A Comparative Study of the Properties of Recycled Concrete Prepared with Nano-SiO2 and CO2 Cured Recycled Coarse Aggregates Subjected to Aggressive Ions Environment

Abstract

This research focused on the modification effects on recycled concrete (RC) prepared with nano-SiO2 and CO2 cured recycled coarse aggregates (RCA) subjected to an aggressive ions environment. For this purpose, RCA was first simply crushed and modified by nano-SiO2 and CO2, 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% Na2SO4 solution for 30 days, respectively. The results show that nano-SiO2 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-SiO2 curing can significantly decrease the microcracks width as well as Cl− and SO42− penetration in ITZ, thus increasing the micro-hardness, compared with CO2 treatment.

A Study on the Cement Gel Formation Process during the Creation of Nanomodified High-Performance Concrete Based on Nanosilica

“…The nano-modification of concrete with nanosilica [ 12 , 13 , 18 , 19 , 23 , 24 , 25 , 35 , 41 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 ] has already shown efficiency in improving the properties of concrete, but still requires a solution for many issues. The main problem associated with the introduction of nanoparticles into cement-based materials is how to evenly distribute them in the matrix [ 23 ].…”