Case Studies in Construction Materials (Jul 2024)
Influence of Multi-walled Carbon Nanotube (MWCNT) on flexural behavior and microstructure characteristics of geopolymer concrete beams
Abstract
This experimental study delves into the impact of Multi-Walled Carbon Nanotubes (MWCNTs) on Geopolymer Concrete (GPC), investigating their effect on compressive strength and load deflection behaviour. MWCNT concentrations ranging from 0.02% to 0.16% were employed to examine their influence on the structural performance of 1500 mm (L) x 150 mm (B) x 150 mm (D) concrete beams. The findings derived from this investigation yielded several significant conclusions. The outcome of research identified the optimum MWCNT dosage for enhancing compressive strength at 0.12%, resulting in a substantial strength of 29.78 MPa. However, surpassing this concentration led to a decline in concrete strength. Notably, a remarkable 26.62% increase in compressive strength was observed with the 0.12% MWCNT concentration when compared to reference specimens. In analysing structural performance, it was observed that the energy absorption capacity (EAC) exhibited consistent behavior up to 0.6% addition of MWCNT. At 0.12% MWCNT inclusion, the EAC of the GPC reached its peak value at 6116 kN.mm. Stiffness maintenance mirrored the EAC trends up to 0.1% MWCNT, beyond which a decrease in stiffness was noted with higher MWCNT concentrations. Furthermore, the Density Index (DI) of GPC beams was sustained up to 0.1% MWCNT, after which DI began to increase. The Flexural Toughness Factor (FTF) of GPC beams retained its value up to 0.06%. However, addition of MWCNT with a higher concentration of 0.12% MWCNT, declined its flexural strength. Additionally, Scanning Electron Microscopy (SEM) images revealed a denser internal structure at the optimal dosage of 0.12% MWCNT. Subsequent additions of MWCNT led to increased agglomeration, potentially hampering effective interaction between the binder, MWCNT, and activator within the concrete matrix. These findings contribute to obtain the optimised MWCNT concentrations for superior performance in Geopolymer Concrete applications.
