矿物掺合料与钢筋表面状态对砂浆中钢筋锈蚀的影响

Effect of Mineral Admixtures and Steel Surface Conditions on Steel Corrosion in Mortar

通过电化学方法和剖型观察方法研究了不同矿物掺合料(硅灰和粉煤灰)和不同钢筋表面状态(预钝、预锈和未处理)对砂浆试样中的钢筋锈蚀行为的影响。用电化学阻抗谱法测试钢筋的腐蚀速率和与钢筋锈蚀相关的电化学参数。结果表明:硅灰由于发生火山灰反应而明显降低体系的pH值,且硅灰结合氯离子的能力明显弱于粉煤灰,氯离子临界值也低于掺粉煤灰试样。基于以上3个负作用,在短期氯盐侵蚀后硅灰的护筋性不佳,相比而言粉煤灰只要掺量合适可以较好地保护钢筋。钢筋表面若无明显腐蚀坑,预锈处理对钢筋锈蚀影响较小(除掺硅灰试样外);预钝化能降低含矿物掺合料砂浆中钢筋的腐蚀速率,但对无掺合料砂浆试样中的钢筋影响很小。

The effects of different mineral admixtures（silica fume and fly ash） and steel surface conditions（pre-passivated,pre-rusted and as-received） on steel corrosion in mortar specimens were investigated by electrochemical method and visual inspection.Electro-chemical impedance spectroscopy（EIS） was used to determine corrosion current density（icorr） and other electrochemical parameters related to steel corrosion.The results show that silica fume reduced the pH value of pore solution in mortar due to the pozzolanic re-action.In addition,both chloride binding capacity and chloride threshold level of specimens with silica fume were lower than that with fly ash.It indicates that the silica fume could not increase the corrosion resistance of steel in mortar effectively during the short-term exposure,but fly ash strongly protected steel against corroison if added in appropriate proportion.Pre-rust on the steel surface had little effect to steel corrosion（except for silica fume mortar）.However,pre-passivation reduced the corrosion rate of steel in mineral admixtures-containing mortars,but it could not affect the corrosion rate of steel without mineral admixtures.