2 - Development of carbon nanofiber aggregate for concrete strain monitoring

Abstract

Because of past success at the University of Houston demonstrating that self-consolidating carbon nanofiber concrete (SCCNFC) can be used as a strain sensor, a carbon nanofiber aggregate (CNFA) was developed to determine localized strain in concrete structures. The development of a CNFA is significant because it is possible to use the strain-sensing capabilities of SCCNFC with a greatly reduced cost since only the CNFAs placed in the structure would contain carbon nanofibers (CNFs). SCCNFC costs nearly 20 times as much as normal concrete. The CNFAs can be embedded in reinforced or prestressed concrete structures and used to determine the localized damage in a structure. For the purpose of compressive strain monitoring, the CNFAs were embedded in concrete cylinders and tested in monotonic and cyclic compression to determine a relationship between compressive strain and electrical resistance. In addition, a system of embedded CNFAs was used for the structural health monitoring of a small-scale beam tested monotonically. It was determined the CNFAs are capable of monitoring compressive and tensile strain. It was also determined that CNFAs are capable of detecting catastrophic damage in concrete structures.