Interactions Between SCM`S and Different Aggregates for Preventing ASR
Klaus-Juergen Huenger and Mario Kositz
Appears on pages(s):
Supplementary Cementing Materials, ASR inhibition, solubility experiments, aggregate types, reaction products
Supplementary cementing materials (SCM) have a great importance for preventing ASR in concrete structures worldwide. Different materials were used, e.g. fly ashes, silica fume or metakaolin. However, the results are often contradictory. What works with one aggregate does not necessarily work with another, or in other cases, the efficiency is not the same. Not all effects can be explained by fluctuations in the SCM composition.
Long-term investigations were carried out using three different aggregates. Concrete prisms were produced, and parallel aggregates were stored together with different SCM`s (different types and concentrations) in highly alkaline solutions with and without calcium hydroxide in the system. The reaction products, which precipitated as a result of the interactions between aggregate and SCM`s at different storage times, could be investigated by NMR and even XRD. The results were surprising because different aggregates formed different reaction products when using the same SCM. Such effects can
only be explained by the release of different soluble minerals that are part of aggregates.
The conclusion is that obviously aggregates control the formation process of reaction products which are formed as a result of the interactions between SCM`s and aggregates. And these products are responsible for preventing ASR when using the SCM`s.