ABSTRACT

This paper investigates high corrosion observed at intersections of steel rebars in the mat as compared to low corrosion in all other areas observed in a typical reinforced concrete structure at multi-scale from macro to micro level. This is a rather new and unusual finding having limited research in the past and needed further investigation to clarify the mechanisms involved therein. Therefore, chloride contaminated reinforced concrete slabs were cast and laboratory controlled experiments were conducted for half-cell potential, corrosion current, concrete resistivity, SEM and MIP measurement. The experimental measurements at the intersection of steel bars were found to be actually much higher than the areas in between them. This high corrosion rate at the steel bars intersections observed in the field in an actual RC structure and verified by experimental measurements in this paper was further investigated to document the effect of variation in rebar spacing, connection type as well as the binding wire material. This research is expected to result in improved steel rebar fixing and placement methods in the future for all reinforced concrete structures. This research will result in established knowledge and material engineering behavior of high corrosion rate at the intersection points in steel mat of reinforced concrete. This research will enable future advances and trends in understanding the effect of steel bar overlapping on the corrosion rate at the microstructure level of reinforced concrete engineering material as well as clarification of the phenomenon involved therein. As a scope for future research, the experiment results presented in this paper can be utilized in the future for the effective role of reinforcement steel arrangement in the mat to improve the corrosion resistance and protection of concrete in civil engineering industry.

INTRODUCTION

Corroding reinforced concrete structures have always been an issue of great concern for professional civil engineers and researchers all over the world. Reinforced concrete (RC) structures are corroded under the effect of various environmental actions such as chloride, carbonation, temperature etc. The rapid deterioration of RC structures due to corrosion is becoming a very serious threat for the world with enormous economic and safety implications. It requires taking necessary countermeasures for the protection and maintenance of corroding infrastructures keeping in view the alleviation of the problem in future construction. According to ACI committee 201,1 the durability of concrete is defined as its ability to withstand the environmental conditions to which it is exposed. This means that durable concrete should resist rebar corrosion, weathering actions, chemical attack, abrasion, or other forms of deterioration. All over the world concrete is the most dominant construction material. The fast deterioration of reinforced concrete is a very serious issue having huge economical drawbacks and serviceability related problems. Therefore, engineers have been facing maintenance problems of aging and deteriorated RC structures due to a number of mechanisms. One of the most severe problems is the corrosion of reinforcing steel. Reinforcement corrosion is the most urgent durability problem when it comes to RC structures throughout the world.

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