COMPUTATIONAL MODELING OF DAMAGE AND FAILURE IN EARLY-AGE CONCRETE BASED ON THE UNIFIED PHASE-FIELD THEORY: CHEMO-THERMO-HYGRO-MECHANICAL MULTI-PHYSICS COUPLING AND MULTI-DEFORMATION COMPETITION

Early-age cracking in concrete has been one of the most commonly encountered and challenging problems in massive concrete structures such as nuclear containment, tunnels and bridges, hydraulic dams and so on, severely threatening the integrity, durability and safety of such structures. This is due to the fact that early-age concrete is affected by complex multi-physics coupling processes, e.g., cement hydration, heat transfer, moisture transport and mechanical loading, etc. The resulting multi-deformation competition among autogenous shrinkage, thermal expansion/contraction, drying shrinkage, and load induced deformations, etc., leading to early-age cracking in concrete structures during the construction period. Within the framework of the unified phase-field theory for damage and fracture in solids, a chemo-thermo-hygro-mechanically coupled phase-field cohesive zone model (PF-CZM) is established in this work, with the multi-physics coupling and the resulting multi-deformation competition incorporated rationally. The proposed model is then applied to several representative benchmark tests of early-age concrete specimens. The cracking induced failure process is quantitatively studied, focusing on the influences of the drying shrinkage on the crack evolution and failure mode. The numerical results show that, the proposed chemo-thermo-hygro-mechanically coupled PF-CZM is able to capture rationally the multi-physics coupling and multi-deformation competition during cracking in early-age concrete such that the failure process of structures can be well predicted. This feature makes it be used in prediction of cracking induced failure during the construction period and in assessment of structural safety during the service life-cycle of practical engineering structures.