Investigation on the Flexural Behavior of Corroded Concrete Beams Repaired by CFRP Sheet Under Different Corrosion Levels

Su Linwang,Chen Qingjun,Li Guobao,Cai Jian,Zhao Juan

doi:10.2174/1874149501610010598

Abstract

The paper presents an investigation on the flexural behavior of corroded reinforced concrete (RC) beam strengthened with Carbon Fiber Reinforced Polymer (CFRP) sheets. Different levels of corrosion are considered as a new method for classifying the corrosion levels of the corroded RC members. Twenty RC beams with five corrosion levels were fabricated by accelerated corrosion equipment, and then the CFRP were used to strengthen these members, considering the effect of different CFRP layers and different strengthened schemes, finally the static flexural load test was carried out. The test results show that the bearing capacity of the CFRP strengthening corroded RC beams is effectively enhanced, the crack width is restrained, and the flexural stiffness is improved. The ultimate flexural capacity of the specimens strengthened by one layer of CFRP sheet raises by 30% to 50% than that of the unstrengthened ones, with the increase of the corrosion level, the enhancement decreased. With the increase of the number of CFRP layers, the bearing capacity increases, while the increasing ratio reduces with the increase in the number of layers. For specimens with obvious cracks, the effectiveness of the strengthening method by bonding CFRP after cutting or chiseling off concrete method (RM1 or RM2) is higher than the method of bonding CFRP directly (DM). It is suggested that the corroded RC members with Level A, B or C1 can be strengthened by DM, while the other level members should be strengthened by RM1 or RM2. The formulae in current design code are used to predict the flexural bearing capacity of the RC beam strengthened with CFRP and their results are compared with experimental ones. A revised formula that can give a better prediction for multi-layer CFRP strengthening members is also proposed.

Highlights

Corrosion and deterioration of reinforced concrete (RC) members in marine environment is a serious problem for coastal structures [1]
The results showed that the state of corrosion of the steel, the water/cement ratio of the concrete material, and the arrangement and the number of carbon fiber reinforced polymer (CFRP) layers all affect the strength of retrofitted RC beams
Fig. (14) shows the increased range of bearing capacity with different CFRP layers. It demonstrates that the bearing capacity increased significantly when strengthened by one layer of CFRP, The ultimate flexural capacity of members with one layer of CFRP raised by 30% to 50% than those unstrengthened ones

Summary

Introduction

Corrosion and deterioration of reinforced concrete (RC) members in marine environment is a serious problem for coastal structures [1]. Used repair techniques for RC members include concrete jacketing, steel jacketing, and carbon fiber reinforced polymer (CFRP) jacketing [1]. Among these techniques, CFRP jacketing is especially suited for repairing the members in marine environment. A series of RC beams was constructed and corroded by accelerated corrosion techniques. They were classified into several corrosion levels according to their damage state, and repaired by different methods with or without CFRP sheets respectively.

Objectives

Methods

Results

Conclusion