Although chloride is the main source for corrosion of reinforcing steel in coastal buildings, concrete carbonation leads to a uniform corrosion of the steel that would accelerate the crack formation and decrease the structure service life. Therefore, carbonation induced corrosion could be minimized by improving the concrete quality and cover thickness. The objective of this investigation was to study the effect of carbonation on public buildings located up to 800 m from the seashore. Preliminary results based on the analysis of carbonation, resistivity and porosity data suggested the need to increase the concrete cover thickness and concrete quality proportional to the distance from the seashore as well as to their elevation. In general, the higher carbonation coefficients corresponded to the top sections of the evaluated buildings where the measured relative humidity was lower. However, the concrete cracks due to corrosion were found in the lower sections where humidity was higher. Data from lab specimens exposed to the same environment buildings. ,
It is well known that in marine environments, chloride is the element with the strongest influence on reinforced concrete corrosion. However, acidification of concrete due to COZ can occur in places where the right climate conditions are available so that a uniform corrosion can develop. This uniform carbonation-induced corrosion accelerates the concrete crack formation and decreases the residual service life of the concrete structures. Both aggressive agents can interact in marine environments and lead to a much faster deterioration than if either one acts alone. In the North of the Yucatan Peninsula as in other places with tropical marine climate, the aggression of the atmosphere allows a combined action of chloride and carbon dioxide. Humidity and temperature conditions of this region2 promote the advance of the carbonation front3. The carbonation rate will depend on several factors4 such as the type and amount of cement, porosity of the concrete, type and quantity of pozzolanic additions,5 etc. Moreover, modifications in concrete properties as compressive strength, superficial hardness and resistance to aggressive agents (e.g. sulfates) are produced.
Chlorides or carbon dioxide can reach the reinforcement causing depassivation and shortening the propagation period? in which any rehabilitation action will be very expensive. From the engineering point of view, an alternative is to design and construct structures according to their geographic orientation, marine breeze direction, sources of humidity and insulation* and elevation and distance regarding the sea (micro-climate) among others. However, few works have been found with this approach?-l? and neither one correlate data from real structures with those from laboratory specimens exposed at the same microclimate.
In our case, a research to propose modifications to the design of concrete structures situated up to 800 m from the sea based on their susceptibility for corrosion initiation as a function of concrete quality and micro-climate conditions has been initiated. This paper discusses preliminary carbonation data obtained in columns from 10 buildings situated at different distances from the seashore. The results are compared with those from cylindrical specimens that were exposed to the same conditions for five years. 12-14
