轻骨料对中等强度混凝土耐久性能影响的研究

Eeffect of lightweight aggregate on durability of moderate strength concrete

研究了不同掺量及种类的轻骨料配制的中等强度混凝土抗渗及抗冻性能,并通过对轻骨料及界面结构的观察研究,分析了轻骨料对中等强度混凝土耐久性能的影响机理。结果表明:对于水灰比较高的中等强度混凝土,轻骨料的掺入可提高混凝土耐久性,这是由于其可细化骨料附近水泥石的孔结构,使得界面区更为致密,而且可使新拌混凝土的含气量有所增加,说明其在混凝土内部具有"引气"作用。但是所选轻骨料吸水率不宜过高,因为其过多的开放连通孔又会对混凝土耐久性不利。本研究条件下,掺量50%的高吸水率粉煤灰陶粒配制的混合骨料混凝土抗渗性已于同水灰比的普通混凝土相当,其抗冻性甚至低于普通混凝土。

The impermeability and frost-resistance of moderate strength concrete prepared with different volume contents and varieties of lightweight aggregate （LWA） were tested, and through the examination of the microstructure of lightweight aggregate and interfacial zone, the in- fluence of lightweight aggregate on durability of moderate strength concrete was studied.The results showed that, as for the moderate strength con- crete prepared with a higher water-cement ratio, the mixing of lightweight aggregate into concrete can improve the concrete durability, that was be- cause it can refine the pore structure of the cement paste around aggregate, and made the microstructure of the interracial zone became denser, fur- thermore increased the air content of fresh concrete, which testified that the porous lightweight aggregate had ＂air-entraining＂ effect.However the water absorption of lightweight aggregate should not be too high, because the lightweight aggregate with excessive open and interconnected pore was disadvantageous to concrete durability.Under this study condition, the impermeability of combined aggregate concrete containing 50% volume content fly ash ceramsite with high water absorption was almost the same with that of ordinary concrete prepared with the same water-cement ra- tio, and the frost-resistance of the combined aggregate concrete was even worse than that of ordinary concrete.