Development of novel concrete with sustainable waste materials: A comprehensive study on strength, pulse velocity, and rebound hammer number at elevated temperatures using predictive models

The present study examines the characteristics of concrete produced by incorporating waste materials, namely ground granulated blast furnace slag (GGBFS) and granite powder at elevated temperatures. Various properties of the concrete, such as compressive strength, rebound hammer, Portable Ultrasonic Non-destructive Digital Indicating Tester (PUNDIT), and slump test, have been investigated. Different concrete mixes have been prepared based on different percentages, i.e., 0, 30, and 50 % by weight of GGBFS and granite powder replacements with cement and fine aggregate. Experimental results demonstrated that concrete with 50 % GGBFS and 30 % granite powder retained 26 MPa compressive strength at 300°C, outperforming conventional concrete (18 MPa at 300°C). At 600°C, the optimized mix maintained 12 MPa strength, showing a 13.1 % improvement over control mixes. Non-destructive testing revealed that ultrasonic pulse velocity (UPV) for GGBFS-granite blends exceeded 4.5 km/s (classified as "excellent" per IS 13311) at ambient conditions. Rebound hammer numbers for modified mixes ranged from 16–24 (28 days) to 18–26 (90 days), correlating with reduced surface hardness but enhanced thermal stability. New models have been proposed to evaluate the age-dependent compressive strength, pulse velocity, and rebound hammer number of concrete containing varying percentages of GGBFS and granite powder, applicable at any temperature and any concrete age. Predictive models achieved 95 % accuracy ( ± 5 % error) in estimating strength, UPV, and rebound number properties. Moreover, multi-objective cost optimization analysis was also conducted using NSGA-II to determine the most cost-effective and economical concrete mix with the highest compressive strength. The present study contributes valuable insights into the suitability of waste materials in concrete production, offering potential benefits for sustainable and durable construction practices.