Mechanical Behavior Evaluation of Tempcore and Hybrid Reinforcing Steel Bars via a Proposed Fatigue Damage Index in Long Terms

Maria Basdeki,Charis Apostolopoulos

doi:10.3390/met11050834

Abstract

As it is widely known, corrosion constitutes a major deterioration factor for reinforced concrete structures which are located in coastal areas. This phenomenon, combined with repeated loads and, especially, intense seismic events, negatively affect their useful service life. It is well known that the microstructure of steel reinforcing bars has a significant impact either on their corrosion resistance or on their fatigue life. In the present manuscript, an effort has been made to study the effect of corrosive factors on fatigue response for two types of steel reinforcement: Tempcore steel B reinforcing bars and a new-generation, dual-phase (DP) steel F reinforcement. The findings of this experimental study showed that DP steel reinforcement’s rate of degradation due to corrosion seemed apparently lighter than Tempcore B with respect to its capacity to bear repeated loads to a satisfactory degree after corrosion. For this purpose, based on a quality material index that characterizes the mechanical performance of materials, an extended damage material indicator for fatigue conditions is similarly proposed for evaluating and classifying these two types of rebars in terms of material quality and durability. The outcomes of this investigation demonstrated the feasibility of fatigue damage indicators in the production cycle as well as at different exposure times, once corrosion phenomena had left their mark in steel reinforcement.

Highlights

The durability of Reinforced concrete (RC) structures is adversely affected due to the corrosion of steel reinforcements because it degrades the mechanical properties of materials, mainly the ductility, which plays a key role in ensuring the bearing capacity of elements and, the whole structural performance in earthquake prone areas
The cumulative effects of fatigue and corrosion impair the mechanical performance of steel reinforcement, a fact directly linked with the microstructure of each class of steel reinforcement
For the goals of the present manuscript, Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analyses were executed both on Tempcore steel B and Dual

Summary

Introduction

Reinforced concrete (RC) comprises the most widely used construction material of existing building stock, providing high bearing capacity and ductility compared to its low production costs. The durability of RC structures is adversely affected due to the corrosion of steel reinforcements because it degrades the mechanical properties of materials, mainly the ductility, which plays a key role in ensuring the bearing capacity of elements and, the whole structural performance in earthquake prone areas. In France [3], environmental material degradation had an estimated cost of 84 billion euros in 2019 in addition to more than 2500 billion dollars worldwide, based on the usually acknowledged cost of about 3.5 percent of the global gross domestic product (GDP)

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