Abstract
This study examined the electrical and self-sensing capacities of ultra-high-performance fiber-reinforced concrete (UHPFRC) with and without carbon nanotubes (CNTs). For this, the effects of steel fiber content, orientation, and pore water content on the electrical and piezoresistive properties of UHPFRC without CNTs were first evaluated. Then, the effect of CNT content on the self-sensing capacities of UHPFRC under compression and flexure was investigated. Test results indicated that higher steel fiber content, better fiber orientation, and higher amount of pore water led to higher electrical conductivity of UHPFRC. The effects of fiber orientation and drying condition on the electrical conductivity became minor as sufficiently high amount of steel fibers, 3% by volume, was added. Including only steel fibers did not impart UHPFRC with piezoresistive properties. Addition of CNTs substantially improved the electrical conductivity of UHPFRC. Under compression, UHPFRC with a CNT content of 0.3% or greater had a self-sensing ability that was activated by the formation of cracks, and better sensing capacity was achieved by including greater amount of CNTs. Furthermore, the pre-peak flexural behavior of UHPFRC was precisely simulated with a fractional change in resistivity when 0.3% CNTs were incorporated. The pre-cracking self-sensing capacity of UHPFRC with CNTs was more effective under tensile stress state than under compressive stress state.
Highlights
Civil structures are frequently constructed using concrete due to its several advantages including low price, high compressive strength, and good durability
Because the ultra-high-performance fiber-reinforced concrete (UHPFRC) incorporated high volume contents of steel fibers, it can be expected that electrical current would be transferred though it by means of conductive pathways formed by electrical current would be transferred though it by means of conductive pathways formed by contacts contacts between steel fibers or electrical tunnels
The electrical conductivity of UHPFRC can between steel fibers the electrical conductivity of electrical
Summary
Civil structures are frequently constructed using concrete due to its several advantages including low price, high compressive strength, and good durability. It is necessary to accurately predict the weakest zone where failure is expected to occur, for which the sensor needs to be located nearby, because conventional sensors are small and discontinuous To overcome these limitations, several researchers [4,5,6,7,8,9,10,11,12,13,14,15,16,17] have worked to develop self-sensing cement composites with conductive materials based on the piezoresistive properties. The specific objectives of this study included evaluating: (1) the effects of steel fiber content, orientation, and pore water content in hardened paste on electrical and piezoresistive properties of UHPFRC under compression; (2) the effects of a sonication process on the electrical conductivity of UHPFRC with CNTs; and (3) the effects of CNT content on mechanical strength and self-sensing capacities of UHPFRC under both compression and flexure
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