Microstructural and crystallographic insights into high strength concrete composites

This study provides an extensive microstructural, crystallographic, and thermal analysis of High Strength Concrete composites that utilize Natural Zeolite, Metakaolin, Fly Ash, and Silica Fume as partial substitutes for cement. This study performed Scanning Electron Microscopy, X-ray Diffraction, Thermo-Gravimetric/Differential Thermal Analysis, and Fourier Transform Infrared Spectroscopy on ten concrete mixes, including three binary SCMs consisting of Natural Zeolite combined separately with Metakaolin, Fly Ash, and Silica Fume. Scanning Electron Microscopy results showed that adding Metakaolin, Fly Ash, and Silica Fume made the microstructural density much better, especially at higher replacement levels. This was shown by less porosity and better particle shape. X-ray Diffraction patterns showed that the main crystalline phases, like quartz, calcium hydroxide, mullite, gypsum, and calcite, were formed. This was affected because of the material used and its proportion in the concrete mix. Thermal analysis showed that the thermal stability of all the mixes got better, and the decomposition onset temperatures for Metakaolin, Fly Ash, and Silica Fume based composites increased. Fourier Transform Infrared spectra confirmed the existence of distinctive functional groups and illustrated alterations in bonding environments linked to aluminosilicate and calcium carbonate phases. In general, the combination of mineral and industrial additives made High Strength Concrete much stronger, better at handling heat, and more likely to last longer. This research study provides information for preparing high strength and more sustainable concrete. The TGA/DTA, SEM, and XRD results suggest enhanced hydration and matrix densification. However, dedicated durability studies are needed to confirm this. Furthermore, this research directly aligns with United Nations Sustainable Development Goal 9 (Industry, Innovation, and Infrastructure) and Goal 12 (Responsible Consumption and Production) by upcycling industrial by-products into high-performance, eco-efficient structural materials.