Optimization of Concrete Compositions for Sprayed Concrete in the Consruction of Underground Structures

Abstract

The formation of concrete structures by spraying method is widely used in the construction of underground structures. The technology of sprayed concrete (otherwise known as shotcrete) is widely used for fixing underground development, in the device of permanent lining of tunnels and collectors, as elements of shells and supporting structures of underground structures of urban infrastructure.
 Sprayed concrete makes it possible to widely vary the shape and thickness of design of underground structures, allowing to eliminate formwork and in some cases reinforcing.
 The creation of shotcrete structures with increased physical and mechanical properties, as well as technological parameters should be carried out taking into account the latest achievements in the field of construction materials science. The authors investigated the opti-mized compositions of sprayed concrete in which modified compound with optimally selected granulometric and mineralogical composition and the introduction of fiber into the concrete mixture are used as a binder.
 Due to the use of different degrees of stability in underground structures with a con-taining soil mass, the requirements for the characteristics of the spray tone can vary widely. Taking into account the spread of the " wet " method of spraying (where the finished concrete mixture is fed to the nozzle at a high speed), special requirements are placed on the rheological characteristics of the mixture and the deformation characteristics during bending (since the bearing capacity of the vaulted coatings depends directly on their ability to withstand loads in stretched zones), especially for lining of hard contour.

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