Drying Shrinkage and Deformation Mechanisms in NaOH-Activated Slag: Investigating Pore Structure, Microcracks Formation, and Autogenous Effects

The necessity to house the worldwide growing population is making the production of Portland cement (PC) grow alongside with its CO2 emissions in the atmosphere. In order to reduce said emissions, the scientific community is looking for viable and greener alternatives with comparable mechanical properties and good durability. Alkali-activated materials seem to represent a possible replacement to PC, even though their long-term durability is still not fully understood.One of the main issues for the durability of construction materials is the volume stability in drying conditions, that is how the volume of the material decreases when exposed to environmental conditions. The main consequence of the volume contraction is the development of microcracks which reduce the mechanical strength, allow for water vapour and CO2 to penetrate further inside the material, and may also lead to failure of the structure. In order to assess the long-term durability of a material is therefore crucial to understand how it shrinks according to the different external conditions.The present study focuses on the activation of Blast Furnace Slag (BFS) using different sodium hydroxide solutions and takes into account three main aspects of durability: the tendency to cracking in restrained conditions, the pore structure and hydraulic conductivity of the material, and the drying shrinkage in free conditions. The first experimental campaign on restrained shrinkage has been conducted using the ring test coupled with the assessment of the mechanical properties both in sealed and drying conditions; the goal is to understand when the formation of microcracks takes place and what is the maximum deformation the material can endure before failure. The second experimental campaign modelled the total porosity, the pore size distribution, and the hydraulic conductivity of the material based on the mass variation of the material exposed to different relative humidity levels. Finally, the third experimental
Doctorat en Sciences de l'ingénieur et technologie
info:eu-repo/semantics/nonPublished