向挖隧弃岩中复掺外加剂配制混凝土的抗渗抗冻性能OA

Tunnel excavation rock slag often develops micro-cracks during crushing,leading to increased porosity in the resulting concrete and compromising its durability.To address this issue,this study proposes incorporating compound admixtures to refine the pore structure and enhance both the impermeability and frost resistance of waste slag concrete.Water penetration tests were conducted to evaluate the average seepage height and relative permeability coefficient across different admixture dosages.Freeze-thaw cycling tests were employed to investigate the degradation patterns of relative dynamic elastic modulus,mass loss,compressive strength,and splitting tensile strength.The mechanisms by which compound admixtures improved concrete durability were also elucidated.The results indicate a positive correlation between admixture content and both impermeability and frost resistance.Specifically,the average seepage height and relative permeability coefficient decrease steadily with increasing admixture dosage,with the most significant improvements observed within the range from 1.6%to 2.4%,where impermeability reaches an optimum and complies with relevant standards.At a dosage of 1.6%,the concrete withstands 225 freeze-thaw cycles before failure,achieving an F200 frost resistance grade while maintaining low losses in dynamic elastic modulus,mass,and strength.Microstructural analysis reveals that the compound admixture promotes cement hydration,generating abundant insoluble hydrates that fill pores,optimize pore structure,and enhance the matrix compactness.This mechanism underpins the synergistic improvement in both impermeability and frost resistance of tunnel waste slag concrete.