Effect of Nano Admixture of CSH on Selected Strength Parameters of Concrete Including Fly Ash

Nowadays, various mineral additives and chemical admixtures are more and more frequently used in concrete mixtures. It is done in order to improve specific parameters of concrete. One of the most frequently used additives are siliceous fly ash (FA). These material are by-products of hard coal combustion processes. Utilization of FA has an ecological aspect (due to reducing the deposit areas of troublesome industrial wastes) as well as the economic aspect (a possibility to replace part of cement binder in the concrete mixture). Research, that carried out so far indicates a significant decrease in strength parameters of concrete with the addition of FA in early ages of curing. On the other hand, numerous experiments prove that using Calcium Silcate Hydrate (CSH) seeds causes an increase in mechanical features of composites with cement matrix. Therefore, it seems possible to strengthen the weakened structure of concrete containing FA through the use of a mixture of active modifiers included in the admixture. Based on the above, the authors of the study decided to carry out laboratory tests on concrete mixtures with the addition of FA and nano admixture of CSH. This study presents the results of tests on concrete with the addition of FA and CSH nanocrystals used as an admixture. Mixtures with 0 and 20% of FA and 4% admixture of CSH were prepared. All experiments were carried out after: 4, 8, 12, 24, 72h, and 7,28 days of curing. (paper)