Smart concrete has a potential to provide non-destructive damage assessment capability, which is important for the timely repair, safety and long-term durability of critical civil infrastructure systems. Moreover, real-time strain monitoring is needed for control of structures. In contrast to concrete rendered smart extrinsically by the use of embedded or attached sensors, this project is focused on concrete that is intrinsically smart. This intrinsically smart concrete is concrete containing as little as 0.2 vol.% short carbon fibers. It is much less expensive per unit sensing volume than concrete with embedded sensors, and sensitive to permanent damage as well as reversible deformation. In this research, technical issues will be addressed in order to characterize this new smart structure material for applications in critical segments of structures. These issues include (1) effect of the degree of damage (controlled by the stress amplitude) on the electrical response, (2) effect of the strain rate, (3) extension from compressive, tensile and flexural loading to torsional loading, (4) dependence of the electrical response on the direction of resistance measurement, (5) extensive testing for statistical analysis of the electrical response, (6) effect of steel reinforcement on the electrical response, (7) multiple electrical signal monitoring during steel reinforced concrete beam and column testing, (8) extension from multiple signal monitoring to two-dimensional mapping by reisistivity tomography, and (9) applications in critical sections of infrastructural systems. In addition to providing the smart behavior, the addition of carbon fibers to concrete also serves to increase the flexural strength, toughness and freeze-thaw durability, and to decrease the drying shrinkage and electrical contact resistivity (when in contact with metals, as encountered in electrical probing). An interdisciplinary team of researchers will participate in this program of study; including a materials scientist (PI) and a structural engineer. This is a an award under the 5th year initiative on structural control research.
