Mossbauer and calorimetric studies of portland cement hydration in the presence of black gram pulse

Effect of different concentrations of naturally occurring admixture in the form of fine powder of black gram pulse (BGP) on the hydration of Portland cement was studied by isothermal calorimetry and Fe-57 Mossbauer spectroscopy. The spectra were recorded for anhydrous cement and the hydration products at room temperature and 77 K. In the presence of BGP, the spectra showed superparamagnetic doublets at room temperature and the sextet at 77 K, due to the presence of fine particles of iron containing component. Mossbauer studies of hydration products confirmed the formation of nanosize hydration products containing Fe3+. The isomer shift (delta) and the quadrupole splitting (Delta E-Q) values of C(4)AF in the cement confirmed iron in an octahedral and tetrahedral environment with +3 oxidation state. The high value of quadrupole splitting showed the high asymmetry of the electron environment around the iron atom. The overall mechanism of the hydration of cement in presence of BGP is discussed.