Experimental study on bonding properties and deformation characteristics of polyurethane polymer mortar-concrete interface

Polymer mortar (PM) is recognized as a promising material for constructing the sealing layer of man-made caverns used in compressed air energy storage (CAES) systems, owing to its excellent airtightness, crack resistance, and deformation adaptability. This paper investigates the bonding properties and deformation adaptability of polyurethane polymer mortar (PPM) with lining concrete in man-made cavern gas storage, focusing on the effects of powder, polymer content, and mixture ratio variations on the PPM-concrete interface. Additionally, the failure characteristics and mechanisms of the interface are analyzed. The results indicate that the primary failure mode of the PPM-concrete interface is material separation on both sides. The relationship between interfacial shear stress and displacement exhibits two-stage approximate linear deformation characteristics prior to the stress peak, with a maximum shear strain of 11.05% during failure. Variations in powder and polymer content, as well as mixture ratio, significantly impact the interfacial bond strength. The maximum bond strength was about 1.21 MPa, while the lowest average bond strength was 0.237 MPa. The interfacial strength and deformability of the PPM-concrete interface satisfy the requirements for underground gas storage in CAES systems.