The Effect of Additives Including Metakaolin on the Freeze Resistance of Concrete

With the help of research studies on the freeze resistance of concrete with complex additives containing metakaolin it is found that its optimum amount with microsilica and plasticizing agents can provide concrete with high freeze resistance of F11000 and more. The use of metakaolin – superplasticizing admixture contributes to a slight increase of freeze resistance of concrete only due to the consolidation of its structure as a result of increasing the degree of hydration of main minerals of concrete С3S and β-С2S under the influence of metakaolin. It is proved that the optimal amount of metakaolin together with superplasticizing admixture helps to form the phase composition of cement stone from highly basic hydrosilicates and stable hydroaluminates. The use of overdosed metakaolin leads to appearance of a great number of metastable hydroaluminates in the cement stone which makes it inefficient for the production of freeze-proof concrete.