In the present experimental study, a number of analytical techniques were used to identify the composition of gel and thus elucidate to a certain extent the mechanisms involved during synthesis of inorganic polymers. The raw materials used, low calcium slag from a ferronickel plant and commercial glass, were alkali activated by Na2SiO3 and KOH solutions. X-ray diffraction (XRD) is used to identify new formed phases; deconvolution of the amorphous peaks in X-ray powder diffraction patterns enables the quantitative estimation of the amorphous phases present. The morphology and composition of the inorganic polymer gel may be defined by optical reflection microscopy (ORM) and scanning electron microscopy (SEM). Fourier transform infrared spectroscopy (FTIR) is a useful tool for the identification of specific molecular structures including Si-O-Si and Al-O bonds, which define the degree of polysialation. Thermogravimetric analysis (TG) determines water evaporation rates in inorganic polymer structures by recording the weight loss under controlled heating. Finally, the effect of the presence in the starting mixture of heavy metals such as Pb or Cu and anions such as NO3 (-) or SO4 (2-) on the quality of the gel formed and subsequently on the compressive strength of inorganic polymers are studied and discussed.