An x-ray diffraction, Fourier-transform infrared spectroscopy, and scanning electron microscopy/energy- dispersive spectroscopic investigation of theeffect of sodium lignosulfonate superplasticizer on the hydration of Portland cement Type V

This study investigated the effects of a common superplasticizer, lignosulf onate, on the hydration of Portland cement Type V. Samples of plain cement and superplasticizer-treated cement have been examined by xray diffraction, Fourier-transform infrared spectroscopy, and scanning electron microscopy/ energy-dispersive spectroscopy. Lignosulfonate has been observed to retard the hydration of cement through specific surface chemical reactions which i nvolve Ca2+ ions in pore solution, The admixture has been found to retard t he formation of Ca(OH)(2) and stabilize ettringite [Ca-6(Al2O6)(SO4)(3). 32 H(2)O]. The inhibition of the rate of conversion of ettringite to monosulfa te [Ca4Al2(OH)(12). SO4. 6H(2)O] is attributed to charge-controlled reactio ns caused by large quantities of Ca2+ ions from initial hydration reactions . Leaching of the admixture doped cement by water-removed lignosulfonate an d caused complete hydration of cement. A charge-controlled-reaction model i nvolving the Ca2+ ions is proposed to explain the role of the admixtures du ring hydration of cement.