Structural kinetics of cement carbonation examined by neutron interferometric imaging (INFER) and SESANS

Cements and concretes are hierarchical porous solids that form the basis of most modern infrastructures, and growing interest exists to sequester atmospheric CO2 in their alkaline structure to offset emissions during cement production. Cement structures vary from nm to cm, and it remains a significant challenge to capture this structural hierarchy as it reacts. NIST is developing a three-grating far-field neutron interferometric imaging instrument (INFER) that aims to quantify hierarchical structures by combining neutron interferometry, tomography, and small-angle scattering. Despite promising results, INFER lacks quantitative validation from an independent method. The SESANS technique is ideal to compare with recent INFER data of carbonated cements. SESANS will also extend the range of comparison beyond SANS limitations, toward length scales of 1000 nm, which is useful to identify granular regions in carbonated cements. We propose to measure the structural kinetics of carbonated cement formulations with different water-to-cement ratios, limestone-to-cement ratios, and carbonation curing times, which are known to influence cement rheological properties and water/CO2 permeabilities. SESANS data will be modeled by a summed mass-surface fractal by a Hankel transformation shown to agree with previous SANS and INFER data of the same carbonated cements. Together, these measurements will improve understanding of cement structural evolution from nanometer to centimeters.