A mix design method of fly ash geopolymer concrete based on factors analysis

The effect of mix proportion of geopolymer concrete on compressive strength has been studied in detail in many previous studies, but there is a lack of a proposed mix design method. This research proposed a mix design method for low calcium fly ash geopolymer concrete (FAGC) by finding the key factors that affect the workability and compressive strength of FAGC. The experiment results showed that the workability is governed by the water content. The data from the experiment and the published literature indicated that the strength is independent of fly ash content and AS/FA ratio, and decreases linearly with the increase of the water to alkaline activator ratio, where the alkaline activator refers to Na2O and effective SiO2 from the alkaline solution. There is a limit for the SiO2/Na2O ratio beyond which additional SiO2 no longer improves the strength. Based on the factors, a new method was proposed to design the mix proportion of FAGC. Target compressive strengths ranging from 30 MPa to 80 MPa at 3 days and target slump of 150 mm were achieved with laboratory experiments, using the proposed mix design method and a new fly ash. Therefore, this research paper provided a novel mix design method for FAGC that allows for high strength and excellent workability at the same time. (C) 2020 Elsevier Ltd. All rights reserved.