Effects of Silica Fume and Fly Ash as Partial Replacement of Cement on Strength of Concrete

Research for sustainable cement alternatives emerged because cement production causes major CO₂ emissions in the surrounding. This study examines the impacts of silica fume (SF) & fly ash (FA) as selective cement replacements in M50-grade concrete. An assessment of concrete properties regarding strength and durability was performed through a substitution of cement with 5% SF and FA at multiple replacement levels ranging from 0–25%. Research outcomes indicated that concrete with 5% SF combined with 20% FA reached its highest 28-day compressive strength at 60.51 MPa which presented a slight improvement beyond the control mix strength. Workability and slump retention improved best when using 25% fly ash as a cement substitution. An excessive amount of FA (more than 20%) resulted in a decrease of compressive strength measurements. Results from this study show that SF and FA jointly improve concrete properties and decrease environmental burden. Future examinations should analyze both the durability and financial stability and options for massive-scale implementation regarding responsible construction methods.