Modified heavy concrete for tunnel structures with increased operational properties

The increasing demands for the quality and reliability of concrete structures, particularly in tunnel construction, necessitate the development of modified concretes with enhanced operational characteristics. This study examines the modification of heavy concrete using a complex chemical additive, comprising a superplasticizer and a water-soluble polymer additive (Polidon-A). The research reveals that the activation process of metakaolin particles is insufficiently studied. Therefore, the investigations presented here, which aim to improve operational characteristics through the pre-treatment of metakaolin in an alkaline environment (pH=10) with a micro-reinforcing component (wollastonite), are highly relevant. The study's objective is to establish the positive effect of metakaolin activation with a complex modifier and a micro-reinforcing component on the modification of heavy concrete's structure to enhance its strength and hydrophysical properties.Object: Modified heavy concrete based on activated metakaolin with a complex modifier (superplasticizer + Polidon-A) and a micro-reinforcing component for concrete tunnel structures.

Research results: The study demonstrates the positive impact of complex modification on the properties of heavy concrete. This is achieved by reducing the cement content (binder) and replacing it with metakaolin, which is pre-activated in an alkaline environment (pH=10) with a modifier and wollastonite. This allows for an increase in strength and hydrophysical characteristics: the compressive strength at 28 days was 68.6 MPa, compared to 39.4 MPa for the control mixture; water absorption was 2.4%; and the waterproofing grade was W14. This makes it possible to use this composition in practice for the production of building products and structures with specified characteristics, operating under conditions of increased load and aggressive environment, in particular, for tunnel structures.

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