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The influence of nano-SiO2 emulsion on sulfate resistance of cement-based grouts

Li Shuiping, Yuan Bin, Cheng Jian, Yu Xiaocheng, Wei Chao, Wu Qisheng, Zhang Youchao

Materials Science Poland

2024

Vol. 42, No. 1

116--125

Sulfate attack is one of the most significant durability issues for cement-based grouts, which are widely used to repair concrete structures in sulfate-rich environments. The purpose of this study was to investigate the impact of nano-SiO2 emulsion on the sulfate resistance of cement-based grouts. The durability of the mixes was evaluated on the basis of weight loss and compressive strength. X-ray diffraction (XRD) and scanning electron microscopy (SEM) of hardened grout matrix were used to analyze the hydration products and microstructure of the hardened grout matrix. The results indicate that the hydration degree of nano-SiO2-modified samples is higher than that of the control sample. The compressive strength from highest to lowest was 16 NSE, 10 NSE, NSP, and the control sample. The XRD and SEM results suggest that the deterioration of properties may be attributed to the formation and growth of ettringite (AFt) crystals, which may result in crack generation and extension and in the corrosion of gypsum, leading to exfoliation. The addition of nano-SiO2 to cement-based grouts through a preprepared emulsion, which facilitates dispersion within the cement matrix, has the potential to reduce AFt and gypsum contents, enhance microstructure density, decrease the migration channels of SO4-2, and ultimately improve the resistance to sulfate attack. This work will provide a novel route to enhance the sulfate resistance of cement-based grouts, which may be serviced in a sulfate-rich environment.

Synthesis and characterization of mesoporous carbon spheres

Li Shuiping, Zhu Huajun, Xu Guilong, Lin Qing, Wang Chengshuang, Wu Qisheng, Wang Zhanhong

Materials Science Poland

2019

Vol. 37, No. 4

585--589

A three-step method was used for the synthesis of mesoporous carbon sphere (MCS) material: firstly, silica (SiO2) nanoparticles were synthesized by the modified Stöber procedure; secondly, tetraethyl orthosilicate (TEOS) and cetyltrimethylammonium chloride (CTAC) were grafted onto SiO2 core nanoparticles to prepare SiO2@ SiO2 -CTAC hard templates; lastly, MCS material was fabricated by carbonizing and selective leaching SiO2/resorcinol-formaldehyde (RF) composites. The influence of the mass ratio of R-F/silica on the structure, morphology and crystal form was studied. The results indicate that the MCS materials have a uniform morphology. The increase of the mass ratio of R-F/silica can increase the specific surface area and pore volume. The three-step method provides a cost-effective procedure for the fabrication of MCS materials with uniform morphology.