Effect of Diameter on Bond Failure of Steel Rebar Embedded into Concrete Using Epoxies at High Temperatures

Abstract

A series of pull-out tests were conducted to examine the bond deterioration of epoxy resins at elevated temperatures through the relationship between the critical temperature and bond stress. The steel rebars investigated were deformed bars with varying diameters of 12 mm, 16 mm, 20 mm and 25 mm. Two different types of epoxy resins were used. The test results show that the critical temperature for both types of epoxy resins tends to decrease with the increasing bond stress. In addition, the critical temperature is significantly lower for steel rebar with larger diameters. Meanwhile, the effect from varying types of epoxy resins on the bond characteristics is negligible. In order to illustrate the effect of rebar size, a mechanical model for the adhesive bonding stress between steel rebar and concrete interface at elevated temperatures is presented. The model provides good prediction of the bond stress at failure temperature.

Epoxy‐based composite adhesives with improved lap shear strengths at high temperatures for steel‐steel bonded joints

“…[14] Adhesion properties of epoxy-based adhesives could be optimized by varying a molecular weight of curing agent, mass ratios of curing agent to monomer, and processing conditions. However, commercially available epoxy adhesives containing DGEBA exhibit a significant decrease of the bond strength due to glassy-to-rubbery state transition at 20-80 C. [15,16] It is critically important to improve adhesion properties of epoxy-based adhesives for applying in demanding engineering applications under severe environmental conditions.…”