Jing Zhang ^1* Xiaolei Zhang ²

• ¹ Inner Mongolia Technical College of Construction, Hohhot, China
• ² Inner Mongolia Baotou Steel Union Co., Ltd., Baotou, China

The integration of carbon nanotubes (CNTs), specifically multi-walled carbon nanotubes (MWCNTs), into concrete matrices has emerged as a pivotal area of advanced materials research. This research is focused on leveraging the inherent strength and conductivity of CNTs to augment the properties of concrete. A key objective of this research is the optimisation of the interfacial transition zone (ITZ), which plays a pivotal role in determining the performance of composite materials. The incorporation of CNTs has led to significant improvements in the ITZ, demonstrating the potential of this approach. The present study examines the precise mechanisms by which MWCNTs reinforce ultralight foamed concrete, guided by empirical data. Raman microscopic spectroscopy was employed to meticulously examine the stress transfer dynamics at the MWCNT-concrete interface, with a particular focus on the impact of MWCNT functionalisation with carboxyl (-COOH) groups. The findings demonstrated that the incorporation of 0.4 wt% MWCNT-COOH into a 200 kg/m³ dry density ultralight foamed concrete mix resulted in a significant enhancement of compressive strength by 75% and flexural strength by 236%. This underscores the crucial role of -COOH groups in enhancing interfacial bonding and stress distribution. These findings not only corroborate existing knowledge on CNT reinforcement strategies but also expand it, emphasising the value of tailored surface modifications for improving load transfer efficiency. The controlled -COOH functionalisation of MWCNTs emerges as a strategic pathway to enhance the composite's mechanical resilience, particularly in terms of compressive and flexural strengths. Consequently, our study emphasises the significance of interface engineering via chemical modification for optimising CNT-reinforced cementitious composites. This paves the way for future advancements in dispersion techniques, dosage optimisation, and the exploration of alternative functional groups to further elevate concrete material properties.