水灰比和矿物掺合料对混凝土结构中钢筋极化电阻的影响

采用加速渗透试验方法和埋入式自制CB型氯离子传感器和MB型参比电极研究了水灰比和矿物掺合料组合对6组混凝土结构中钢筋极化电阻Rp的影响。研究表明:当水灰比为0.35时,混凝土在25 h内可保持较高的极化电阻钢筋,钢筋严重锈蚀要60 h,而水灰比为0.40和0.45混凝土中的钢筋极化电阻则持续下降,特别是对于水灰比较高的混凝土试件,氯离子渗透时间超过18 h后,钢筋已严重锈蚀。矿物掺合料有助于减缓钢筋的锈蚀,且复掺粉煤灰和硅灰效果最佳,复掺粉煤灰和矿渣次之;且掺有矿物掺合料混凝土试件中钢筋极化电阻都大于未掺矿物掺合料混凝土试件。当钢筋极化电阻下降至2.7×105Ω.cm2时,继续加速,钢筋极化电阻Rp值会突然下降,钢筋开始锈蚀,钢筋钝化膜发生了破坏,结论认为钢筋极化电阻Rp值为2.7×105Ω.cm2是钢筋在混凝土中钝化膜破坏的临界点。

Effect of water-cement ratio and mineral admixtures on the steel polarization resistance of concrete structure reinforced

The accelerated penetration test method and buried self-made CB typed sensor for chloride ion are applied to investigate the effect of water-cement ratio and mineral admixtures on polarization resistance Rp of six reinforced concrete structures.The results show that the polarization resistance of steel can be kept high value during 25 hours when the water-cement ratio is 0.35,and the serious corrosion happened after 60 hours.However,when the water-cement ratio is 0.40 and 0.45,the polarization resistance continues to decrease.Especially for reinforce concrete with high water-cement ratio,the steel is severely corroded when chloride ion penetration period is more than 18 h.Mineral admixtures are beneficial to delay steel corrosion.The combination of fly ash and silica fume has the best effect on reducing the steel corrosion,the combination of fly ash and slag is better.In addition,the steel polarization resistance value of concrete with mineral admixtures is bigger than that of concrete without mineral admixtures.Additionally,when the steel polarization resistance decreases to 2.7×105 Ω·cm2,if the accelerated penetration test method is continued,the polarization resistance Rp has a sharp decline,indicating that the steel bar begin to rust and the passive film of steel is destroyed.Therefore,considered the Rp value of 2.7×105 Ω·cm2 as the critical point of steel in concrete structures.