A comprehensive assessment of nanomaterials reinforced lightweight aggregate concrete containing high-volume artificial shale ceramsite

Abstract

Poor mechanical behavior of lightweight aggregate concrete limits its application. To improve this situation, nano-silica (NS) and carbon nanotubes (CNTs) were used in this study. The impact of NS and CNTs on fresh and mechanical properties, general microstructure and interfacial transition zone (ITZ) of lightweight aggregate concrete containing high-volume artificial shale ceramsite (ASC-LAC) was evaluated. Furthermore, economic sustainability was conducted to provide a comprehensive evaluation on the overall performance of ASC-LAC. Results showed that the synergic effects of NS and CNTs were positive when the replacement of NS and CNTs was smaller than 2.5 wt% and 0.25 wt%, respectively. Incorporating NS caused a decrease in both slump and air content, while adding CNTs caused a decrease in slump but a slight increase in air content. ASC-LAC incorporating 1.0 wt% NS and 0.10 wt% CNTs was found to have the best mechanical performance given a rise of 47.7 % and 17.0 % in compressive and flexural strength, respectively. However, given a higher NS and CNTs replacement (i.e., 2.5 wt% and 0.25 wt%, respectively), a worsened ITZ with less C-S-H gel was identified, which was responsible for the decreased concrete performance. Multi-criteria optimization results showed that ASC-LAC at a mono doped of 1.0 wt% NS or 0.10 wt% CNTs or combined 1.0 wt% NS and 0.10 wt% CNTs had better overall performance considering five-dimensional indices, i.e., slump, air content, compressive strength, flexural strength and cost efficiency.