阳离子类型对混凝土固化氯离子能力的影响机理

Effect of cationic types on concrete resistance to chloride ingress

为了研究阳离子类型(Na+、K+、Mg2+和Ca2+)对混凝土固化氯离子能力的影响,对尺寸为100 mm×100 mm×100 mm,预埋钢棒的18个混凝土试件进行24个周期的干湿循环试验,采用电位滴定法进行游离态氯离子浓度测试和总的氯离子浓度测试,并用酸度计测定剩余溶液的pH值。采用衍射仪定性分析胶凝材料水化产物,同时利用综合热分析仪进行热重法和微分热重法定量分析水化产物。试验结果表明,阳离子的类型显著的影响着混凝土固化氯离子的能力及孔隙液pH值,对应的固化氯离子能力大小趋势为Ca2+>Mg2+>Na+≈K+,K+与Na+较为相似,导致孔隙液pH值升高,结合氯离子量及总氯离子含量则相对降低。Mg2+消耗水化C-S-H导致孔隙液pH值下降,相应的pH及游离态氯离子含量较Na+和K+的较低。Ca2+导致结合氯离子量较Mg2+要高,导致的总氯离子含量也高于Mg2+。

In order to reveal the effect of cationic types on concrete resistance to chloride ingress.The 24 dry-wet cycles were experimented on 18 concrete specimens which were 100 mmxl00 mmxl00 ram,and imbedded by steel bars.Free chlorine ion concentration test and total chlorine ion concentration test were executed by potentiometric titration method.The pH of the residual solution was tested by acidimeter.The dffractometer was used to analyse the hydration product of cementitious material qualitatively.And Integrated Thermal Gravimetric Analyzer was used to analyse the hydration product with digital thermogravimetry and differential digital thermogravimetry.The data indicated that catinonic types had a remarkable influence on ability of concrete resistance to chloride ingress and the pH of pore solution.The ability of con- crete resistance to chloride ingress was Ca^2＋〉Mg^2＋〉Na^＋ =K^＋.Both K^＋ and Na^＋ lead to increase ofpH in pore solution,decrease in combined and total chlorine ion concentration.Mg^＋ which consume C-S-H lead to decrease ofpH in pore solution.The relevant pH and free chlorine ion concentration was lower than K＋ and Na^＋.Ca^2＋ lead to higher combined and total chlorine ion concentration than Mg2＋.