纳米SiO2分散液对水泥基材料性能的影响及机理

Influences and mechanisms of nano-silica dispersionon properties of cement-based materials

对团聚粒径较大的沉淀纳米SiO2微粉进行湿法球磨,制备纳米SiO2分散液,研究了掺纳米SiO2分散液对新拌和硬化水泥基材料性能的影响及机理。结果表明:纳米SiO2掺量为1%时,随球磨时间延长,其促进水泥水化、改善新拌水泥砂浆流动性和对硬化水泥砂浆的增强效果均渐趋显著,其原因是由于球磨处理可有效减小纳米SiO 2团聚粒径,改善其吸钙能力和填充效应;纳米SiO2掺量增加到2%时,其对砂浆流动性和强度的进一步改善未见明显效果,其原因可能是由于掺量较高时,其发挥填充效应所需纳米SiO2出现冗余,而硬化团聚颗粒本身因强度和弹性模量较小,反而成为硬化水泥石中的薄弱环节。

Nano-SiO2 dispersion was prepared by wet-milling of precipitated nano-SiO2 powder with large agglomerated particle size.The influences and mechanisms of the nano-SiO2 dispersion on properties of the fresh and hardened cement-based materials were studied.The results showed that,when the addition of the nano-SiO2 was 1%,the cement hydration,the fluidity of the fresh cement mortar and the strengthening of the hardened cement mortar were increasingly improved with the milling time.The reason was that the ball-milling could effectively reduce the agglomerated particle size of the nano-SiO2,which then improved the calcium-absorption capacity and the filling effect of the nano-SiO2.However,when the addition of the nano-SiO2 was further increased to 2%,negligible improvement of the fluidity and the strength of the mortar was observed,of which the reason might be that the nano-particles acted as the filler in the paste showed redundancy when the addition of nano-SiO2 was high and the hardened agglomerated particles became weak zones in the hardened cement paste due to their low strength and elastic modulus.