Experimental and analytical investigation of long-term bond performance of basalt FRP-geopolymer concrete with varying alkalinities in marine environment

Abstract

The degradation of basalt fiber reinforced polymer (BFRP) bars in alkaline environment affects their bond performance with concrete and limits their application as reinforcing materials. To address this issue, this study explores the use of geopolymer concrete as a replacement for traditional concrete, examining how the alkalinity of geopolymer affects the bond durability between BFRP bars and geopolymer concrete. The deterioration of bond performance and physicochemical properties were studied through pull-out tests and microscale characterization. After exposure at 55 °C for 135 days, the bond stress retention for specimens with a low pH level of 11.74 was 73 %. Reducing the alkalinity helps to minimize BFRP bar degradation by decreasing debonding at the fiber-resin interface and reducing fiber cracking. The revised chemical etching theory predicts the time required for the long-term bond strength retention of specimens with controlled alkalinity to decrease to 70 %. Additionally, a new bond-slip model is proposed to describe the bond-slip behavior between BFRP bars and geopolymer concrete. This study provides insight into using low-alkalinity geopolymer to mitigate the deterioration of bond performance between BFRP bars and concrete.