Influence of high curing pressure on the mechanical performance and micro-scale characterization of concrete

Due to the pressure exerted by the self-weight of support slurry， the cut-off wall concrete would cure under high curing pressure conditions. However， there is still a lack of experimental verification on how high pressure environments affect the mechanical performance and microstructure of concrete. This research investigated the evolution of mechanical performance and micro-structure of concrete hardened under high curing pressure via a series of multi-scale tests. The results showed that under the high curing pressure， the initial loading stage of the specimens was shortened， and the elastic phase of the stress-strain curve became steeper. The compressive strength and elastic modulus increased by 35.60% and 44.51%， respectively， indicating an overall enhancement in mechanical performance. In micro-scale， sample cured in pressure exhibited a denser microstructure with highly developed solid skeleton than that cured in ambient condition， which has inhibited the growth of crack. The pore size distribution within the pressurized specimens performed a refinement trend from larger to smaller pores， indicating an effective densification of the pore structure. The content of bound water and the degree of hydration were significantly increased under curing pressure， which facilitated the dissolution of cement grains and promoted the precipitation of high-density hydration products. Furthermore， high curing pressure enhanced the polymerization of silicate chains within the hydration products， strengthened the bonding between interlayer water and hydration products， and promotes the development of a highly connected silicate tetrahedral network structure.