Features of distribution of impregnating liquids in the process of impulse impregnation of concrete

One of the promising areas of concrete modification is using pulsed impregnation, which is based on application of pressure pulses to improve distribution of the impregnating liquid in the capillary-porous structure of concrete. However, despite the existing studies on distribution of liquids in the capillary-porous structure of concrete and impregnation methods, there remain problems that have not received comprehensive scientific justification. In particular, the relationship between capillary pressure losses, capillary pressure and shock pressure, which is caused by fluid pulses, has not been sufficiently studied. The purpose of the study is to determine the features of distribution of impregnating liquids in concrete under the influence of pulsed impregnation, to establish the main regularities of the process, in particular, the relationship between capillary pressure losses, capillary and pulsed pressure to justify effective use of the pulsed method of concrete treatment. In the paper, the effect of pulse pressure on the penetration of liquid into the capillary-porous structure of the material is analysed, in particular on the depth of impregnation, the uniformity of the distribution of the impregnating liquid in the volume of concrete and the efficiency of processing. The relationship between pressure losses, capillary pressure and pulse pressure, which determine the dynamics of the movement of the impregnating composition, is established. The mechanisms of liquid penetration into closed and open pores of concrete under the action of pulse loading are considered. Taking into account the geometric structure of the pore, which is represented by the model in the form of a spherical figure, as well as the size of the capillaries of concrete, allows us to establish their relationship with the speed of movement of the impregnating liquid under the action of excess static and pulse pressure. The obtained equations for both the open pore and the closed pore with trapped residual air inside reflect the pressure drop caused by the application of pressure pulses according to the adopted sinusoidal law, which determines the movement of the impregnating composition in the concrete structure. The established relationship between the pressure drop, pressure loss in the capillaries and the pulse effect of the liquid pressure makes it possible to predict the behavior of various impregnating compositions, which allows adapting the impregnation technology and increasing its efficiency for concretes with different densities and porosity. Practical significance of the work lies in possible application of the obtained results to develop technological solutions for improving protective and strengthening methods of concrete processing in the construction industry.