Analysis On The Crack Process And Effect Factors Of Concrete Cover Induced By Steel Corrosion

When the steel corrodes, the volume of rust is almost 2-4 times than the original and, thus, exerts pressure on the concrete around the rebar; as the corrosion turn worse, the cover of concrete would crack. Once the crack happened, the corrosion would accelerated and the crack branch out, which results in destroy of the structures and the failure of the durability. So, it has practical value to analyze the crack process of the concrete cover due to the corrosion.Based on the existing research, the main work of this paper can be summarized as follows:1. For the case of the rebar uniform corrosion, the concept of destroyed-radius is brought up. The cracking process of the concrete cover is simulated by FEM analysis software, with assuming an uniform pressure applied on the concrete around the rebar to simulate rebar uniform corrosion. Based on the analytical results, the formula of destroyed-radius of cover and the formula of critical corrosion expansive force are obtained; furthermore, the concrete cover cracking is analyzed and the formula of the corrosion expansive force and corrosion ratio are obtained, which is used to predict the cracking time of the cover concrete. The analytical cracking time achieves agreement with the test result well.2. In order to simulate the cracking process of the concrete cover due to rebar non-uniform corrosion, the concept of corrosion-degree-ratio is induced. On the basis of the FEM analysis results by applying non-uniform displacement on the concrete around the rebar, the formula of corrosion-degree-ratio and corrosion ratio are developed, which is used to predict the cracking time of the cover concrete. The analytical cracking time achieves agreement with the test result well.3. The effect factors analysis based on FEM shows that: Raising the strength of concrete and the thickness of cover concrete would delay the cracking of concrete; Stress superposition would appear due to the influence of adjacent rebar, and increasing the rebar space would postpone the time of cover cracking; Stirrup could suppress the cracking of cover concrete, however, the effect is limited and the corrosion-degree-ratio and corrosion expansive force would not increase until the cover concrete cracking happens completely.