The rebar-concrete interface plays a critical role in initiating corrosion of steel reinforcing bars embedded in concrete. The intimate physical contact between a steel rebar and the Ca(OH)₂-rich interfacial transition zone of concrete provides physical protection and buffering action against corrosion. However, the mechanism of the buffering action is not well understood and a systematic study has not yet been conducted. This paper investigates acidification at the rebar-concrete interface, buffering capabilities and corrosion behavior of a rebar embedded in concrete made with 100% Portland cement and with 50% fly ash or ground-granulated slag as cement replacement. It was found that a simple technique with filter paper wrapped around the steel rebar and using high impressed anodic current and a severe chloride environment allowed for interface solution to be accumulated, squeezed out, and collected for analysis. The solutions had pH values less than 2, thus proving acidification at the interface during the accelerated corrosion test. With a high content of Ca(OH)₂ in the matrix, the concrete with 100% cement as binder was shown to have a higher buffering capacity as compared to the matrix with 50% fly ash or slag as cement replacement. This acidification phenomenon promoted steel dissolution and subsequent corrosion activity although the presence of cracks in the concrete cover could also play a dominant role in controlling the subsequent corrosion rates. Acidification was also shown to occur under natural corrosion of lower corrosion activity.

钢筋混凝土界面在引发嵌入混凝土中的钢筋腐蚀方面起着至关重要的作用。钢筋与Ca（OH）₂的紧密物理接触丰富的混凝土界面过渡区可提供物理保护和缓冲作用以防腐蚀。但是，缓冲作用的机理尚不完全清楚，还没有进行系统的研究。本文研究了用100％硅酸盐水泥和50％粉煤灰或磨碎的矿渣代替水泥制成的混凝土中埋入的钢筋的酸化作用，钢筋混凝土界面的缓冲能力和腐蚀行为。结果发现，一种简单的技术是将滤纸包裹在钢筋上，并使用高施加的阳极电流和严酷的氯化物环境，使界面溶液得以积聚，挤出并收集用于分析。溶液的pH值小于2，从而在加速腐蚀测试过程中证明了界面处的酸化。高含量的Ca（OH）_如图2中所示，与具有50％粉煤灰或矿渣作为水泥替代物的基质相比，具有100％水泥作为粘合剂的混凝土显示出更高的缓冲能力。这种酸化现象促进了钢的溶解和随后的腐蚀活性，尽管混凝土表层中裂缝的出现也可以在控制随后的腐蚀速率中起主要作用。还显示出酸化在较低腐蚀活性的自然腐蚀下发生。