Sustainable Concrete from Industrial and Agricultural By-Products: Performance and Life-Cycle Assessment of Slag-Bagasse Blends in Treated Recycled Aggregate Concrete

Developing sustainable concrete from industrial and agricultural by-products addresses environmental challenges of cement production and construction waste. The research focuses on the synergistic effects of incorporating ground granulated blast furnace slag (GGBS) and sugarcane bagasse ash (SCBA) as partial cement replacements in concrete made with 33% treated recycled concrete aggregates. Mix designs were prepared with varying SCBA (0%, 5%, 10%) and GGBS (0%, 25%, 50%) contents. The SCBA was characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM) to confirm its reactivity. The aggregates were treated using a three-stage method involving sodium silicate and silica fume (SF), the latter also being included in the concrete matrix. The performance of these sustainable mixes was evaluated through compressive strength test, rapid chloride permeability test (RCPT), a comprehensive life cycle assessment (LCA), and an economic feasibility study. Based on the findings, the mix with 50% GGBS and no SCBA achieved the best balance of mechanical properties, economic benefit, and a lower environmental impact, with notably a 19.6% reduction in CO₂ emissions for every 25% increment of GGBS compared to the control mix with 0% GGBS (R-S0-B0). Replacing 20% of the remaining cement with SCBA in this optimal mix further enhanced durability, reducing chloride ion permeability by over 67%, although it incurred a slight strength reduction and higher cost. The critical role of SF was demonstrated, as its omission severely compromised chloride resistance. Moreover, the significant potential of tailored GGBS and SCBA combinations in producing high-performance, sustainable recycled aggregate concrete is confirmed.