纳米二氧化硅改性大掺量矿粉-水泥胶凝体系性能与微结构研究

利用沉淀法制备的纳米二氧化硅(PNS)极强的火山灰活性,能改善大掺量矿粉-水泥胶凝体系早期抗压强度低、内部结构疏松等缺陷,研究了PNS对大掺量矿粉-水泥胶凝体系抗压强度、抗氯离子渗透性的影响,通过XRD、TG-DSC及MIP对该体系的水化产物与孔结构进行微观分析。研究表明:随着PNS掺量的增加,试件的抗压强度也随之提高,尤其是7 d抗压强度,掺5%(质量分数,下同)PNS试件的强度增幅达到了20%;同时,水泥抗氯离子渗透能力先上升后下降,PNS掺量为3%时,达到最优,其28 d氯离子扩散系数较不掺PNS降低44.8%。PNS在早期能够大量消耗Ca(OH)₂,生成更多的C-S-H凝胶等水化产物,使得孔结构更加致密,降低孔隙率,在适宜范围内掺入PNS还可有效细化孔径。

Property and Pore Structure of Nano-SiO2 Modified High Volume Slag Powder-Cement Cementitious System

Using the strong pozzolanic activity of precipitation method nano-silica (PNS) to improve the early compressive strength and loose internal structure of the high volume slag powder-cement cementitious system. The influence of PNS on the compressive strength and the resistance to chloride ion permeability of high volume slag powder-cement cementing system were studied. The hydration products and pore structure of the system were analysed by XRD, TG-DSC and MIP. Research shows that with the increase of PNS content, the compressive strength of the specimens increases, especially the 7 d compressive strength. The strength of specimens with 5% (mass fraction, the same blow) PNS increases by 20%. The resistance to chlcride ion penetration capacity first increases and then decreaces. When PNS content is 3%, it reaches the optimal level, and its 28 d chloride ion diffusion coefficient is 44.8% lower than that without PNS. PNS can consume a large amount of Ca(OH)₂ in the early stage and generate more hydration products such as C-S-H gel, which makes the pore structure more compact and reduces the porosity. Incorporating PNS within the range also refines the pore size.