The microstructures of some alkali-silica reactive aggregates used in
China have been examined by means of an optical microscope. The aggreg
ates included andesite, tuff, basalt, felsite, diorite-porphyrite, bas
altic volcaniclastic rock, chert, siliceous dolostone and limestone, m
eta-granite, metagranite-porphyry and cataclastic quartzite, belonging
to Proterozoic, Palaeozoic or Mesozoic. Dominant reactive phases are
chalcedony, cryptocrystalline to microcrystalline quartz and strained
quartz.