矿物掺合料对蒸养混凝土传输性能和孔结构的影响

为提高混凝土预制构件耐久性,试验研究了单掺及复掺矿物掺合料对蒸养混凝土毛细吸水性和抗氯离子渗透的影响,结合可蒸发水含量法测孔结构探讨了作用机理。结果表明:矿物掺合料在低水胶比下能更为有效地改善蒸养混凝土的传输性能;在脱模和28d龄期时,矿物掺合料对蒸养混凝土传输性能的改善效果从高到低依次为硅灰、偏高岭土、矿渣、粉煤灰;90d龄期时,偏高岭土与硅灰相当,且均优于矿渣和粉煤灰;混凝土孔结构与传输性能关系密切,孔隙率降低和孔径细化是蒸养混凝土传输性能得以改善的主要原因。

Influence of mineral admixtures on transportation properties and pore structure of steam-cured concrete

For improving the durability of prefabricated components made of steam-cured concrete, the effect of individual and compound mineral admixture on the capillary absorption coefficient and resistance of chloride ion penetration were analyzed, and its mechanism was studied with concrete porosity tested by the evaporable water content method. Results indicated that the transportation properties of steam-cured concrete was greatly improved by mineral admixture at low water-binder ratio. The improvement effect of mineral admixture on the transportation properties of steam-cured concrete from the greatest to the least is silica fume (SF), metakaolin (MK), ground slag (GS) and fly ash (FA) at the stage of demould and 28-day. The effect of MK was equivalent to that of SF at 90-day stage, and these two mineral admixtures were superior to GS and FA. The concrete pore structure had close relationship with transportation performance. The decrease of porosity and the refinement of pore size contributed mostly to the improvement of the transportation properties of steam-cured concrete.