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V. N. Derevianko, N. V. Kondratieva, H. M. Hryshko, and V. Y. Moroz
Nanomodifying of Gypsum Binders with Carbon Nanotubes
0127–0144 (2022)

PACS numbers: 61.05.cp, 61.46.Np, 61.48.De, 62.23.Pq, 65.80.-g, 78.30.Na, 83.80.-k

One of the directions in development of nanotechnologies used for production of building materials, development of theoretical and practical methods applied for improving the properties of finished products and operational constructions in Ukraine consists in use of nanosystems for regulation of material structure and binder properties. The hydration mechanism of mineral binders in the presence of nanomodifiers is quite poorly described in the scientific literature, but the results of laboratory studies confirm their significant impact on the technological process and changes in physical and mechanical properties. Studies on both the influence caused by nanomodifiers and the mechanism of gypsum binder hydration in the presence of nanomodifiers are topical. The goal of this article is studying the mechanism of hydration process, structure and properties of gypsum binders in the presence of carbon nanomodifiers. As revealed, introduction of carbon nanostructures into gypsum compositions affects, first of all, the rate of chemical reactions (hydration of binders), morphology of crystals and composition structure. Use of a relatively small amount of modifier makes it possible to change the structure of mortar or concrete, to increase significantly the strength characteristics and to improve the physicochemical properties. Carbon nanotubes (CNTs) are one of modifiers. They are mainly neutral with respect to the components of the binder solution and affect the hydration process by increasing the surface energy, creating crystallization centres and nanoreinforcing the structure. For achieving a more efficient action of the nanomodifier, mechanical or chemical destruction of separate chemical bonds on the surface of nanotubes is applied (functionalization). Functionalization of CNTs’ surface gives an opportunity to disperse them more evenly throughout the bulk of the modified material; it also contributes to reduction of sedimentation effect and provides chemical interaction between nanotubes and matrix of the substance. Modification of gypsum with nanomaterials increases its compression strength and bending strength as well as water tightness. It is experimentally established that the optimal concentration of CNTs with the greatest increase in strength observed is of 0.005–0.05% of the binder dry mass. Providing the same content of nanomodifiers in the gypsum matrix (0.035%), the maximum increase of compression strength (28–30%) is achieved by means of using CNTs functionalized with hydroxyl groups.

Key words: nanomodifying, gypsum binders, carbon nanotubes, hydration, nanosystem, solidified (hardened) structure.

https://doi.org/10.15407/nnn.20.01.127