The production of portland cement - the key ingredient in concrete - generates a significant amount of carbon dioxide. However, due to its incredible versatility, availability, and relatively low cost, concrete is the most consumed synthetic material on the planet. One method of reducing concrete's contribution to greenhouse-gas emissions is the use of fly ash to replace a significant amount of the cement. This paper compares two experimental studies that were conducted to investigate the shear strength of full-scale beams constructed with both high-volume fly ash concrete (HVFAC) - concrete with at least 50% of the cement replaced with fly ash - and conventional concrete (CC). The primary difference between the two studies involved the amount of cementitious material, with one mix having a relatively high-total cementitious content [502kg/m3 (850lb/yd3)] and the other mix having a relatively low-total cementitious content [337kg/m3 (570lb/yd3)]. Both HVFAC mixes used a 70% mass replacement of portland cement with Class C fly ash. Each of these experimental programs consisted of 16 beams - eight constructed from HVFAC and eight constructed from CC - with three different longitudinal reinforcement ratios. The beams were tested under a simply supported four-point-loading condition. The experimental shear strengths of the beams were compared with both the shear provisions of selected standards (United States, Australia, Canada, Europe, and Japan) and a shear database of CC specimens. This comparison indicates that the HVFAC beams possess superior shear strength compared with the CC beams.