• Diethylene glycol on particle surface reduces porosity of sand/cement mixture. • Diethylene glycol on particle surface increases bulk density of sand/cement mixture. • Diethylene glycol on particle surface increases concrete strength in SCA. • Bulk density of sand/cement mixture correlates with concrete strength in SCA. This study investigates the influence of particle surface modifications on particle bed concrete 3D printing by Selective Cement Activation (SCA). Prior research suggests that enhancing particle wettability and reducing bulk porosity of the particle bed increases the performance of SCA components. In this work, the effects of dry coatings (nanoscale SiO 2 and TiO 2 ) and a liquid grinding aid (diethylene glycol – DEG) on the wettability and bulk density of two sand fractions and a sand/cement mixture were examined. Nanoscale SiO 2 was found to improve the wettability of the sand/cement mixture, while DEG and nanoscale TiO 2 increased the bulk density and, consequently, reduced the bulk porosity. Based on the results, specimens were 3D printed using the modified materials. Surface modification by DEG increased the compressive strength of printed specimens by 30 % compared to the unmodified, reference material. This increase is attributed to a higher bulk density and, thus, particle bed density compared to the reference material. We conclude that surface modifications enhancing the bulk density can significantly increase the compressive strength of SCA components, thereby expanding SCA’s potential and facilitating its use in construction.

• Novel DEM derives both normal and tangential forces exclusively from strain energy. • Energy dissipation emerges naturally, no explicit friction coefficient required. • Benchmarks show consistent particle dynamics and emergent dissipation. • OxDEM bypasses parameter calibration, enhancing modelling reliability. • Framework supports future extensions to fluid-particle and non-spherical systems. This study introduces OxDEM, a novel strain-energy-based formulation of the Discrete Element Method, in which both normal and tangential contact forces are derived exclusively from strain energy. Unlike the widely used Hertz-Mindlin approach that relies on empirically calibrated stiffness and friction parameters, OxDEM eliminates the need for such inputs. Tangential interactions emerge naturally from relative velocities and shear strains, introducing an intrinsic dissipation mechanism without requiring empirical parameters. A series of benchmark simulations, ranging from single-particle impacts to multi-particle settling, demonstrate that OxDEM reproduces physically consistent dynamics, including energy transfer, emergent dissipation through tangential interactions, and collective particle rearrangements, while avoiding artefacts linked to parameter calibration. The present formulation deliberately omits explicit damping forces to isolate the core mechanics, leaving their incorporation for future development. By unifying normal and tangential responses under a common strain energy framework, OxDEM establishes a physically grounded and parameter-efficient pathway for predictive modelling of granular systems, with clear potential for extension to fluid-particle systems and non-spherical discrete element interactions.