缓黏结预应力混凝土梁耐久性能试验研究

Research on durability of retard-bonded prestressed concrete beams

为研究缓黏结预应力混凝土梁在长期荷载与腐蚀共同作用下的耐久性能,文章进行了14根缓黏结预应力混凝土梁及普通混凝土梁在荷载与氯盐干湿循环共同作用下的侵蚀试验,总结了荷载比、预应力度、干湿循环时间对不同受力部位的氯离子浓度沿深度分布和钢筋锈蚀的影响规律,以及荷载比和干湿循环时间对氯离子输运速度的影响规律。结果表明:在混凝土梁中施加预应力能有效减缓氯离子的渗透速度,增强构件的抗氯盐腐蚀能力;相同深度处的氯离子浓度随荷载比的增大而增大、干湿循环时间的增加而增大、与跨中距离的减小而增大;缓黏结预应力混凝土氯离子扩散系数与荷载比之间呈指数函数关系;荷载作用加速了钢筋锈蚀的进程;在裂缝控制等级相同的情况下,承担更大荷载比的缓黏结预应力混凝土梁的钢筋锈蚀程度与无预应力梁相当,体现出更佳的耐久性能。

To investigate the durability of retard-bonded prestressed concrete beams under the combined actions of long-term load and corrosion, the corrosion tests on total 14 retard-bonded prestressed concrete beams and ordinary reinforced concrete beams were conducted under the combined actions of loading and dry-wet cycles of chlorine salt. The effects of load ratio, degree of prestressing action, and dry-wet cycle time on the distribution of chloride ion concentration along the depth of different sections and on the rule of corrosion of steel reinforcements, as well as the influence of load ratio and dry-wet cycle time on the chloride ion transport velocity, are summarized. The results show that the application of prestress in concrete beams can effectively slow down the penetration rate of chloride ions and enhance the corrosion resistance of members to chloride salt. The chloride ion concentration at the same depth increases with the increase of load ratio, the increase of dry-wet cycle time, and the decrease of the distance of the detected section and the mid-span section. The relationship between the chloride diffusion coefficient and the load ratio of retard-bonded prestressed concrete appears to be exponential. The action of load accelerates the process of reinforcement corrosion. In the case of the same crack control grade, the corrosion degree of the steel reinforcements of the retard-bonded prestressed concrete beam with a larger load ratio is equivalent to that of the non-prestressed beam, indicating its better durability.