by BRE (27-Jul-2004)
This Digest includes advice on using recycled or reclaimed aggregates. Additional methods of controlling ASR by adding metakaolin or lithium salts to the concrete mix are described. Silica fume can also be effective. Part 1 gives the background to the detailed and simplified guidance contained in Parts 2 and 4. Part 2 gives detailed guidance for minimising the risk of damaging ASR in new construction. Part 3 gives worked examples. Part 4 gives simplified guidance for new construction using aggregates of normal reactivity.
Concrete can deteriorate as a result of an interaction between alkaline pore fluids (principally originating from the Portland cements) and reactive minerals in certain types of aggregates. The mechanism of deterioration is known as alkali-aggregate reaction (AAR); it can occur in a number of forms, the most common being alkali-silica reaction (ASR). 12 pages.