Review of Hypo Sludge, Metakaolin, and Sea Shell Ash as Supplementary Cementitious Materials for Eco-Efficient Concrete

The manufacturing of cement is a major source of CO2 emissions worldwide, which has raised interest in supplemental cementitious materials (SCMs).The impacts of Hypo Sludge Powder (HSP), Metakaolin Powder (MK), and Sea Shell Ash (SSA) as partial cement substitutes are examined in this study both separately and in combination.Replacement levels ranging from 5 to 25% were assessed.The performance of hardened concrete (compressive, tensile, and flexural strength, durability indices) and fresh concrete (workability) were examined.The findings indicate that whereas Hypo Sludge adds sustainability advantages with moderate performance losses at higher replacement levels, Metakaolin and Sea Shell Ash generally improve strength and durability at optimal dosages.At a total replacement level of 15-20%, ternary blends achieved strengths equal to or greater than control mixes, exhibiting enhanced microstructure and synergistic effects.