Enhancing Damage-Sensing Capacity of Strain-Hardening Macro-Steel Fiber-Reinforced Concrete by Adding Low Amount of Discrete Carbons

Abstract

The effects of adding micro-carbon fibers on the electro-mechanical response of macro-steel fiber-reinforced concretes (MSFRCs) under tension were investigated. Two MSFRCs were investigated and they had identical mortar matrix but different fiber contents: MSFRC1 and MSFRC2 contained 1.0 and 1.5 vol.% fibers, respectively. The volume contents of added micro-carbon fibers were 0 to 1.5 vol.% in MSFRC1 and 0 to 0.75 vol.% in MSFRC2, respectively. The addition of 0.5 vol.% micro-carbon fibers, in both MSFRC1 and MSFRC2, produced significantly enhanced damage-sensing capability and still retained their strain-hardening performance together with multiple micro cracks. However, when the content of carbon fibers was more than 0.5 vol.%, the MSFRCs generated tensile strain-softening behavior and reduced damage-sensing capability. Furthermore, the effects of temperature and humidity on the electrical resistivity of MSFRCs were investigated, as were the effects of adding multi-walled carbon nanotubes on the damage-sensing capability of MSFRCs.

Influence of Carbon Fibres on Strain Sensing and Structural Properties of RC Beams without Stirrups

“…This is probably because of presence of reinforcement that increased strain sensing sensitivity of the CFBC at tension side. Similar growth in GF's (enhanced damage-sensing property) was observed by Nguyen et al [27], when macro-steel fibre-reinforced concrete (MSFRCs) was embedded with 0.5 vol.% micro carbon fibres.…”

Electromechanical Response of Smart Ultra-High Performance Concrete under External Loads Corresponding to Different Electrical Measurements

“…The self-sensing mechanisms of smart UHPCs based on the AC measurement commonly include tunneling effects and conductive networks. In other words, the change in the electrical resistance (or response) of smart UHPCs under AC measurement was primarily due to the tunneling effects between two conductive particles and electrically connected (conductive) networks, including continuously connected pores and connected steel or carbon fibers [ 11 , 13 ]. However, under DC measurements, such changes were mostly dependent on the fiber crack bridging effects at cracked parts, as explained before.…”

“…Carbon black, granulated blast furnace slag, milled glass fibers, and fine steel slag aggregates have been utilized as additional fillers to further enhance the self-sensing capacity of SH-SFRCs [7,[11][12][13]. The SH-SFRCs containing fine steel slag aggregates (FSSAs) instead of silica sand (i.e., smart ultra-high-performance concretes (smart UHPCs)) have demonstrated noticeably enhanced stress self-sensing capacity under compression [8].…”

Influence of fiber size on mechanical properties of strain-hardening fiber-reinforced concrete

“…This could be attributed to the different failure-crack types in the tensile 148 and compressive specimen although the crack bridging of the fibers could prevent 149 crack propagation in both tension and compression. The failure of tensile specimen 150 was dominated by fully fiber pull-out mechanism that was greatly influenced by the 151 interfacial bond resistance of fiber-matrix, and the failure crack in this case was 152 perpendicular to the direction of applied stress [12,13]. On the contrary, the failure of 153 compressive specimen was controlled by shear resistance or locally tensile resistance, 154 with a failure crack not perpendicular to the direction of applied stress, as described in normalized by corresponding parameters of the plain matrix, as performed in Fig.…”