The contribution of class-F fly ash to the strength of cementitious mixtures |
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| Authors: | R.I. Malek Z.H. Khalil D.M. Roy |
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| Affiliation: | a Materials Research Laboratory, Materials Research Institute, Penn State University, University Park, PA 16802, USA
b Departments of Chemistry and Mining Engineering, Assuit University, Assuit, Egypt |
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| Abstract: | The contribution of fly ash to the physical properties of cementitious mixtures has received considerable attention since its inclusion as an essential ingredient of High Performance Concrete (HPC). However, the chemical contribution to the overall structure development has not been fully understood because of the masking of its hydration products by those of cement. In a mixture of class-F fly ash and lime (Ca/Si=2), portlandite diminishes and C4AH13 forms due to addition of Al to solution. The latter converts to hydrogarnet and C3ASH4. CSH is detected at 3 days and continues to increase in intensity. The 29Si magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR) showed that the Al/Si ratio is 0.24 and the average chain length is 10 units. The presence of Al as approximately one-fifth of the Si in a chain length of 10 units suggests that Al tetrahedra may be present in bridging positions. |
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| Keywords: | C4AH13 C3ASH4 Hydrogarnet Fly ash Mass NMR Zeta-potential |
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