Influence of agricultural waste ash slurry-treated recycled brick aggregates on the mechanical and durability performance of concrete

Recycled brick aggregates (RBAs), a major component of construction and demolition waste (CDW), offer a sustainable alternative to natural coarse aggregates (NCA) by conserving resources and reducing landfill accumulation. However, its high porosity, weakly adhered mortar, and low strength restrict its structural applications. This study investigates a sustainable and cost-effective surface treatment method to enhance the inferior properties of RBAs using agricultural waste biomass ashes. Three types of pozzolanic slurries (sugarcane bagasse ash-cement (SBA-C), rice husk ash-cement (RHA-C), and corn cob ash-cement (CCA-C)) were formulated with a fixed proportion of 70% agricultural waste ash and 30% cement by mass. These slurries were prepared at varying water-to-binder (w/b) ratios of 2, 4, and 6 to optimize the treatment efficacy. The results showed that RBAs treated with various types of agricultural waste slurries exhibited 22.9–33.3% reduction in water absorption, 2.3–8.5% increase in particle density, 23.7–29.4% improvement in crushing resistance, 16.9–20.6% decrease in impact value, and 25.1–29.2% enhancement in abrasion resistance, compared to untreated RBAs. Among the tested agricultural waste slurries with different w/b ratios, the RHA-C slurry with a w/b ratio of 2 showed the greatest improvement, followed by the SBA-C and CCA-C slurries. Mercury intrusion porosimetry (MIP) showed reduced harmful pores (>200 nm), while X-ray diffraction and scanning electron microscopy confirmed the formation of additional hydration products and surface densification, confirming microstructural enhancement in treated RBAs. Moreover, concrete prepared with treated RBAs showed superior mechanical and durability performance compared with untreated RBA concrete, while maintaining comparable cost and CO₂ emissions to conventional concrete. Overall, this approach valorizes both CDW and agricultural waste, advancing circular economy principles and enabling more sustainable concrete production. • Agricultural waste slurries offer a low-cost, eco-friendly way to upgrade RBA. • Microstructural densification of RBA through pozzolanic reactions is observed via XRD. • RHA-C slurry is most effective due to high silica content and fine particle size. • Concrete with treated RBA has comparable cost and CO₂ footprint to NAC.