Effect of admixtures such as black gram pulse (BGP) and sulfonated naphthalene based superplasticizer (SP) on the hydration of Portland cement has been studied. The hydration characteristics of OPC in the presence of BGP and SP were studied with the help of non evaporable water content determinations, calorimetric method, Mössbauer spectroscopic and atomic force microscopic techniques. Results have shown that both BGP and SP get adsorbed at the surface of cement and its hydration products. The hydration of Portland cement is retarded in the presence of both the admixtures and nanosize hydration products are formed.

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Naturally occurring black gram pulse (BGP) in the form of fine powder was used as an admixture during the hydration of ordinary Portland cement (OPC). The hydration characteristics of OPC in the presence of different concentrations of BGP were studied with the help of calorimetric, differential scanning calorimetric, powder Xray diffraction, UV-visible, Fourier transform-infrared and Mössbauer spectroscopic techniques. The results suggested that BGP is adsorbed on the surface of cement/hydration products and a weak interaction occurs between them. Due to this interaction, BGP retards the hydration process of the cement. Mössbauer studies suggest that the addition of BGP in OPC increases the asymmetry of the electronic environment around Fe 3þ ions and leads to the formation of nano-sized hydration products.

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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 57 Fe Mössbauer 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. Mössbauer studies of hydration products confirmed the formation of nanosize hydration products containing Fe 3+ . The isomer shift (δ) and the quadrupole splitting ( 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.