Effectiveness of CFRP Strengthening on Lightweight High-Strength Hollow-Core Slabs

Lightweight hollow-core slabs utilizing Light Expanded Clay Aggregate (LECA) offer significant self-weight reduction for precast construction, yet the combination of longitudinal voids and lightweight aggregates introduces challenges in flexural stiffness and cracking behavior. While externally bonded carbon fiber–reinforced polymer (CFRP) strengthening has proven effective for normal-weight concrete, its application to lightweight hollow-core slabs remains insufficiently investigated. This study experimentally evaluates the flexural performance of full-scale LECA hollow-core slabs strengthened with CFRP sheets. Two slabs were tested under four-point bending with displacement control at 2 mm/min, with deflections recorded using LVDTs. The strengthened slab achieved 54.27 kN versus 39.0 kN for the control (39.1% increase), with higher stiffness but reduced ductility and a sharp post-peak load drop of approximately 20%.