Structure and mechanical properties of aluminosilicate geopolymer composites with Portland cement and its constituent minerals

摘要: abstract Article history:Received 8 July 2009Accepted December 2009Keywords:Composites (E)Mechanical properties (C)Microstructure (B)NMR The compressive strengths and structures of composites aluminosilicate geopolymer with the syntheticcement minerals C 3 S, β-C 2 A commercial OPC were investigated. All showed lowerstrengths than paste alone. X-ray diffraction, 29 Si 27 Al MAS NMR SEM/EDSobservations indicate that hydration cement is hindered in presence ofgeopolymer, even though sufficient water was present mix for to occur. In absence ofSEM evidence formation an impervious layer around mineral grains, poor strengthdevelopment suggested be due retarded development C–S–H because preferentialremoval from system available more rapid ofthe minerals. This possibility supported by experiments which rate formationis substitution potassium sodium, reduction alkali content thegeopolymer or addition borate. all these cases strength OPC–geopolymercomposite increased, particularly combination borate additive potassiumgeopolymer, producing OPC–geopolymer composite stronger hydrated alone.© 2009 Elsevier Ltd. rights reserved.