Carbonated water erosion characteristics and mechanism of tunnel lining cement-based materials in karst environment

• Carbonated water erosion causes surface roughening, porosity increase, and pore enlargement in tunnel lining cement-based materials. • Erosion is spontaneous and driven by Gibbs free energy, with higher Ca/Si molar ratio in hydration products leading to more extensive reactions. • Model-building concrete with C-S-H gel and portlandite is more susceptible to erosion than shotcrete with ettringite as main hydration product. • Adding silicon-rich mineral admixtures can enhance erosion resistance, offering practical insights for karst tunnel engineering.