Synergistic effects of graphene oxide and fly ash on rheology, mechanical properties, and microstructure of highly-flowable cementitious grouts

Abstract

Due to their excellent mechanical strength and low pric, cementitious grouts have emerged as the popular for grouting applications. However, excessive use of cement results in significant energy consumption and associated carbon emissions, which is a concern from a sustainability perspective. In this study, inexpensive industrial waste fly ash (FA) was used to enhance the performance of graphene oxide (GO)-based cementitious grouts. The influence of varying dosages of GO and FA on the rheology, mechanical strength, durability, and microstructure development of cementitious pastes was investigated. The results show that adding FA to GO-based cementitious grouts improves the workability of the paste. The high-flowability cementitious grouts with combined GO and FA exhibit Bingham's fluid behavior, indicating that the synergistic effect of GO and FA does not alter the flow behavior of the paste. Further, the relationship between the rheological parameters of the modified paste and time was developed. For 0.03 wt% GO and 20 wt% FA incorporation, the flexural and compressive strengths of the paste at 28 days increased by 28.5% and 30.4%, respectively, compared to the blank group. The chloride ion penetration coefficient at 180 days was 1.007, indicating that FA could effectively replace a portion of the cement while enhancing the durability of the grout. Microstructural investigations confirmed that the synergistic effect of GO and FA does not generate new hydration products. GO accelerates the hydration reaction and activates the secondary pozzolanic effect of FA, forming more hydration products and thereby enhancing the mechanical strength and durability of the grout.