Effect of the dosage of MWCNT's on deterioration resistant of concrete subjected to combined freeze–thaw cycles and sulfate attack

Abstract

In this study, the deterioration resistant of concrete with and without multi‐walled carbon nanotubes (MWCNTs) against combined freeze–thaw cycles and sulfate attack was studied, and concretes incorporating MWCNTs (i.e., 0.05, 0.10, and 0.15 wt%) as partial replacement of Portland cement were exposed to 5% sodium sulfate solution under freeze–thaw cycles. The performance, including compressive strength, relative dynamic elastic modulus, mass loss, microstructure, deterioration resistant coefficient of concretes were evaluated. Results show that when exposed to 5% sodium sulfate solution, MWCNTs could enhance the mechanical and durability properties of concrete subjected to combined freeze–thaw cycles and sulfate attack, regardless of the dosage of MWCNTs. The deterioration resistant of MWCNTs concrete was not increase with the increase dosage of MWCNTs. And the best resistance performance was obtained in concrete containing lower dosage of MWCNTs. In addition, MWCNTs could promote formation of hydration and corrosion products, and delay deterioration of concrete was demonstrated by SEM and thermogravimetric analysis.

Degradation mechanism and life prediction of tailings and waste rock aggregate geopolymer concrete under freeze-thaw corrosion

“…In the early stage of the freezing-thawing corrosion cycle, crystals precipitate and fill with aggregates, with a small number of microcracks (figure 1 group). In the later stage of the cycle, due to product generation, microcracks increase and gradually expand into larger cracks (figure 2 group), accompanied by slurry spalling and aggregate exposure (figure 3 group) [20]. After 150 freeze-thaw corrosion cycles, the TWGPC specimens with the highest concentrations of FC10, FS10 and FC10S5 in the single solution and composite solution suffered the most serious damage.…”

Study on dynamic mechanical properties of carbon nanotubes reinforced concrete subjected to freeze–thaw cycles

“…At this time, the cement mortar was powdered while the aggregates were basically complete due to the weakening of the bond strength of the interface between the aggregate and the cement mortar. Additionally, it should be noted that under the same freeze–thaw cycles and impact velocity, the crushing degree of MWCNT reinforced concrete sample was slighter than that of ordinary plain concrete samples, resulting from strengthening of concrete matrix and improvement of meso adhesion by addition of MWCNTs 19,28,29 …”

“…Lanzhou tap water is used for mixing materials. Additionally, because of smaller diameter and amount of MWCNTs are conducive to pores distribution resulting from better dispersion and filling effect 28,29 . Therefore, MWCNT produced by Shenzhen Nanoport Co., Ltd. was used in this study.…”

“…The concrete samples soaked in water for 4 days were put into the freeze–thaw machine for rapid freeze–thaw cycles test according to GB/T 50082‐2009 30 . Tian and coworkers 28 reported that carbon nanotubes have the best performance in improving the mechanical properties of concrete at the early stage of freeze–thaw cycles (i.e., below 50 freeze–thaw cycles), so the number of freeze–thaw cycles in this test was set to 0, 25, and 50, respectively. The time of one freeze–thaw cycle should be controlled within 2–4 h, and the freeze–thaw temperature in the center of the sample should be kept at −18 ± 2°C in freezing and 5 ± 2°C in thawing.…”

“…The results show that 0.1% mass fraction of MWCNT has a better effect on improving the durability of concrete. Tian and coworkers 28 studied the deterioration resistance of concrete with and without MWCNTs under freeze–thaw cycle and sulfate erosion. The results show that MWCNTs can promote the formation of hydration and corrosion products, delay the deterioration of concrete in freeze–thaw cycle, and the compressive performance of concrete is better at low content.…”