Research On Mechanism And Impervious Behavious Of Cement Based Composites With Carbon Nanotube

Carbon nanotubes(MWCNTs) are considered as one of the most superiornanomaterials for its excellent physical properties such as the admirableelectrical, mechanical, thermal properties and chemical stability. Moreover, thehigh ratio of length to diameter property of MWCNTs, which can enhance thecement ductility and fill cement pores. Therefore, cement based composites withcarbon nanotubes should have high strength, high volume stability and highpermeability. Currently, there are only preliminary studies on cement basedcomposites with carbon nanotubes. And most scholars focus their studies onmechanical and electrical performance of cement composites with carbonnanotubes which cannot provide more theories and codes to promote theacceptance on a broader scale in civil engineering. As a result, conducting morecomprehensive studies on the cement based composites with carbon nanotubesare necesssary. This study focus on highly effective dispersion of MWCNTs,mechanical and impermeability of cement based composites with MWCNTs.Main research results of this thesis are as follow.Achieving admirable dispersion of MWCNTs in cement based compositesis the key and difficult point.to deliver its excellent values. So this researchstudies the MWCNTs dispersion under different dispersion method. Theobservasion of the dispersion state after predetermined standing time and theresults of the laser particle instrument measuring particle size and SEM wereused as the criterions to evaluate the effectivity of every method. The aboveresearch results indicate that using PVP as surfactant combined with ultrasonicdispersion to attain optimal dispersion in cement based composites with carbonnanotubes. Compared with portland cement material, the mechanicalperformance of cement based composites with carbon nanotubes has beenimproved significantly.The mechanical and shrinkage performances of the cement basedcomposites with carbon nanotubes and portland cement material were evaluatedby three-point bending, axial compression and measurement of shrinkage. Aseries of microscopic experimental analysis the improvemtal mechanism of MWCNTs. The mechanical properties(flexural,compressive strength) of cementbased composites, which the MWCNTs content is0.02%, are obviously enhancedcompared with these of portland cement material. The shrinkage of cement basedcomposites with carbon nanotubes were reduced, especially for the early age.The improvement of the cement based composites with carbon nanotubes on themechanical and sharinkage effect enhances the ability of portland cementmaterial to resist cracking as well as decrease the internal defects.For portland cement material, moisture permeability has great influenceson the material durability. Comparative study the resistance to water penetrationbetween cement based composites with carbon nanotubes and portland cementmaterial through the water absorption test, resistance to penetration experimentsand mercury injection experiment. The research results show that porecharacteristics and water impermeability of cement based composites withcarbon nanotubes are improved. This results of the research have the vitalsignificance on the durability of the cement base composites with carbonnanotubes.