Effectoftemperatureonstructuralqualityofthecementpasteandhigh-strengthconcretewithsilicafumeOriginalResearchArticle

Experimentalinvestigationconductedtostudythethermo-mechanicalpropertiesofconcreteatTemelin(CzechRepublic),Mochovce(Slovakia),andPenly(France)nuclearpowerplantsrevealsstructuralintegritydegradationbetween100and200°Cduetobothalossofwaterboundinhydratedcementmineralsandsubsequentlyairvoidformation.Testresultsindicatechangesinstrength,averageporeradiusandcalculatedpermeabilitycoefficientsforMochovcespecimensexposedtotemperaturesupto400°C.Itdemonstratesthatthepermeabilitycoefficientmeasuredonthebasisofporesizesusingmercuryintrusionporosimetryissuitabletechniquefortheevaluationofconcretequality.Itconfirmsthatstrengthandpermeabilitycoefficientareequivalentstructuralqualityvariablesofconcrete.At400°Cgel-likehydrationproductsaredecomposed,at600°CCa(OH)2isdehydroxylated,andCaCO3dissociationtoCaOandCO2accompaniedwiththere-crystallisationofnon-bindingphasesfromhydratedcementunderre-combustionaredominantprocessesbetween600and800°C.Thisstageofconcreteischaracterisedbythecollapseofitsstructuralintegrity,revealingresidualcompressivestrength.