A Hygro-Thermo-Chemo Mechanical Model for the Simulation of Early Age Behavior of Ultra-High-Performance Concrete

Ultra-high performance concretes (UHPCs) are cementitious composite materials with high level of performance including but not limited to high compressive strength, tensile strength and durability, reached by a low water-to-binder ratio, an optimized aggregate size distribution, thermal activation, and fiber reinforcement. In the past couple of decades, more and more UHPCs have been developed and found their way into practice. Thus, also the demand for computational models capable of describing and predicting relevant aging phenomenon to assist design and planning is increasing. This paper presents the early age experimental characterization as well as the results of subsequent simulations of a typical UHPC. Performed and simulated tests include unconfined compression, splitting, and 3-point-bending tests. The computational framework is formulated by coupling a hygro-thermal-chemical (HTC) theory with a comprehensive mesoscale discrete model: the HTC component allows taking into account various types of curing conditions with varying temperature and relative humidity and predicting the level of concrete aging, while the mechanical component, based on a recently formulated discrete model, the Lattice Discrete Particle Model (LDPM), permits the simulation of the failure behavior of concrete at the coarse aggregate level. The obtained results provide both insight in UHPC early age mechanisms and a computational model for the analysis of aging UHPC structures.