Mechanical Properties and Durability of Variatropic Concrete with Complex Mineral Modifying Additives
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In this study, a waste-based complex mineral-modifying additive (CMMA), composed of fly ash (FA), microsilica (MS), and metakaolin (MK) derived from industrial waste, was developed. Concrete specimens were produced using vibration (V), centrifugation (C), and vibro-centrifugation (VC) methods; CMMA was used for replacing cement in amounts ranging from 0% to 20%, with increments of 4%. The compressive strength, water permeability, and freeze-thaw resistance of the resulting concrete were evaluated. The results showed that the optimal CMMA ratio for all production methods was 12%. At this ratio, the compressive strength reached 49.7 MPa, 59.3 MPa, and 63.5 MPa for V, C, and VC concrete mixtures, respectively, corresponding to increases of 10.7%, 15.8%, and 18.7% compared to the control mixture. The same mixtures demonstrated the highest performance in terms of water impermeability, achieving W10, W12, and W14 classifications, respectively. Under freeze-thaw conditions, the lowest strength losses were again observed in the specimens containing 12% CMMA, which were 5.9%, 4.8%, and 3.7%, respectively. Microstructural analyzes have shown that CMMA produces a denser, more homogeneous, lower-porosity cement matrix and reduces microcrack formation. The findings indicate that CMMA is particularly effective when used with centrifugal and vibro-centrifugal production technologies.
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