Frost Resistance of Alkali-Activated Concrete with Different Compositions – Parametric Study

Alkali-Activated Materials (AAM) are often considered to be very durable and also frost-resistant. However, there are also contrary experiences. This paper focuses on the frost resistance of AAMs of different compositions – different amounts of activator and different ratios between alkali (R2O) and silicon oxide content. Sodium water glass was used as the activator and its silicate modulus was modified by the addition of KOH. The R2O content was 4 -10 % and the R2O/SiO2 weight ratio was 33/67 (water glass only) up to 100/0 (KOH only). The frost resistance index was tested at the ages of 28, 91 and 365 days. Specimens were cured in foil or water and comparative specimens were also stored in foil or water.The results obtained are inconclusive. Firstly, when the reference specimens are stored in water, their bending strength decreases. This means that the frost resistance index is dependent on the use of the reference specimens – better results of frost resistance index are obtained for water-cured beams as reference specimens as they show lower strengths. The composition has a marginal effect on the frost resistance. Longer curing times also do not increase frost resistance.