RELATIONSHIP BETWEEN FATIGUE BEHAVIOR AND MICROSTRUCTURE

In this contribution, porosity of matrix and microhardness of the vicinity of aggregate were tested by means of mercury intrusion porosimetry and nano-inndentation respectively for concrete with different slag/fly ash content. Fatigue behavior of concrete was also exanimate under cyclic-flexural load. Relationship between microstructure features of matrix, the interface transition zone and fatigue behavior are estabilshed by adopting two indexes, i.e. matrix index M and the ITZ index I, which charactering effects of matrix and the interface transition zone on fatigue behavior respectively. Results show that the interface transition zone index I increase with the decrease in difference of microhardness between the interface transition zone and bulk matrix. The matrix index M decreases with the increase in bulk matrix porosity. The findings suggest a basic way to improve concrete fatigue behavior by improving the interface transition zone structure and/or strengthening bulk matrix.