Some of the aggregates used today contain alkali-reactive silicic acid. This can react with the alkali hydroxide dissolved in the concrete pore water to form an alkali-silicic acid gel. This reaction is called the 'alkali-silica reaction' (ASR) and can lead under certain circumstances to massive damage to the concrete. The introduction of the new Alkali Directive [5] by the building authorities and the new DIN 1045 2 [1] has resulted in far-reaching consequences throughout Germany, not only for the manufacturers of aggregates and concretes, but also for the planners of buildings constructed from concrete and steel reinforced concrete.