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Title: Shrinkage of Alkali-Activated Combined Slag and Fly Ash Concrete Cured at Ambient Temperature

Author(s): Alexandre Rodrigue, Benoit Bissonnette, Josée Duchesne, and Benoit Fournier

Publication: Materials Journal

Volume: 119

Issue: 3

Appears on pages(s): 15-23

Keywords: alkali-activated materials; durability; fly ash; shrinkage; slag

Date: 5/1/2022

Abstract:
In alkali-activated slag/fly ash systems, autogenous shrinkage represents the dominant type of shrinkage. Increasing contents of added water and fly ash contents both reduce the importance of autogenous shrinkage. For a constant added water content (AW/B = 0.14), increasing the fly ash content from 20 to 40% resulted in an autogenous shrinkage reduction on paste specimens (from 5644 to 2168 μm/m at 28 days). The autogenous shrinkage of control ordinary portland cement (OPC) paste (water-cement ratio [w/cm] of 0.50) reached 505 μm/m. Alkali-activated slag/fly ash mixtures of this study had average pore radius values ranging between 3.40 and 3.55 nm, compared to 8.25 nm for the OPC paste control specimen. Smaller pores and high sodium concentrations result in higher internal pressure during the process of self-desiccation and could be the main causes for the very high autogenous shrinkage values recorded.


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