Flexural durability of BFRP bars reinforced geopolymer-based coral aggregate concrete beams conditioned in marine environments

Geopolymer is an environmentally friendly material that utilizes industrial solid waste, boasting reduced greenhouse gas emissions and energy consumption. It exhibits superior performance in terms of corrosion resistance and thermal stability compared to ordinary Portland cement (OPC). These excellent properties are crucial for marine engineering construction, offering significant value and application potential in marine engineering materials. In this study, geopolymer was employed as the cementitious material, with marine resources like seawater and coral aggregates sourced from remote island areas effectively utilized, and basalt fiber -reinforced polymer (BFRP) bars were incorporated as reinforcements to develop BFRP bars reinforced geopolymer-based coral aggregate concrete (GPCAC) beams. Laboratory aging procedures were employed to investigate the deterioration patterns and damage mechanisms affecting the flexural behavior of GPCAC beams under seawater immersion and dry -wet cycling conditions, comparing them with cement -based coral aggregate concrete (CAC) beams. The experimental results indicated that both CAC and GPCAC beams under simulated marine environments experienced a reduction in the number of cracks upon damage, but their crack spacing and width increased. Moreover, the flexural stiffness of CAC and GPCAC beams after seawater attacks tended to increase, but this increased stiffness did not translate to a higher loading capacity. Conversely, as the corrosion age increased, the ultimate load and deflection values of both CAC and GPCAC beams decreased to varying extents, with the load -carrying capacity degradation more pronounced in seawater drywet cycling environments than in seawater immersion conditions. Compared to CAC beams, GPCAC beams exhibited superior resistance to seawater erosion. Following 12 months of seawater dry -wet cycling, the ultimate loading capacity of CAC beams decreased by 12.2%, while that of GPCAC beams only degraded by 9.5%. Predictions of the flexural capacity of GPCAC beams using equations from existing FRP-reinforced normal aggregate concrete (NAC) specifications indicated slightly higher values than the experimental values, with an error margin of less than 15%. Overall, the formulas for the flexural capacity of NAC beams in existing FRP-reinforced NAC codes remained applicable to CAC and GPCAC beams.