Extent of stabilized streambed region by alkaline activated cement around bridge piers and abutments in clear water condition

Bridge scour remains one of the leading causes of hydraulic failure in bridge foundations, posing severe economic and safety risks. Conventional countermeasures such as riprap may be costly, while Portland cement raises sustainability concerns. This study investigates the use of Alkaline-Activated Cement (AAC) as an innovative and eco-friendly stabilization method to determine the optimal extent of treated streambeds around cylindrical and rectangular piers, as well as wing-wall and vertical-wall abutments. Laboratory flume experiments were conducted under flow intensities of 0.75 and 0.9, with trial-and-error testing applied to establish effective protection geometries. Results show that with the AAC optimal extent found in each case, maximum scour depths reduced by 70-80% compared to untreated conditions and successfully shifted scour holes downstream without compromising stability. The findings highlight AAC-treated streambeds as a practical and sustainable countermeasure for bridge scour, while also underscoring the need for further research on the influence of flow angle of attack, Froude number, and live-bed conditions to refine design guidelines.