Nano-modification effect on the pore characteristics and the water multiscale transport properties of concrete in winter construction of tunnel engineering

Abstract

Seepage has become the dominant damage that affected tunnel stability. Although drainage and the waterproofing system are frequently employed in seepage tunnels, the poor performance of shotcrete is still an inducement for the waterproofing system failure. Further, the frost damage caused by seepage becomes more pronounced when tunnel construction locates in cold region environments. Therefore, the objective of the study is to explore the nano-modification effects on the water multiscale transport behaviors of concrete in winter construction environments. Firstly, the pore characteristics of the hydrated cement were experimentally determined by the mercury intrusion porosimetry (MIP) test. The meso-structures of concrete were obtained via the X-ray computed tomography (CT) test. Secondly, the fractal analysis was conducted to derive the permeability of the hydrated cement based on the capillary model with the interaction of solid and fluid molecules considered. Then, the permeability distribution of concrete was calculated by combining test results at the micro-scale and that at the meso-scale. Finally, the unified multiscale simulations based on the generalized Lattice Boltzmann method (GLBM) were conducted to obtain the permeability of all groups. The water transport process of concrete on the meso-scale was simulated by considering the influence of micro-structures. The permeability tests were conducted to verify the simulation results. Results indicated that the addition of nano-materials can markedly increase the complexity of the pore structure and decrease the porosity, thereby enhancing the impermeability of concrete.