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MONTEIRO, P. J. M.; KURTIS, K. E.; RODRIGUES, F. A. Integrated research on the microstructure and surface chemistry of reinforced concrete durability. In: CONGRESSO BRASILEIRO DO CONCRETO, 40., 1998, Rio de Janeiro. Anais… Rio de Janeiro: IBRACON, 1998.
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Abstract

Most concrete durability problems involve complex interactions between diverse deterioration mechanisms. Even though a significant amount of research on specific topics has been performed, Mehta [1] points out that a "an overemphasis on the reductionism of science the belief that all aspects of a complex structure or phenomenon can be understood by reducing them to parts has led to fragmentation and limitation of knowledge." He also strongly suggests that research on concrete durability should follow a holistic approach, integrating "the experimental knowledge with the totality of available scientific knowledge." The objective of this proposal is to establish an integrated study of durability of reinforced concrete. The research will focus on the three main chemical attacks to concrete structures: corrosion of reinforced concrete. sulfate attack, and alkali-aggregate reaction. All deleterious attacks on reinforced concrete involve expansive phase transformations of colloidal or gel-like materials that result in stresses on the concrete. In the case of alkali-silica reaction (ASR), it is the formation of an alkali-rich silica gel. In delayed sulfate attack, it is the transformation of aluminum hydroxide gels and calcium sulfate minerals into ettringite. In the case of steel corrosion, it is the depassivation of the surface layer by conversion from tight iron oxides to loose hydrous rust. These transformations are influenced by solution chemistry (especially alkalies, Cl and pH), temperature and atmospheric gases (oxygen and carbon dioxide). Another common factor is that they all develop expansion through incorporation of water molecules into the crystal/gel structure. Finally, they can also interact with each other, for example, ASR and ettringite formation are found in.combination in deteriorated concrete, and techniques to repassify steel in reinforced concrete can promote ASR. Up to now, it has been very difficult to characterize these processes because of the lack of experimental methods that can observe structures on the very fine length scales 10 -100nm of colloidal particles, especially under hydrous conditions. Consequently, it has not been possible to develop reliable chemical and physical models of the mechanisms of damage or methods to prevent their occurrence. However, an array of materials characterization techniques developed by Berkeley and the National Labs now make it possible to make detailed observations of these processes. Moreover, theoretical developments in colloid and surface science pioneered at Berkeley now make a coordinated attack on these problems feasible
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