青海氯盐渍土地区半埋混凝土耐久性研究

Study of the durability of partially-exposed concrete in chloride saline soil areas of Qinghai Province

文章在现场调查的基础上,针对青海察尔汗盐湖至格尔木高速公路上使用的混凝土进行氯盐快速腐蚀试验和氯离子测试实验。试验结果表明:混凝土相对动弹性模量先上升后下降;混凝土吸附区氯离子的分布规律为先随着距表层距离的增加而增加,在0.75cm处达到最大值,之后随着距表层距离的增加而下降。结合半埋状态下混凝土各部位和周围盐渍土之间的离子交换传输机理,以及氯离子的腐蚀机理,对半埋混凝土状态下钢筋混凝土的使用寿命进行了预测。结果表明:半埋状态下混凝土和周围盐渍土之间的离子交换机理是外部"蒸发-浓缩"和毛细管吸附,内部为扩散;氯离子在半埋混凝土靠近表层处浅层区域的传输机理主要是毛细管吸入,深层区域为扩散;钢筋混凝土腐蚀的主要原因是氯离子使钢筋表面钝化膜破坏,形成腐蚀电池并产生孔蚀,随着铁锈体积增大,导致混凝土保护层开裂。最后,研究得出的青海氯盐渍土地区的半埋钢筋混凝土使用寿命和钢筋保护层厚度之间的关系与调查结果基本一致,说明了文中的寿命预测方法的合理性。

Based on the field investigation, the chlorine accelerated corrosion test and chlorine ion testing exper- iment on the concrete used in the highway between Chaerhan Salt Lake and Golmud, Qinghai Province were made. The experimental result shows that the dynamic elastic modulus of concrete increases first, afterwards deceases as dry-wet circulation increases. And the distribution of chlorine ion in adsorption zone increases first with the increase of the distance from the surface, reaching the maximum at 0.75 cm, then decreases with the increase of the distance from the surface. Based on the ion transport mechanism model between the partially- exposed concrete and sulfate soil around and the corrosion mechanism of the chloride ion, the service life of partially-exposed reinforced concrete was predicte＆ The results show that the transport mechanism of the chloride ion in the shallow area near the surface is ＂evaporation-enrichment＂ and capillary suction, and in the deep area is diffusion of the partially-exposed concrete; the corrosion mechanism of the reinforced concrete is that the chloride ion makes the passive film damage on the surface of steel, producing the corrosion cell and pitting corrosion, with the rust volume increases, the concrete protective cover cracks. Finally, the relation- ship between the service life of partially-exposed reinforced concrete and the thickness of the cover was gotten, and the service condition of the partially-exposed reinforced concrete in chloride saline soil areas of Qinghai Province was basically identical with the prediction, which can explain the rationality of this paper.