ASR-氯盐腐蚀协同作用下混凝土的损伤特点

Distinguishing Characteristicts of Concrete Damage under Cooperation of ASR and Chloride Corrosion

以碱+氯盐复合溶液浸泡的方式进行了ASR-氯盐腐蚀协同作用下混凝土加速劣化的实验。通过定期测量长度和动弹性模量,研究了混凝土在承受ASR、氯盐腐蚀双重破坏因素作用下的损伤特点以及混凝土初始碱含量、氯盐溶液浓度对损伤发展的影响。试验结果表明,不同浸泡液中当混凝土碱含量高时,各龄期的膨胀值均大于混凝土低碱时的膨胀值,同期的动弹性模量损失也更大。浓度较高的氯盐溶液主要在短期内对ASR膨胀的加速显著,但浓度较低的氯盐溶液则具有持续的加速作用。ASR-氯盐腐蚀作用下动弹性模量变化的具体特点是:劣化初期混凝土动弹性模量即急剧下降,当剩余动弹性模量在70%左右时,其下降减缓,随后发展极其缓慢至完全失效。分析动弹模量损失和膨胀率之间的关系,发现膨胀率低于0.5%时动弹性模量对因膨胀引起的混凝土损伤更为敏感。

By measuring the expansion rate and relative dynamic elasitc modulus of concrete speciments at different age, that are immersed in the solution with 1M NaOH and a few different contents of NaC1, the tests of concrete under twofold factors of ASR and chloride corrosion are carried out. The rezults show that the expansion of concrete with high alkali content, immersed in different solution and in different age, is greater than that with low aklali content, and the loss of dynamic elastic modulus of former is also greater. The solution with higher concentration of chloride will obviousely accelerate the ASR expansion, mainly in the short time of early age, but the solution with lower content of chloride will oontinually keep the acceleration. And the change of dynamic elastic modulus for this time is as follow： at the initial stage of deterioration the modulus decreases rapidly and when the remainded modulus is at ＇about 70% the drop slows down, then the progress of decreasing is very slow and up to lose efficacy entirely. Analysed the relationship between the dynamic elastic modulus and expansian rate, it is found that the damage of concrete by expansion is more sensitive when the expansion rate is lower than 0.5%.