Title:
Pozzolan Mitigated Alkali-Silica Reaction in Hungry Horse Dam: 70-Year Contrast Between Interior and Exterior Concretes (Prepublished)
Author(s):
Mahipal Kasaniya, Michael Thomas, Catherine Lucero, Ashlee Hossack, Ted Moffatt, and Doug Hooton
Publication:
Materials Journal
Volume:
Issue:
Appears on pages(s):
Keywords:
alkali-silica reaction; durability; fly ash; get pat test; Hungry Horse Dam; microstructure; pozzola; thermogravimetry
DOI:
10.14359/51750604
Date:
3/19/2026
Abstract:
This paper presents an experimental and analytical study conducted on concrete cores extracted from the Hungry Horse Dam, located in Montana, United States. The dam, constructed over a five-year period (1948–1953), represents the first major application of fly ash as a pozzolan for the partial replacement of portland cement in structural and mass concrete. Two cores were obtained from the same borehole at different depths, representing the interior and exterior mixtures. The measured mechanical properties of both concretes are largely consistent with values reported in the literature. Bulk electrical resistivity tests reveal significant differences in concrete quality, which are subsequently substantiated by microstructural and analytical investigations that identify variations in both the cementitious materials used and the current condition of the concretes. Microstructural examination exhibits evidence of deleterious alkali-silica reaction in the exterior concrete, while both interior and exterior concretes are found to contain reactive aggregates, as confirmed by petrographic analysis and gel pat testing. The study highlights and attempts to explain the remarkable long-term concrete durability enabled by a pozzolan after more than 70 years of deterioration-free field service offered by the Hungry Horse Dam concrete.