基于灰色系统理论的高寒盐沼泽区混凝土耐久性评估

依托青海省德香高速工程, 通过混凝土室内损伤试验, 分析了冻融干湿循环和盐腐蚀耦合作用下混凝土动弹性模量的演化过程与特征; 基于灰色系统理论, 建立了不同工况下混凝土相对动弹性模量GM (1, 1) 预测模型, 预测了2种损伤条件下3种配合比混凝土耐久年限; 依据室内损伤试验与灰色系统理论GM (1, 1) 模型预测结果分析了混凝土的组分, 研究了不同掺合料对混凝土耐久性的影响。研究结果表明: 混凝土耐久性GM (1, 1) 预测模型的相对误差在6%以内, 且后验差比值小于0.35, 小概率误差大于0.95, 预测精度较高; 不同使用环境对混凝土耐久性影响差异较大, 复合盐腐蚀-养护冻融循环的影响程度较复合盐腐蚀-浸泡冻融循环提高了42.8%~46.2%;掺加了粉煤灰、硅灰与膨胀剂的配合比Ⅲ的混凝土耐久性最好, 耐久年限较基准配合比混凝土提高了50%以上, 因此, 为了保证混凝土耐久性, 在类似地区工程实践中, 可参考配合比Ⅲ进行现场混凝土配比设计; 粉煤灰与矿渣同时使用将会生成钙矾石, 相比基准配合比, 不同配合比下混凝土耐久年限降低率均在50%以上, 严重损伤混凝土耐久性。 

Durability evaluation of concrete in alpine salt marsh area based on gray system theory

Based on the project of Qinghai Dexiang Highway, the evolution process and characteristics of the concrete's dynamic elastic modulus under the coupling effect of freezingthawing dry-wet cycle and salt corrosion were analyzed through the indoor damage test.Based on the grey system theory, the GM (1, 1) prediction models of the concrete's relative dynamic elastic modulus were established under different conditions, and the durabilities of the concretes with three mix ratios under two damage conditions were predicted by using the prediction models.According to the indoor damage test result and the prediction results of the GM (1, 1) models, thecompositions of the concrete were analyzed, and the influence of different mixtures on the durability of the concrete was studied.Research result shows that the relative errors of the prediction models for the concrete durability are within 6%, the posterior difference ratio is less than 0.35, and the small probability error is more than 0.95. Therefore, the prediction accuracy is higher.The durability of concrete varies greatly under different working conditions, and the effect degree of composite salt corrosion-curing freezing-thawing cycles is 42.8%-46.2% higher than the value of composite salt corrosion-immersion freezing-thawing cycles.The durability of the concrete mix proportion Ⅲ with fly ash, silica fume and expansive agent is the best and 50% higher than the value of standard mix proportion.Therefore, in order to ensure the durability of the concrete, the concrete mix proportion Ⅲ can be used as a reference in site concrete mix proportion design in similar areas.The simultaneous use of fly ash and slag will produce ettringite, which can seriously affect the durability of concrete.Compared with the reference mix ratio, the durability reduction rates of the concrete are more than 50% under different mix proportions.