Neutralization Durability and Prediction Model of Lining Shotcrete with Multi-factor Action

Based on the engineering background of shotcrete single layer lining highway tunnel, in order to research the effect of the neutralization depth on shotcrete with nitrogen oxide from automobile exhaust and frost damage, the experiment of shotcrete neutralization durability was carried out by using freeze-thaw cycles, nitric acid immersing and accelerated carbonation method. Results have shown that neutralization rate of shotcrete was accelerated which corrosion and/or damaged by nitric acid and frost. Neutralization depth of shotcrete was influenced by water-to-binder ratio, dosage of fly ash, steel fiber content, concrete formed method, nitric acid attack and frost damage, respectively. Under the accumulative action of nitric acid corrosion, the difference between neutralization depth and accelerated carbonation depth was increased with increasing of equivalent carbonation aging. While, the difference between carbonation depth of frost damaged shotcrete and that of undamaged concrete was decreased. There was a positive exponential relationship between the relative compressive strength and neutralization depth of shotcrete. By fitting the experimental data, the prediction models of shotcrete neutralization depth were established in term of shotcrete mixture indexes, forming method, nitric acid corrosion and frost damage. © 2019, Materials Review Magazine. All right reserved.