CHEMICAL COMPOSITION OF NANOMODIFIED COMPOSITE BINDER WITH NANO- AND MICROSIZED BARIUM SILICATE <sup>2</sup>
There are several possibilities to improve cement-based binders. In particular, many properties of cement stone can be enhanced by means of micro- and nanoscale modification. In a number of previous works we had shown that application of barium hydrosilicates leads to such improvement. The present article is devoted to the investigation of the chemical composition of the cement stone which is modified by means of addition of barium hydrosilicates. The modification was performed on different scales: micro- and nanoscale; the results of simultaneous multi-scale modification are also presented. The examination was carried out with help of different modern research techniques - FT IR spectroscopy, differential thermal analysis and X-ray phase analysis. Identification of the new phases and comparative quantitative assessment of their content are performed. It is found that the use of nano- and micro-sized barium hydrosilicates as additives leads to reduction of portlandite by 27...28%; by means of multi-scale modification it is possible to reduce the content of portlandite much more (by 83.3%). Due to addition of nano- and micro-sized barium-based modifiers both the amount of calcium hydrosilicates in reaction products is enlarged, and structure of the mentioned hydrosilicates is changed (the formation of a fine-grained structure of hydration products takes place). Micro-sized barium hydrosilicates are chemically active additives and promote the formation of an additional quantity of calcium hydrosilicates of type CSH (I). The use of nanoscale barium hydrosilicates promotes the formation of CSH (I) and CSH (II) calcium hydrosilicates, and also both riversidite and xonotlite. As a result of simultaneous application of nano- and micro-sized barium hydrosilicates the content of CSH (II) increases. This can be confirmed by means of differential thermal and X-ray analysis. The amount of CSH (I), riversidite and various tobermorites is also increases. It is shown that efficiency of the application of nanoscale barium hydrosilicates can be improved when such hydrosilicates are administered in a composite binder optimized at the micro-scale.