Microstructure characteristics and evolution of the bonding interface between SCC and steam-cured concrete

Abstract

The microstructure of the bonding interface in CRTS III ballastless track structures is critical to the mechanical properties and durability of high-speed railway structures. The microstructure evolution of the bonding interfacial zone between steam-cured concrete and SCC (self-compacting concrete) is widely studied. This paper investigates the pore structure and phase evolution of the bonding interface zone using backscattered electronic and energy dispersive spectroscopy (BSE + EDS). Based on the nanoindentation test, the microstructure characteristics of the bonding interfacial zone were studied. The results show that the microstructure reveals a gradient change at the bonding interface zone, and the gradient characteristics of the microstructure weaken as curing age increases (especially at 7 days and 56 days). The width of the bonding interface zone is about 15 μm, and the width is more about 20 μm at 1 day. The elastic modulus of C-S-H at the bonding interface zone is low and the C-S-H is mostly LD C-S-H. VMA is beneficial to improve the elastic modulus of C-S-H.