Bond assessment of two types of SRP strengthening systems subjected to severe conditions

Abstract

Using composite materials to retrofit structures has expanded quickly the last few years due to its applicability and economic feasibility. For most of these systems including the new ones, their mechanical properties have been investigated extensively, but their durability bond performance still has not. Therefore, due to the lack of data regarding the long term performance, it is has been hard on the construction industry to implement these systems. Thus, to enrich the construction and design standards with bond durability information, an investigation was carried out at Missouri University of Science and Technology, Rolla, Missouri, USA to study the bond durability of Steel Reinforced Polymer (SRP) strengthening system. Two types of SRP systems were applied including: micro-fine galvanized (RG) and micro-fine brass coating (RNG) steel fibers where both of them were exposed to several harsh conditions. The conditions used in this study included tap water submersion for 3000 h, hot water submersion for 4000 h at 50 °C (122° F), and salt water submersion for 1500 and 4000 h. Additionally, other specimens were made and placed outside for real-time weather exposure. The real-time weather exposure included subjecting the specimens to temperature and humidity fluctuations, freeze–thaw cycles, and ultraviolet (UV) radiation from the sun. Upon completion the desired exposure duration, all the specimens were tested for bending using a three-point load fixture to evaluate the bond performance of the strengthening system. All the results were then compared with control specimens to obtain a better evaluation of their bond performance. Furthermore, tensile coupon tests were made as well to enhance the mechanical evaluation. The results showed that there was a substantial decrease in bond strength resulted from the water immersion. In addition to the water influence, temperature also negatively affected the durability of bond strength. On the other hand, salt presence did not affect the bond strength. Based on the performance of the strengthening system, an environmental reduction factor, CE, of 0.75 was proposed for wet environment and 0.65 for harsh environment.