Material Conditions Necessary for Strengthening Concrete Structures

The maintenance and repair of accumulated infrastructures to prolong their service lives is a major challenge in the construction field to achieve sustainability. Strengthening is often needed for deteriorated and inappropriately constructed structures. Structural ways and materials for strengthening are vary greatly, implying that we have not yet determined the optimum way for strengthening. External bonding, as a way of strengthening, has introduced a new type of failure mode, namely debonding (peeling). Material properties to improve debonding strength are new to structural engineers. Strengthening materials as a substitute of steel, such as fiber reinforced polymers (FRP), have quite different material properties. Conventional concepts for structural design and material are no longer true for those materials. As a structural material, durability is important, but we do not have enough data concerning the durability of the new strengthening materials. This paper explains the material properties and conditions necessary for strengthening, and suggests the necessity of closer collaboration between material scientists and structural engineers.