Performance of Fly Ash-Modified Self-Compacting Concrete Under Realistic Field Curing Conditions: A Combined Maturity and Microstructural Analysis

This study examines how fly ash-modified self-compacting concrete (SCC) behaves during curing under real conditions, focusing on changes in temperature and heat during the first days. Unlike typical lab tests at steady temperatures, three settings were used to copy real-life conditions: summer, winter with heating, and winter without heating. Temperature changes were tracked with built-in temperature sensors. Concrete maturity was calculated using a standard method (the Freiesleben-Hansen and Pedersen approach in ASTM C1074). The results show that heat in the first 72 h affects the maturity and strength of the concrete. After 7 days, strengths were measured as 32.7 MPa in summer, 27.2 MPa in winter-heated, and 15.7 MPa in winter-unheated settings. Predictions of strength based on maturity closely matched the measured values, proving that this approach works well in real settings. Examining the concrete's structure with SEM and XRD tools showed that fly ash alters how the concrete forms and becomes denser, while lower temperatures slow key reactions, making the material more porous. These results show why early heat control matters. The maturity approach helps reliably estimate in situ strength and guide mix design for real projects.