Effects of salts and adsorption on the performance of air entraining agent with different charge type in solution and cement mortar

In this paper, the effect of salts in solution and the adsorption of surfactant are studied to give the answer why the air entraining agents fail. The high valence cations (e.g. Ca2+) weaken the surface activity of anionic surfactant solution but have no effect on the surface activity of cationic and nonionic surfactant solution. The calcium induces the decreased surface activity of anionic surfactant solution, the low foamability, the big bubble size, and the depressed the air-entraining performance. Anionic surfactant has stronger adsorption on surface of cement than that on surface of montmorillonite, granite and limestone. But cationic and nonionic surfactants have much stronger adsorption on surface of montmorillonite and granite than that on surface of cement. When montmorillonite, granite and limestone are added into cement mortar, the air-entraining performance of anionic surfactant is not depressed, but the air-entraining performance of cationic and nonionic surfactants are obviously depressed. (C) 2020 Elsevier Ltd. All rights reserved.