ABSTRACT

Inthemicroscopicsensemostengineeringmaterialsarenothomogeneous buthavedomainswithdifferentmicrostructures.Theproperties,whether physical,chemicalormechanical,measuredonthesematerialsarenomore thantheaverageofthesedomains.Thus,cementitiousmaterials,suchas pastes,mortarsandconcretes,areheterogeneousmaterialswithvery complexmicrostructuresthatincreaseincomplexityfromcementpastesto concretes.Incementpastes,hydratedcementsformfromthereactionof cementparticleswithwater,andthemicrostructureconsistsofboth unhydratedcementandhydratedproducts(seeFigure2.1).Thehydrated cementconsistsofahierarchyofneedle-likecolloidalparticlesofcalcium silicatehydrate(C-S-H)surroundingandintergrowingwithcalcium hydroxide(CH)crystals(seeFigure2.2).Inmortarsandconcretesthereis anadditionalphaseofaggregatesofvarioussizesandshapeswhichbecomes boundedbythecementpastematrixasithardens.Manyoftheseaggregates arechemicallystablerockmaterialssuchasrivergravelsorcrushedparticles. Whilsttheshapesandsizesoftheaggregatesdoaffectthemechanicalpropertiestheyarenotasimportantastheinterfacialbondstrengthbetweenthe pasteandtheaggregates.