Improvement of the modified heavy concrete properties based on the use of activated silica fume

Abstract

This article deals with the use of silica fume and ways of its activation to modify the structure of cement stone and concrete on its basis. With regard to any type of filler, namely silica fume, questions that are relevant: how to enter and how many, what mechanisms are involved in the process of structure formation, how much it costs achieved by the effect of modifying the structure and others. Formation of the answers to these questions require a systematic approach to vision problems. Therefore the role of microdispersed fillers in the modification process of the cement stone and concrete structures based on it must be considered together with other sized inclusions at different scale levels. The technology of synthesis of the complex additive based on ultrafine microsilica and superplasticizer “Plastilit RK” with characteristics allowing to use it as an effective additive in concrete has been developed. Studies have confirmed the effect of micro-silica fume in an acid medium (pH=2.1), enriched with oxonium H3O + ions, oxonium cations provide H+, and in an alkaline medium (pH=10-11), enriched with hydroxyl groups OH– - anions OH-, with obtaining dimers of orthosilicic acid Si (OH)4. It was shown that orthosilicic acid particles formed during the chemical dispersion of silica fume are additional crystallization centers, which allows speeding up the process of cement hydration.