Nano-engineered the interfacial transition zone between recycled fine aggregates and paste with graphene oxide for sustainable cement composites

The high water absorption and porosity of recycled aggregate often led to a compromised interface transition zone (ITZ), thereby adversely impacting the mechanical properties and durability of recycled aggregate concrete. This research presents a feasible, straightforward, and targeted strategy to reinforce the ITZ between recycled fine aggregate (RFA) and paste by utilizing RFA particles adsorbed with graphene oxide (GO), termed WGO@RFA. The experimental outcomes demonstrate that incorporating WGO@RFA can enhance the 28-day compressive and flexural strengths of recycled mortars by approximately 25 % and 20 %, respectively, compared to mortars containing only RFA. Furthermore, it can decrease the water sorptivity and chloride ion diffusion coefficients of recycled mortars (28 days) by about 20 % and 27 %, respectively. Notably, using WGO@RFA particles offers significant advantages, such as enhanced mechanical strengths, reduced transport properties, and a densified microstructure within the ITZ, compared to the conventional method of modifying the cement matrix with GO and then binding it with RFA. Highlighting the application of WGO@RFA shows a targeted strengthening of the ITZ, as the sub-nanometer thickness of GO adsorbed on the uneven RFA surface facilitates localized cement hydration at the ITZ. The findings of this research offer novel avenues for reusing aggregate and developing sustainable concrete.