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Effect of silica fume-enhanced carbon nanotube dispersion on the strength and damping properties of cement composites

Carbon nanotubes (CNTs) tend to agglomerate in cement paste, which impedes the effect of performance reinforcement. This paper applies silica fume as an active factor to enhance the dispersion of CNTs and investigates the influence of silica fume on the strength and damping properties
 of CNT-reinforced cement composites. Mechanical strength tests and dynamic mechanical analysis on specimens with different contents of CNTs (0%, 0.1% and 0.2%) and silica fume (0%, 5%, 10% and 15%) are conducted. The microstructure is characterized by Scanning Electron Microscopy (SEM), and
 the pore size distribution is measured by Mercury Intrusion Porosimetry (MIP). Due to the CNT dispersion enhancement, both the number of gel pores and the size of microcapillary pores are reduced. The incorporation of silica fume also facilitates the interfacial friction between CNTs and cement
 hydration products and promotes heat generation, when reciprocating loads are applied. The result indicates that the mixture proportion of CNTs and silica fume strongly influences the extent of the dispersion enhancement, which is optimized at 0.1% and 5%, respectively. Excessive addition
 of either CNTs or silica fume will hinder CNT dispersion and subsequently reduce the strength and damping properties of the material, which should be avoided in practical applications.