The research objective of this award is to develop a new modeling framework that enables utilizing the fundamentals of material science to uncover the mechanisms of nanoscale contact phenomena in cement hydrate, Calcium-Silicate-Hydrate (C-S-H), and link them to microstructure properties. The core strategy is based on exploring atomistic deformation-based mechanisms, "unit processes", that govern instability and mechanics of semi-crystalline C-S-H. First, by developing a reactive atomistic modeling framework, the complex deformation mechanisms of friction and nanoscale surface interactions within the C-S-H will be investigated. Second, under various chemical and physical environments, precursors will be identified upon which two or more unit processes propagate across particle boundaries or within a particle. This will help identify strategies for "engineering particle boundaries" akin to engineering grain boundaries in nanocrystalline metallic systems. Third, the fundamentals of nanoscale interactions will be upscaled to C-S-H microstructure properties using computational nanoindentation tests on statistically representative volumes of C-S-H. Regions and directions of defect nucleation and instabilities will be quantified by a position-sensitive instability criterion. Finally statistical analysis tools will be employed to study various random configurations and C-S-H assemblies to identify nanoscale variables that are most influential in microstructural response.
If successful, the outcomes of this project will significantly impact science and engineering curricula to better understand the influence of nanoscale friction and instability in mechanics of complex infrastructure materials. The research will critically advance the scientific knowledge on cement hydrate and particulate materials to develop unifying strategies for discovering new mechanisms and processes that lead to instability, cracking and fracture. This potentially-transformative approach rooted in inherent, non-intuitive nanoscale features of materials, can have a broad impact on the design of concrete infrastructure with improved safety and durability, and will be applicable to several other fields such as colloidal systems, polymer science, and ceramic-like materials. The educational plan focuses on recruiting and training undergraduate and graduate students and outreach to a nearby college in Houston to involve underrepresented students and stimulate their interest in cutting-edge materials science and mechanics techniques.
