Rheological Properties, Setting Time and Compressive Strength of Low Calcium Fly Ash Geopolymer

Abstract

Abstract: The geopolymer has the advantages of low carbon and environmental protection, but for low calcium fly ash geopolymer, however, there exists some issues including high viscosity, excessively long setting time at room temperature and low strength. The effects of different factors including liquid/solid ratio, alkaline solution concentration, superplasticizer content and slag content on rheological properties, setting time and compressive strength of low calcium fly ash geopolymer were investigated. The results show that the modified Bingham model fits relatively well with the rheological properties of fresh geopolymer. Yield stress is affected most by slag content, and increases with the increase of slag content. Plastic viscosity is affected most by liquid/solid ratio, and decreases significantly with the increase of liquid/solid ratio. The setting process is rather slow for pure low calcium fly ash geopolymer at room temperature, and the initial setting time is over 8 h and the final setting time is over 23 h. When liquid/solid ratio is 0.40, alkaline solution concentration is 29% (mass fraction) and slag content is 25% (mass fraction), the corresponding initial and final setting time are 54 and 145 min, respectively, and the 7 d compressive strength is 23.2 MPa. Adding 0.3%~0.5% (mass fraction) polycarbonate superplasticizer, the 28 d compressive strength of pure fly ash geopolymer increases by around 20%。

Key words: low calcium fly ash, geopolymer, viscosity, yield stress, setting time, compressive strength

CLC Number:

TU526

YANG Mengjun, CAO Yidong, LIN Chang, XU Shuying, PAN Lisha. Rheological Properties, Setting Time and Compressive Strength of Low Calcium Fly Ash Geopolymer[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2023, 42(5): 1721-1730.

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