Evaluation of the Surfactant Leaching from Alkali-Activated Slag-Based Composites Using Surface-Tension Measurements

Abstract

This work tries to evaluatethe amount of surfactant leached from the AAS-based mortars using a very simple surface-tension (ST) measuring technique.Mortars based on AAS with and without2%ofPEGvarying in molecular weight (MW) were prepared. Waterglass with aSiO2-to-Na2O ratio equal to 2.0 was used at a dose corresponding to8%Na2O with respect to the slag weight. Mortarspecimens were prepared and sealed for 24 h, 3 d and 7 d. Then they were demolded and immersed in demineralized water,whose ST was monitored over time. During the early stages (from minutes to a few hours) the ST dropped rapidly, while itremained approximately constant after a few days, which indicates that organic molecules are leached from the AAS specimensvery quickly. It was observed that a relatively small fraction of PEGs can be leached out, which indicates that organic moleculesare rather bound in the matrix, unable to reduce the ST of the pore solution.This work tries to evaluatethe amount of surfactant leached from the AAS-based mortars using a very simple surface-tension (ST) measuring technique.Mortars based on AAS with and without2%ofPEGvarying in molecular weight (MW) were prepared. Waterglass with aSiO2-to-Na2O ratio equal to 2.0 was used at a dose corresponding to8%Na2O with respect to the slag weight. Mortarspecimens were prepared and sealed for 24 h, 3 d and 7 d. Then they were demolded and immersed in demineralized water,whose ST was monitored over time. During the early stages (from minutes to a few hours) the ST dropped rapidly, while itremained approximately constant after a few days, which indicates that organic molecules are leached from the AAS specimensvery quickly. It was observed that a relatively small fraction of PEGs can be leached out, which indicates that organic moleculesare rather bound in the matrix, unable to reduce the ST of the pore solution.