There
are relatively frequent cases, that even the experienced research centers make
mistakes in explanation of the reasons of concrete damage and erroneously
foresee its failure threat. The research procedure, outwardly correct, consists
in chemical determination of sulphates as well as sodium and potassium content
in concrete sample. This approach is sometimes completed with X-ray and thermal
analysis. The chemical analysis give frequently “too high” content of mentioned
above components which is caused by too small, non representative sample of
concrete in question. Such sample contains too much cement paste and
consequently also too much sulphates and alkalis. On this basis it is supposed
“a priori” sulphate corrosion and ASR as a reasons of damage which
simultaneously gives threat of concrete failure. Simultaneously the kinetics of
these processes are not taken into consideration, consequently the time which
is necessary from concrete mix production until damage formation. Also the
physical reasons are omitted, principally thermal gradient and concrete curing
conditions. These mistakes can be avoided if representative i.e. grater
concrete sample is under examination, and its microstructure observed under
SEM. Also possible physical reasons of concrete damage should be taken under
consideration.