Study On Corrosion Cracking Mechanism Of RC Beam With Transverse Cracks In Natural Environment

The durability of reinforced concrete structure have attracted accumulated concerns. the corrosion of reinforcement is the major cause for durability problem, expansion of corrosion product volume lead to concrete cover cracks, So the analysis on cover corrosive cracking mechanism of concrete structure and uneven distribution of corrosion products are of great significance to the service life of concrete structures. Also, components in practical engineering occurs in load effect and natural degradation, testing process should simulate practical settings as close as possible. This paper introduce research results according to arguments above:(1) Slice research on a four-year natural corroded reinforced concrete beam that is under loa d effect. Based on observation on cracks on the beam:their widths, distributions and shapes, also , the filled corrosion products in corrosive cracks and transverse cracks, propagation mode of cor rosive cracking is analyzed. We could find out propagation mode and distribution regulation of c orrosion products under different stress states. Then effect regulation on corrosive cracks by tran sverse cracks is elaborated to get a closer look at the long-time reinforcement corrosion process. All these contribute to the analyses of corrosive cracking.(2) Adopt of 3D laser scanning technology to scan the surface of corroded reinforcement in concrete beam, describe the process of establishment of three dimensional entity model, get the cross-sectional area and cross-sectional circumference every 1 mm of corroded reinforced longitudinally. Based on the initial steel cross-sectional area and cross-sectional circumference, determine the corrosion rate of the cross section and the circumference, explore the effects of different stress state on rebar corrosion; on the base of transverse crack pattern, explore the effects of transverse crack on rebar corrosion rate. Then discuss the relationship between average steel section corrosion rate of truncation length of 20 mm and the largest section corrosion rate of truncation length of 20 mm.(3) Adopt electronic probe analysis technology to conduct accurate surface scan and line scan analysis on the face of the biopsy specimen. Considering the color depth changes in surface scan results, observe distributions of three kinds of corrosion products in the corrosive cracks, and research on impacts of stress state and corrosion degree on the distribution of the corrosion product in further. Analyze the inhomogeneous distribution of rust layer on the surface of the steel/concrete. Qualitative and quantitative analysis of the emergence and development process of rust peak. In terms of change of oxygen content and iron content in line scan results, study the corrosion product distribution in internal cracks of rust layer. By means of scanning electronic microscope under back scattered electron model, observe the millscale on the surface of the steel, then put forward qualitative description of the characteristics of the millscale and its inhomogeneous distribution on the surface of the corroded reinforcement.