Preparation And Performance Of Carbon Nanotubes Sulfuraluminate Cement-based Composite Materials

Sulphoaluminate cement is a kind of special cement which has early strength, fast hardening characteristics. The production of sulphoaluminate cement clinker is an eco-friendly cement with the low energy consumption, easy grinding, less carbon dioxide emissions (that is only half of the emissions of the Portland cement). However, sulphoaluminate cement also has characteristics of weak toughness, low tensile strength and easy broken that is extremely vulnerable to the service life and safety of construction. Therefore, it is important to enhance the toughness of concrete and cement material security.Multi-wall Carbon Nanotubes(MWNTs) belongs to the family of Fullerenes, Its length is several microns. The diameter is between several nanometers and dozens of nanometers. The MWNTs is composed of hollow cylindrical nesting together. In 1991, Japanese Iijima, who was the first one, observed MWNTs using the high resolution TEM analysis. It was known as the most promising nano-materials in 21st century's. Carbon nanotubes have a lot of excellent properties, including mechanical properties, electrical properties, excellent mechanical properties and so on.This papers combined subject group for carbon nanotubes dispersed performance of research, select gum arabic powder as carbon nanotubes dispersed agent. The effects of different ultrasonic time and ultrasonic energy on the dispersion of carbon nanotubes were studied; then the mechanical properties and microscopic mechanism of carbon nanotubes sulfur cement-based composite materials were studied. Through the composite of carbon nanotubes and Sulphoaluminate special cement, expanding carbon nanotubes applications in cement-based materials.(1)We used the GA as the dispersant agent and prepared the carbon nanotube suspension at different ultrasonic time and ultrasonic power. We tested the absorbance by uv-vis spectrophotometer to analyse the effect of time on absorbency. We also characterized the carbon nanotube dispersity in GA solution by many microscopic test methods such as the nano-particle size, Zeta potential, TEM and so on. The results showed that with the ultrasonic time increases, the absorbance and the concentration of carbon nanotube suspension is higher and higher. When the ultrasonic time reaches 100min, the absorbance and the concentration are maximum. The absolute value of Zeta potential increases with the ultrasonic time increases that shows the stability of the dispersive solution. The ultrasonic power experimental results and the ultrasonic time have similar impact on the dispersion of carbon nanotubes. The absorbance and the concentration of carbon nanotubes increase with the increasing ultrasonic power. When the ultrasonic power is 360W, both of them have the maximum values, that are 2.62g/L and 0.205g/L, respectively. When we continue to increase the ultrasonic power, both of them decrease. The absolute value of Zeta potential is also the largest value(22.3mV) when the ultrasonic power is 360W. It shows that the dispersed solution is most stable at this time.(2)The flexural strength and compressive strength of the carbon nanotubes sulphoaluminate cement paste increased and then decreased with increasing content of carbon nanotubesn. For flexural strength, in the curing period for the 28d, cement ratio of 0.25, carbon nanotube content 0.08wt.%, under these conditions, the flexural strength reach 21.3 MPa, compared to blank test pieces of 13.4MPa increases 58.9%..Carbon nanotubes also improved the compressive strength of sulphoaluminate cement, and when the water-cement ratio of 0.25 and 0.30, the dosage amount of carbon nanotubes was 0.08wt.%, sulphoaluminate cement paste compressive strength increased 8.6% and 20.6% compared with the blank specimen,under these conditions, the carbon nanotubes can improve the toughness of sulfur aluminate cement-based materials, the bend-press ratio of sulfur aluminate cement paste increased by 46.2% and 29.0%; when the water-cement ratio of 0.35 and 0.40, the dosage amount of carbon nanotubes was 0.10wt.%, sulphoaluminate cement paste compressive strength increased 6.2% and 4.2%.(3)Addition of MWCNTs increases both the compressive and flexural strengths of sulphoaluminate cement mortar. The compressive strength of mortars reinforced with 0.10wt.% addition of MWCNTs resulted in an increase of 13.2% reched 80.6 MPa compared with the blank specimen. The addition of MWCNTs also improved the flexural strength of the composites. A 0.08wt.% addition of MWCNTs increased flexural strength by 13.16% reched 12.9MPa, However, the maximum addition of 0.15wt.% resulted in a slight decrease. The mechanical strength develovped with the increase of the curing age.Finally, combined with a variety of microscopic test method, and analyses the micro mechanism of the properties of sulphoaluminate cement reinforced by carbon nanotubes. The results were as follows:disperse the well performance of the carbon nanotubes into the sulphoaluminate cement paste can accelerate hydration, dense paste, so as to improve the sulphoaluminate cement paste microstructure, improve the performance.