LEACHING EFFECTS ON SILICATE POLYMERIZATION - AN FTIR AND SI-29 NMR-STUDY OF LEAD AND ZINC IN PORTLAND-CEMENT

Portland cement samples doped with lead and zinc nitrate have been investigated by Si-29 solid-state NMR and Fourier transform infrared spectroscopy. Results indicate that silicate polymerization is slightly enhanced with lead doping and retarded in the presence of zinc. Leaching studies reveal that silicate polymerization occurs when the samples are exposed to acidic leaching media. The degree of cross-linking is directly proportional to the acidity of the leaching solution, being pronounced when pH 5 buffers are employed. Values for the nu-3 and nu-4 silicate infrared bands and the chemical shifts of the NMR-active Si-29 nuclei (Q0-Q4) are tabulated and discussed in relation to the chemical binding and leaching mechanisms of the solidified metals.