Effect of surfactants on the yield stress of cement paste

Although many surfactant molecules are available to produce stable aqueous foams, these molecules can strongly interact with cement grains. We focus therefore here on the interactions between various surfactants and cement grains in order to identify some selection criteria for surfactants dedicated to foam cement production. First, we check the surfactant ability to produce aqueous foam in synthetic cement pore solution. Then, we observe that most surfactants do adsorb on cement grains, inducing concentration-dependent effects on the yield stress of cement paste. Our results suggest that, for some of these surfactants, the yield stress increases significantly as inter-particle hydrophobic attractive forces develop at the surface of the grains. However, above a concentration threshold, those attractive forces sharply drop because of the formation of surface micelles acting as steric barriers between particles, which results in a strong decrease in yield stress