Hydration-drying interactions in a high-volume ground granulated blast-furnace slag mortar

An experimental study of interactions between hydration and early drying was carried out on a mortar with a GGBFS volume as high as the OPC volume. 1 day after casting, the mortar was subjected to 6-month unidirectional drying in natural surrounding conditions in laboratory. At the end of the exposure period, Portlandite content, water porosity and pore size distribution were found to be not uniform along the material. When approaching the exposed surface, due to the early drying, the material gradually becomes less hydrated, more porous, and less dense. This causes strong gradients of transfer properties between the exposed surface and the core of the material, which facilitates exchanges with the surrounding environment near the surface and lowers the resistance against the penetration of aggressive agents. For instance, it was shown that considering properties only within the core of the material, sheltered from drying, significantly underestimates the risk of carbonation, and thus the risk of corrosion of reinforcement in concrete. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

This experimental study reveals that as hydration decreases due to early drying, the density of concrete material gradually decreases, porosity increases, leading to a significant gradient of transfer properties between the exposed surface and the core of the material. This phenomenon increases exchanges with the surrounding environment, reducing resistance against penetration of aggressive agents.