氯离子与硫酸根离子在水泥浆体中的耦合扩散

Coupled Diffusion of Chloride and Sulfate Ions in Cement Pastes

摘要:

研究了不同复合盐环境下Cl⁻与SO42-在水泥浆体中的耦合扩散。结果表明：对于普通硅酸盐水泥浆体，复合氯盐溶液中的SO42-早期会抑制Cl⁻扩散，后期则转为促进作用；与复合氯盐溶液相比，亚硫酸盐溶液中SO42-对Cl⁻扩散的抑制作用更强，但该抑制作用随浸泡时间延长而减弱；普通硅酸盐水泥浆体对Cl⁻的吸附能力较弱，在SO42-作用下释放的自由Cl⁻更易向浆体内部扩散，对Cl⁻总扩散进程影响显著；矿渣-水泥浆体在单氯盐、复合氯盐及亚硫酸盐溶液中的180 d自由Cl⁻扩散系数分别为0.96×10⁻¹²、0.81×10⁻¹²、0.77×10⁻¹² m²/s；矿渣-水泥浆体对Cl⁻的吸附能力较强，SO42-作用下表层浆体释放的自由Cl⁻易被内部浆体的水化产物重新吸附，对总体扩散进程影响较小。

Abstract:

The coupled diffusion of Cl⁻ and SO42- in cement pastes under different composite salt environments was investigated. The results show that for ordinary Portland cement pastes， SO42- in composite chloride solution inhibits Cl⁻ diffusion in the early stage but turns to promote it in the later stage. Compared to composite chloride solution， SO42- in sulfite solution exerts a stronger inhibitory effect on Cl⁻ diffusion， yet this inhibition weakens with time extension. The adsorption capacity of ordinary Portland cement pastes for Cl⁻ is weak， and the free Cl⁻ released under SO42- attack diffuse is more readily into the interior of the pastes， leading to significant influence on the overall Cl⁻ diffusion process. For slag-cement， the 180 d free Cl⁻ diffusion coefficients in single chloride， composite chloride and sulfite solutions are 0.96×10⁻¹²， 0.81×10⁻¹² and 0.77×10⁻¹² m²/s， respectively. Slag-cement pastes have strong adsorption capacity for Cl⁻. Free Cl⁻ released from the superficial pastes is readily re-adsorbed by the hydration products of the inner pastes， resulting in a comparatively minor impact on the overall diffusion process.