Satisfactory history of use of an aggregate in conditions similar to those proposed can often be used to deem an aggregate acceptable. Where this is not possible Standard EN 12620 includes an informative annex containing guidance on verifying the freeze-thaw resistance of an aggregate. It also identifies potential examples of susceptible material, including the following: altered porous basalt, chalk, marl, mica schist, phyllite, porous flint, schist, and particles loosely cemented by clay minerals. Petrographic examination can highlight cases requiring further investigation by physical tests. Some guidance is given on the value of water absorption as an indicator of freeze-thaw resistance. It is noted that aggregates with water absorptions of less than one per cent, determined in accordance with Standard EN 1097-6, are generally considered resistant. It is recognised in the Standard that some materials with higher absorption values are also resistant. The likely durability of an aggregate against freeze-thaw can be indicated by the producer by declaring the magnesium sulfate or freeze-thaw value `MS’ or `F’. Informative guidance on selecting an aggregate is provided in Standard EN 12620 for a particular climate and end use through the advice presented in Table 8.5.
