4. Mass concreting

Massive structures such as dikes, dams and replacement concretes require the use of large unit quantities of concrete. In such cases, the main problem is thermal in origin, as the large volume of concrete generates a high level of heat release, which in turn causes thermal expansion of the mass, while the surface remains relatively cooler (particularly after stripping): this can lead to cracking.

In general, to mitigate these degradations, the engineer will tend to :

• reduce heat release from cement hydration by lowering its dosage and compensating with mineral additions;

• use larger chippings, taking care to avoid segregation of the concrete during placement;

• evacuate the heat released by the concrete (circulation of cold water through pipes in the...