ABSTRACT
There are two types of mechanism producing thermally induced stresses, i.e. internal and external confinement. Let us consider a new concrete placement cast on a previously constructed one or on a rock foundation as
shown in Figure 7.1 [1]. The first mechanism is that the gradient of temperature over the section of the structure gives rise to different thermal expansions. Due to the continuity of structure, a selfequilibrated stress will be introduced. The sectional force (integral to the local stress developing over a section) should be zero but the local stress is not zero even if there is no external confinement. In general, tension arises around the surface of a massive concrete structure and compression is observed inside the structure by this mechanism. On the other hand, if the newly cast structure has external confinement through a construction joint or a basement interface, externally induced compression and tension forces will arise according to the change of temperature and solidification. Once thermal cracking occurs during the stage of temperature decay in structures, the cracks never close but continue to open with time. This cracking tends to pass through whole sections of the structure.
