International Summit on Cement Hydration Kinetics

Andreas Luttge (aluttge@rice.edu)

Crystal growth, dissolution, and related crystal-fluid interactions can be observed and quantified at different length and time scales.  Overall (bulk) dissolution rates, surface-normal retreat rates, step velocities at the nanometer scale, and bond breaking and formation are key examples.  A fundamental understanding of crystal reaction kinetics is critical for successful application of high-performance cements, and requires the understanding of all these processes and their interactions in the three-dimensional crystal lattice.  We therefore employ a combination of computer simulations using ab initio calculations, parameterized Monte Carlo techniques and direct observational methods such as vertical scanning interferometry (VSI) to study these key processes at various length and time scales. 

Here we discuss the state-of-the-art in theoretical and observational treatment of crystal-fluid interactions.  Our approach leaves the path of closed-equation treatment that we often call “rate laws” and moves to a treatment that understands crystal dissolution as a dynamic, many-body problem that should be solved stochastically.  This change has significant consequences.  First, we must re-think the concept of reactive surface area that proved to be a mainly unquantifiable parameter.  A second consequence is that there is no single or “true” value for a so-called rate constant.  Instead, a range of rates is possible for any mineral in a given environment, with a certain probability for any given rate within this neighborhood.  This insight has significant implication and consequences for our ability to predict system behavior in the complex environments characteristic of industrial cements.

luttge-Presentation