Enhancing the performance and environmental impact of alkali-activated binder-based composites containing graphene oxide and industrial by-products. (17th May 2021) - Ho, Van Dac
Highlights: Graphene oxide (GO) is added to waste-based alkali-activated binder (AAB) mortars. Two GO dosages of 0.05% and 0.1% were used in the mixes. Mortars with 0.05% and 0.1% GO have better properties than control mixes. Oxygen functional groups of GO sheets have been reduced in alkaline solution. Interactions between GO and hydration products decrease crack propagations in mixes. Abstract: The growing production of industrial by-products, such as fly ash (FA), ground granulated blast furnace slag (GGBS), and lead smelter slag (LSS), has resulted in significant negative impacts on the environment. Meanwhile, the high demand for ordinary Portland cement (OPC) and the over-exploitation of natural sand (NS) has also negatively impacted the ecosystem. The use of the mentioned industrial by-products to replace OPC and NS offers great potential for reducing the environmental impact of both the industrial wastes and conventional concrete. This study investigates the possible improvements to mechanical and durability properties of combined FA and GGBS-based alkali-activated binder (AAB) mortars prepared with NS and LSS sands through the addition of graphene oxide (GO). The results show that the increase of GGBS content in the binder of AAB composites (i.e. 20% and 50% GGBS) results in a significant increase in compressive and tensile strengths, and a decrease in drying shrinkage, flowability, and water absorption of the mortars. It is found that mortars with 0.05% and 0.1% GO additives provide better mechanical and durability properties than the control mortars. The study also shows that oxygen functional groups of GO sheets have been reduced in alkaline solution, and they were turned into the form of reduced graphene oxide (rGO) sheets with a higher wrinkling degree in their shapes. The better performance of AAB mortars containing GO additives is attributed to the improvement of the gel matrix formed through the combination of chemical and mechanical interactions between rGO sheets and the gel products. The outcomes of this study point to the great potential of the combined use of waste materials and GO additives to enhance the performance of AAB composites.