Experimental Research Of Cement Mortar Reinforced By Carbon Nanotubes

Carbon Nanotubes （CNTs） are new nano-fiber materials, which has been a hotmaterial issue in focus, because of its excellent mechanical and electrical properties. Itis found that, if a certain proportion of carbon nano tubes are mixed in metals, orceramics, the toughness of the matrix material can be effectively increased. As similaras ceramic material, the capability of cement, such as inherent brittleness, can beimproved by adding a certain amount of CNTs.This paper mainly studies CNTs cement mortar composites preparation methods inlaboratory, including the CNTs dispersion properties in aqueous solution, CNTs cementmortar casting process, and the mix proportion of CNTs cement mortar. On this basis,cement mortar with normal CNTs, cement mortar with CNTs of functional group（-COOH/-OH） and cement mortar with CNTs coatedSiO₂were investigatedrespectively. Theeffect of different concentration of CNTs was also investigated.Compressive strength and flexural strength were used to evaluate the mechanicalproperties of the specimen; Mercury porosimetry was used tomeasure pore sizedistributionand scanning electron microscopy to evaluate the micro-structure of thespecimen.The results show that, the mechanical properties of the specimen withnormal CNTsdecreased by70%. Thechange of CNTs dosage has little effect on the mechanicalproperties.The change in the diameter （10-20nm⁴0-60nm） of CNTshas slight effecton the mechanical properties, mechanical properties of specimen with larger diameterCNTs increased by5%. There is an increase of100%in the overall porosity of thespecimen, and the average pore size increased substantially, SEM revealed the presenceof a large number of pores in the cement matrix, mainly because of the dispersant ofSDS brought a large number of bubbles affect the experimental results; The mechanicalproperties of specimen with functional groups （-COOH/-OH） of CNTs increased by upto15%. The average strength of specimen with a carboxyl group CNTs is higherthanspecimen with a hydroxyl group CNTs. The overall porosity is essentially the same,but the average pore size decreased by30%, SEM revealed that CNTs played a role ofbridging micro-cracks, fill micro pores in the cement matrix; the mechanical propertiesof specimen with CNTs coatedSiO₂increased slightly.TEM showed that nano-SiO₂film successfully attached to the surface of CNTs, the average thickness of50nm, CNTs incement matrix formed the mesh connection cement hydration products.