Unraveling polycarboxylate superplasticizer (PCE) compatibility in muscovite-blended cement paste through aggregation mechanisms

Muscovite is a common harmful mineral in manufactured sand, and has always led to the poor compatibility of superplasticizers in fresh concrete. Currently, the failure mechanism is usually explained by competitive adsorption and interlayer adsorption. In addition to the adsorption point of view, as a kind of surfactant, the self-aggregation conformation of superplasticizers in solutions also requires attention. This study explored the compatibility of polycarboxylate superplasticizer (PCE) in cement paste containing muscovite and explained the failure mechanism from the PCE aggregation point of view. Results showed that at the saturated dosage of PCE (0.14 wt%), the introduction of 6 wt% muscovite resulted in a complete loss of fluidity. In the pore solution of cement paste blended with muscovite, the PCE exhibited a lower critical micelle concentration (CMC) and larger aggregation size. The aggregation of PCE is due to the high ionic concentration in cement paste with muscovite, which increases the hydrophobic interaction between PCE and counter ion.