ICME or Integrated Computational Materials Engineering is an approach to design products, the materials that comprise them, and their associated materials processing methods by linking materials models at multiple length scales. In this concept, the terms Integrated and Engineering respectively refer to integrate models of material at different length scales and signifying industrial utility.
ICME tries to focus on the relationship between the production process, structure, properties, and applications of materials to target material engineering and science. This relationship is highly reciprocal so that each parameter can influence the rest of the others. The processes used to produce a material affects the materials structure, properties, and thus its applications. The existing structure of the material determines its properties and applications whilst to reach to a specific structure, special processing methods need to be employed in the production of the material. Properties and application of a particular material are highly under the influence of its structure and production process. This reciprocal relationship can be shown in a paradigm like below.
As mentioned earlier, ICME tries to integrate materials properties and behavior at different length scales. For this purpose multiscale modeling and study is required. This method aims to evaluate material properties or behavior on one level using information or models from different levels and properties of elementary processes.
Concrete as the second most used construction material of the present era is a complex material consisting of cement, water, aggregate, and other optional components with various properties and behavior in different situations. As the most important component of this complex, cement and in the same way supplementary cementitious materials are capable to influence almost every single properties of concrete in different ages. These components react with water and after hydration, C-S-H, as the main hydration product is responsible for the strength and durability of concrete. Both cement and SCMs are chemicals that can be studied in different length and time scales to form a multiscale study. Although the target of this article is cementitious materials, this technique can be used to study other components or even other construction materials. In the following, different length scales and phenomenon can be addressed at, in addition to usual methods and tools of specific scales are given:
- Structural scale: Finite element, finite volume and finite difference partial differential equation are solvers used to simulate structural responses such as solid mechanics and at large scales (meters). While almost all of the desired properties that engineers seek like concrete’ strength, workability, and durability related properties are on this scale, but they are rooted in smaller length scales. Although, some of them can be investigated in the structural scale, for a deep understanding of any given phenomena multi-scale study is inevitable.
- Macroscale: constitutive (rheology) equations are used at the continuum level in solid mechanics and transport phenomena at millimetre scales.
- Mesoscale: continuum level formulations are used with discrete quantities at multiple micrometre scale. “Meso” is an ambiguous term that means “intermediate” so it has been used as representing different intermediate scales. In this context, it can represent modelling from crystal plasticity for metals, Eshelby solutions for any materials, homogenization methods, and unit cell methods.
- Microscale: modelling techniques that represent the micrometre scale such as dislocation dynamics codes for metals and phase-field models for multiphase materials. Phase-field models of phase transitions and microstructure formation and evolution on nanometer to millimetre scales. The microstructure of material including crystallographic properties and phenomena related to this scale, like C-S-H formation or detrimental ones such as crack formation and propagation can be studied in this scale.
- Nanoscale: in this scale, atomistic methods such as molecular dynamics (MD), molecular statics (MS), Monte Carlo (MC), and kinetic Monte Carlo (KMC) can be used to study different chemical phenomena happening on molecules and crystals of cementitious materials. Many properties like mechanical properties of a material are able to be estimated in this scale. Length scale in these methods is in the range of angstrom to nanometers.
- Electronic scale: Schroedinger equations are used in the computational framework as density functional theory (DFT) models of electron orbitals and bonding on angstrom to nanometer scales. In this scale, first principal methods are employed to study materials at subatomic particles level. Many properties such as bond strength can be studied on this scale.
