The deteriorations of reinforced concrete and the option of high performances reinforced concrete

摘要

The durability of a reinforced concrete construction could be defined as the ability of the two materials, concrete and the embedded reinforcing steel, to maintain their physical and mechanical performances in satisfactory security conditions during the prescribed service life of the structure and in prescribed working conditions. From this, it can be deduced that the durability of a concrete construction is strongly related to that of concrete, the reinforcement being protected inside. Both, designers and contractors using this building material should concentrate on this acute durability problem particularly that environments nowadays are becoming more and more aggressive and the performances of the material are pushed to higher limits. In general, the sources of deterioration of concrete are linked to the direct influence of the external environment such as harmful chemical attacks and freeze-thawing. In these cases, the permeability of the concrete material is a crucial factor, which is strongly related to the quality of the concrete mix used. In this sense, high performances concrete, with its reduced quantity of mixing water and hence a reduced porosity and a compact internal structure, is expected to have a better behaviour by not allowing external aggressive agents to penetrate deeper inside. The sources of deterioration may also develop within the internal structure of the material and in this case the constituents of the concrete itself are the causes of the deteriorations of the material such as the Alkali-Silicate reaction, which induces an internal disruption ending up in a complete cracking of the concrete material and eventually in a strength reduction or a precipitated failure of the structure. This work studies the main causes of concrete deteriorations and emphasises on the challenges of high performances concrete as a viable option to enhance the durability of concrete constructions and hence to fulfil the need for a sustainable built environment.