Mechanical Properties and Durability of Ultra High Strength Concrete Incorporating Multi-Walled Carbon Nanotubes

Abstract

In this work, the effect of the addition of multi-walled carbon nanotubes (MWCNTs) on the mechanical properties and durability of ultra high strength concrete (UHSC) is reported. First, the MWCNTs were dispersed by a nano sand-mill in the presence of a surfactant in water. The UHSC specimens were prepared with various amounts of MWCNTs, ranging from 0% to 0.15% by weight of cement (bwoc). Results indicated that use of an optimal percentage of MWCNTs (0.05% bwoc) caused a 4.63% increase in compressive strength and a 24.0% decrease in chloride diffusion coefficient of UHSC at 28 days curing. Moreover, the addition of MWCNTs also improved the flexural strength and deformation ability. Furthermore, a field-emission scanning electron microscopy (FE-SEM) was used to observe the dispersion of MWCNTs in the cement matrix and morphology of the hardened cement paste containing MWCNTs. FE-SEM observation revealed that MWCNTs were well dispersed in the matrix and no agglomerate was found and the reinforcing effect of MWCNTs on UHSC was thought to be pulling out and microcrack bridging of MWCNTs, which transferred the load in tension.

Properties of Cement Mortar and Ultra-High Strength Concrete Incorporating Graphene Oxide Nanosheets

“…The water in the GONS dispersions and PCs solution should be deducted in the mixing water. The detailed preparation process is described in our previous work [ 1 ]. After four minutes of being prepared, the mixtures were poured into oiled molds and compacted on a vibration table.…”

“…It has a relatively high compressive strength, but low flexural and tensile strengths. Moreover, cracks are one of the main hidden defects in concrete structures; they cause brittle fractures, shorten the service life, and lower the durability [ 1 ]. Generally, the damage and failure of concrete are caused by the nucleation, growth, and coalescence of microcracks [ 2 , 3 , 4 ].…”

“…Recently, high-performance CNTs have been used to reinforce concrete by improving these defects at the nanoscopic level. The results of our previous research have shown that CNTs improve the flexural strength and deformation ability of UHSC [ 1 ]. Song et al [ 24 ] reported that CNTs lead to large increases in the tensile strength and ultimate strain of the concrete.…”

Carbon nanomaterials enhanced cement-based composites: advances and challenges

“…For example, the flexural strength and toughness of cement-based materials containing 0.2 wt.% CNFs have been found to be about 20% and 60% higher than plain cement after decalcification for 125 days [126]. In [129], the addition of 0.03-0.10 wt.% CNTs to ultra-high-strength concrete resulted in a reduction of about 8.8-24.0% in the chloride diffusion coefficient, and a reduction of about 70% in this coefficient for cement was reported when 2.5 wt.% of GNPs was added [139]. The refined pore structure also improves the anti-permeability, and the refined pores inhibit water from freezing, as water molecules are less likely to freeze in pores with smaller volumes, and thus the resistance to free-thaw cycles is increased.…”

Design and predicting performance of carbon nanotube reinforced cementitious materials : mechanical properties and dispersion characteristics.

“…Despite the ongoing research efforts, there is yet no consensus on the contribution of CNTs to the mechanical properties of cementitious materials. Some researchers have reported significant improvement in mechanical properties [11,63,66,75,[110][111][112][113][114][115], while others have reported negligible improvement or even degradation in mechanical properties [20,26,29,60,64,65,99,[116][117][118]. The mechanical properties investigated include compressive strength, flexural (or tensile) strength, elastic modulus, and toughness.…”