Critical Evaluation and Computational Meta-Analysis of UHPC Concrete Fracture Mechanics (2015-2025): Paradigm Shift from Isotropic Models to Hybrid Phase-Field Models with Meso-Scale Interactions

This study presents an in-depth Systematic Literature Review and Meta-Analysis (SLR-MA) on the evolution of numerical fracture mechanics simulations in Ultra-High Performance Concrete (UHPC) over the past decade. Amidst increasingly complex civil infrastructure demands, UHPC offers a material solution with ultra-high strength and extreme durability. However, its quasi-brittle failure behaviour and high dependence on micro-structural interactions require modelling approaches that go beyond conventional continuum mechanics. This study specifically evaluates the superiority of the Hybrid Phase-Field Modelling (PFM) approach, which implements a tension-compression split, compared to standard isotropic damage models. The focus of the analysis is extended to the meso-scale domain, covering the explicit representation of aggregates, matrix, and interfacial transition zones (ITZ), as well as specific challenges in interlayer fracture in 3D concrete printing applications. Through the synthesis of quantitative data from recent literature, this study establishes deterministic correlations between model parameters—such as the ITZ Energy Degradation Ratio and Length Scale Ratio—and the accuracy of peak load and total energy dissipation predictions. The findings of this study not only confirm the validity of the hybrid model in preventing non-physical compressive damage, but also provide a roadmap for the development of future cement material digital twins that integrate stochastic heterogeneity and post-cracking behaviour of steel fibres.