Preventative measures
For concrete in contact with aggressive ground, it is obviously desirable that cement with a good record of sulfate resistance […]
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.
For concrete in contact with aggressive ground, it is obviously desirable that cement with a good record of sulfate resistance […]
There are various methods available for minimizing the risk of ASR-induced expansion in concrete, including: · use of non-reactive aggregate (or
Bonded post-tensioning In this method, the prestressing steel is placed in ducts and, after stressing, is bonded to the surrounding
Post-tensioning with or without bonding of tendons Read Post »
Introduction In the previous section it was rather cavalierly remarked that at setting, `the mix solution is seamlessly carried over
Widespread international use is made of these materials, e.g. as grouts and mortar patches for finish and repair work and
Polymer-modified cement, mortar and concrete Nature of systems Read Post »
Mechanisms The development of microstructure is considered to proceed by a basic three- step process (Isenburg, 1974; Ohama, 1987). Immediately
Polymer-modified cement, mortar and concrete Microstructure development Read Post »
Thaumasite is normally formed at temperatures below ca. 15ëC and preferably at 0±5ëC, which seems to be the optimal temperature
Possibility of thaumasite formation under pressure at ambient and higher temperatures Read Post »
Stiffness It is generally considered (Ohama, 1998) that the addition of polymer will reduce the stiffness of the PMC and will
Polymer-modified cement, mortar and concrete Mechanical properties Read Post »
Water absorption When comparing PMC of given type produced at constant workability, it is found that the water absorption and permeability
Polymer-modified cement, mortar and concrete Durability Read Post »