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Institute
It is well known that SCMs containing alumina can prevent the damaging alkali silica reaction in concrete. This paper deals with the direct interactions between aggregate grain surfaces (quartzitic rock material Q1) and the dissolved amounts of SCMs (metakaolin, aluminum hydroxide). Investigations have confirmed that the presence of such SCMs can strongly decrease the silica release from aggregates in comparison to solubility experiments without SCM addition. The reason for this effect is the formation of a thin alumina containing layer (some nanometers thick) on the grain surfaces. The existence of this layer could be determined by XPS. Only this method provides data of the strongly increased alumina concentration in a thin surface area and also of the layer thickness in dependence on reaction parameters. Dissolution experiments of grains coated with such layer demonstrate the effectiveness of this process and can give a further contribution for understanding the preventing mechanisms of SCMs.