Effects of activator characteristics on the reaction product formation in slag binders activated using alkali silicate powder and NaOH

The influence of different levels of alkalinity, expressed using the Na2O-to-source material ratio (n) and activator SiO2-to-Na2O ratio (Ms), on the compressive strength development of, and reaction product formation in sodium silicate and NaOH powder activated slag binder systems is discussed. Higher n value mixtures are found to exhibit higher early and later age compressive strengths. An increase in Ms results in reduced early age and slightly increased later age strengths. Compositional coefficients, which are functions of n and Ms are proposed, that relate to the early and later age strengths of the activated slag binders as well as to the shift in the FTIR spectra. The reaction product formation in these systems as a function of the total alkalinity is explained using the shifts of the dominant peak in the FTIR spectra. Fundamental changes in reaction products of powder activated binders as a function of alkalinity is observed. The deductions from the peak shifts are substantiated using the FTIR spectra of the pastes before and after salicylic acid–methanol (SAM) attack.