The mechanical properties of cement mortars with 0~2.0% (by mass) polyvinyl alcohol (PVA) were experimentally studied, and the effects of PVA incorporation on the hydration products and microstructure of the cement mortar were determined with differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The results show that the rational content of PVA formed evenly dispersed network-like thin films within the cement matrix, and these network-like films can bridge cracks in the cement matrix and improve the mechanical properties of the cement mortar. Over-incorporation of PVA may result in the formation of large piece polymer films that coat the cement particles, delay the hydration of the cement mortar and adversely affect its performance. The mechanical properties of the cement mortar show a significant increase and then decrease with a change in the PVA incorporation. When the PVA content was 0.6% and 1.0%, the mortar had the best compressive and flexural strengths, respectively. The compressive strength of the cement mortar increased by 12.15% for a PVA content of 0.6%, and the flexural strength of the cement mortar increased by 24.83% for a PVA content of 1.0%.change occurs under 140 • C), light, and chemical stability but also has excellent gas and water barrier properties (the inside of polyvinyl alcohol can remain dry under high humidity) [19,20]. The good physical and chemical properties of polyvinyl alcohol and its formed films enable its wide use in the textile, construction, chemical, and papermaking industries, to name a few.Owing to the excellent performance as described above, researchers have utilized PVA to modify the mechanical properties of a cement-based material. Singh et al. [21] found that the addition of 3% of PVA could increase the compressive strength of cement mortar about 12 % due to there exists chemical interaction between PVA and cement hydration. This chemical interaction is effective in improving the interfacial bond between cement hydration and aggregates. Moreover, the chemical products could fill the pores of the cement matrix, resulting in the mechanical properties of the cement matrix increase greatly. Similarly, Kapen et al. [22] demonstrated that the flexural strengths of cement mortar increased by 21% after loading 1% PVA when cured in dry condition, respectively. They stated that this improvement was mainly attributed to the formation of PVA film within the cement matrix. Kim et al. [23] found that the improvement in bond strength after loading PVA seems to arise from suppression of the porous interfacial transition zone and inhibition of calcium hydroxide nucleation on the aggregate surface.Using PVA to enhance the properties of cement composites has attracted extensive attention. However, the previous research mainly focused on the hydration and mechanical properties after loading a mono content of PVA, there is limited information on the effect of PVA with different content on the fresh properties and ...

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.