Moisture-induced degradation of interfacial bond in FRP-strengthened masonry

Abstract

Externally bonded strengthening of masonry structures using Fiber Reinforced Polymers (FRPs) has been accepted as a promising technique. Although the effectiveness of FRPs in improving the performance of masonry components has been extensively investigated, their long-term performance and durability remain poorly addressed.This paper, tackling one of the aspects related to durability of these systems, presents an experimental investigation on the effect of long-term (one year) water immersion on the performance of GFRP-strengthened bricks. The tests include materials' mechanical tests, as well as pull-off and single-lap shear bond tests, to investigate the changes in material properties and bond behavior with immersion time, respectively. The effect of mechanical surface treatment on the durability of the strengthened system as well as the reversibility of the degradation upon partial drying are also investigated. The experimental results are presented and critically discussed.

FRP–brick masonry bond degradation under hygrothermal conditions

“…The coefficient of variation of the results is at an acceptable range of 6 to 14%. The moisture absorption level (0.25% water mass after 960 cycles) is negligible in comparison to 12.5% saturation level reported in[40] for the same bricks. The results show suitable durability of the bricks used in this study under the considered hygrothermal conditions.The changes in mechanical properties and moisture content of epoxy resin with the number of exposure cycles (n) are presented inFig 11.The coefficient of variation (CoV) of the results is at an acceptable range of 3-14% for elastic modulus and tensile strength[41], but larger variations were observed for ultimate strain.…”

“…It also seems that epoxy is near saturation at the end of exposure period. A comparison with water immersion tests performed on the same epoxy resin in [40], see Fig 11b, shows that a similar degradation level is occurred in tensile strength at low moisture absorption levels (until 1.6%). However, the degradation is larger in hygrothermal conditions at higher moisture absorption levels in contrary to the larger T g obtained from DSC…”

“…Fig 13b shows that the degradation starts earlier than water immersion tests performed in [40], which can be due to the presence of thermal cycles in the present study. The changes in the elastic modulus were negligible during the exposure, see of epoxy, fibers and epoxy/fiber interface [42].…”

“…These parameters are calibrated with water immersion tests performed on the same epoxy resin in [40] and are obtained as A=0.0047, B=-0.056 and C=1. Eq.…”

Properties of Aged GFRP Reinforcement Grids Related to Fatigue Life and Alkaline Environment

“…The long term behavior of FRPs materials used in masonry strengthening needs to be investigated, especially when composite materials are in the form of thin sheets or grids. FRPs are usually bonded to the external surface of an existing masonry structure: bonding is often achieved using epoxy adhesives; recently, however, FRP materials has been employed also in combination with inorganic matrix such as lime mortars and cement, to fulfill new needs in retrofit of historical constructions [5][6][7][8][9][10][11].…”