Anchoring Performance of FRP Bar Connectors for Alkali-Activated Lightweight Aggregate Concrete Wall Panels in a Wet–Hot Acid Rain Environment

Abstract This study investigated the bond behavior of basalt fiber–reinforced polymer bars (BFRP) and glass fiber–reinforced polymer (GFRP) bars embedded in alkali-activated ceramsite concrete using direct pull-out tests on 150-mm cubic specimens. The tests were conducted under both standard laboratory conditions and cyclic wet–thermal acid rain exposure. The results indicate that, for any given bar diameter, GFRP bars exhibited lower bond strength than BFRP bars within the alkali-activated ceramsite matrix. In both environments, the bond strength decreased with increasing bar diameter. Under standard conditions, the mean bond strengths of 8, 10, and 12 mm BFRP bars were 15.24, 14.35, and 11.00 MPa, respectively, whereas those of GFRP bars were 10.00, 9.46, and 8.32 MPa, respectively. When subjected to repeated wet–thermal acid rain cycles, the bond strength initially increased, likely due to ongoing hydration and pore-structure refinement, but subsequently decreased as damage accumulated. To characterize the postcycling bond–slip response, both the modified bond–pair envelope (mBPE) model and the Cosenza-Manfredi-Realfonzo model were fitted to the experimental data. The mBPE model exhibited a higher coefficient of determination ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="upper R squared greater than 0.97" display="inline" overflow="scroll"> <mml:msup> <mml:mi>R</mml:mi> <mml:mn>2</mml:mn> </mml:msup> <mml:mo>&gt;</mml:mo> <mml:mn>0.97</mml:mn> </mml:math> ) than the CMR model, indicating its superior predictive capability for the bond behavior of fiber-reinforced polymer (FRP) bars in alkali-activated ceramsite concrete under severe wet–thermal acid rain cycling.