Effect of Adding Carbon Nanotubes on Corrosion Rates and Steel-Concrete Bond

Ahmed Hassan,Hala Elkady,Ibrahim G Shaaban

doi:10.1038/s41598-019-42761-2

Ahmed Hassan, Hala Elkady + Show 1 more

Open Access

https://doi.org/10.1038/s41598-019-42761-2

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Abstract

This paper presents a continuation of the evaluation of utilizing Nano Carbon Tubes (CNTs) in reinforced concrete (CNT-CRETE). The compressive, tensile and bond strengths of the samples with and without CNTs were investigated. Scanning Electron Microscope (SME) was utilized to study the microstructure of the prepared samples. In addition, the corrosion resistance of CNT-CRETE, was measured and compared to traditional concrete. Four mixes were prepared, with 0.01%, 0.02%, and 0.03%, CNTs by weight of cement, along with a control mix without CNTs. The results of the experimental work showed that adding CNTs led to an increase in the compressive, tensile and bond strengths of specimens compared to those of the control specimen. SEM examination for control and CNTs specimens showed that CNTs specimen were well structured compared with the control specimen and this affirms that CNTs act as bridges across micro cracks, which explains the improvement in mechanical properties. The diameter of steel bars played a significant role in failure mechanism for pull-out testing and corrosion resistance. In general, adding CNTs to the concrete mix increased the rate of corrosion for steel bars within the low risk limits. Benefits from using CNTs were limited to moderate. Mineral/chemical admixtures or fibers provide better improvements in the mechanical properties of concrete without the problems associated with dispersing CNTs and the health hazard of handling a Nano material.

Highlights

Bond strength of steel reinforcement in concrete structures is one of the important factors in structural design[1,2]
It can be seen that the addition of Carbon Nanotubes (CNTs) to the concrete mix led to an increase in the compressive strength of specimens compared to that of the control specimen
An increase of up to 20% was reported[33,34] when up to 0.06% CNTs were included in concrete mixes

Summary

Concrete Bond

This paper presents a continuation of the evaluation of utilizing Nano Carbon Tubes (CNTs) in reinforced concrete (CNT-CRETE). As a result of exposure of reinforced concrete to aggressive environments, has a negative effect on the bond strength of steel reinforcement in structural concrete. The bond behaviour of steel reinforcement in reinforced concrete elements, including the ultimate bond strength, the load-slip relationships and the effect of different corrosion rates were studied in literature[16,17,18]. CNTs have high flexibility, and its microstructure shape as tubes is capable of bending in circles and forming bridges crossing the micro and Nano-cracks developed in the cement composites, which in turn, increases the strength of the cement composites[26]. CNTs possess a high modulus of elasticity, tensile strength, and yield strain Such properties make CNTs an attractive reinforcing material for concrete. CNTs improve cement composites in tension due to its ability to prevent the initiation of micro cracks in the cement matrix[30]

Research Significance

Pull out Accelerated Corrosion Test

Results and Discussion

Conclusions

Additional Information