硫铝酸盐与硅酸盐水泥复合对砂浆中钢筋腐蚀的影响

The influence of sulphoaluminate and Portland mixed cement on the corrosion of steel in mortar

研究了钢筋在硫铝酸盐水泥(CSA)与硅酸盐水泥(OPC)不同比例复合砂浆中的腐蚀行为,并分析了孔隙液碱度、砂浆电阻率对钢筋腐蚀的影响。结果表明:当OPC复合比例≤50%时,砂浆中水化生成的铝相较多,孔隙液碱度较低,砂浆电阻率下降,28 d时未掺OPC组电阻率从124.9Ω·m快速下降至30%OPC组的13.0Ω·m,导致腐蚀电位下降,腐蚀电流密度增大,钢筋易发生腐蚀;当OPC复合比例≥70%时,砂浆中水化生成的铝相消失,氢氧化钙含量增加,显著提高孔隙液碱度,pH值均高于12.73,促进钢筋快速钝化。当砂浆电阻率接近时,50%OPC组28 d龄期的pH值为11.90,高于30%OPC组的10.31,故其腐蚀电位也相应较高。

The corrosion behavior of steel in the mortar mixed with sulphoaluminate and Portland cements in different proportions are studied and the effects of alkalinity of pore solution and resistivity of mortar on corrosion of steel are analyzed.The results indicate that when the mixing ratio of OPC is less than or equal to 50%,multiple aluminum phases are formed in the mortar by hydration,the alkalinity of the pore solution is low,and the resistivity of the mortar decreases.At 28 days,the resistivity of group 0%OPC drops rapidly from 124.9Ω·m to 13.0Ω·m of group 30%OPC.As a result,the corrosion potential decreases,the corrosion current density increases,and the steel are prone to corrosion.When the mixing ratio of OPC is more than or equal to 70%,the aluminum phase generated by hydration in the mortar disappears,and the content of calcium hydroxide increases,which improves the alkalinity of the pore solution to over 12.73 and promotes the passivation of the steel.When the resistivity of the mortar is similar,the pH value of the group 50%OPC is 11.90 at 28 days higher than 10.31 of group 30%OPC,so the corrosion potential is correspondingly higher.