@article {72, title = {Combinatorial molecular optimization of cement hydrates}, journal = {Nat Commun}, volume = {5}, year = {2014}, month = {Sep-24-2014}, pages = {Article Number: 4960}, abstract = {

Despite its ubiquitous presence in the built environment, concrete\â\€$(1s (Bmolecular-level properties are only recently being explored using experimental and simulation studies. Increasing societal concerns about concrete\â\€$(1s (Benvironmental 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.

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}, doi = {10.1038/ncomms5960}, author = {Mohammad Javad Abdolhosseini Qomi and Konrad J. Krakowiak and Mathieu Bauchy and Stewart, K.L. and Rouzbeh Shahsavari and Jagannathan, D. and Brommer, D.B. and Alain Baronnet and Markus J Buehler and Sidney Yip and Franz-Josef Ulm and Krystyn J. Van Vliet and Roland Jean-Marc Pellenq} } @article {51, title = {Hydration of calcium oxide surface predicted by reactive force field molecular dynamics}, journal = {Langmuir}, volume = {28}, year = {2012}, month = {Mar-06-2012}, pages = {4187{\textendash}4197}, abstract = {
Abstract Image

In this work, we present the parametrization of Ca\–O/H interactions within the reactive force field ReaxFF, and its application to study the hydration of calcium oxide surface. The force field has been fitted using density functional theory calculations on gas phase calcium\–water clusters, calcium oxide bulk and surface properties, calcium hydroxide, bcc and fcc Ca, and proton transfer reactions in the presence of calcium. Then, the reactive force field has been used to study the hydration of the calcium oxide {001} surface with different water contents. Calcium oxide is used as a catalyzer in many applications such as CO2 sequestration and biodiesel production, and the degree of surface hydroxylation is a key factor in its catalytic performance. The results show that the water dissociates very fast on CaO {001} bare surfaces without any defect or vacancy. The surface structure is maintained up to a certain amount of water, after which the surface undergoes a structural rearrangement, becoming a disordered calcium hydroxyl layer. This transformation is the most probable reason for the CaO catalytic activity decrease.

}, doi = {10.1021/la204338m}, author = {Hegoi Manzano and Roland Jean-Marc Pellenq and Franz-Josef Ulm and Markus J Buehler and Adri CT Van Duin} } @article {53, title = {Set in stone? A perspective on the concrete sustainability challenge}, journal = {MRS bulletin}, volume = {37}, year = {2012}, month = {Apr-09-2012}, pages = {395{\textendash}402}, abstract = {

As the most abundant engineered material on Earth, concrete is essential to the physical infrastructure of all modern societies. There are no known materials that can replace concrete in terms of cost and availability. There are, however, environmental concerns, including the significant CO2 emissions associated with cement production, which create new incentives for university\–industry collaboration to address concrete sustainability. Herein, we examine one aspect of this challenge\—the translation of scientific understanding at the microscale into industrial innovation at the macroscale\—by seeking improvements in cement-paste processing, performance, and sustainability through control of the mechanisms that govern microstructure development. Specifically, we consider modeling, simulation, and experimental advances in fracture, dissolution, precipitation, and hydration of cement paste precursors, as well as properties of the hardened cement paste within concrete. The aim of such studies is to optimize the chemical reactivity, mechanical performance, and other physical properties of cement paste to enable more sustainable processing routes for this ubiquitous material.

}, doi = {10.1557/mrs.2012.55}, author = {Krystyn J. Van Vliet and Roland Jean-Marc Pellenq and Markus J Buehler and Jeffrey C Grossman and Hamlin M. Jennings and Franz-Josef Ulm and Sidney Yip} }