Abstract
The essential role of the air void size distribution in air-entrained cementitious materials is widely accepted. However, how the air-entraining behavior is affected by features such as the molecular structure of air-entraining agents (AEAs), the type of solid particles, or the chemical environment of the pore solution in fresh mortars is still not well understood. Besides, methods to assess the interaction between AEAs and cement particles are limited. Thus, in this study, the air-entraining behaviors of three kinds of surfactant (cationic, anionic, and nonionic) were examined. The general working mechanisms of these surfactants were studied by zeta potential and attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. Results indicate that the cationic surfactant entrains improper coarse air voids due to the strong electrical interaction between air bubbles formed by the cationic surfactant and negatively charged cement particles. The anionic surfactant interacts with the positively charged part of cement particles, and thus entrains finer air voids. The interaction between the nonionic surfactant and cement particles is very weak; as a result, the nonionic surfactant entrains the finest and homogeneous air voids.
Highlights
An air-entraining agent (AEA) is a kind of chemical admixture that can entrain air voids throughout concrete by mechanical mixing
Spectroscopy was introduced in a recent study attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy was introduced in a ofrecent a cementitious system as a surface-sensitive technique that can provide mechanistic information on study of a cementitious system as a surface-sensitive technique that can provide mechanistic adsorption
AEAs and so far, the literature shows a limited number of studies dealing with the interaction between AEAs cement particles, and further, the associated air-entraining behavior
Summary
An air-entraining agent (AEA) is a kind of chemical admixture that can entrain air voids throughout concrete by mechanical mixing. Thethe adsorption of of particles onto an air bubble surface decreases itsimprove buoyancy may stability [19,20]. Results show Results that theshow zeta potential can interaction betweenand surfactants and cement particles that the behavior zeta potential reflect the can adsorption mechanism ofmechanism surfactantsof onto solid particles. Situ attenuated behavior reflect the adsorption surfactants onto solid particles. AEAs and so far, the literature shows a limited number of studies dealing with the interaction between AEAs cement particles, and further, the associated air-entraining behavior. Mostthe critical and cement particles, and further, the associated air-entraining behavior. The zeta potentials surfactant solutions in were determined to revealwere the possible mechanisms influencing the air-entraining cement particles surfactant solutions determined to reveal the possible mechanisms behavior. In situ ATR-FTIR spectra were measured to study these mechanisms
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