不同腐蚀性离子对掺合料混凝土性能及微观形貌的影响

Effect of different corrosive ions on properties and micro morphology of concrete with admixtures

为了研究单个离子以及多种离子复合后对掺合料混凝土的降解破坏情况,将清水作为对照组,分别以5%NaCl溶液、5%MgCl_(2)溶液、5%Na_(2)SO_(4)溶液、5%MgSO_(4)溶液以及5%MgSO_(4)+3.5%NaCl混合溶液作为侵蚀介质。通过干湿循环的方法对掺合料混凝土进行耐久性试验,结果表明:Mg^(2+)与SO_(4)^(2-)的复合对混凝土的侵蚀破坏效果最为明显,单一Cl^(-)对混凝土没有破坏性,Cl^(-)与SO_(4)^(2-)和Mg^(2+)复合后能抑制钙矾石的生成,降低混凝土被腐蚀溶液侵蚀破坏的速度。通过X射线衍射(XRD)和扫描电子显微镜(SEM)的分析可知,造成掺合料混凝土性能下降的原因一方面是侵蚀产物钙矾石和石膏含量的增加以及体积的膨胀导致试件的开裂破坏,另一方面是侵蚀产物M-S-H的生成使得水泥基体软化造成骨料的剥落。

To study the degradation and deterioration of mineral admixtures concrete under the condition of the combination of a single ion and multiple ions,we used water as a control group,5%NaCl solution,5%MgCl_(2) solution,5%Na_(2)SO_(4) solution,5%MgSO_(4) solution,and 5%MgSO_(4)+3.5%NaCl mixed solution as corrosion medium,respectively.The durability of mineral admixture concrete was investigated by wet-dry cycling method.The results show that the combination of Mg^(2+)and SO_(4)^(2-)could significantly corrode and deteriorate the concrete,whereas single Cl^(-)could not cause deterioration of the concrete.In particular,the combination of Cl^(-),SO_(4)^(2-)and Mg^(2+)could inhibit the formation of ettringite,reducing the rate at which the concrete was attacked by corrosive solutions.The experimental results of X-ray diffraction(XRD)and scanning electron microscopy(SEM)methods indicate that the increase of ettringite and gypsum as well as the volume expansion could lead to the cracking of specimens,which are the main reasons for the performance decline of the mineral admixture concrete.In addition,the generation of corrosion product M-S-H could lead to the softening of the cement matrix and then result in the spallation of the aggregate.