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荷载和环境作用影响着混凝土中的氯盐传输过程和混凝土结构的服役寿命。采用弹簧加载系统对8根钢筋混凝土梁施加极限抗弯承载力28%、22%、16%和10%的持续弯曲荷载,并测定混凝土梁跨中部位的局部应变;氯盐侵蚀试验在多功能人工模拟环境试验箱中进行,4根混凝土梁置于5%的Na Cl溶液并在环境温度为50℃下进行浸泡试验,其余4根钢筋混凝土梁在全自动干湿循环试验箱中进行干湿循环试验,干燥过程中环境相对湿度为60%。氯盐侵蚀60 d后对混凝土梁受拉区和受压区取粉分析氯离子浓度。结果表明:与未承受荷载混凝土试件的氯离子传输速率相比,拉应变达到526με时氯离子扩散系数达到未承受荷载时的2.4倍,压应变达到90με时氯离子扩散系数无明显改变,而当压应变达到175με时氯离子扩散系数降低为无荷载作用时的0.4倍,拉应力加速了氯离子的传输速率,而压应力在一定范围内能够抑制氯离子的传输;且干湿循环条件下混凝土的氯离子传输速率明显高于浸泡条件的混凝土。“拉应力+干湿循环”条件对氯离子的传输影响最大;混凝土局部应变与氯离子扩散系数的相关性较好,能够反映荷载作用对氯盐传输的影响。在一定应变范围内,氯离子扩散系数随拉应变的增大而提高,随压应变增大而降低。
Load and environmental effects affect the transmission of chloride salts in concrete and the service life of concrete structures. The spring loaded system was used to apply constant bending loads of 28%, 22%, 16% and 10% to the eight reinforced concrete beams and to measure the local strain of the concrete mid-span of the concrete beams. Artificial simulated environmental chamber, four concrete beams placed in 5% NaCl solution and immersed in the test at an ambient temperature of 50 ℃, the remaining four reinforced concrete beams in a fully automatic wet and dry cycle chamber wet and dry cycle test , The relative humidity during the drying process is 60%. After 60 days of chloride salt erosion, the concrete beam tension zone and compression zone were taken out and analyzed for chloride ion concentration. The results show that the diffusion coefficient of chloride ion reaches 2.4 times that of unloaded specimen when the tensile strain reaches 526με and the chloride ion diffusion coefficient does not change obviously when the compressive strain reaches 90με When the compressive strain reaches 175με, the diffusion coefficient of chloride ions decreases to 0.4 times that of no-load, tensile stress accelerates the transfer rate of chloride ion, and the compressive stress can inhibit the chloride ion transport within a certain range; Concrete chloride ion transport rate was significantly higher than the immersion conditions of concrete. The tensile stress + wet-dry cycle condition has the greatest influence on the chloride ion transport. The correlation between the local strain and the chloride ion diffusion coefficient is better, which can reflect the influence of the loading on the chloride transport. Within a certain strain range, the chloride ion diffusion coefficient increases with the increase of tensile strain and decreases with the increase of compressive strain.