Morphology-structural change of C-A-S-H gel in blended cements
Xiaohong Zhu, I.G. Richardson
Abstract
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 < 1.30 and Al/Si 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.