Microscopic reinforcement mechanism of shotcrete performance regulated by nanomaterial admixtures

Abstract

Considering serious concrete diseases from tunnel lining structure, the pre-suspended nanomaterials combined with superfine admixtures (nano-SA) are used to improve mechanical properties and durability of concrete. Fly ash combined with ultrafine particle microspheres were selected as composite admixtures based on comprehensive performance and application research analysis on the mineral nanomaterial admixtures. Compressive strength and flexural strength for the mortar specimens at different ages were investigated by the single or composite incorporation of the silica fume and the other nanomaterials with the different physical properties. The nano-SA determined by experiment was applied to regulate strength and durability of the concrete. The Scanning Electron Microscopy (SEM) was used to analyze microstructure of concrete with different prescriptions under freeze–thaw cycles. The effects of the nano-SA acting on concrete compactness were studied. The pre-suspended nanomaterial combined with superfine admixture is used for the experimental shotcrete of tunnel. The experimental results indicate that the nano-SA not only improves the workability and compressive strength of the shotcrete but also significantly reduces the rebound rate of the shotcrete. The rebound amount of the shotcrete incorporated with the nano-SA is decreased approximately 30% than without the nano-SA. It proves the excellent performance of the nano-SA and obvious economic benefits.

Keywords

• Microscopic structure
• Mechanical property
• Nanomaterial admixtures
• Concrete
• Reinforcement mechanism