Metakaolin-based geopolymers (containing no calcium) at early ages are typically seen to contain soluble silicates, geopolymer gel and unreacted metakaolin.The objective of this study was to establish a protocol to probe nanostructural evolution of the geopolymer gel.First, the soluble silicates were removed and the geopolymer reaction was stopped at selected reaction times.HCl extraction was used to further separate geopolymer gel and unreacted metakaolin.Specimens before and after extraction were examined using 29Si and 27Al MAS NMR.The 29Si spectrum of the geopolymer gel was obtained by subtraction, and deconvoluted peaks were assigned to Q4 and small amounts of lower-Q-number aluminosilicates.To assist in the deconvolution,fully-reacted geopolymers were characterized to determine the peak position and width for Q4 geopolymer gels,while peak parameters and relative intensities for lower Q-number aluminosilicate phases were estimated using cross-polarization 1H-29Si MAS NMR.The Si/Al ratio of the geopolymer gel was estimated from intensities of these deconvoluted peaks.In addition, moles of Si and Al in each phase were estimated based on intensities of the 29Si and 27Al spectra and found to be consistent with the Si/Al estimated from deconvolution of the geopolymer gel spectra.The weight of each phase was computed from the intensities of the 29Si and 27Al spectra and found to be consistent with the residue weights measured from the extraction.This study is the first attempt to quantify structures of early age geopolymers.