Discrete element method investigation of particle size distribution effects on the flexural properties of cement-treated base

The particle size distribution (PSD) has a significant implication on the mechanical behaviour of cement-treated base (CTB). Traditional approaches rely on experiments to characterise its influences on the mechanical response of CTB. However, these approaches often face difficulties in controlling the material microstructural properties, thus leading to poor repeatability of experimental results when changing PSD. To address this issue, in this study we combine experiments and a numerical modelling approach to investigate the effects of PSD on the flexural response of CTB. In particular, standard experiments of CTB are first conducted to provide data of the material microstructure and fracture responses when subjected to flexural loading. In parallel with this, the Discrete Element Method (DEM), capable of representing the material microstructural properties, is employed for numerical simulations of CTB. An enriched contact model based on the cohesive damage-plasticity theory is then utilised to properly describe the failure behaviour of bonding contacts that form the mortar matrix in DEM samples. Through a calibration and validation process on two independent sets of CTB samples, numerical results show good agreements with their experimental counterparts. This suggests the proposed modelling approach, once fully calibrated, can be used to describe the flexural response of CTB samples with the same material properties. Further numerical investigations reveal a noticeable change of the flexural properties of CTB when varying PSD and these changes are independent of the specimen size