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Ultra-high performance concrete (UHPCs) are cementitious composite materials with high level of performances reached by a low water-binder ratio, an optimized gradation curve, and with the use of thermal activation. In the past decades, various UHPC’s have been developed and utilized, however, very limited research is conducted studying their early age strength development. Hence, a comprehensive mathematical model capable of describing the early age effects is needed to facilitate construction planning and reliability assessments. The literature will show the experimental characterization as well as the results of subsequent aging simulations utilizing and coupling the Hygro-Thermo-Chemical model and the Lattice Discrete Particle Model with aging effects (HTC-A-LDPM) for a UHPC at various early ages. Investigated tests include unconfined compression, cylinder Brazilian, and beam threepoint-bending. The HTC component of the computational framework allows taking into account various curing conditions as well as known material constituents and predicts the concrete maturity. The LDPM component, which is a discrete mechanical model, simulates the failure behavior of concrete at the coarse aggregate mesoscale level. Connecting the two components, the aging functions are developed with great simplicity to compute accurately the material properties. The proposed hygro-thermo-chemo-mechanical coupled early age framework (HTC-A-LDPM) can comprehensively capture cement hydration effects as well as strength development for the UHPC. Furthermore, with the comprehensively calibrated and validated aging model, size …