The role of the micron-scale in reactive transport processes

Abstract

Quantitative predictions for durability issues are necessary to adapt the formulations of cement blends with novel supplementary cementitious materials. These predictions are usually carried out with reactive transport models which are solved at the macroscopic scale. Upscaling laws are necessary to ensure that effective transport properties represent the lower scales properties. Therefore, to define reasonable laws, we need to understand the mechanisms at lower scales. In this work, we focus on the impact of the micron-scale on reactive transport models. We employ the edxia framework to investigate chemical mappings of samples subjected to macroscopic durability tests (obtained with energy dispersive spectroscopy in a scanning electron microscope). The samples investigated are (1) a carbonating cement paste sample, (2) a specimen of 16-year old concrete exposed to sea water, and a cement paste subjected to chloride electro-migration. We demonstrate that both profiles and quantitative chemistry of phases can be readily obtained to characterize reactive transport processes at the micron scale. The results are used to discuss the definition of the representative elementary volume in the case of carbonation and chloride ingress. In addition, we demonstrate that we can quantify the AFm solid solution along the depth of the sample.