碳化-冻融作用对风积沙混凝土氯离子传输的影响

Effect of carbonation freeze-thaw on chloride ion transport in aeolian sand concrete

为研究碳化-冻融循环作用对风积沙混凝土氯离子传输的影响,进行全风积沙混凝土经历碳化(0、14、28 d)后的冻融循环(50、100、150、200次)试验研究,根据碳化时间分为C0组、C1组、C2组。通过化学滴定法检测不同深度处混凝土中的氯离子质量分数,进而分析氯离子质量分数、分布、氯离子扩散系数以及碳化深度与时间依赖性的关系,并通过扫描电镜观察混凝土内部结构。结果表明:碳化生成的碳化产物使混凝土更加密实,能够有效抵抗氯离子的侵蚀,且碳化时间越长,抵抗氯离子侵蚀效果越明显;冻融循环增大混凝土裂缝的产生,为氯离子向内部传输提供通道;随着冻融循环次数增多,氯离子侵蚀也越严重,当冻融循环100次时,C0组氯离子侵入深度为30 mm,冻融循环150次时,所有混凝土氯离子侵入深度为30 mm;200次冻融循环条件下,C1组时间依赖性系数较C0组增加42.22%,C2组较C0组增加57.78%,较C1组增加10.94%。风积沙混凝土内部氯离子质量分数随冻融循环次数增加逐步增加,随碳化深度的增加逐步降低。

In order to study the effect of carbonation freeze-thaw cycle on chloride ion transmission of aeolian sand concrete,the experimental study of freeze-thaw cycle(50,100,150,200) of all aeolian sand concrete after carbonation(0,14,28 d) was carried out.The chloride ion in concrete at different depths was detected by chemical titration,and then the relationship between chloride ion content,distribution,chloride ion diffusion coefficient,carbonation depth and time dependence was analyzed.The internal structure of concrete was observed by scanning electron microscope.The results showed that the carbonation products produced by carbonation made the concrete more dense and could effectively resist the corrosion of chloride ions,and the longer the carbonation time was,the more obvious the effect of resisting the corrosion of chloride ions was.The freeze-thaw cycle increased the generation of concrete cracks and provided a channel for the internal transmission of chloride ions;With the increase of the number of freeze-thaw cycles,the chloride ion erosion was also more serious.When the freeze-thaw cycle was 100 times,C0 group was invaded by chloride ion at chloride ion invasion depth 30 mm,and when the freeze-thaw cycle was 150 times,chloride ion invasion depth 30 mm of all concrete was eroded by chloride ions.Under the condition of 200 freeze-thaw cycles,the time-dependent coefficient of group C1 increased by 42.22% compared with group C0,group C2 increased by 57.78% compared with group C0,and increased by 10.94% compared with group C1.The mass fraction of chloride ions in aeolian sand concrete increased with the increase of freeze-thaw cycles and decreased with the increase of carbonation depth.