Effect of cement and metakaolin on the compressive response and numerical stability of hemp concrete

Hemp concrete is a low-density, highly deformable bio-based composite whose macroscopic compressive response is commonly associated with binder formulation, density, compaction and internal pore-aggregate rearrangement. This study examines how cement and metakaolin modifications affect mean experimental compressive strength, stiffness and ε peak in four formulations, and how these effects influence finite-element convergence under large compressive deformation. The mechanistic interpretation is treated as plausible and literature-supported rather than as direct microstructural evidence from the present experiments. A three-dimensional cylindrical specimen was compressed between rigid platens in Abaqus/Standard with surface contact and friction. A simplified phenomenological elastic–plastic material model was calibrated from the available experimental summary properties. Python was used only to reconstruct the analytical calibration response from the same inputs, not as independent validation. The campaign covered baseline simulations, mesh assessment, contact effects and mechanical-parameter sensitivity. For the three completed formulations, the formulation-specific numerical maxima differed from the corresponding mean experimental strengths by 8.63%, 11.43% and 6.97%. These percentages quantify calibration consistency within each formulation; they do not demonstrate equivalence of stress at a common strain and are not used to rank intrinsic material properties across the different endpoint strains. Agreement in elastic modulus was 1.72%, 3.57% and 1.11%, respectively. Because no damage-softening law was included, the model did not independently predict ε peak, exp . The selected 11 mm mesh should therefore be understood as a practical reference that provides stable global response metrics within the adopted material and contact framework, rather than as an independent proof of intrinsic constitutive behaviour unaffected by boundary restraint.