摘   要：针对粉煤灰（FA）提高抗渗性而降低碱度对混凝土护筋性存在矛盾的复合作用，通过不同粉煤灰掺量下混凝土的氯离子渗透性、碱度和干湿循环下钢筋的腐蚀电位、加速腐蚀条件下混凝土的开裂时间和最大阳极电流等的试验测定来研究FA掺量对混凝土护筋性的复合影响。结果表明，随FA掺量增加(0～40%)，混凝土pH值逐渐降低而抗渗性逐渐提高,尽管掺40%FA混凝土的抗渗性高于掺30%FA的混凝土，但前者的护筋性下降。混凝土护筋性不仅取决于抗渗性，还与基体内能否保持较高的碱度有关。为保证混凝土的高碱性和护筋性，FA掺量不宜超过40%。而FA掺量30%的混凝土不仅有高的碱度和抗氯离子渗透性，还有很好的护筋性。

Abstract: Considered that the fly ash can improve impermeability and also reduce the alkalinity of concrete, the compound influences of adding fly ash on protectionness from corrosion of steel bar in concrete was studied by tests including of chloride permeability, alkalinity of concrete, corrosion potential on steel bar, cracking time and maximum anodic current in accelerated corrosion test. The rezults show that, as the content of fly ash increasing(0～40%),the alkalinity was reduced and the impermeability of concrete was improved. Though the impermeability of concrete with 40% fly ash was higher than concrete with 30% fly ash, the former was poorer in protectional ability on steel bar, i.e. which is not only depended on chloride impermeability, but also on the alkalinity of pore solution. To ensure the high alkalinity and protectional ability on steel bar of concrete, the content of fly ash in binders should not exceed 40%. Concrete with the addition of fly ash by 30% in binders possesses both high alkalinity and impermeability, so has excellent protectional ability on steel bar.