International Concrete Abstracts Portal

Based on an analysis of the experimental results of a proposed bond test method, significant differences are shown to exist between the local FRP bond stress-slip relationships in the uncracked anchorage regions and in the regions between cracks. The proposed method simulates the bond behavior between the flexural cracks and anchorage regions of a flexurally FRP-strengthened RC beam. The boundary conditions, including the presence of cracks and steel, are shown to have significant effects on the local bond stress-slip models. The results showed that, at the same force, the bond stresses in the regions between cracks were lower than in regions outside the cracks, so the debonding formed in the anchorage regions. The local bond stress-slip models in the anchorage regions can be obtained from the conventional bond test methods but these do not mimic the conditions between the cracks.

Adhesively bonded FRP plate on the tension face of RC beams and slabs increases their flexural strength. The behaviour of the strengthened structure depends on the robustness of the FRP-RC interface bond. Correct modelling of this interface bond behaviour is very important to understand and characterize the common intermediate crack-induced (IC) debonding failure. Existing literature based on simple pull-off test is inadequate to fully analyse this failure due to the differences in the mechanics of failure. This paper considers axial forces, transverse shear forces and bending moments in the adherends of the bonded joint and provides solutions for the different states of the interface experienced using a linearly softening bond-slip model. The inclusion of bending and shear deformations introduces difficulties in relating the applied loading and the interfacial deformation but they are overcome in this study through a section analysis with partial interaction and a closed-form solution is obtained.

This research investigated the development and characterization of different discrete fiber-reinforced polyurea systems for infrastructure applications. The behavior of various systems consisting of several polyureas with different fiber configurations was evaluated. Polyurea coating systems were previously evaluated for blast mitigation and impact resistance, and showed to be adequate in containing debris scatter from blast and impact. The purpose of further testing was an effort to develop a polyurea system for multi-hazard and/or repair-retrofit applications. The addition of fiber to a polymer coating provides improved stiffness and strength to the composite system while the polyurea base material provides ductility. Coupon tensile testing was conducted to determine the material mechanical properties in this study. The two parameters that were varied throughout testing were fiber volume fraction and fiber length. E-Glass fiber was used during specimen fabrication. Several optimal composite configurations of polyurea and fiber resulted from this coupon testing.

This paper presents an evaluation of the use of a new innovative cementitious material, commercially known as Grancrete PCW, as an alternative to epoxy for FRP strengthening systems used for reinforced concrete (RC) structures. Grancrete is an environmentally friendly material that develops high early bond strength and possesses an excellent resistance to fire. The study includes an experimental program to evaluate the behavior of seventeen RC slabs strengthened by using different types of fibers. The load carrying capacity, ductility, and mode of failure of the strengthened specimens were evaluated and the results were compared to control specimens. Results of the experimental program showed that Grancrete PCW paste could be used as an alternative bonding material.

This paper presents an overview of an experimental study to determine the oxygen barrier characteristics of materials used for infrastructure repair. In the study, a new diffusion cell was developed and a quasi-steady state model used to determine oxygen permeation constants. Results obtained are in broad agreement with the limited published data available. The study found that epoxy was a better oxygen barrier than FRP, with concrete being the poorest. However, bonding FRP to a concrete surface significantly reduced its oxygen permeability. This finding explains why FRP slows down but cannot stop chloride-induced corrosion of steel in concrete. A parametric study was conducted to evaluate the performance of FRP-concrete systems for differing FRP/concrete oxygen permeability combinations. It was found that the greatest reduction in corrosion rate occurred in concretes with the highest oxygen permeability. This result makes it possible to custom design FRP-concrete corrosion repair systems.