氯离子对粉煤灰混凝土表层渗透性的影响

Influence of chloride ions penetration on surface permeability of fly ash incorporated concrete

采用不同配合比的混凝土试件浸泡在超纯水和Na Cl溶液中,定期测定浸泡环境下混凝土表层的渗透系数,研究氯离子渗透对粉煤灰混凝土表层渗透系数的作用规律。结合扫描电镜观察,在微观结构上分析氯离子及粉煤灰对混凝土表层渗透性能影响的机理。研究结果表明:掺入粉煤灰后,改善了水泥浆体与集料界面的过渡区结构,超纯水长期浸泡后,掺入粉煤灰样品的表层渗水系数显著降低,仅为普通混凝土试件的0.4左右;Na Cl溶液浸泡下,表层渗水系数初期的发展和粉煤灰掺量相关,浸泡90 d,粉煤灰15%(质量分数)掺量的混凝土,在Na Cl溶液浸泡的表层渗水系数小于超纯水浸泡的结果,掺量达到30%时,则大于超纯水浸泡的结果;浸泡150 d后,在Na Cl溶液浸泡下,2种粉煤灰掺量混凝土的表层渗透系数比超纯水浸泡中的有显著提高。

The influence of chloride penetration on the surface permeability of fly ash incorporated concrete was investigated. The surface permeability indices of different concretes as immersed in ultrapure water and Na Cl solution were measured and compared respectively at specific immersion ages. In addition, SEM was employed to observe the microstructures so that the mechanisms of the influences of chloride and fly ash on the surface permeability of concrete can be revealed. The results show that the incorporation of fly ash improves the interfacial transition zone between the bulk paste and aggregate particles; after a long period of immersion in ultrapure water, the surface permeability coefficient of fly ash incorporated concrete is much lower than that of pure cement concrete at the same age, that is to say,the value of the former is only 40% of the later. If immersed in Na Cl solution, the initial evolution of concrete surface permeability coefficient depends on the amount of fly ash incorporated, e.g. when immersed to 90 d, the surface permeability coefficient of the concrete with 15% fly ash replacement is lower than that immersed in ultrapure water,while the concrete with 30% fly ash replacement has higher surface permeability coefficient than that immersed in ultrapure water. However, at relatively long immersion period（immersed for 150 d）, the surface permeability indices of fly ash incorporated concretes are all significantly higher than those immersed in ultrapure water, irrespective of the replacement ratio of fly ash.