In simply-supported reinforced-concrete (RC) beams strengthened by carbon-fiber-reinforced polymer (CFRP) plates, plate debonding is initiated at the beam ends, where the principal compression, predominantly composed of a vertical component, detaches the plate externally bonded to the unconfined cover concrete. A CFRP wrap acting as a U-clamp can provide confinement to enhance the moment capacity by resisting premature cover debonding. The wrap design parameters in terms of clamping location, width, and stiffness were identified from a set of fundamental experiments. The ultimate moment capacities of 22 tested specimens with different end anchorage conditions were compared against control specimens. The debonding strain, and consequently the ultimate moment capacity, gradually increased with increasing U-clamp width and stiffness. The failure patterns confirmed the effect of U-clamps in inducing a partial confinement effect on the sides and bottom of a beam end. The resulting changes in the compre...

The adhered cement mortar in coarse aggregates and fines from demolished concrete has the potential to induce a residual cementing property upon recycling. A procedure for quantifying the contribution of recycled fines to the strength gain within the new mortar matrix is proposed. The strength gain is found to be more significant in recycled aggregates and fines from brick aggregate concrete than in those from stone aggregate concrete. Isothermal calorimetry measurements indicate the existence of large heat flows immediately after wetting and a prolonged initial reaction period during the hydration of recycled fines because of the presence of unreacted cement compound fractions and depleted amounts of gypsum. This phenomenon has been further confirmed, particularly in recycled fines from brick aggregate concrete, through electron microscopy observations of the formation of new gel structures caused by rehydration. The chemical compositions determined using two independent methods indicated possible interactions between CH (the hydration product) and pozzolan (from brick) to induce strength gain in new mortars and new concrete obtained by recycling brick aggregate concrete. This explanation is consistent with the strength test results and the evolution of the heat events observed calorimetrically.