Composite durability and aging in civil infrastructures

Abstract

As composite materials are finding increasing use in infrastructure projects, their durability over the life span of a structure needs to be quantified. The design life for a typical bridge is 50 years or more. As infrastructure demand is outstripping resources, the life of a bridge can exceed 75 years and sometimes approach 100 years. Additionally with the introduction of the American Concrete Institute (ACI) Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Concrete Structures, ACI 440.2R-02, allowable stress knockdown factors are incorporated into the design guidelines for exposure to the environment. Consequently, in order to have high confidence that composite material systems, utilized as either structural component parts or for the strengthening of structures, will last the remaining life of the structure, the degradation mechanisms due to exposure to the natural environment must be known. Thus, effects due to the freeze-thaw cycles, de-icing chemicals, humidity, UV radiation, and erosion on the material behaviors need to be studied in order to establish proper design methodologies to account for these conditions over the life of the structure. This chapter will highlight the recent research for understanding composite material behavior when subjected to the naturally occurring environmental conditions. It will also highlight design methodologies suggested in the literature to properly account for these exposures over the structures' lifetime.