Precast, Prestressed Concrete Made with Fly Ash-Based Alkali-Activated Cement: Mixture Design and Procedure, Mechanical, and Structural Performance
2021-06
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Precast, Prestressed Concrete Made with Fly Ash-Based Alkali-Activated Cement: Mixture Design and Procedure, Mechanical, and Structural Performance
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2021-06
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Abstract
Alkali-activated concrete (AAC), a potentially environmentally friendly alternative to portland cement concrete (PCC), contains no portland cement and typically uses recycled waste
materials as its binder. It is made with chemical activators and aluminosilicate precursors,
commonly fly ash. Elevated temperature curing is required for many AACs, which makes the
precast concrete market a promising application. Most precast concrete facilities already have the
infrastructure necessary to heat, cure, and produce specimens at temperatures above ambient.
However, there are limited data available on the structural performance of large membersfabricated
with alkali-activated precast concrete. This research investigated the practicality of developing and
implementing a fly ash-based AAC mixture suitable for making precast, prestressed concrete beams
using the existing infrastructure at a regional precast plant. The AAC mixture was developed to conform to required production parameters, includingbatching and setting time constraints, curing time and temperature limitations, and utilization of
the Class C fly ash and aggregates currently used at the precast plant. More than 40 different mortar
mixtures were investigated, and the most suitable mixture design was used to make precast,
prestressed concrete beams at the precast plant. Fresh properties including flow, slump, air content,
and unit weight were measured during laboratory testing; hardened properties including
compressive strength, modulus of elasticity, modulus of rupture, and splitting tensile strength were
also characterized. Flexural and shear testing of full-scale prestressed precast AAC beams was
conducted and the results were compared to control beams made with PCC. An unplanned increase
in the water content of the AAC mixtures and reduced curing temperatures at the plant had a
negative impact on the compressive strength of the AAC specimens. However, structural
performance results indicated the AAC beam performance aligned with the calculated predictions.
In addition to performance data, a discussion of the observations made during this research as well
as future considerations for implementing AAC in precast concrete applications is also provided.
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University of Minnesota M.S. thesis. June 2021. Major: Civil Engineering. Advisors: Mary Christiansen, Benjamin Dymond. 1 computer file (PDF); ix, 149 pages.
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Magnuson, Grant. (2021). Precast, Prestressed Concrete Made with Fly Ash-Based Alkali-Activated Cement: Mixture Design and Procedure, Mechanical, and Structural Performance. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/224483.
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