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Abstract The dissolution of silicate glasses has implications in diverse fields ranging from the immobilization of radioactive waste to the development of sustainable alternatives to Portland cement. Here, we used ab initio molecular dynamics simulations biased with well-tempered metadynamics to study Si-O-T bridge dissociation in calcium aluminosilicate glasses, crucial for understanding their dissolution. In a departure from the conventional Michalske-Freiman model, our findings reveal a nucleophilic substitution reaction mechanism characterized by a short-lived, 5-fold coordinated Si intermediate or transition state, depending on the Si bridge coordination, with a near-trigonal bipyramidal geometry. We find that the reorganization required for reaching this state causes the activation energy barriers to be dependent on the Si bridge coordination, with Si Q³species serving as the rate-limiting step in the dissolution reaction. Our findings not only challenge long-standing theoretical models but also pave the way for more accurate and comprehensive frameworks for understanding the dissolution of silicate glasses in various applications. 

Abstract Interfaces, the boundary that separates two or more chemical compositions and/or phases of matter, alters basic chemical and physical properties including the thermodynamics of selectivity, transition states, and pathways of chemical reactions, nucleation events and phase growth, and kinetic barriers and mechanisms for mass transport and heat transport. While progress has been made in advancing more interface‐sensitive experimental approaches, their interpretation requires new theoretical methods and models that in turn can further elaborate on the microscopic physics that make interfacial chemistry so unique compared to the bulk phase. In this review, we describe some of the most recent theoretical efforts in modeling interfaces, and what has been learned about the transport and chemical transformations that occur at the air–liquid and solid–liquid interfaces. This article is categorized under:Structure and Mechanism > Reaction Mechanisms and CatalysisStructure and Mechanism > Computational Materials ScienceSoftware > Quantum ChemistrySoftware > Simulation Methods 

Identification and rapid characterization of novel supplementary cementitious materials (SCMs) is a critical need, driven by shortfalls in conventional SCMs. In this study, we present a discussion of recently developed reactivity tests – the R3 test, the modified R3 test, the lime strength test, and the bulk resistivity index test. These tests measure reactivity parameters such as heat release, bound water, calcium hydroxide consumption, strength, and bulk resistivity. All tests can screen inert from reactive materials. To additionally differentiate pozzolanic and latent hydraulic materials, two parameters, for example, calcium hydroxide consumption and heat release, are needed. The influences of SCM bulk chemistry, amorphous content, and fineness on measured reactivity are outlined. Reactivity test outputs can predict strength and durability of cement paste/mortar/concrete; however, caution must be exercised as these properties are influenced by a variety of other factors independent of reactivity. Thoughts are provided on using reactivity tests to screen materials for concrete durability.