Coupled mesoscale analysis of concrete shrinkage

Cracking, driven by shrinkage and thermal strains, strongly influences the serviceability and durability of concrete structures. After several decades of use, cracking can cause structural deterioration and damage. Concrete shrinkage is sensitive to temperature and humidity variations in a complex hygrothermal environment. Therefore, an efficient numerical framework is essential to predict the structural response for all potential geometries and environmental conditions. This work presents a new multi-physics simulation framework coupling the mechanical behavior with chemical/physical processes of concrete while considering the meso-structure of concrete. The Lattice Discrete Particle Model (LDPM) is used the describe the mechanical response. The Hygro-Thermo-Chemical (HTC) model, which describes the moisture transport, heat transfer, and curing reaction, is solved using a flow lattice element (FLE) system dual to the mechanical mesh. The development of mechanical characteristics, as well as thermal and hygral eigenstrains owing to continued curing, is driven by the HTC model. In addition, a newly proposed 2-phase formulation for concrete shrinkage is introduced, considering the effect of aggregate volume and stiffness on concrete shrinkage. The results give robust predictions of macroscopic shrinkage for concretes with different mix proportions and indicate a better representation of meso-structural features than the previously proposed 1-phase formulation. To ensure the reliability of the results, five experimental campaigns from the literature were selected to calibrate and validate the numerical model. The model agrees well with the experimental data and offers new insights into local strain distribution and cracking behavior in heterogeneous materials at an acceptable computational cost.