Optimization of cementitious and fine electric arc furnace slag on the concrete mixes through mechanical, durability, and microstructural testing

To reduce the depletion of natural resources, the study focuses on using slag from electric arc furnaces to substitute cement and fine aggregates by up to 50 and 70%. On the basis of experimental analysis, the ideal percentages of cementitious slag (SC) and fine aggregate slag (SF) were 30 and 50%, respectively, in comparison to conventional concrete (NC). Further, the mechanical properties of the optimized mix designated as SCF3050 were studied for the combined effect of 30% of SC and 50% of SF in the concrete mixes and compared with the normal concrete. The SACF3050 mix's compressive strength was found to be 12.5% lower than NC's, although the slag significantly increased the flexural strength. Incorporation of slag in the concrete mix. To check the durability of all the modified concrete water permeability, sulphate & chloride attack, alkalinity & carbonation tests were conducted. The water permeability value in case of SC and SF was found to be increased up to 275% and 108% respectively in comparison to NC value of 24 mm. Besides this, existence of CSH, ettringite, and portlandite was also confirmed by microstructural investigation which helps in concrete's setting time, strength accumulation, and shrinkage. A linear regression analysis on the SC and SF mix was performed, and the predicted compressive strength deviated by 23% and 15%, respectively, as compared to the measured strength.