多因素作用衬砌喷射混凝土中性化及预测模型

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

以喷射混凝土单层永久衬砌长大公路隧道为工程背景,采用快速碳化法、硝酸浸泡法和气冻气融法开展衬砌喷射混凝土中性化试验,研究多因素作用喷射混凝土的中性化性能。研究结果表明,多因素作用喷射混凝土中性化深度符合Fick第一定律,硝酸侵蚀和冻融损伤均会加速混凝土的中性化。低水胶比喷射混凝土及喷射钢纤维混凝土中性化深度小。随粉煤灰掺量增大,混凝土中性化深度先减小后增大。在硝酸侵蚀累积作用下,喷射混凝土中性化深度与碳化深度差值随等效碳化龄期的延长而增大;冻融损伤喷射混凝土中性化深度与未损伤混凝土中性化深度差值随龄期延长而减小。喷射混凝土相对抗压强度与中性化深度之间呈正指数关系。本工作还建立了考虑喷射混凝土配合比、成型方式、硝酸侵蚀及冻融损伤的中性化深度预测模型。

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-bin-der 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.