Alkalis in Portland cement
The predominant source of alkalis in concrete is the Portland cement. As noted in Chapter 2, Portland cement contains relatively […]
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.
The predominant source of alkalis in concrete is the Portland cement. As noted in Chapter 2, Portland cement contains relatively […]
Briefly, alkali-silica reaction is a reaction between the alkali hydroxides in the pore solution of concrete and thermodynamically unstable silica
The alkali-carbonate reaction occurs between alkali hydroxides and certain argillaceous dolomitic limestones; these dolomites are characterized by a matrix of
Traditionally, enhanced durability of concrete is associated with reducing the water/cement ratio. This has some benefit in the case of