Enhancement effect of multiwalled carbon nanotubes on mortars prepared with different grades of recycled fine aggregates.

Recycling construction waste while reducing natural sand mining has proven to be a sustainable option for environmental protection. Multiwalled Carbon nanotubes (MWCNTs) have the potential to enhance the mechanical characteristics of recycled fine aggregates (RFA) mortars. This research aims to explore the feasibility of applying MWCNTs in the RFA mortars. Various concentrations of MWCNTs were added to different grades of RFA-prepared mortar to obtain an optimal concentration. Besides, the scanning electron microscopy (SEM) analysis was conducted to observe the microstructure inside the RFA-prepared mortar. The nuclear magnetic resonance (NMR) test was used to test the pore structure of mortars. The results show that the RFA quality is relevant to the initial compressive strength of the RFA resource. The optimal concentration and the enhancement effect of MWCNTs on the three different RFA-prepared mortars are obtained with mechanical properties proven. The SEM images show that more cracks exist in the RFA-prepared mortars, and the NMR test shows that the number of pores inside the RFA-prepared mortars is significantly larger than that in the natural sand mortar. Nevertheless, an appropriate amount of MWCNTs can create a dense network and great bond inside the mortar, improving its mechanical properties. [ABSTRACT FROM AUTHOR]