Alkali-silica reaction (ASR) has become a challenge in concrete technology. Be it a high alkali content of cement or the use of alkali reactive aggregates, many damages are noted today.
The use of mineral additions like fly ash, slag, microsilica and metakaolin reduces the alkali silicate reaction to different extends. This is probably due on one side to the lower diffusion coefficient and on the other side to the lowering of the hydroxyl concentration in the pore solution.
A technical note by F. B. Nelson and L. J. Struble of the University of Illinos shows that an addition of 10% of metakaolin gives the best results of all mineral additives.