Influence of amorphous silica on the hydration of tricalcium aluminate

Jong, J. G. M. de; Stein, H.N.; Stevels, J.M.

doi:10.1002/jctb.5010190107

Cited by 12 publications

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“…The effect of nano-SiO 2 on the hydration heat release rate of C 3 A was studied using the isothermal calorimetry, and the results can be seen in Figure 3 . De Jong et al [ 26 ] previously found a second exothermic peak observed in the C 3 A hydration process after adding amorphous silica, which appeared in the first hours of hydration but being at later stage when the amorphous silica content increased. However, as shown in Figure 3 a, this study showed different results.…”

Section: Resultsmentioning

confidence: 99%

Hydration Characteristics of Tricalcium Aluminate in the Presence of Nano-Silica

et al. 2021

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Tricalcium aluminate (C3A) is the most reactive component of the Portland cement and its hydration has an important impact on the workability and early strength of concrete. Recently, nanomaterials such as nano-silica (nano-SiO2) have attracted much attention in cement-based materials because of its pozzolanic reactivity and the pore-filling effect. However, its influence on the hydration of C3A needs to be well understood. In this study, the hydration kinetics of C3A mixed with different percentages of nano-SiO2 were studied and compared with pure C3A. The hydration products were examined by different characterization techniques including XRD, XPS, and NMR spectroscopy and isothermal calorimetry analyses. The XRD results showed that the addition of nano-SiO2 promoted the conversion of the intermediate product C4AH13. The isothermal calorimetry results showed that the addition of nano-SiO2 significantly reduced the hydration exotherm rate of C3A from 0.34 to less than 0.1 mW/g. With the presence of nano-SiO2, the peaks for Q1 were observed in 29Si MAS-NMR measurements, and the content of Q1 increased from 6.74% to 30.6% when the nano-SiO2 content increased from 2 wt.% to 8 wt.%, whereas the proportion of Q4 gradually decreased from 89.1% to 63.6%. These results indicated a pozzolanic reaction provoked by the nano-SiO2 combined with aluminate structures generating C-A-S-H gel.

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Section: Resultsmentioning

confidence: 99%