Research of High-strength Cement Compositions Modified by Complex Organic-silica Additives

Forming the optimal structure of the cement stone using various chemical modifiers is one of the most promising areas of technological progress in concrete technology. In most cases, these modifiers are complex additives that may include various plasticizing additives and active mineral substances, such as fly ash, silica fume, metakaolin.At the same time, the problem of silica fume compatibility with various types of superplasticizers, used in modern binding systems is partially disclosed. This necessitates more research in this area.In the paper, the physical and mechanical properties of cement compositions, modified by complex organic-silica additives were investigated, and it was shown that the complex additive efficiency reaches 100% when compared with pure Portland cement and 30% when compared with the cement systems, modified by superplasticizers only. It was found that the complex organic-silica additive, represented by polycarboxylate superplasticizer and silica fume of different nature, creates conditions for forming the low-basic hydrosilicates, plazolite and hydrogarnets, which provide a high-strength dense structure of cement stone, which were used to obtain high-strength lightweight ceramsite concrete of classes С20/25…С32/40 (В25…В40) with an average density of 1600...1800 kg/m3, while using unmodified Portland cement allows to obtain ceramsite concrete of classes С10/12,5…С20/25 (В12,5…В25) with the same average density