Effect of Field's metal particles coated with PVA, nano-SiO2 and PVA@nano-SiO2 on the performance of cement pastes

In this paper, a modification method for physical surface coating of Field's metal particles (FMP) using individual/combined polyvinyl alcohol (PVA) and nano-silica (NS) is proposed. The properties of cement pastes modified by FMP@H 2 O, FMP@PVA, FMP@PVA@NS, FMP@NS were evaluated by mechanical test, EIS, NMR, XRD, TG, and SEM. The results showed that the flexural strength and compressive strength of cement pastes with FMP@PVA, FMP@PVA@NS, FMP@NS at 7 days increased 2.74–13.01 % and 9.18–18.10 %, respectively, compared to the control samples, due to the inhibition of calcium hydroxide (CH) nucleation crystallization in the connection region between FMP and matrix by PVA, and CH reacting with NS to generate CSH gels. The cement paste with FMP@PVA has the best matrix strength at 28 days, resulting from the optimized connection region. Additionally, the mechanism of modified FMP strengthening connection region was proposed to explain the uniform distribution of FMP in fresh state, and the directional growth of CH crystals, which has a good agreement with the results of mechanical properties, phase analysis, thermal analysis and SEM observation. In accordance with the research in this paper, FMP as a new functional raw material is expected to be applied in the mix design of large-volume concrete, oil-gas well cement, and geothermal cement, especially used for temperature self-regulation and crack self-healing of cementitious materials.