Some reinforced concrete structures must be repaired at an early stage in their life due to the oxidation processes suffered by their reinforcements; such processes involve serious pathologies that affect the stability and safety of buildings. Spanish legislation distinguishes several classes of environments, with non-aggressive and normal exposure providing a longer useful life of the structure. The present study shows that some structural elements in reinforced concrete, mainly the pillars in the area of contact with the ground, are exposed to significant corrosion by carbonation. This position of the structural elements dramatically and abruptly shortens the useful life of the models provided for the current regulations. A total of 17 pillars in 10 buildings of different ages and locations in the Spanish Mediterranean area, not subject to the presence of chlorides, have been analyzed. These buildings are situated in environments considered by the standard as normal and non-aggressive. The actual carbonation that these elements present have been compared with that which can be derived from the model established by Spanish regulations. Of these pillars, 14 present a carbonation higher than that derived from the model, and the last three pillars largely conform to the figures of the model. This significant deviation shows the need for a revision of the Spanish EHE 08 regulation, which should include aspects such as the action of dampness by capillarity and the differences in electrochemical potential between the different materials.

This research presents a new intervention methodology on arches and vaults of a Renaissance factory in the Colegio Santo Domingo de Orihuela (16th century) using 3D software LIDAR technology that verifies the execution process of the works studying the different charges states and structure behavior. This document aims to explain a working methodology in the monitoring of structural repair interventions in the architectural heritage, in the specific case of the replacement of traditional one-way timber joist frame slabs on structures of former, splay and groin arches between vaults. This involves the compilation and processing of two types of data: on the one hand, the analysis of the different load states to which the intervention is exposed in its different phases: initial, dismantling of the different layers of traditional construction and replacement by the new structural system; and, on the other hand, the graphic information provided by the photogrammetry techniques used to dimension and define the spatial position of the structural elements that have historically resolved the covering of the architectural space in this type of Renaissance solution. The different layers and demolished materials have been verified by analysing their constructive disposition, thicknesses, and dimensions of the elements that formed part of the initial construction system and their own weights. In addition, the new construction systems used in the restoration project generate a state of loads similar to the existing one. The LIDAR technology used in the research process provides graphic data of the spatial position of the arches and vaults studied in the different states of the construction intervention. The point clouds obtained are analysed by taking as reference fixed points (considered unalterable and infinitely rigid) of the refectory and the coordinates of the initial and final states are compared. The results show minimal variations between the two positions, which justifies the goodness of the construction methods used and the structural safety obtained in the complex. This methodology applied to arches and vaults in heritage architecture guarantees the control and recording of the movements produced in the process.

The structural systems of residential buildings in many developed countries have widely utilized reinforced concrete as the most common solution in construction systems since the early 20th century. The durability of reinforced concrete columns and beams is compromised, in most cases, by pathologies caused by the corrosion of their reinforcements. This study analyses the corrosion processes induced by carbonation in 25 buildings with reinforced concrete structures. The models estimate the service life of reinforced concrete elements by differentiating between the initiation period and the propagation period of damage, considering two possible stages: the time of corrosion propagation until the cracking of the concrete cover, and the time of propagation until a loss of section is considered unacceptable for structural safety. However, the mathematical expressions that model the propagation periods consider the same corrosion rate in both cases. This research has found that the average corrosion rate in elements with an unacceptable loss of reinforcement section was in the order of 8 times higher than the corrosion rate in cracked columns and beams without a loss of reinforcement. This opens up a path to improve the definition of the different stages experienced by a reinforced concrete element suffering corrosion of its reinforcements due to carbonation, because once the concrete has cracked, the corrosion rate increases significantly.

This paper provides a solution to the covering of spaces in buildings by substituting masonry vaults comprising voussoirs for traditional horizontal slabs. They are made of precast concrete with cement mortar joints. They are intended for covers with maintenance loads but without live loads and their function is to create a singular vaulted interior space. The vaults must be supported by a vertical auxiliary traditional structure, such as a plane frame of beams and pillars made of reinforced concrete, or by masonry walls. The horizontal reaction forces have to be borne by steel braces or buttresses. The basic geometry is standardized by a span of 6 m, with a rise in the key of 0.80 m and a constant vault thickness of 0.28 m. The curvature of the arch is achieved by the modification of the thickness of the mortar joints; spans of 3–6 m, with different rises of the arch, can be easily obtained. The main aim of this research is the reintroduction of arches and vaults as structural elements in present day architecture, which have the added advantage of not needing the addition of steel; this eliminates the risk of steel corrosion. The use of these techniques can also provide an easy way to construct homes in developing countries that lack adequate resources and tools. The solution aims toward more sustainable construction and is specifically designed for new buildings; however, it can also be used in building rehabilitation cases.

Most regulations on the manufacturing of concrete for reinforced concrete structures rest on durability models that consider the corrosion of reinforcements. Those models are based on factors such as humidity, frost, presence of chlorides, and internal characteristics of the concrete itself, like resistance, porosity, type of cement, water/cement ratio, etc. No regulations, however, adopt a purely constructive perspective when evaluating the risk of corrosion, i.e., the relative position of the reinforced concrete in buildings. The present work focuses on the relationship between the position of the damaged element and the building envelope. A total of 84 elements (columns and reinforced concrete beams) across twenty buildings were analysed in the provinces of Alicante and Murcia (Spain). The reinforcement concrete of these elements underwent carbonation-induced corrosion according to their positions in the buildings: (A) façade columns in contact with the ground; (B) interior columns in contact with the ground; (C) columns of walls in contact with the ground; (D) columns and external beams protected from rain; (E) columns and external beams exposed to rain; (F) columns and beams in air chambers under sanitary slabs; and (G), columns and interior beams. Of all types, elements (E) and (F) suffered carbonation-induced corrosion faster than the models used in the regulations, and type (G) underwent slower carbonation.

In the present work, the composition of a corroded reinforcing steel surface is studied at different pH values (related to different degrees of development in the corroding zones of the corrosion process) in solutions simulating chloride-contaminated environments. The media considered consist of saturated calcium hydroxide solutions, progressively neutralized with FeCl₂ or by adding 0.5 M NaCl to the solution. The results found in present work confirm higher levels of acidity in the solutions with higher concentrations of Fe²⁺.In the present work, emphasis is given to the composition of the oxides in solutions that simulate the conditions that exist inside of a localized corrosion pit as a consequence of the reaction of chloride on reinforcing steel. The oxides were studied using Raman and XPS techniques; the results obtained with both techniques are mutually coherent. Thus, in the passive state, the oxides found are those reported previously by other authors, while in the corroding state, the present results are more comprehensive because the conditions tested studied a variety of pore solution composition with several pH values; we tried to reproduce these values inside the pits in conditions of heavy corrosion (very acidic). The oxides found are those typically produced during iron dissolution and seem not the best route to study the corrosion process of steel in concrete; the electrochemical tests better characterize the corrosion stage.