Mixture portioning for Lock 25 expansion

<jats:p>This report documents the development, proportioning, and characterization of four specialized concrete mixtures required for the construction of the new 1,200 ft lock at Lock and Dam 25, near Winfield, Missouri, which is under the Navigation and Ecosystem Sustainability Program (NESP). In support of the US Army Corps of Engineers–St. Louis District, the US Army Engineer Research and Development Center designed the government-furnished concrete mixtures to meet the performance demands of large-scale mass and underwater concrete placements. The four mixtures include interior mass, exterior mass, underwater mass, and a combined underwater concrete and drilled shaft mixture. Mixture development followed a tiered approach consisting of three phases: an initial scoping phase for preliminary screening, a candidate mixture phase for detailed evaluation, and a final characterization phase for selected mixtures. Each phase involved standardized testing in accordance with USACE Engineer Manual 1110-2-2000. This report presents the mixture designs, testing methodologies, and key results from each development phase to support future mass concrete construction under NESP.</jats:p>