Damage of reinforced concrete in structures like bridges and highways is related to factors like environmental aggression, service loads, construction technologies and, exceptionally, seismic events. Chemicals and physical agents may induce a gradual increase in the concrete porosity and permeability, causing loss of the material integrity. In bridge decks, damage is also dependent on low fatigue level due to cyclic loads, on thermal loads and corrosion of steel bars. The object of the present study is a viaduct of the Orte-Ravenna highway, built in the first seventies. The reinforced concrete slab of the viaduct exhibited serious structural deficiencies and, therefore, was destined to demolition and subsequent reconstruction. Parts of the removed slab were carried to the Ferrara University Laboratories in order to evaluate the concrete damage level and to assess a possible strengthening technique for repair. In the paper, the investigation results are reported. The investigation consists of non destructive evaluation as well as experimental tests on concrete specimens. At the structural scale a thermography is carried out in order to observe homogeneity of concrete and to point out anomalous zones with cracks, cavities or incoherent aggregates. Thermography is based on the emission of thermic radiation and, according to Wien law, the range of medium and far IR (2-15 μm) turns out to be suitable to characterise thermic emission of objects at ambient temperature. Surface temperature difference corresponds to different intensity of infrared rays and this produces, in the radiographic apparatus, contrast of the thermographic image. At the specimen scale, the investigation is carried out by mercury porosimetry, compression test, three-point bending test, ultrasound measurements, scanning electron microscope equipped with an energy dispersive X-ray (EDX) analyser. Concerning the strengthening techniques, the application of fibre reinforced polymers (FRP) is considered. In particular, the problem of fibre debonding and concrete cover separation, in the presence of damaged concrete, is addressed and experimental results are reported showing the effectiveness of different practical approaches to improve the composite-concrete interface.
Damage of Concrete and Bonding of FRP Reinforcement
APRILE, Alessandra;CAPUANI, Domenico;
2006
Abstract
Damage of reinforced concrete in structures like bridges and highways is related to factors like environmental aggression, service loads, construction technologies and, exceptionally, seismic events. Chemicals and physical agents may induce a gradual increase in the concrete porosity and permeability, causing loss of the material integrity. In bridge decks, damage is also dependent on low fatigue level due to cyclic loads, on thermal loads and corrosion of steel bars. The object of the present study is a viaduct of the Orte-Ravenna highway, built in the first seventies. The reinforced concrete slab of the viaduct exhibited serious structural deficiencies and, therefore, was destined to demolition and subsequent reconstruction. Parts of the removed slab were carried to the Ferrara University Laboratories in order to evaluate the concrete damage level and to assess a possible strengthening technique for repair. In the paper, the investigation results are reported. The investigation consists of non destructive evaluation as well as experimental tests on concrete specimens. At the structural scale a thermography is carried out in order to observe homogeneity of concrete and to point out anomalous zones with cracks, cavities or incoherent aggregates. Thermography is based on the emission of thermic radiation and, according to Wien law, the range of medium and far IR (2-15 μm) turns out to be suitable to characterise thermic emission of objects at ambient temperature. Surface temperature difference corresponds to different intensity of infrared rays and this produces, in the radiographic apparatus, contrast of the thermographic image. At the specimen scale, the investigation is carried out by mercury porosimetry, compression test, three-point bending test, ultrasound measurements, scanning electron microscope equipped with an energy dispersive X-ray (EDX) analyser. Concerning the strengthening techniques, the application of fibre reinforced polymers (FRP) is considered. In particular, the problem of fibre debonding and concrete cover separation, in the presence of damaged concrete, is addressed and experimental results are reported showing the effectiveness of different practical approaches to improve the composite-concrete interface.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
