The shrinkage of concrete is one of its greatest disadvantages for concrete structures. The expansive cement is worthy of note as it has disolved the problem of dry shrinkage.
The theory of expansive cement is as follows: at early age, cured in moist atmosphere, the concrete expand to some extent, so the following shrinkage, under drying condition, is compensated.
The self-stressing cement in USSR and the chemical pre-stressed cement in USA are typical expansive cements whose expansive energy is generated by the formation of Ettringite. V. V. Mikhailov, A. Klein and other investigators studied on the application of expansive cement on the pre-stressed concrete, and it was found that some expansive cement could be employed in the manufacture of pre-stressed concrete.
There are many factors, however, having influences on the magnitude and the rate of expansion, the amount of expansive component, the water cement ratio of the mix, the curing condition, the method of restraining the expansion, etc. For the industrial application of the expansive cement, therefore, it is necessary to establish the technique that controls the expansion exactly.
