The performance of CFRP-strengthened heat-damaged metakaolin-based geopolymer concrete cylinders containing reclaimed asphalt aggregate

Concrete structures are extremely vulnerable to fire damage, which greatly undermines their structural strength and durability. Recently, there has been a concerted effort to develop sustainable concrete materials. Geopolymer concrete (GPC) is a promising substitute for conventional cement concrete due to its use of recycled materials. However, despite the positive effect it has on the environment, GPC is susceptible to heat, which can cause it to deteriorate over time. In response to this issue, the use of carbon-fiber reinforced polymer (CFRP) has been proposed as a means of strengthening heat-damaged GPC. This study aims to investigate the effectiveness of CFRP-strengthened heat-damaged metakaolin-based GPC made from reclaimed asphalt pavement (RAP) aggregate. Three concrete mixtures were used, in which the conventional aggregate was substituted with RAP aggregate at 0%, 25%, and 50% replacement levels. In addition, the concrete cylinders were tested under ambient conditions and subjected to 300°C. The results indicated that the substitution with 25% RAP aggregate significantly reduced compressive strength by 39.1%, while 50% replacement resulted in a 66.8% decrease compared with the control mixture. The use of CFRP sheets to strengthen heat-damaged GPC specimens was proven to be effective in increasing the resistance of the heated specimens and restoring the compressive strength and confinement energy to their original state before reaching the ultimate failure point. The use of CFRP sheets significantly increased compressive strengths, with increases ranging from 87.7% to 368.8% at 26°C and 58.8% to 153.9% at 300°C, compared with each mixture’s unstrengthened control specimen.