Abstract
We examined a change over time of such properties of fine-grained concrete as strength at compression and deformation under the action of an external load. The studies were conducted for the possibility of determining the physicomechanical properties of concretes, required to calculate the ferroconcrete structures, first of all monolithic, at different age of their fabrication. We established a relation between the rates of formation of the deformation properties and the strength at compression of fine-grained concrete. It is found that the strength of fine-grained concrete and its deformations under the action of an external load depend on the composition of concrete and the presence in it of the surface-active substances that form micelles. The existence of micelles ensures the catalysis of synthesis reactions of hydro silicate during the hardening of cement. This leads to the acceleration of formation of compressive strength and the deformative properties of concrete. An increase in the content of the given surface-active substances to a specific magnitude, which depends on the type of the used cement and the composition of concrete, leads to an increase in the strength of concretes and the rate of its formation. The magnitudes of strength of the obtained concrete and the rate of its formation also depend on the type of the utilized cement and the composition of concrete. At the same time, the optimum content of these surface-active substances, which ensures maximum magnitude of the initial modulus of elasticity of concrete prior to the age of concrete of 28 days, has not been practically established. The value of initial modulus of elasticity of concrete at this age is proportional to its content of the surface-active substances that form micelles. The studies conducted make it possible to determine the methods of control over the strength and deformativeness of fine-grained concretes for shortening the time of constructing the monolithic and the duration of hardening of the prefabricated ferroconcrete structures.
Highlights
Sandy concrete of the new generation, in addition to dispersed cement, includes the combination of dispersed and fine-grained additives
The aim of present study is to determine the influence of the micelle forming surface-active substances (MSAS) on the rate of formation of the deformation properties of finegrained concretes and to compare it to the speed of strength formation
Results of experiments revealed that the introduction into the composition of reaction-powder concretes of the surface-active substances, which form micelles (MSAS), due to the emergence of effect of the micellar catalysis when forming the properties of concrete stone, leads to an increase in the strength of the given concretes at compression
Summary
Sandy (fine-grained) concrete of the new generation, in addition to dispersed cement, includes the combination of dispersed and fine-grained additives. The composition and technology of such concretes substantially increase their cost, even in comparison with the high-functional and ultra high-functional concretes This is why the fine-grained concretes, including the reaction-powder ones, are practically not utilized at present in the technology of manufacturing the bearing structures both in the prefabricated and in the monolithic construction. This is linked to the fact that the given concretes are characterized by increased consumption of cement. The established phenomenon of increased speed of the formation and the magnitude of strength at compression of fine-grained concretes through the application of the micellar catalysis [9, 10] makes it possible to decrease the cement consumption and to reduce the period of constructing the monolithic structures. This indicates the determination of the period when a building is fully constructed, which is a relevant task in the monolithic construction
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