With the growing demand for higher mechanical properties and durability, the water-to-cement mass ratio (W/C) of modern cementitious materials is progressively decreasing, leading to poor workability. In this paper, we focus on the effects of polycarboxylate superplasticizers (PCE) on the rheological properties of highly concentrated cement pastes to optimize the mix design for high-performance concrete. Our adsorption measurements show that PCE adsorption at low W/C still follows the Langmuir-type isotherm. In line with the previous work, the rheological measurements suggest that the adsorbed PCE can indeed deflocculate the concentrated system, which is at the origin of the decreasing yield stress and residual viscosity. Moreover, the residual viscosity scales with the square root of yield stress for a given solid volume fraction. We, therefore, suggest that the role and the action mechanism of PCE should not be affected by the W/C ratio. All the consensuses drawn from previous studies can be applied to highly concentrated cementitious materials.

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