IMPROVEMENT OF COLD CONCRETE JOINTS USING WET GRINDING METHOD
DOI:
https://doi.org/10.31650/2786-6696-2025-14-122-128Keywords:
cold joint concreting, wet shotcrete method, repair work, partial shotcrete, experimental planning.Abstract
The article considers the process of cold joints formation that arise as a result of interruptions during the placement of concrete mix and can significantly affect the subsequent mechanical behavior of concrete and reinforced concrete structures. The characteristic defects that are formed both at the manufacturing stage and during the operation of structural elements, as well as their impact on durability and load-bearing capacity, are analyzed in detail. Special attention is paid to modern methods and materials used for the repair and restoration of damaged concrete elements, in particular, special repair mixtures, modified cements, chemical additives and approaches to base preparation. One of the key methods considered in the work is the technology of wet shotcrete, which allows for effective restoration of damaged areas and ensuring high-quality adhesion between old and new concrete. The features of regulating the technical properties of repair mixtures by using optimal compositions, selection of aggregates, modification of the mixture and control of hardening conditions are presented. The importance of proper surface preparation of existing concrete is emphasized, which largely determines the quality of the contact zone.
The study is aimed at determining the optimal parameters for applying repair materials by shotcrete. In laboratory conditions, partial application of a 1 cm thick layer of repair mixture was used using a compact test rig. A method for determining the tensile strength of fine-grained concrete during bending was developed using standardized forms modernized with special partitions. Prepared halves of beams with surface angles of 90°, 45° and 22.5° to the horizontal were used as elements of "old concrete". Such a design solution allowed to increase the contact area, minimize flow turbulence during spraying and assess the influence of the spatial position of the cold joint.
Within the framework of the study, a two-factor nine-point experimental design was formed, in which the angle of the cold joint plane (90°, 45°, 22.5°) and the speed of spraying the shotcrete-fiber concrete mixture (0 m/s, 35 m/s, 70 m/s) were varied. A set of experimental tests was carried out, the results of which are presented and analyzed in the work, which allowed us to establish the regularities of changes in the strength and nature of the fracture of the repaired samples.
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