Application of expanding cements for sprayed concrete in tunnel construction

Introduction. The paper substantiates the actuality of the problem connected with obtaining efficient fine concretes possessing enhanced crack resistance, tightness, and duration for tunnel construction. This aim is pursued with the application of expansive cements (EC). Materials and methods. Various types of expansive agents were used in composition binders. Portland cement PTs 500 D0 was taken as the basic Portland cement. Studying hydration and structure formation processes during hardening of the ECs and EC-based concretes was executed utilizing a system of physicochemical methods. Assessment of construction and technical properties of the fine concretes based on composition binders was accomplished using standard research methods. Results. Analysis results are given for the effect of type and amount of the expansive agents on strength and volume deformation values of the concretes used in tunnel installation construction. Improvement of physical, mechanical, and technological properties and performance of sprayed concrete is shown. A general mechanism of influence of expansive additives (EA) on fine concrete properties is established. A classification of expansive cements for solving various tasks in tunnel installation construction is suggested. Conclusions. EA application efficiency is theoretically substantiated and experimentally proved for the case when the EA is used as an active agent in the composition binder for sprayed concrete in tunnel construction. General enhancement of technical indicators of concrete mixture and concretes is determined. EA classification is suggested for the different extent of hydrated EA expansion and various construction tasks. Replacement of standard Portland cement for an EC for underground structures concrete used in tunnel construction provides a significant increase in their maintainability.