高活性硅灰改性渠道衬砌胶材性能及微观机理研究

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

【目的】探明矿物掺合料对衬砌胶材的宏、微观性能的影响。【方法】分别以普通硅酸盐水泥(PO)、硫铝酸盐水泥(SAC)、铝酸盐水泥(AC)为基础材料,以硅灰为替代材料,制备了15种复合胶材。基于抗压强度和抗渗试验,联合SEM、EDS、XRD表征手段,探究复合胶材力学演变规律,揭示其微观水化机理。【结果】随着硅灰替代率的增加,PO、SAC和AC硬化体的抗渗性能逐渐增强;硅灰替代率为6%时,PO的早期抗压强度显著提高,C-S-H凝胶和AFt晶体彼此胶结构成三维网络结构,有效减缓了因Ca(OH)_(2)简单堆叠引起的剪切滑移和基体早期强度衰退,C-S-H凝胶的Ca/Si降低、聚合度增加提高了体系强度的稳定性;SAC硬化体3、28d龄期的抗压强度均随着硅灰替代率的增加呈先增大后减小的变化趋势,硅灰的成核效应、火山灰效应促使SAC水化产物增加;随着硅灰替代率的增加,AC硬化体3、28 d龄期强度呈负增长,90 d龄期强度先增大后降低,掺入4%硅灰制约了CAH_(10)、C_(2)AH_(8)的转晶反应,孔隙率明显降低,改善了AC的后期强度倒缩现象。【结论】适宜的硅灰掺量可提高衬砌板胶材强度、优化体系微观形貌,从而提升抗渗特性,因此建议将硅灰应用至渠道衬砌。

【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 AH_(3) 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 CAH_(10) and C_(2)AH_(8),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.