纳米硅溶胶改性水泥基材料性能及机理分析

Performance and Mechanism Analysis of Nano-silica Sol Modified Cement-based Materials

针对普通水泥基材料存在早期强度低、抗变形能力弱等问题,通过纳米硅溶胶对水泥基材料进行改性,采用电液伺服万能试验机、X射线衍射及扫描电镜等手段对纳米硅溶胶改性不同水灰比水泥基材料的流动性、结石率、单轴抗压强度、弹性模量、水化产物及微观形貌进行研究。结果表明:硅溶胶掺量在0.5%以内、水灰比小于1.0时可显著提高水泥浆液的流动性,最大提高20.24%;结石率随着纳米硅溶胶掺量的增加而增大,且硅溶胶对水灰比大于0.7浆液的结石率提高明显,最大提高24.49%;当硅溶胶掺量为2%时,结石体的抗压强度增幅最大且随着养护龄期的增加,硅溶胶对试样强度的增幅效果逐渐减弱;纳米硅溶胶的掺入促进水泥基早期的水化反应,与水化产物反应生成水化硅酸钙凝胶(C-S-H)并使微观形貌更加致密,使结石体的早期抗压强度及弹性模量显著提高;纳米硅溶胶通过缩短诱导期以及在颗粒空隙中为C-S-H提供成核位点促进水化反应,提高水泥基材料性能。

In view of the problems of low early strength and weak deformation resistance of ordinary cement-based materials, the cement-based materials were modified by nano-silica sol. The nano-silica sol was charasterized by means of electro-hydraulic servo universal testing, X-ray diffraction, and scanning electron microscopy. The fluidity, stone rate, uniaxial compressive strength, elastic modulus, hydration products, and microstructure of cement-based materials with different water-cement ratios were evaluated. The results show that when the content of silica sol is within 0.5% and the water-cement ratio is less than 1.0, the fluidity of cement slurry can be significantly improved, and the maximum increase is 20.24%. The stone formation rate increases with the increase of nano-silica sol admixture, and the silica sol increases the stone formation rate of slurry with water-cement ratio greater than 0.7 significantly, with a maximum increase of 24.49%. When the content of silica sol is 2%, the compressive strength of the stone body increases the most. The effect of increasing the strength gradually weakens.The incorporation of nano-silica sol promotes the early hydration reaction of cementitious, and reacts with the hydration products to produce hydrated calcium silicate gel(C—S—H) and makes the microscopic morphology more dense, so that the early compressive strength and elastic modulus of the stone body are significantly increased. Nano-silica sol promotes the hydration reaction by shortening the induction period and providing nucleation sites for C—S—H in the particle voids, which improves the performance of cementitious materials.