纳米改性碱激发胶凝材料的研究进展

Research Progress on Nano-Modified Alkali-Activated Cementitious Materials

以添加纳米组分为手段的纳米技术为胶凝材料改性提供了新方法。本文综述了纳米SiO2等纳米颗粒及碳纳米管等纳米材料对碱激发胶凝材料工作性能、凝结硬化行为、力学性能与耐久性的影响。纳米SiO2等高活性纳米颗粒发挥提供可溶性硅的化学作用,诸如纳米TiO2等其他超细颗粒发挥成核位点、颗粒填充的物理效应,可加速反应、致密基体、提升强度、降低渗透等,从而获得性能更优异的纳米改性碱激发胶凝材料。碳纳米管及石墨烯等多维纳米材料具有优异的力学性能,可提升碱激发胶凝材料的韧性、改善其脆性,且优异的电学性能可赋予碱激发胶凝材料损伤自诊断、光催化等功能。本文还分析了已有研究中改性浆体流动性、凝结时间及硬化体强度、抗渗透等结果并不一致的原因,指出纳米SiO2对液相环境的影响及其与溶液中Ca^2+的作用是导致结果差异的主要原因。此外,还展望了该领域未来研究重点。

A nano-modification method is proposed to improve the performance of alkali activated cementitious materials(AAM). This paper reviewed the effects of nano-particles(i.e., silica particles) and nano-materials(i.e., cabon nano-tube) on the workability, setting and hardening behavior, mechanical property and durability of AAM. The acceleration of geopolymerization, the more compact matrix, the higher strength and the lower permeability of nano-modified AAM occur due to the presence of soluble silica in alkali solution from silica nanoparticles and the nucleation site effect, filling effect derived from other nano-particles such as TiO2 nanoparticles. The modified AAM with a higher toughness and a lower brittleness is available for the incorporation of carbon nano-tube or graphene oxide. Furthermore, the carbon nano-tube or graphene oxide modified AAM exhibits some functional characteristics like the self-sensing capacity to detect its own structural damage and the photocatalytic performance to treat wastewater. Some controversial issues on the flowability and setting time of fersh mixtures, strength and permeability of hardened samples containing silica nanoparticles in previous studies were also represented. The reason for the controversial issues above could be due to the interaction bewteen silica nanoparticles and alkaline solution and the initial chemical reaction between silica nanoparticles and Ca^2+ ions in solution. In addition, some further research works on nano-modified AAM were also given.