areas, where there is a concentration of lines with a variation equal to or greater than 150 mV. The presence of corrosion products, detected in the visual examination of the reinforcement under the patch repairs, validated the active corrosion state. The rough surface of the concrete, the low cover to depassivated reinforcement and the active corrosion state emphasize the need for monitoring the façades and the urgency of implementing a preventive maintenance plan, along with a conservation project in order to preserve the heritage values of the building.
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