Abstract
The strengthening and rehabilitation of reinforced concrete structures is an important issue all over the world. Fiber-reinforced composites (FRC) are mainly used for the strength and rehabilitation of concrete members. However, its use is limited due to its high price and environmental effects and its adoption of epoxy as an adhesive, where epoxy is considered inefficient at high temperatures and loses most of its properties. The solution to this problem leads to the use of low-cost locally available geopolymer adhesive paste, with the possibility of adding fibers to improve the mechanical properties. This paper presents the experimental results of the circular RC columns confined by carbon fiber reinforced geopolymer adhesive (CFRGA) with fibers at geopolymer adhesive (GPA). Variables included; Geopolymer adhesive with or without fibers and type of fiber added to GPA (micro steel fibers, carbon fibers, and polypropylene fibers) with the volumetric ratio of (2%, 0.4%, 0.2%), respectively. The results where it was found that confinement by carbon fiber reinforced fibrous geopolymer adhesive improved the columns compressive strength estimated by (215%) and the axial strain improved by (268%). When adding (micro steel fibers, carbon fibers, and polypropylene fibers) to the adhesive led to an improvement in the strength of about (16.1%, 8.4%, and 7.96%) respectively, compared with the confined RC column without fibers at (GPA). Finally, confinements by carbon fiber reinforced geopolymer adhesive are more suitable for use in strengthening and rehabilitation of RC columns in areas with a hot climate.
Highlights
Structures in the world need to rehabilitate and strengthen the cause of their deterioration resulting from actual use, aging, and exposure to various environmental conditions or modernization in proportion to the requirements of age [1]
One RC column is unconfined and symbolized it RCC. one RC column is confined by two layers of carbon fiber jacket without fibers at geopolymer adhesive (GPA) and symbolized it C2LCF, three RC columns confined by two layers of carbon fiber jacket with fibers at GPA, used three types of fibers included; micro steel fiber (SF) with volumetric ratio (2%), carbon fiber (CF) with volumetric ratio (0.2%)and polypropylene fiber (PPF) with volumetric ratio ( 0.4%), These ratios were determined from a previous paper [8], which were designed and fabricated .symbolized by (C2LCF-sf, C2LCF-cf, C2LCF-ppf)
The unconfined RC columns showed failure in the upper quadrant of the column. The reason for this may be due to the method of casting, where the casting was performed in a vertical manner corresponding to the reality with the use of vibrators, and as a result of gravity and weight, this led to the collection of coarse aggregates at the bottom of the column and fine aggregates at the top, which made the upper part of RC column the weakest area, the RC columns confined by two layer of CFRG without fiber in GPA showed a rupture at the upper quadrant as the weakest area accompanied with a sudden decrease in the applied load, the RC columns confined by two layer of CFRG with fiber in GPA showed a rupture at the first third of the RC columns
Summary
Structures in the world need to rehabilitate and strengthen the cause of their deterioration resulting from actual use, aging, and exposure to various environmental conditions or modernization in proportion to the requirements of age [1]. RC columns are brittle members, affected by bending and high loads due to vastly different factors, such as unbalanced moments when connecting beams, lateral forces from wind, seismic activity, or unexpected overloads, and civil engineering researchers have found many of the techniques for strengthening the RC columns, one of these techniques is the external confining which is represented by confining the RC columns with FRP techniques [2] It is an effective technique in improving the strength and ductility of columns but the efficiency of these techniques depends on the type of material used for confinement and the bonding material between the granulation material and the concrete member. Test variables are types of fibers included; micro steel fiber (SF) with volumetric ratio (2%), carbon fiber (CF) with volumetric ratio (0.2%), and polypropylene fiber (PPF) with volumetric ratio (0.4%)
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