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研究了轻骨料预湿程度对不同水胶比混合骨料混凝土28 d和90 d抗冻性能以及界面区微观结构的影响。结果表明:风干轻骨料自身的多孔结构在混凝土内部起到了“引气”的作用,同时其强烈的吸水作用使得界面层厚度约为预湿轻骨料的2倍,结构也较致密,故其配制的混凝土抗冻性最优。随着轻骨料预湿程度的增加,骨料引气及吸水作用均减弱,故混凝土抗冻性逐渐降低,但预湿轻骨料后期较强的返水作用可使其附近水泥石中的有害孔含量减少,显微硬度提高,界面结构得到持续改善,特别是当水胶比较低时对提高混凝土长期抗冻性能有利。当水胶比较高时,由于水泥石结构比较疏松,此时轻骨料在冻压下导致内部较高的含水率对混凝土抗冻性的不利影响更为突出。即使饱和预湿的轻骨料配制的低水胶比混合骨料混凝土,其抗冻性仍优于同条件下的普通混凝土。
The effects of light aggregate pre-wetting degree on frost resistance and interfacial zone microstructures at 28 d and 90 d with different W / C ratios of mixed aggregate concrete were studied. The results show that the porous structure of air-dried lightweight aggregate plays the role of “air-entraining” inside the concrete, and its strong water absorption makes the thickness of the interfacial layer about twice that of the pre-wet lightweight aggregate, and the structure is also denser , So the preparation of concrete frost resistance best. With the increase of pre-wetting degree of light aggregate, air-entrainment and water absorption of aggregate are weakened, so the frost resistance of concrete is gradually reduced. However, the strong backwater effect of pre-wet light aggregate can make it The content of harmful holes decreased, the microhardness increased, and the interface structure was continuously improved, especially when the water-binder ratio was low, which was beneficial to improve the long-term frost resistance of concrete. When the water-cement ratio is relatively high, the unfavorable influence of frost resistance of concrete is more prominent due to the loose cement structure. Even though the low water-cement ratio mixed aggregate concrete with saturated pre-wetted light aggregate is better than the ordinary concrete under the same conditions, the frost resistance is still better.