Mineralogy of tricalcium aluminate hydration with silica nanoparticles

Formation of siliceous-hydrogarnet (Si-hydrogarnet) and stability of katoite (C(3)AH(6)) in tricalcium aluminate (C(3)A) system in presence of silica nanoparticles (n-SiO2) have been examined in the present study. C(3)A hydration in presence of n-SiO2 upto 24 h show retardation in hydration due to the surface coverage of C(3)A grain through calcium-silicate-hydrate (C-S-H)/calcium-alumino-silicate-hydrate (C-A-S-H) (previous study). However, in the present investigation, hydration was studied upto 10 days using QXRD, TGA, FTIR, FESEM, EDS and Mapping and Si-29 NMR techniques. QXRD results show that in case of control samples, the katoite content increases from 61 to 73%, while in n-SiO2 incorporated C(3)A samples, it decreases from 28 to 15% as the hydration proceeds showing katoite phase destabilization in presence of n-SiO2. Further, FTIR results show symmetric stretching vibration of Si-O-Si at similar to 784 cm(-1) and similar to 818 cm(-1), while asymmetric stretching vibration of Si-O-Si/Si-O-Al at similar to 1028 cm(-1 )indicating the formation of C-S-H/C-A-S-H and Si-hydrogarnet in presence of n-SiO2. In Si-29 NMR results, Q(2u) peak at -89 ppm confirm the formation of Si-hydrogarnet at 10 days of hydration. The present study is important from performance and durability point of view as formation of C-A-S-H and Si-hydrogarnet can act as an aluminum reservoir, which may prevent severe chloride and sulphate attack.

Automated summary

The formation of siliceous-hydrogarnet (Si-hydrogarnet) and the stability of katoite (C(3)AH(6)) in the tricalcium aluminate (C(3)A) system in the presence of silica nanoparticles (n-SiO2) were investigated in this study. The results showed that the presence of n-SiO2 destabilizes the katoite phase and promotes the formation of C-S-H/C-A-S-H and Si-hydrogarnet during hydration. These findings are important for the performance and durability of materials.