Influence of metakaolin and residual cement sludge from ready-mix concrete on strength and durability properties of concrete microstructure

Strength and durability characteristics of the concrete partially substituted with waste by-products have been reported. The optimal cement replacement percentage with cement sludge and metakaolin has been experimentally verified. The plausibility of replacing cement sludge and metakaolin with cement in concrete has been assessed based on test results. The percentage proportions of cement sludge were varied between 2% and 10%, increasing in 2% increments by weight of cement, with the optimal content identified as 4%. Subsequently, the metakaolin content was tested in the range of 3% to 15% by weight of cement, with the optimal proportion found to be 9% when combined with 4% cement sludge. An empirical model has been established between the 28-day compressive and flexural strength to assess the strength. The microstructure of cement sludge and metakaolin incorporated mix has been evaluated.