The possibility of obtaining effective highly dispersed additives from natural wollastonite is substantiated and their influence on the properties of fine-grained concrete is investigated. On the basis of wollastonite, a complex micro-filler with particle sizes up to 100 microns was developed, obtained by joint grinding with quartz sand in a 3:1 ratio in a ball mill in the presence of an anionic surfactant naphthalene-formaldehyde type C-3 and a calcium stearate hydrophobizer technical C-17. A suspension of wollastonite with a modal particle diameter of 405 nm was obtained by pre-grinding wollastonite and anionic surfactant in a ball mill, with their further ultrasonic treatment in a bath-type activator. Mathematical models of the dependence of compression and bending strength on the content of the initial components are developed. It is established that the complex microfill leads to an increase in the strength of fine-grained concrete in bending by 2 times, in compression by 1.7 times with its content in the composition of fine-grained concrete in the amount of 10% by weight of cement. Wollastonite suspension increases the bending strength of fine-grained concrete to 3.1 MPa, compression to 57.8 MPa. The results of qualitative x-ray phase analysis showed that the total intensity of diffraction maxima of not fully hydrated alite C3S, belite C2S grains and their aggregates in cement stone with wollastonite decreases by 1.5-2 times compared to the control composition. This is most likely due to the amorphous nature of the wollastonite surface after grinding in a ball mill and ultrasonic dispersion in a bath-type activator. In addition, such particles are the centers of crystallization. Their needle-like shape contributes to the reinforcement of the structure by crystallizing new formations of cement stone.

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The effective highly-dispersed additive on the basis of the natural mineral wollastonite has been developed and studied. It enables obtaining fine concrete with the bending strength of up to 21.6 MPa and the strength of compression of up to 55 MPa, and the content of 0.5% (in terms of dry matter). The additive is a suspension of wollastonite after mechanical, and then ultrasonic processing in the aquatic environment of the anionic stabilizer of naphthalene-formaldehyde type. Due to the laser granulometry it has been ascertained that grinding wollastonite together with the anionic stabilizer leads to a change in the specific surface from 20 400 to 32 600 cm2/cm3 and to forming the particles with a modal diameter of 10.31 μm. After ultrasonic processing in the aquatic stabilizer environment the wollastonite particle size reduces to 0.4 μm. The positive heat and humidity effect on the structure and strength of the concrete with highly-dispersed wollastonite-based additive under the mode 3+4+3 h at the isothermal hardening temperature of 80оС is shown. The application of the developed additive in the fine concrete composition makes it possible to save up to 15% of cement due to the strength increase.

The composition of a highly dispersed additive for concrete based on the natural mineral raw material wollastonite is developed. The properties of the modified fine-grained concrete (FGC) are studied. The three-factor experiment planning made it possible to obtain mathematical dependences of the bending and compressive strength after 3 and 28 days of hardening, density, and water-cement ratio of the fine-grained concrete on such factors as the content of anionic surfactant of naphthalene-formaldehyde type in the composition of the raw material wollastonite being an activator of mechanic-chemical processing, the suspension stabilizer of the pre-activated material, and the content of S-3+wollastonite in powder after mechanic-chemical activation in the suspension. The dependence nomograms are built. The optimal strength parameters of the modified fine-grained concrete with the content of a highly dispersed additive of 5% by weight of cement in its composition, and the wollastonite concentration of 3 g/l in the water medium of the suspension stabilizer S-3 are ascertained. The developed highly dispersed additive allows obtaining fine-grained concrete with the bending strength of 3.1 MPa and the compressive strength of 57.8 MPa.