Combinatorial molecular optimization of cement hydrates

Abstract

Despite its ubiquitous presence in the built environment, concrete’s molecular-level properties are only recently being explored using experimental and simulation studies. Increasing societal concerns about concrete’s environmental footprint have provided strong motivation to develop new concrete with greater specific stiffness or strength (for structures with less material). Herein, a combinatorial approach is described to optimize properties of cement hydrates. The method entails screening a computationally generated database of atomic structures of calcium-silicate-hydrate, the binding phase of concrete, against a set of three defect attributes: calcium-to-silicon ratio as compositional index and two correlation distances describing medium-range silicon-oxygen and calcium-oxygen environments. Although structural and mechanical properties correlate well with calcium-to-silicon ratio, the cross-correlation between all three defect attributes reveals an indentation modulus-to-hardness ratio extremum, analogous to identifying optimum network connectivity in glass rheology. We also comment on implications of the present findings for a novel route to optimize the nanoscale mechanical properties of cement hydrate.

Data analytics for simplifying thermal efficiency planning in cities

“…The method is portable to cities in different climates, requiring solely data that are readily available for billing and urban planning purposes. This physical approach would benefit from the interaction with new advancement in materials design [46,47] and policy analyses to shed light on energy price-dependent [48], cost-effectiveness [49] and properties' tenure-dependent considerations [50] in various city-scale retrofit scenarios. Hence, from a practical view point, we consider mitigation of city-scale gas consumption and associated carbon emissions to be a multi-objective optimization problem characterized by a Pareto front in the space of technical, economical, legal and political aspects.…”

Advances in understanding hydration of Portland cement

“…Richardson [147] criticized many of Ca-O distances predicted by the model, and that more than half the Ca atoms in the model are coordinated to fewer than six O atoms. Qomi et al [148] used the model to create a database of atomic configurations for a broad range of C-S-H chemical compositions, and determined their corresponding defect attributes and mechanical properties. The authors then proposed a combinatorial approach to optimize the properties of C-S-H considering the following defect attributes: calcium-to-silicon ratio and two correlation distances describing medium-range siliconoxygen and calcium-oxygen environments.…”

Experimental chemo-mechanics of early-age fracture properties of cement paste

“…On the other hand, one could inquire whether the FPZ size is the most appropriate way to quantify brittleness, respectively its counterpart ductility. To answer this question, we consider another measurement of ductility, namely the ratio of [86], whereas low-density and high-density C-S-H gels show much higher values of 40 and 35, respectively [85], due to their propensity to localize stresses around the gelpores. In this sense, the M/H ratio can be viewed as a measure of the competition between plastic dissipation and elastic energy storage in indentation testing, and it appears to us as a meaningful property to quantify ductility.…”