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Collaborating Authors
Results
Corrosion Effects on the Cultural Heritage
Sanchez, Miguel A. (Universidad del Zulia) | Esteso, Miguel A. (Universidad de La Laguna)
ABSTRACT In the last few years a bigger consciousness for the preservation of the cultural heritage has been developed. However, if problems associated with corrosion are not considered, during the necessary interventions on related works, by avoiding the use of materials and resources that make this phenomenon possible, problems associated with the durability of those materials, structure and safety for the citizens will appear. The aim of the present work is to identify, through various examples detected in several historical structures, certain corrosion problems that some of its components present, to establish the origin of the damages and to suggest guidelines for their refurbishment. The last point is the most important one, in order that the specialists in restoration leave rigid and unfounded intervention patterns that cause, in most of the cases, serious damages and put the own restoration in danger, as a consequence of a lack of knowledge about the mechanisms that proceed and which will act in a future if qualified personal on both basic and applied principles of corrosion not be requested. INTRODUCTION Most of the corrosion literature ~3 only highlights the aspects related to economics, preservation of the natural resources, contamination and security, when the corrosion phenomenon is analysed. Some authors mention social aspects 4, although without making reference to the conservation of the historical heritage, and in very few cases the action of raininess on the degradation of the materials is mentioned 5. In the last years consciousness toward the care of the cultural heritage has been stimulated and the protection of both historical monuments as modem artistic works encouraged. At present it is evident that man's great concern to maintain the signs of his existence in each lived time exist. However, in many cases the absence of an appropriate social behaviour toward such preservation is still appreciated which threatens the survival of the heritage. In fact, a great number of structures, those which have remained during centuries, are now liable to suffer a strong degradation mainly as a consequence of mainly the changes in the environment due to an irrational industrial development. For both conservation and restoration, it must be kept in mind the incidence of corrosion. Otherwise, its destructive results will seriously affect the durability of the pieces to protect. In this sense it is necessary to highlight the interaction between materials and the environmental factors (particularly the effect of the average raininess of the region) which promote or facilitate the degradation of this type of structures 5. Within the different materials that conform these structures they emphasize the following: reinforced concrete, stone, bricks, concrete, mortar, lime, plaster and wood. Among them, concrete is one of the most abundant components in the majority of historically interesting structures. Concrete, whose application goes back to several thousands of years, is basically a mixture of an agglomerant, aggregates and water. It is a porous material in which a solid phase exists, made up of hydrated minerals, and a liquid phase contained inside the pores (pore solution). Different searches 6 have shown that when the pore solution contains high quantities of sodium and potassium salts, its pH value remains high. The composition of the solution pore is critical in the case of reinforced concrete. A very alkaline surrounding round the steel armor promotes the formation of a protective passive layer on it, at the time that neutralizes the action of chlorides. The size, distribution and interconnection of the pores fit both the oxygen availability and necessary h
- North America > United States (0.68)
- Europe > Spain (0.47)
- Materials > Construction Materials (0.55)
- Construction & Engineering (0.55)
Evaluation, Diagnosis and Rehabilitation of Buildings in Rural Environments
de Rincon, Oladis (Centro de Estudios de Corrosion) | Perez, Orlando (Centro de Estudios de Corrosion) | Garcia, Octavio (Centro de Estudios de Corrosion) | Sanchez, Miguel A. (Universidad del Zulia) | Vezga, Cesar (Universidad del Zulia) | de Bustillos, Arrieta (Universidad Lisandro Alvarado)
ABSTRACT The objective of this paper is to present, from the structural and corrosion point of view, an evaluation, diagnosis and rehabilitation plan for fifty-two 3-story buildings set in a complex within a rural environment. The construction system is semi-prefabricated, tunnel-type, enclosed within prefabricated no-load- resisting panels. Each building was constructed in two stages, with the two parts of each separated by an expansion joint through which the gas, water and electricity supply were piped. At the end of the first year after delivery, the buildings began to suffer from severe problems: filtration, electrical and structural failures, which increased in volume and complexity. Basically, these were due to the fact that the buildings were set up in expandable clay soils. Structural faults and corrosion were two of the many problems detected-not only of the reinforcing steel in different areas but also of the pipes embedded in the masonry and concrete. Different techniques were used for the evaluation: visual inspection; sounding (hammer); potentials measurements (ASTM Standard C-876); degree of carbonation (Phenolphthalein) and physicochemical analysis of the concrete. Results indicate that both the foundation and superstructure system were inadequate for the structural demands produced by the volumetric changes in the soil and/or continuing settlings. Besides, that reinforcement corrosion in the prefabricated panel/slabs is due to concrete carbonation, given its bad quality. This notwithstanding, corrosion in the roof and ceilings was due to the presence of chlorides in the plaster. Rehabilitation was planned in accordance with the type and extent of damage found. INTRODUCTION Reinforced concrete is one of the most important structural materials used in the construction industry worldwide. Generally speaking it has excellent structural and durability performance but there are examples of early deterioration due to a number of factors, one of the most important being the corrosion of the reinforcement. This leads ultimately to the accumulation of insoluble corrosion products, within the concrete pores near the embedded surface and, subsequently, to the development of tensile hoop stresses and cracking. This can have serious implications both from the point of view of expensive maintenance requirements and, in the longer term, loss of structural integrity if no action is taken. While reinforcement corrosion occurs in poor quality concrete throughout the world, more severe problems are encountered in tropical climates, particularly in coastal locations such as the Venezuelan seashore and the Lake of Maracaibo ~1~. Serious reinforcement corrosion has occurred after short periods since the structures were set up, leading to their virtual re-building or even demolition within less than ten years, in some cases. Such deterioration rates are much higher than those reported in milder climates. Regardless of the exposure condition, steel will only corrode in concrete when it becomes depassivated. This can happen either because of concrete-alkalinity loss or by aggressive-ion attack, or by a combination of both factors.
- North America > United States (0.46)
- South America > Venezuela > Zulia > Maracaibo (0.25)
- Construction & Engineering (1.00)
- Energy > Oil & Gas > Upstream (0.55)
- Materials > Construction Materials (0.36)