Reducing setting time of blended cement paste containing high-SO3 fly ash (HSFA) using chemical/physical accelerators and by fly ash pre-washing

Published

March 20, 2018

Author(s)

Franco Zunino, Dale P. Bentz, Javier Castro

Abstract

Reducing the carbon footprint of the cement industry has become one of the main concerns of researchers in the field. This study explores different strategies to reduce the setting retardation effect of high-SO3 fly ash (HSFA) on cement paste. The SO3 phase was found to correspond to hannebachite (CaSO3·0.5H2O). Chemical (calcium chloride), physical (fine limestone powder) and pre-washing strategies were investigated as means to reduce or eliminate the retardation. All of the strategies showed some potential to decrease the retardation effect. A combination of fine limestone powder and HSFA pre-washing showed almost the same accelerating power as calcium chloride, offering a good alternative where chloride incorporation is restricted. It was found that the retardation effect can be associated with a combined extension of the induction period and a depression of the initial silicate reaction of the clinker phases. A methodology to assess the hannebachite content based on a thermogravimetric analysis is proposed, allowing a good alternative control approach for field conditions or for where XRD or XRF equipment is not available.

Citation

Cement and Concrete Composites

Volume

90

Pub Type

Journals

Download Paper

https://doi.org/10.1016/j.cemconcomp.2018.03.018

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Keywords

Flue-gas desulfurization (FGD), hannebachite, hydration kinetics, isothermal calorimetry, supplementary cementitious materials, sustainability.

Citation

Zunino, F. , Bentz, D. and Castro, J. (2018), Reducing setting time of blended cement paste containing high-SO3 fly ash (HSFA) using chemical/physical accelerators and by fly ash pre-washing, Cement and Concrete Composites, [online], https://doi.org/10.1016/j.cemconcomp.2018.03.018, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=924230 (Accessed October 18, 2025)