Durability and strength development of recycled aggregate concrete with binary, ternary, and multi-blended SCMs under hot-water curing

This study presents a comprehensive evaluation of the mechanical and durability performance of recycled aggregate concrete (RAC) incorporating binary, ternary, and multi-blended supplementary cementitious materials (SCMs) such as fly ash (FA), silica fume (SF), ground granulated blast furnace slag (GGBS), and rice husk ash (RHA) under accelerated hot-water curing. Unlike previous works limited to single SCMs or conventional curing, this research investigates the comparative synergistic behavior of multiple SCM systems at elevated temperatures. Results reveal that binary blends, particularly FA-RHA and RHA-GGBS, provide the most significant improvement in compressive and tensile strengths, while ternary mixes such as FA-RHA and FA-SF achieve superior microstructural refinement with reduced pore diameters (60-150 nm). In contrast, multi-blended systems demonstrate moderate strength and durability gains due to less efficient particle packing, though they maintain enhanced long-term stability. XRD and TGA-DTG analyses confirm the reduction of portlandite and formation of C-S-H/C-(A)-S-H gels in all SCM-modified RACs, indicating improved pozzolanic reactivity and densification under hot-water curing. The study establishes clear performance hierarchies among SCM blending modes and provides valuable insights into designing sustainable and high-performance RAC for elevated-temperature environments. • Multi-SCM blends enhance RAC mechanical performance under hot-water curing. • FA-RHA mixes refine pore sizes to 60-100 nm, improving microstructure. • GGBS-rich blends boost C-S-H/C-(A)-S-H formation, reducing portlandite. • Optimized RAC shows significant durability and strength gains with RCA use.