Crack tracking and fatigue resistance in fibre-reinforced cement treated aggregates by parallel bond damage modelling

Despite extensive investigations using macroscopic surface crack analysis and static microscopic imaging, the dynamic evolution of microcracks in fibre-reinforced cement treated aggregate (F-CTA) remains inadequately understood. To address this gap, this study develops a parallel bond damage model (PBDM) that employs Paris' law as a fatigue evolution criterion for particle contacts. This model was implemented within the Particle Flow Code (PFC) framework to simulate indirect tensile fatigue tests and analyse the fatigue degradation of F-CTA with varying fibre lengths (10, 15 and 20 mm) and contents (0.9, 2.0 and 3.0 kg/m³). The results indicate that microcracks initiate preferentially at the interfaces between the cement mortar and coarse aggregates, subsequently propagating into the mortar matrix, where the majority concentrate. Fibre incorporation was found to homogenize the internal stress distribution and promote broader microcrack dispersion. At fatigue failure, fibres are observed to be pulled out, bridging the cement mortar particles. An optimal combination of fibre content (0.9–2.0 kg/m³) and length (15–20 mm) was identified, which effectively harnesses the energy dissipation capacity of the mortar matrix to significantly enhance the fatigue resistance of F-CTA.