No abstract

The interface between new concrete (overlay) and old concrete (substrate) plays an important role in the overall success of any repair. A good bond ensures long-term durability and monolithic action (i.e. the overlay contributes to both the stiffness and load-carrying capacity). Research has shown that the substrate roughness, which is highly dependent on the surface preparation method, has an influence on the interface bond strength, though there is no consensus on the extent of this effect. Thus, through a new bond test, an experimental study was conducted to evaluate the effect of substrate roughness on bond strength, also considering the effect of overlay strength. In addition, the possible consequence of roughness on interface ductility was evaluated. The results indicate an increase in bond strength with an increase in surface roughness, although the resulting increase in ductility with surface roughness was more pronounced. The strength of the overlay was also found to be an important parameter for smooth substrates or substrates with low roughness

No abstract

The state of road infrastructures in many advanced countries is rapidly changing under the impulse of massive funding from governments, eager to have more efficient and safer transportation systems. The use of well-known materials such as fibre-reinforced concrete (FRC) is finding a growing space for structural rehabilitation of bridges; the adopted material is often defined as High performance fibre reinforced concrete (HPFRC) due to its enhanced performance. The paper presents the principal findings of an EU-funded project that involved the repair of two road bridges in Italy using HPFRC. The project has successfully carried out the jacketing of bridge piers and cap-beams, heavily damaged by corrosion, with a new HPFRC layer of reduced thickness (40-60 mm) and limited use of steel reinforcements. Experimental tests carried out in the laboratory of the University of Brescia on 1:2 scaled specimens have shown the possibility to increase the load bearing capacity of the cap beams (with respect to vertical loading) up to 73%, with moderate effects on the change in stiffness and ductility of the existing structure. Based on field and laboratory experience, the article eventually presents some new challenges for the use of HPFRC in the reduction of environmental impact of construction industry.