TY - CHAP A1 - Hünger, Klaus-Jürgen A1 - Kronemann, Jens A1 - Hübert, Cornelia A1 - Scholz, Yvonne T1 - On the mechanism of ASR inhibition by Si and Al containing SCMs T2 - 13th International Conference on Recent Advances in Concrete Technology and Sustainability Issues, Ottawa, Canada N2 - The use of supplementary cementing materials (SCMs) added to concrete mixtures can avoid the alkali-silica reaction. Such materials have a wide range of composition and therefore the inhibition mechanisms can be very differently. The effectiveness of SCMs which provide silica and alumina into the alkaline solution cannot only be explained by reducing the OH--concentration of the pore solution. From dissolution experiments in potassium hydroxide solutions, an interaction was noted between the aggregate and five SCMs via the alkaline solution. Under specific conditions, no silica is released from the aggregate grains. Mineralogical investigations (XRD, SEM+EDX) of the grain surfaces confirm that quartz is the main source of silica. In the presence of alumina providing SCMs, the quartz dissolution is strongly reduced or even sometimes stopped. On surfaces of grains a very thin layer can be observed which is probably responsible for reduction or stopping of the silica dissolution and therefore for the inhibition of ASR. KW - Alkali-silica reaction KW - alkali reactivity KW - solubility KW - supplementary cementing materials KW - surface layer Y1 - 2015 SN - 978-1-9427272-3-1 SP - 437 EP - 451 PB - American Concrete Institute ER - TY - CHAP A1 - Kronemann, Jens A1 - Hünger, Klaus-Jürgen T1 - Aggregate Reactivity and the Efficiency of Supplementary Cementing Materials T2 - 13th International conference on recent advances in concrete technology and sustainability issues N2 - The knowledge of dissolution processes of aggregates and supplementary cementing materials (SCMs) in alkaline solutions can help to describe the expansion of concretes caused by alkali-silica reaction (ASR) and the effects to avoid ASR by using SCMs in more details. Therefore, dissolution experiments in alkaline solutions under different pH values and different temperatures were performed using aggregates in the original grain size and SCMs in different ratios. The concentrations of soluble silica and additionally alumina were determined by ICP-OES. The investigations showed that up to now the “best” conditions to explain the damage behavior of concrete structures are a pH value of 13 (e.g. 0.1 M KOH solution) and a temperature of 80 °C. The evaluation bases on the parameter “excess silica” which is calculated from the dissolved silica and alumina of the aggregates and the SCMs. It was demonstrated that SCMs reduce and sometimes stop the dissolution of aggregates. The efficiency of the SCMs depends on their amount and chemical composition. KW - alkali silica reaction KW - aggregate reactivity KW - dissolution of silica and alumina KW - dissolution rate Y1 - 2015 SN - 978-1-9427272-3-1 SP - 355 EP - 370 PB - American Concrete Institute ER -