Abstract: The influence rule of pore structure of three kinds of fine aggregate concrete on the mechanical properties was studied by low field nuclear magnetic resonance instrument, and the micro morphology of the three kinds of concrete was observed by scanning electron microscope. The research results show that the mixed sand concrete meeting the requirements of mechanical properties can be prepared by replacing part of natural sand with machine-made sand. Under the condition of constant water binder ratio, the mechanical property index of concrete with 50% replacement rate of machine-made sand is the best. The total porosity of mixed sand concrete is 3.4%, the proportion of micropore (r≤0.1 μm), small hole (0.1 μm＜r≤1 μm), large hole (1 μm＜r≤1 000 μm) is all smaller than that of natural sand concrete and machine-made sand concrete, and the uniformity of pore size distribution is also better than that of natural sand concrete and machine-made sand concrete. The hydration products of cement slurry and appropriate amount of stone powder in mixed sand concrete make the interface transition zone more compact, which can improve the internal structure and enhance the mechanical properties.

Key words: highway engineering; mixed sand; concrete; pore structure; mechanical properties; micro morphology

摘要： 通过低场核磁共振仪分析了3种不同细集料混凝土孔隙结构对力学性能的影响规律，并采用扫描电镜对这3种混凝土的微观形貌进行了观察。研究结果表明：利用机制砂取代部分天然砂可配置出满足力学性能要求的混合砂混凝土。在保证水胶比不变情况下，机制砂取代率为50%的混凝土力学性能指标最佳；混合砂混凝土总孔隙率为3.4%，微孔(r≤0.1 μm)、小孔(0.1 μm＜r≤1 μm)、大孔(1 μm＜r≤1 000 μm)占比均小于天然砂混凝土和机制砂混凝土，孔径分布均匀性也优于天然砂混凝土和机制砂混凝土；混合砂混凝土中水泥浆体与适量石粉的水化产物使界面过渡区更严实，能改善内部结构，有利于提升力学性能。

关键词: 道路工程；混合砂；混凝土；孔隙结构；力学性能；微观形貌