Mechanical Properties And Microscopic Study Of Modified Carbon Nanotubes Reinforced Cement Composites

Carbon nanotubes have a small size and a large specific surface area,there is a strong van der waals attraction between them,which makes them prone to reunion or entanglement.The dispersion effect of carbon nanotubes in cement slurry directly affects the mechanical properties and performance of the final product,adding dispersant can improve the dispersion of carbon nanotubes to some extent,through the modification of carbon nanotubes to improve its compatibility with the matrix material,it can also achieve good dispersion effect.Treatment of carbon nanotubes with dichloromethane and m-chloroperoxybenzoic acid,study on the effect of modified carbon nanotubes on the mechanical properties of cement-based composites.The effect of modified carbon nanotubes on the mechanical properties of cement-based composites was studied,the change rule of elastic modulus and hardness of carbon nanotube-reinforced cement-based composites was analyzed using nano indenter.Study on the enhancement mechanism of carbon nanotubes from the change of microstructure.The main research content are as follows:(1)The dispersive effect of carbon nanotubes in aqueous systems after addition of dispersants carboxymethylcellulose sodium(CMC)and polyvinylpyrrolidone(PVP)was investigated,the results showed that the dispersion effect of polyvinylpyrrolidone(PVP)was better.(2)Using polyvinylpyrrolidone(PVP)as a dispersant to prepare a standard test block of carbon nanotube cement mortar,after 28 days of standard curing,its compressive strength,flexural strength,and flexural strength were measured to be59.2MPa,8.9MPa,and 8.3MPa,respectively,compared with plain cement mortar,it increased by 40.3%,20.25% and 30.7% respectively.The experimental results show thatwith the increase of the amount of carbon nanotubes,the mechanical properties of the specimens are gradually improved,However,the compressive strength and flexural strength tend to be saturated when the content is 0.1wt% by weight,flexural strength peaks at 0.08 wt%.(3)Preparation of cement mortar using carbon nanotubes treated with methylene chloride and m-chloroperoxybenzoic acid,the maximum compressive strength,flexural strength,and flexural strength are 62.4 MPa,11.3 MPa,and 9.3 MPa,increased by 47.5%,52.7%,and 47.6%,respectively,compared to plain cement mortar.When the content of modified carbon nanotubes is 0.05wt%,the specimen's compressive strength,flexural strength,and flexural strength peak,it shows that the low content of modified carbon nanotubes can play a very good enhancement effect.(4)Test of Elastic Modulus and Hardness of Carbon Nanotube Grout Samples Using Nano Indenter,the experimental results show that with the increase of the amount of carbon nanotubes,the elastic modulus of the specimen gradually increases,the area fraction of the low density calcium silicate gel gradually decreases,and the area fraction of the high density calcium silicate gel gradually increases,the modification of hydrated calcium silicate gel by carbon nanotubes is the main reason for improving the mechanical properties of products.