Analysis of hydration processes in concrete mixtures modified by the introduction of a nanomodifier by electromagnetic activation

Introduction. Traditional Portland cement-based concretes are characterized by low flexural tensile strength and a tendency to crack formation. One of the promising ways to solve this problem is the use of carbon nanotubes, which act as crystallization centers and provide discrete reinforcement of the material at the nanoscale. The aim of the work is to experimentally confirm the effectiveness of using a nanomodifier based on CNT “Taunit-m” in the composition of fine-grained concrete. Materials and methods. M500D0 Portland cement was used as a binder, sand from the Pescovatsky quarry was used as a fine filler, and crushed stone of 5–20 mm fraction was used as a coarse filler. The complex additive included the superplasticizer “SP-3” and CNT “Taunit-M.” Nanotubes were introduced into a dry cement-sand mixture using a linear induction rotator liv-100, which provides homogenization and mechanochemical activation. The phase composition was studied using a Bruker d8 Advance diffractometer. Results and discussion. It was found that the maximum increase in strength was achieved with a CNT content of 0.005% of the cement weight: compressive strength increased by 29%, bending strength increased by 23% compared with the control composition. X-ray phase analysis data showed a 25% increase in the degree of hydration of the lithic phase, as well as accelerated formation of portlandite and ettringite. Non-destructive testing confirmed that by the 7th day of hardening, the increase in compressive strength was 25%, which indicates an intensification of structure formation. The effect is explained by the uniform distribution of CNTs and the mechanochemical activation of the surface of cement grains in LIV-100. Conclusion. The introduction of carbon nanotubes “Taunit-m” in combination with superplasticizer “sp-3” and the use of linear induction rotator liv-100 can significantly improve the strength characteristics of fine-grained concrete. The increase in strength correlates with an acceleration of hydration and a change in the phase composition of the cement stone. The optimal concentration of CNT is 0.005% by weight of cement.