• Ultrasonic dispersion for 30 min increases compressive strength by 37.7%, but excessive ultrasonication (60 min) hydrolyzes CNF and retards hydration.
• Polycarboxylate superplasticizer (PCE) at 0.4wt% achieves a 29.1% strength increase while improving hydration products and microstructure.
• PCE offers superior cost-effectiveness and operational convenience compared to ultrasonic dispersion, making it more viable for industrial adoption.
• This study provides a theoretical basis for nano-enhanced cemented rockfill, supporting solid waste recycling and high-performance material development.