Abstract
This study comparatively evaluated lightweight structural and thermal-insulating concrete containing unground rice husk (RH) and commercially supplied ground rice husk (GRH). Two comparative mixture series, one containing unground rice husk (RH) and the other containing ground rice husk (GRH), were produced at four binder levels using cement, fly ash, quartz sand, a polycarboxylate superplasticizer, and an organosilicon water repellent. The study assessed particle characteristics, fresh and hardened density, 28-day compressive strength, thermal conductivity, water absorption, and microstructure. The commercially supplied GRH consisted of fragmented particles with a median size of approximately 0.72 mm, facilitating its incorporation into the granular skeleton. The hardened density remained within 1402–1478 kg/m3, while the average compressive strength increased from 7.38 MPa for RH mixtures to 10.43 MPa for GRH mixtures. Depending on the composition, the GRH mixtures exhibited 26.7–65.0% higher compressive strength than the corresponding RH mixtures at comparable densities. Thermal conductivity remained within the range of 0.36–0.42 W/(m·K), and water absorption varied only from 28.0 to 29.5%. Scanning electron microscopy (SEM) observations revealed more uniform particle distribution, improved particle–matrix contact, and fewer pronounced interfacial defects in GRH composites. The GRH-4 mixture demonstrated the best overall performance, combining a compressive strength of 11.47 MPa, a density of 1462 kg/m3, and a thermal conductivity of 0.42 W/(m·K). These findings show that the investigated GRH-based formulations achieved higher structural efficiency than the corresponding RH-based formulations while largely maintaining their thermal insulation performance; however, the differences reflect the combined effects of particle characteristics, husk dosage, moisture conditions, and associated mixture adjustments.