ABSTRACT
This study investigates the influence of indenter geometry and loading conditions on the determination of viscoelastic parameters of hydrated cement pastes through nanoindentation. Experimental tests with various tip shapes (spherical, Berkovich, cube corner) and load levels were combined with finite element modeling to analyze the stress–strain fields beneath the indenter. The results show that sharp tips generate extremely high stresses and significant plastic strains, violating the assumptions of linear viscoelasticity. In contrast, blunt or spherical tips produce stress levels within the linear regime, allowing reliable evaluation of creep compliance and viscoelastic constants. Analytical models based on the Vandamme approaches were used to interpret the holding segments of indentation curves. The study establishes limits for the applicability of linear creep models at the microscale and provides methodological guidance for obtaining intrinsic viscoelastic properties of cement hydrates for use in multiscale modeling of concrete behavior.
