Chemical degradation of concrete
Chemical attack on concrete is a rather complicated subject since the chemistry of concrete itself is complex and the material […]
The purpose of this book is to bring together a series of reviews on topics of current relevance to the durability of concrete and cement-based composites. One might reasonably ask why such a book is now believed to be needed as concrete and related materials have been used with outstanding success in major construction projects for well over two thousand years. Indeed numerous ancient concrete structures, such as the Pantheon in Rome, and masonry structures with mortar joints, such as the Pont du Gard Aqueduct near NõÃmes in southern France (see Fig. 1.1), have survived to the present day in excellent states of preserva- tion. These and other examples of Roman construction works incorporating hydraulic cements made from lime and volcanic earth (or similar vitrified alumino-silicates, known collectively as pozzolanas, after Pozzuoli near Naples where a natural source of such material exists) have shown remarkable dur- ability even where they have been exposed to damp, aggressive environments. An impressive illustration was provided by Davey (1974) whose photograph of part of a Roman breakwater that had been exposed to the sea near Naples for two millennia (reproduced in Fig. 1.2), demonstrates that the mortar joints had endured far more successfully than the now heavily eroded stone blocks which they had been connecting.
Chemical attack on concrete is a rather complicated subject since the chemistry of concrete itself is complex and the material […]
Samples which have undergone DEF exhibit a characteristic microstructure after expansion, in which clear rims are seen around aggregate particles,
Microstructural features and proposed mechanisms of DEF expansion Read Post »
From the foregoing sections, it will be evident that guidance on measures to minimise the risks of premature degradation of
Pure water dissolves lime and, to some extent, alumina from the compounds in the cement matrix resulting in increased permeability
Many other chemicals, e.g. oils, fats, sugars, alkalis and salts, may attack concrete in particular circumstances. A wide range of such
The knowledge of movements and cracking processes presented in this chapter has been developed from theories, research and technical field
Conclusions Dimensional stability and cracking processes in concrete Read Post »
Modelling the chemical degradation of concrete is complex because of the numerous chemical reactions and variety of conditions potentially involved.
The expansive ettringite form of sulfate attack in concrete exposed to aggressive ground is probably the most familiar type that
External sulfate attack involving expansive ettringite formation Read Post »
Three exposure classes (XA1, XA2 and XA3) are described in BS EN 206-1 (2000) according to the aggressiveness of attack on
Sources of guidance for attack on concrete by acid and other aggressive chemicals Read Post »
Groundwaters and soils containing sulfate salts may be liable to cause expansive sulfate attack. Sulfuric acid can also occur naturally