Physical and mechanical properties and micro characteristics of fly ash-based geopolymer paste incorporated with waste Granulated Blast Furnace Slag (GBFS) and functionalized Multi-Walled Carbon Nanotubes (MWCNTs)

摘要

Geopolymers are highly durable and have favorable mechanical properties, and are thus regarded as an eco-friendly alternative to traditional ordinary Portland cement binder. In this study, MWCNTs are obtained through a modification method using a compound of nitric acid and sulfuric acid, and are then dispersed using three types of dispersants. Fly ash-based geopolymers are prepared to validate the effectiveness and feasibility of adopting 0.05 wt. %, 0.10 wt.%, and 0.15 wt.% functionalized MWCNTs and substitution ratios of 10 %-40 % of fly ash with GBFS. The structure and dispersity of the functionalized MWCNTs in aqueous solutions are characterized using FT-IR and TEM, respectively. Then, the setting time, water absorption capacity, and mechanical behaviors are evaluated. In addition, SEM-EDS, FT-IR, TG-DSC, Si-29 NMR, and XRD are employed to investigate the morphology, elemental components, mineralogical phases, and geopolymerization degree of the gel products. The experimental results show that the functionalized MWCNTs comprise COOH and OH groups and can be uniformly dispersed in aqueous solution containing SDS dispersant. Furthermore, geopolymer paste incorporated with 0.1 wt.% functionalized MWCNTs and having 30 % substitution of fly ash with GBFS exhibits a higher compressive and flexural strength and a lower water absorption capacity compared with all other geopolymer pastes.