Reinforcing effects on Portland cement paste with graphene oxide obtained Green chemistry methods

ABSTRACT The main objective of this paper is to synthesize graphene oxide (GO) in a more sustainable way and add it to Portland cement paste. The most commonly used method of obtaining GO is the Hummers method, in which the washing of the material is done with water, resulting in large amounts of aqueous acid waste. This process leads to environmental sustainability problem, due to the possible damages to the environment. Aiming for a modern approach in the precepts of green chemistry for obtaining GO, it is proposed to replace the washing with water by neutralizing the solution with calcium carbonate to reduce these toxic residues. To verify the efficiency of green synthesis, physicochemical comparisons of GO samples obtained by both the Hummers method (GO) and the green method (GOv) were performed. The samples were analyzed by XRD, FTIR and RAMAN,and SEM. The analyses of the GOv suspension did not indicate the presence of new crystalline phases, but the formation of the gypsum phase was observed in the dry sample in the hot chamber. The results showed the efficiency in the production of GO. For the production of Portland cement paste, we added a proportion of 0,1; 0,2; 0,3; 0,4; 0,5; 0,75 and 1% of GOv and, then compressive strength tests were performed on the specimens. A maximum efficiency in the mechanical strength property was observed with addition of 0.3% of GOv in the traces. In comparative studies of electron microscopy in the 0.3% traces against 1.0% of GOv traces, the aggregation of GO lamellae in the traces with higher concentration can be observed, which results in lower resistance of the latter. This research presented a proposal with less environmental impact for the production of cement composites GO by a simple method.