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.碱激发材料（Alkali-Activated Materials, AAM）通常被认为具备优异的耐久性与抗冻性能，但也存在与之相悖的实际应用经验。本研究聚焦于不同配比下碱激发材料的抗冻性能——包括激发剂的不同掺量，以及碱（R₂O）与氧化硅含量间的不同比例。试验采用硅酸钠水玻璃作为激发剂，并通过掺入氢氧化钾（KOH）调整其硅模数。试验中碱（R₂O）的质量掺量为4%~10%，R₂O与SiO₂的质量比范围为33/67（仅使用硅酸钠水玻璃）至100/0（仅使用氢氧化钾）。分别在养护龄期28天、91天与365天时测试抗冻性指标。试样分别采用铝箔封存养护或水中养护，参照试样亦采用相同的养护存储方式。试验所得结果尚无定论：其一，当参照试样置于水中养护时，其抗弯强度会出现下降。这表明抗冻性指标的测试结果依赖于参照试样的养护方式——以水中养护的小梁试样作为参照时，抗冻性指标的测试结果更优，因其初始抗弯强度更低。材料配比对抗冻性能仅存在微弱影响，更长的养护龄期亦未提升其抗冻性能。