Investigation on the compressive strength, chloride migration of MK-FA-LS blended cementitious materials with electrochemical techniques

Abstract

Blended cementitious materials has become an efficient method to reduce the CO2 emission while improving the long-time performance in construction filed, especially for the application of combined supplementary cementitious materials. However, the microstructure and performance evolution of the new materials need further deep investigation. In this study, metakaolin (MK), fly ash (FA) and limestone (LS) was introduced in cementitious materials to form a complicated quaternary system. The compressive strength and chloride migration performance are evaluated, with different MK/FA proportions. Then through the calorimetry test, X-ray Diffraction (XRD)/Rietveld analysis, free water content measurements, and electrochemical impedance spectroscopy (EIS) test, the phase assemblage and microstructure quantification of the blended systems are compared. Finally, to better understand the performance change, the correlation between the compressive strength/chloride migration coefficient and the electrochemical parameters are established. Results showed that the combination of MK, FA and LS is beneficial for the improvement of compressive strength and the chloride resistance in a proper mix design. EIS is a proper nondestructive method to understand the microstructure evolution of blended systems and even predict the chloride resistance of similar systems. This study shields a light for the application of the quaternary system, with a better durability, higher CO2 emission reduction and lower price.