Morphology-structural change of C-A-S-H gel in blended cements

Pastes of white Portland cement (wPC) and wPC-30 % pulverized fuel ash (PFA), -60 % ground granulated blast furnace slag (GGBS), -30 % or 60 % inert filler (anatase-type TiO2) blends were prepared to investigate the dominant factors for morphological change of outer product (OP) C-A-S-H gel in blended cement systems. The OP C-A-S-H gel in SCMs-blended cements changes its morphology from fibrillar-like to mixed fine-fibrillar/foil-like when its Ca/(Si + Al) ratio 0.15. Meanwhile, the fine-fibrillar/foil-like C-A-S-H has the mean length of the aluminosilicate chain longer than 7– 8, of which, the SiO4 bridging site occupancy factor (SOFBT) is higher than 0.6 and the AlO4 SOFBT is higher than 0.3. The pore solutions show the characteristics of effective saturation index (ESI) of CH < −0.15 and ESI of jennite-based C-S-H gel < 0.10. The morphology of C-A-S-H gel in inert filler blends remains fibrillar throughout the hydration.