Multi-scale modeling of hydrogel-based concrete formed under the ambient environment and the extremely harsh environment of Mars

Abstract

Hydrogel-based concretes (HBCs) are an emerging class of load-bearing composite materials consisting of inert particles joined together by micro-hydrogel joints. As HBCs can harden via sol-gel process and H₂O phase changes under a freezing temperature and vacuum, they are suitable for future exterritorial constructions. Previous studies have demonstrated that the internal microstructure of the hydrogel joints in HBC varies significantly with curing temperature and air pressure, leading to variations in their mechanical properties. In this study, we present a new multi-scale model that quantitatively predicts the mechanical properties of HBC formed under different curing environments including Martian atmosphere. On the micro-scale, four representative joint microstructures are studied, including tubular, foamy, honeycomb, and tube-cased-foam joints. We experimentally studied and analytically derived the constitutive relationship between the joint force and displacement. Particularly, we determined the process of hydrogel skin peeling from the particle's surface of tubular joints based on force and energy equilibrium. On the macro-scale, we simplified the constitutive joint relationships in a linear parallel bond model (LPM) and employed them to quantify interparticle relationships in a discrete element method (DEM)-based HBC model. The Weibull distribution is used to consider the variation of tensile and shear strengths of the hydrogel joints in the DEM. The modeling results are not only validated with the experimentally acquired compressive stress-strain curves of HBC, but also accurately predict the combined influence of mix design and curing conditions on the mechanical properties.