Surface phenomena related to applications regarding optimum dosages of casein superplasticizer in self-leveling underlayment cements

Abstract

We experimentally investigated the optimum dosage of casein superplasticizer (SP) in self-leveling underlayments (SLUs). The undersaturated adsorption state of casein in cement pore solution was characterized by zeta potential measurements. Different amounts of casein were dosed in SLU pastes and their dispersion performance was investigated by a mini slump test. Flow values of the SLU pastes were found to increase with casein dosage, but an obvious segregation of the pastes was observed at high dose levels of SP. At an SP dosage of 0.12 wt.% bwob (by weight of binder), a homogeneous SLU paste with a spread flow of >15 cm over a time span of 30 min was obtained, which was identified as the optimum casein dosage for SLUs. Casein was found to adsorb significantly onto the surface of cement, thus producing strong dispersive power at low dose levels.