Modification of concrete to improve the stability of geometric characteristics of industrial and mechanical engineering structures

This article addresses the problem of ensuring the geometric stability of concrete elements in industrial and mechanical engineering structures exposed to temperature, humidity, and dynamic stress. The objective is to develop and experimentally validate the composition of modified concrete with low shrinkage strains and enhanced vibrodynamic properties, as well as the selection of a protective surface coating. Portland cement CEM 0 52.5N, quartz sand, polycarboxylate hyperplasticizer, ground marble, Denka CSA20 sulfoaluminate expanding additive, and butyl cellosolve were used as raw materials. The strength, shrinkage, dynamic modulus of elasticity, logarithmic decrement of vibrations, coefficient of linear thermal expansion, as well as the effect of cyclic freeze-thaw and the effectiveness of water-repellent coatings were evaluated. It has been established that the combined use of 10 % sulfoaluminate additive and 1.2 % butyl cellosolve (by weight of cement) produces shrinkage-compensated concrete (strains less than 0.05 mm/m) with a strength of 70–80 MPa and a dynamic modulus of elasticity of 43–47 GPa. After 15 freeze-thaw cycles, the optimal compositions retain their dynamic properties, whereas an excess of the expanding additive leads to microcracks and a decrease in the modulus of elasticity of up to 60 %. A two-layer coating with ED-20 epoxy resin reduces water absorption by 67.5 %. The developed compositions and protection methods allow the concrete to be used as an alternative to cast iron and polymer concrete for the manufacture of geometrically stable industrial equipment components.