Fang, G;
Zhang, M;
(2017)
Autogenous shrinkage of alkali-activated fly ash slag paste.
In:
Proceedings of the 37th Annual Cement and Concrete Science Conference.
IOM³: London, UK.
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Abstract
The autogenous shrinkage of alkali-activated fly ash/slag (AAFS) pastes during first 24 h after casting is an important engineering property, as it significantly contributes to ultimate shrinkage and cracking risk. However, the studies on this property are still limited. The objective of this work is to provide a better understanding of autogenous shrinkage of AAFS pastes at very early age (<24 h). The autogenous shrinkage of AAFS pastes with 10%, 20% and 30% slag replacement ratios of fly ash are estimated. A series of tests including workability, setting time and chemical reaction tests are conducted to investigate shrinkage mechanism of AAFS pastes. The results show that the ultimate autogenous shrinkage and the highest shrinkage rate of AAFS pastes increases significantly from 1271 to 1740 µɛ and from 201 to 943 µɛ/h respectively as slag replacement ratio increases from 10% to 30%. This is likely because the additional slag contents accelerate the formation of aluminosilicate gels and result in reorganization and rearrangement of microstructures. Additionally, AAFS paste with a larger autogenous shrinkage exhibits a worse workability and shorter setting time. The different reaction processes lead to the different early-age autogenous shrinkage of these AAFS mixtures.
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