Synergism effects of coconut diethanol amide and anionic surfactants for entraining stable air bubbles into concrete

Entraining tiny and stable bubbles into cement and concrete is becoming more and more important with the complex composition of cement and concrete. In this work, multi-component surfactants are compounded to improve the air-void stability in fresh concrete. The surface tensions, foam properties of their solutions, and the air contents and air-void parameters of the fresh and hardened cement mortars were tested. The results show that there are strong interactions on the interface of multi-components by calculating the important parameters of surface activity. When coconut diethanol amide molecules are introduced into the interface for co-assembly, the electrostatic repulsion between the anionic surfactant molecules is effectively diminished, thereby decreasing the interfacial free energy and making the interface more stable. The multi-component surfactants induced smaller bubbles with larger amounts in aqueous solutions, which also have higher stability of air bubbles in both cement mortars and concretes. So it is of great practical significance to compound nonionic and anionic surfactants to improve the air-void stability in concrete. (C) 2019 Elsevier Ltd. All rights reserved.