Page 492 - AWSAR 2.0

468 || AWSAR Awarded Popular Science Stories - 2019
that can take multiple chemical structures on the nanoscale and varying microstructures on higher scales. A closer look into the system transforms the boring old subject of civil engineering into an interesting array of complex chemo-mechanical processes that exist in a delicate balance with its environment. Multi- scale modelling considers these finer details and tries to assess how they influence the final mechanical strength of the final structure/ building.
Why is this approach important? Concrete has become the second most consumed material by humans in the world next to water. It is estimated that every single person uses a tonne of concrete per year. For each tonne of concrete produced, the cement industry releases a tonne of CO2 into the atmosphere. Thus, cumulatively cement production is responsible for 7% of global CO2 emission. A solution to this problem is to develop more sustainable types of cement
that do not have such a huge
carbon footprint. However,
while doing so, we cannot
compromise on the properties
such as strength and durability
of our buildings. Hence, it is
important to ensure that the
performance of the alternatives
is at par with the existing
technology. Fundamental understanding of cement paste microstructure and chemical
composition plays an important
role in this quality control.
As part of my research,
I have proposed a combined
experimental and modelling
approach to incorporate the
finer details of the C-S-H needle geometries and distribution of mechanical properties in an interface-based multi-scale mechanical model for hydrating cement. A lattice spring model is
developed to determine the bulk mechanical strength of the cement matrix, where the spring stiffness is derived from a 2D finite element model of a single grain interface. That is, the grains can be imagined as balls, and the interface connecting them can be imagined as springs. First, the properties of constitutive phases in the heterogenous fibrillar matrix are determined on the nanoscale. These fibrils intertwine to form the interfaces that are considered as springs. The strength of these springs is determined on the microscale, and the ball–spring system lets you predict the properties on the macro scale. The model is then extended to more complex systems such as varying percentage combinations of C3S and C2S (the constitutive minerals in cement), C3S with nano-silica addition, etc. The model developed can be reliably applied to predict the properties of the bulk cement under different hydrating conditions where the fundamental
microstructure of the matrix is altered or the mechanical properties of constitutive phases are modified. I have also simulated the effect of mineral surfaces (C3S/C2S) on confined water using molecular dynamics simulations to understand the behaviour of the adsorbed water layer on these surfaces. Molecular scale models of cementitious systems are a relatively new field of study. This is partly because cement has been considered a technologically unsophisticated material so far, and the research on it has been predominantly empirical and on its macroscale behaviour.
The building is composed
of beams and columns that impart structural strength to the structure. These structural elements are in turn made of concrete, which consists of cement, sand, aggregate and water. Cement is a complex mixture of minerals that acts as a binder or glue holding together the various components of concrete.
concentrated
However, the
have proved this as an understatement. It has opened a wide array of avenues of
findings in the last decade