A Comparative Study of the Properties of Recycled Concrete Prepared with Nano-SiO(2) and CO(2) Cured Recycled Coarse Aggregates Subjected to Aggressive Ions Environment

This research focused on the modification effects on recycled concrete (RC) prepared with nano-SiO(2) and CO(2) cured recycled coarse aggregates (RCA) subjected to an aggressive ions environment. For this purpose, RCA was first simply crushed and modified by nano-SiO(2) and CO(2,) respectively, and the compressive strength, ions permeability as well as the macro properties and features of the interface transition zone (ITZ) of RC were investigated after soaking in 3.5% NaCl solution and 5% Na(2)SO(4) solution for 30 days, respectively. The results show that nano-SiO(2) modified RC displays higher compressive strength and ions penetration resistance than that treated by carbonation. Besides, we find that ions attack has a significant influence on the microcracks width and micro-hardness of the ITZ between old aggregate and old mortar. The surface topography, elemental distribution and micro-hardness demonstrate that nano-SiO(2) curing can significantly decrease the microcracks width as well as Cl(−) and SO(4)(2−) penetration in ITZ, thus increasing the micro-hardness, compared with CO(2) treatment.