2011 Volume 52 Issue 2 Pages 210-218
To enhance the early strength of grounded granulated blast furnace slag (GGBFS) blended cement, the activation characteristics of GGBFS were examined by a potassium aluminum sulfate (PSA) clinker, consisting of KAl(SO4)2 and amorphous Al2O3 by calcining alunite [K2SO4·Al2(SO4)3·4Al(OH)3] at 650°C for 30 min. The PSA clinker reacted with calcium hydroxide and gypsum to form ettringite (3CaO·Al2O3·3CaSO4·32H2O, AFt) by following reaction: 2KAl(SO4)2+2Al2O3+13Ca(OH)2+5(CaSO4·2H2O)+74H2O→3(3CaO·Al2O3·3CaSO4·32H2O)+2KOH. Mortar was prepared by mixing a blended cement of GGBFS and ordinary Portland cement (OPC) with PSA clinker as activator. The compressive strength of the GGBFS blended cement mortar was compared with that of OPC mortar. When the PSA clinker and gypsum activator was added to the blended cement of GGBFS and OPC, the hydration products investigated by DTA and X-ray diffraction were mainly ettringite and calcium silicate hydrate(C-S-H) gel. The early and long-term strengths of the GGBFS blended cement were higher than those of OPC. Therefore, PSA clinker as activator was shown to improve the early and long-term strengths of GGBFS blended cement.
