Compressive strength and cracking of composite concrete in hot-humid environments based on microscopic quantitative analysis

Abstract

Hot-humid geological environments cause cement substrates to bulge and crack, which seriously affects the strength of lining concrete structures. This paper proposed a composite concrete material suitable for hot-humid environments, using three additives of steel fibers, polypropylene fibers and vitrified beads. The compressive properties of composite concrete were studied, and the relationship between the pore structure and compressive properties was described by a microscopic quantitative method. At the same time, the failure characteristics of the composite concrete in a hot-humid environment were studied in combination with the acoustic emission (AE) events. The results show that the combination of steel fibers, polypropylene fibers and vitrified beads renders the highest compressive strength for the concrete at all temperatures. The strength loss rate is the lowest with increasing temperature, and the toughness is also greatly improved, which indicates that the composite concrete can adequately adapt to the hot-humid environment. The microstructure parameters of concrete have a good nonlinear relationship with the compressive strength. The continuous high number of AE events in an adjacent timing event can be used as precursor information for the failure of the composite concrete. The use of the three additives causes the failure mode to change from tensile to shear. The results can provide a theoretical basis for the research and quantitative evaluation of the tunnel lining structure in hot-humid geological environments.