硅灰对再生混凝土界面过渡区的影响

Effect of Silica Fume on Interfacial Transition Zone of Recycled Concrete

为改善再生混凝土的力学和耐久性能,以硅灰为增强材料对再生混凝土进行改良。研究了硅灰对再生混凝土3 d、28 d、90 d抗压强度和28 d、90 d抗氯离子渗透性能的影响。结合扫描电镜、显微硬度等微观观测手段,分析了28 d再生混凝土试样微观结构和性能变化。采用压汞法测试了再生混凝土的孔结构参数,探究硅灰对再生混凝土孔隙性能的影响。结果表明:硅灰可以提升再生混凝土的抗氯离子渗透性能,随掺量的增加提升效果先增后减;掺入硅灰可以改善再生混凝土多重界面过渡区结构,增加界面过渡区(ITZ)显微硬度,降低孔隙率。再生混凝土内部存在较多有害孔隙,硅灰可以细化孔隙结构,降低孔隙率,掺量为6%时效果最佳。

In order to improve recycled concrete s mechanical properties and durability,silica fume was used as a reinforcing material.The influence of silica fume on the compressive strength at 3 days,28 days,and 90 days and the ability to resist chloride ion penetration at 28 and 90 days for the recycled concrete were investigated.The microstructure of recycled concrete at 28 days was analyzed by micro-testing equipment such as scanning electron microscopy,microhardness tester.The Mercury Intrusion Porosimetry was used to investigate pore structure parameters and analyze the effect of silica fume on the pore properties.The results show that silica fume is beneficial to improve the ability to resist chloride ion penetration for recycled concrete,and the strengthening effect increases first and then decreases with the increasing of silica fume dosage.Silica fume improves the structure of multiple interfacial transition zones for recycled concrete,increasing ITZ microhardness and reducing ITZ porosity.There are many harmful pores in recycled concrete,silica fume refines the pore structure and reduces the porosity of the recycled concrete,the improvement effect is the best at the dosage of 6%.