混凝土保护层锈胀开裂时间的预测方法

A method for predicting corrosion expansion time-to-cracking of concrete cover

钢筋锈蚀引起的混凝土保护层锈胀开裂时间是工程技术人员对钢筋混凝土结构进行维修加固决策的关键.为合理准确的预测混凝土保护层锈胀开裂时间,采用厚壁筒理论,假设圆筒内壁钢筋表面位置处存在2条初始径向裂纹,混凝土裂缝尖端的应力强度因子为钢筋与混凝土接触面完全光滑和理想粘结2种情况下应力强度因子的线性组合,通过断裂韧度与最大荷载的关系建立了考虑混凝土结构初始缺陷和微裂缝的临界锈胀力预测模型,进而提出了一种同时考虑界面间隙和钢筋锈损厚度混凝土保护层锈胀开裂时间的预测方法,并对方法的有效性进行了初步验证.该方法的显著特点在于,通过确定实验常数α,既适用于光圆钢筋又适用于变形钢筋情况下的混凝土耐久寿命预测.

The time-to-cracking of concrete cover induced by steel corrosion is one of the critical problems faced by engineers,operators and asset managers in making strategies for the maintenance and repairs of reinforced concrete（RC）structures affected by corrosion.For reasonably predicting the time-to-cracking of concrete cover,based on the thick-wall cylinder theory,by assuming existing two initial radial cracks on the inner surface of the cylinder,and assuming the stress intensity factor at concrete crack tip as a linear combination of perfectly smooth and perfectly bonded state,a critical corrosive force predicting model which considering the initial flaw and micro-crack of the concrete was derived through the relationship between fracture toughness and the maximum load.And then the time-to-cracking of concrete cover predicting method which simultaneously considers the interface gap and the thickness of steel corrosion was proposed.The validity of the proposed model was verified preliminarily by compared with available experimental results.A remarkable advantage of the proposed method is that it can be applied to predict the service life of RC structures made of deformed steel bars as well as those of round bars by determining an experimental constant.