²⁷Al NMR MAS Spectral Studies Inferring the Initiation of Geopolymerization Reaction on Together Mechanochemical Grinding of Raw Materials

Abstract

Chemical shifts and intensities of the 27Al NMR signals provide structural information about the environment of Al nuclei in presence of an external magnetic field. This paper analyzes the structural information of the aluminum nuclei present in the precursor material after mechanochemical co‐grinding of the raw materials, namely fly ash, NaOH, and amorphous tricalcium phosphate [Ca3(PO4)2], with the help of 27Al MAS NMR spectral studies. The results indicate transformation of the sixfold coordination Al ions with oxygen AlQ6 present in aluminosilicate material fly ash to fourfold AlQ4 and fivefold AlQ5 in the precursor material. The variation in chemical shift is between δ 64 and 65 ppm. This indicates that, in addition to direct bonding to the oxygen atom, the Al tetrahedron is also bonded to Si as [AlQ4(4Si)]. Thus, the mechanochemical co‐grinding of the raw materials initiates a solid‐state chemical reaction among them. The addition of water alone to this precursor material results in the formation of the geopolymeric material unlike the conventional geopolymeric system which requires the addition of a highly alkaline aqueous solution to fly ash. This study helps in the determination of the reaction mechanism during the mechanochemical transformation of raw materials into the geopolymeric product by a novel process.

Advanced Geopolymerization Technology

“…Advanced Geopolymerization Technology DOI: http://dx.doi.org /10.5772/intechopen.87250 Later on, established by a number of experimental analyses, it can be said that advanced geopolymer possesses improved properties in terms of strength of the material and excellent corrosion protection [8,9,[33][34][35].…”

Monitoring the Geopolymerization Reaction of Geopolymer Foams Using 29Si and 27Al MAS NMR

“…Additionally, MAS-NMR can be used to determine the chemical shifts, coupling constants, and quadrupolar interaction parameters, which provide further insight into the structure and bonding of the material. The results obtained from MAS-NMR can be compared with other characterization techniques such as X-ray diffraction and infrared spectroscopy to obtain a comprehensive understanding of geopolymers' structure and properties [14,15].…”