Study on the Perspective of Mechanical Properties and Corrosion Behaviour of Stainless Steel, Plain and TMT Rebars

Nisith Kumar Tewary,Pallabi Manna,Muralidhar Yadav,Indrajit Dey,Swarup Kumar Ghosh,Jayanta Kumar Saha

doi:10.5772/intechopen.101388

Abstract

In the present research, the effects of various alloying elements and microstructural constituents on the mechanical properties and corrosion behaviour have been studied for four different rebars. The microstructures of stainless steel and plain rebar primarily reveal equiaxed ferrite grains and ferrite-pearlite microstructures, respectively, with no evidence of transition zone, whereas tempered martensite at the outer rim, followed by a narrow bainitic transition zone with an internal core of ferrite-pearlite, has been observed for the thermomechanically treated (TMT) rebars. The hardness profiles obtained from this study display maximum hardness at the periphery, which decreases gradually towards the centre, thereby providing the classical U-shaped hardness profile for TMT rebars. The tensile test results confirm that stainless steel rebar exhibits the highest combination of strength (≈755 MPa) and ductility (≈27%). It has been witnessed that in Tafel plots, the corrosion rate increases for all the experimental rebars in 1% HCl solution, which is well expected because the acid solutions generally possess a higher corrosive environment than seawater (3.5% NaCl) due to their acidic nature and lower pH values. However, all the experimental results obtained from Tafel and Nyquist plots correlate well for both 1% HCl and 3.5% NaCl solutions.

Highlights

For the past few years, an inspection of reinforced concrete structures with steel rebars has become a subject of research because concrete provides an alkaline environment that is suitable for the spontaneous passivation of steel rebars
It has been already reported that an increase in yield strength of reinforcing bars occurs by raising carbon as well as manganese content or by microalloying
The important conclusions drawn from this study are as follows: 1. Microstructures of all the thermomechanically treated (TMT) rebars consist of an outer martensitic rim with an intermediate narrow bainitic transition zone followed by a ferrite-pearlite inner core, whereas stainless steel and plain rebars show equiaxed ferrite grain and ferrite-pearlite microstructure throughout the sample with no transition zone between core and rim due to the absence of TMT

Summary

Introduction

For the past few years, an inspection of reinforced concrete structures with steel rebars has become a subject of research because concrete provides an alkaline environment that is suitable for the spontaneous passivation of steel rebars. Extensive research has been carried out to date on corrosion in steel rebars but a modest solution can be the usage of stainless steels rebars as a partial or complete replacement of the reinforcements in concrete. This solution is economically viable because there may be a higher initial investment cost but this can be compensated by low-repairing cost, less maintenance effort and most importantly long-range services of the designed structures [4]. It is true that, since the cost of these steels can be compared with the cost of common black steel reinforcement rather than the cost of highly alloyed stainless steels, the use of low alloyed stainless steel reinforcement has been accepted as economically more convenient [6]

Methods

Results

Conclusion