The aim of the study was to identify mechanisms acting at internal frost destruction of concrete. By 'internal frost destruction' is meant damage caused inside concrete that is moisture insulated from the surroundings, i.e. when no moisture exchange with the surroundings is possible during freeze-thaw. Thus, the aim was not to investigate destruction processes (scaling) taking place at the surface of concrete exposed to water or salt solution. The aim should be reached by experimental work at which different parameters, that are supposed to influence destruction, such as concrete quality, moisture content, freezing rate, and duration of freezing temperature were varied independently of each other. The effect of these parameters on formation of ice, and on the behaviour of the concrete during freeze-thaw should be monitored. In this way it was imagined that the individual effect of each fundamental parameter could be identified. The aim was to use the experimental results to test different existing destruction theories like the hydraulic pressure theory and the microscopic ice lens theory. The aim was not to build a quantitative model for internal frost destruction.