Optimizing concrete performance through metakaolin and flyash incorporation: a critical appraisal of regression modeling and design code applicability

ABSTRACT

An investigation into the use of metakaolin (MK) and fly ash (FA) as partial cement replacements in concrete was conducted to enhance the sustainability of the construction industry. The MK and FA were incorporated into the concrete mix design by weight, replacing a portion of the portland cement content. The replacement percentages varied in two sets: 5%, 7.5%, 10%, 12.5%, and 15% for MK; and 5%, 10%, 15%, 20%, and 25% for FA. Workability of the fresh concrete was evaluated using the slump cone test to identify the optimal replacement level. Subsequently, the mechanical properties of the hardened concrete were investigated using compressive strength (CS), split tensile strength (STS), flexural strength (FS), modulus of elasticity (MoE). The results revealed that incorporating MK improved the mechanical properties: CS increased by 12.06%, STS by 16.84%, and FS by 15.42% compared to the control mix. In comparison, FA substitution resulted in a slightly lower increase: CS by 9.72%, STS by 12.84%, and FS by 8.57%. The study concluded that MK exhibited a superior performance in enhancing the strength properties of concrete compared to FA. Additionally, linear regression analysis was employed to establish correlations between the experimentally determined strength properties and the mix design parameters. This analysis demonstrated a strong correlation between the predicted and experimental values, making it a valuable tool for future concrete mix design optimization.

Keywords:
metakaolin; flyash; compressive strength; split tensile strength; flexural strength; linear regression analysis