Experimental Study On Bending Creep Of Carbon Nanotube Cement Based Composite Beams

Cement matrix composites are widely used in various structural projects,and construction,field maintenance,mix proportion design,and other factors will cause structural cracking,affecting the safety and durability of the structure.Therefore,many scholars consider adding fibers,particles and other materials to improve the mechanical properties of cement-based composites.As composite reinforcements,multi-wall carbon nanotubes have a small diameters and large aspect ratios.They have excellent mechanical,electrical and magnetic properties,and can reduce the generation and propagation of microcracks.In this study,the mechanical properties of cement mortar specimens mixed with multi-wall carbon nanotubes are studied.In this study,the influence of the content of multi-wall carbon nanotubes on the mechanical properties of the test piece is analyzed based on the results of the bending and compression test of the cement-based composite material with different carbon nanotubes,and the optimal doping value of 0.05 g is obtained.The distribution of multi-walled carbon nanotubes in the matrix was observed by a scanning electron microscope.It can be seen from the micro-morphology that the carbon tube and carbon tube are bonded,the carbon tube and the carbon tube are staggered,and the carbon tube forms a mesh system in the cement base,which shows that the bridging and the anti-pulling effect of the multi-wall carbon nano-tube can improve the macroscopic mechanical property of the test piece.Multi-walled carbon nanotubes can reduce and hinder the generation and development of micro-cracks and fill micro-pores in the matrix.The specimen beams with different multi-wall carbon nanotube content(0g,0.05 g,0.1g)were divided into 9 groups with 3 beams in each group.The bending and tensile creep tests with different stress ratios(0.7,0.8,0.9)were carried out under different stress ratios(0.7,0.8,0.9).The maintenance age was 7 days.According to the test data,the selected model is determined,and the calculated value curve is compared with the test value curve,and the influence of carbon nanotube content and stress ratio on the bending and tensile creep of concrete is analyzed.The results show that the addition of 0.05 g of carbon nanotube can effectively reduce the bending,tensile and creep of the specimen.The results of this study can provide reference and theoretical support for the application of carbon nanotube cement-based composites in engineering.