Researchers from Hohai University, Northwestern University, and Politecnico di Milano have introduced a pioneering mesoscale mechanical discrete model, LDPM-MicroF, to simulate the fracture behavior of micro fiber-reinforced concrete (FRC), as reported in Engineering.

Microfibers, with diameters less than 100 µm, are crucial in preventing early shrinkage cracking and reducing pore pressure during fires. However, formulating an accurate mechanical constitutive law for micro-FRC has been challenging due to difficulties in understanding physical principles and the high computational cost of existing models with numerous randomly oriented fibers.

The LDPM-MicroF model addresses these issues by defining an equivalent fiber diameter coefficient. This innovation allows it to balance modeling accuracy and computational efficiency, making it capable of simulating the mechanical responses of engineered cementitious composites. Through this model, the unimodal variation in tensile strength caused by increasing microfiber dosage can be quantitatively reproduced and explained.

In direct tension tests, the model’s validity was verified using concrete samples with micro-polypropylene (PP) fibers. By controlling the equivalent fiber diameter coefficient (r_f), the model demonstrated good agreement with experimental results in both parallel and randomly oriented fiber distributions. In splitting tension tests of steel fiber and micro-PP FRC, LDPM-MicroF accurately predicted the strength changes. For micro-PFRC, the splitting tensile strength initially increased and then decreased with increasing PP fiber volume fraction, which was successfully captured by the model. In four-point bending tests of micro-basalt FRC, the model reproduced the observed cracking patterns and the unimodal strength variation.

Moreover, in the tension test of engineered cementitious composites (ECC), LDPM-MicroF showed its ability to handle high microfiber dosages. By setting an appropriate r_f, the model could simulate the test while significantly reducing computation time.

This research provides new insights into the mechanical properties of micro-FRC. It distinguishes between the areas of fiber intersection and effective matrix on crack surfaces and considers the “near-field effect” of microfibers. These contributions enhance the understanding of micro-FRC and offer valuable tools for future research and engineering applications in the field of cementitious composites.

The paper “Mesoscale Mechanical Discrete Model for Cementitious Composites with Microfibers,” authored by Lei Shen, Linfeng Hu, Giovanni Di Luzio, Maosen Cao, Lei Xu, Gianluca Cusatis. Full text of the open access paper: https://doi.org/10.1016/j.eng.2024.11.017. For more information about the Engineering, follow us on X (https://twitter.com/EngineeringJrnl) & like us on Facebook (https://www.facebook.com/EngineeringJrnl).