Mechanical Properties And Microstructural Studies Of Silica-fume Doped CNTs Reinforced Cement Mortar Composites

Carbon nanotubes（CNTs）have been playing an increasingly important role in the field of material research due to their excellent mechanical properties,good electrical conductivity and corrosion resistance.Many studies indicated that adding a certain amount of CNTs into the cement matrix can improve the inherent properties（such as brittleness）of the cement matrix and thus enhance the reliability of material to a certain extent.This paper mainly studies the dispersion properties of CNTs in the anionic surfactant SDBS（sodium dodecylbenzene sulfonate）and non-ionic surfactant TNWDIS,the preparation process of CNTs cement mortar composite and the mix ratio of CNTs cement mortar.On this basis,CNTs cement mortar specimen and silica fume doped CNTs reinforced cement mortar composite（denoted by CNTs/cement）specimen were studied experimentally.The compressive and flexural strength are used to evaluate the macroscopic mechanical properties of the specimens.Moreover,scanning electron microscopy,IPP（SEM-Image Pro Plus）and X-ray diffraction were used to evaluate the microstructure characteristics of the specimens.The Research indicates that that both the mechanical properties and microstructures of cement mortar specimens could be upgraded due to the addition of CNTs,comparing with the blank group:（1）using SDBS as surfactants,while the CNTs content is 0.2 wt.%,the flexural and compressive strength are obtained maximum value,and the strength is increased 44.8% and 11.7% comparing with the blank group,respectively,moreover the crystal nucleus effect of CNTs is more obvious,which is reflected by the improvement of the compactness of cement hydration products due to the addition of CNTs.;（2）using TNWDIS as the surfactants,the mechanical properties of the CNTs/cements are the best when the content of CNTs is 0.1%,which is 22.8% and 15.3% higher than that of the blank group,respectively,and the improvement effect of CNTs on large-diameter pores is not obvious at this time,and the filling effect is mainly manifested in the cement matrix.In addition,adding a proper amount of SF to CNTs reinforced cement composite can improve further the mechanical properties of the cement matrix: when TNWDIS is used as the surfactant,the addition of SF can improve obviously the mechanical properties of CNTs/cement.At this point,SF exerted its steric hindrance effect and CNTs were dispersed in the hydration products;in contrast,while the SDBS is used as surfactant,the mechanical properties of CNTs/cement decreases,this is because the incorporation of SF bonds SDBS molecules and forms microflocs,which weakens the electrostatic repulsion caused by the adsorption of dodecylbenzene sulfonate on the surface of CNTs,and causes CNTs to agglomerate to varying degrees,thus degrading the mechanical properties of the matrix.