Experimental Study on the Performance and Micro-mechanism of Concrete Channel Adhesive Modified by High-activity Silica Fume

Abstract

【Objective】 Soil salinization in the Ningxia Yellow River diversion irrigation area has been found to damage the microstructure and reduce the strength of concrete linings of the channels. The objective of this paper is to study the efficacy of using high-activity silica fume to enhance the concrete linings. 【Method】 Fifteen types of composite cementing materials were prepared using ordinary Portland cement (PO), sulphoaluminate cement (SAC), and aluminate cement (AC) with silica fume as a substitute. The mechanical behavior of the composite adhesives was studied using compressive strength and impermeability tests, combined with SEM, EDS, and XRD characterization. The micro hydration mechanism was also investigated. 【Result】 With the increase in silica fume content, the impermeability of PO, SAC and AC increased gradually. Adding 6% of silica fume significantly increased the strength of PO at the early stage. The C-S-H gel and AFt crystals cemented and interlocked with each other to form a three-dimensional network structure, effectively reducing early deterioration of the strength of the matrix caused by stacking of Ca(OH)2. The Ca/Si of C-S-H gel decreased, and the degree of polymerization increased, ensuring the stability of the system strength. The strength of SAC pastes measured 3 and 28 days after the test increased first and then decreased with the increase in silica fume replacement rate. The nucleation effect and pozzolanic effect of silica fume promoted the increase in SAC hydration products. The coarse rod like AFt crystals played a skeleton role in hardening pastes and were covered by AH3 gel, forming a stronger combination. With the increase in the replacement rate of silica fume, the strength of AC paste measured 3 and 28 days after the test showed a negative increase, and the strength measured 90 days after the test increased first and then decreased with the silica fume replacement rate. The addition of 4% silica fume restricted the crystallization reaction of CAH10 and C2AH8, and reduced the porosity significantly, which improved the strength reversion phenomenon at the later stage of AC. 【Conclusion】 Adding an appropriate amount of silica fume can significantly enhance the strength of the concrete lining and optimize its microscopic morphology, thereby improving its impermeability. Further studies could explore the effect of varying amounts of silica fume on other types of cementing materials and in different environmental conditions.

Keywords

• silica fume
• channel lining cementing material
• mechanical property
• c2ah8
• microstructure analysis