This document provides guidance on using ACPs and associated standard mechanical test methods to assess the durability of FRP composite reinforcement for concrete with the objective to enable manufacturers to characterize the durability of their FRP products and to encourage researchers and testing laboratories to adopt common test protocols to build a meaningful database of durability test results for FRP materials. Results of the tests conducted using the recommended protocols are not intended for use directly in the design of FRP composites. They are meant to generate a database of consistent test results that can be used in the future to refine the environmental factors recommended in ACI 440.1R@ 440.2R@ and 440.7R. Recommended environmental reduction factors used in the design of FRP composite reinforcement are provided in ACI 440.1R and 440.2R and are outside the scope of this guide. The results of the conditioning and testing recommended in this guide are not intended to be useful in the prediction of service life. The use of these methods in conjunction with field evaluations of the performance of structures with FRP composite reinforcement in service conditions is encouraged. Future correlation of accelerated methods with field performance can help validate and improve confidence in their use. Physicochemical tests that measure the changes in the physical and chemical properties of FRP materials can also be useful in assessing degradation of the material and its constituents after being subjected to the ACPs described in this guide.