The presence of alunimosilicate based fine aggregates(2.5to7.5wt%)effectively actedtodensifythe
microstructure of the interfacial zone with are duction of pore threshold and mean poresize jointly with
change on the fracture mode oftheSelf-Compacting(SC)geopolymer concretes.From the results,pumice
and recycled glass with amorphous structure improved thebi-axialfour-point flexuralstrengthfrom5to
8 MPa whilesemi-crystallinefeldspar sludge(nepheline syenite)reached 11MPa.The formationofad-
ditional geopolymer gels were responsible for the streng thening mechanism.The specimens with
amorphous fines show edthetendencytodelaythedesorptioninthelaboratoryconditionsindicatingthe
need foraverylongcuringtimeforthe final consolidation.Thesemi-crystalline fines -nephelinesyenite-
appeared appropriateforthedesignofself-compactinggeopolymerconcretesduetotheirbulkcom-
position, capacitytoenhancedensification andstrengthwithlowdeformationrate,inashortrangeof
curing togetherwithahighrateofdesorption,allimportantparametersforthepredictionofthedur-
ability ofconcretes.