Accelerating strength development through pozzolanic activity in hydrated fly-ash cement using plasma-activated water

Plasma technology is an innovative approach to improving the properties of cementitious materials. This study investigated the effects of Plasma-Activated Water (PAW) on the compressive strength and pozzolanic activity of cement paste at 3, 7, 28, and 56 days, with varying levels of fly ash (FA) replacement. PAW, with highly reactive hydroxyl radicals (·OH) in a stable form of hydrogen peroxide (H₂O₂), significantly accelerates the pozzolanic activity of FA, leading to improvements in compressive strength, especially at higher FA replacement levels (30 %). This enhancement is attributed to the accelerated formation of calcium silicate hydrate (C–S–H), as confirmed by Scanning Electron Microscope, X-ray diffraction, and Differential Thermal Analysis, which revealed greater portlandite consumption and increased C–S–H formation in the PAW mixtures. Additionally, Synchrotron X-ray tomographic Microscope analysis showed a significant reduction in porosity in the PAW samples, highlighting its potential to optimize FA performance in cementitious activity. These findings suggest that plasma-activated water is a promising technique for enhancing the use of FA in concrete applications.