Carbon nanotubes (CNTs) are considered as one of the ideal modifiers of cement materials, since CNTs can improve the mechanical properties of cement paste effectively. However, the interfacial interaction between CNTs and the cement matrix is weak. Moreover, it is difficult to disperse CNTs within cement paste. To overcome these shortages, in this study, CNTs were firstly dispersed into a styrene-acrylic emulsion (SAE). Then the homo-dispersion CNT/SAE emulsion was incorporated into cement paste. The effect of the CNT/SAE hybrid-system on the mechanical properties and microstructure of cement paste was studied. For purposes of comparison, the properties of cement paste mono incorporating CNTs or SAE are also investigated. The results show that CNT/SAE network films could be observed in cement paste by using a field emission scanning electron microscope (FESEM). These network films could bridge the cracks and refine the pores of a cement matrix. Infrared analysis and Raman spectroscopy show that the CNT/SAE hybrid modifier has stronger interfacial adhesion and better load transfer ability over the mono adding of CNTs and SAE emulsion. As a result, the hybrid addition of CNT/SAE significantly improved the flexural strength of cement paste. Especially, the addition of 0.1% CNTs and 15% SAE by mass of cement improved the 28-day flexural strength of cement paste by 21% and 25% as compared to the mono addition of CNTs or SAE, respectively.
Keywords: carbon nanotube; cement paste; mechanical properties; microstructure; styrene-acrylic emulsion.