Title: Effect of Preconditioning on Durability Indices of Alkali-Activated Concretes
Author(s): Maxim Kovtun
Publication: Symposium Paper
Appears on pages(s): 19.1-19.6
Keywords: alkali-activated concrete; chloride conductivity; compressive strength, durability; oxygen permeability index (OPI); preconditioning procedure; sorptivity
According to literature, alkali-activated concretes can show poor durability performance during laboratory testing which can be caused by aggressive preconditioning procedure used in existing durability tests. In this study, effect of two preconditioning methods on results of durability tests was investigated. Along with the standard elevated temperature drying method, "vacuum-acetone" drying method was studied. Mixture of unclassified fly ash and ground granulated blast-furnace slag, 1:1 weight ratio, was used for preparation of alkali-activated concretes. Sodium hydroxide and sodium metasilicate solutions were used as sole activators. Oxygen permeability index, water sorptivity and chloride conductivity were determined for produced concretes. Results show that alkali-activated concretes are more sensitive to testing procedure than Portland cement concrete is. Existing durability tests can lead to misleading results on durability performance of alkali-activated concretes if specimens are aggressively preconditioned at elevated temperatures. In future, new methods should be developed for testing durability performance of alkali-activated concretes putting special emphasis on samples preparation procedure which would not alter material’s structure affecting its performance indicators.