Magnuson, Grant2021-09-242021-09-242021-06https://hdl.handle.net/11299/224483University of Minnesota M.S. thesis. June 2021. Major: Civil Engineering. Advisors: Mary Christiansen, Benjamin Dymond. 1 computer file (PDF); ix, 149 pages.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.enThesis or Dissertation