Cold-bonded lightweight aggregates as replacement materials for road applications

The development of road materials as alternatives to mineral aggregates has become an important research direction. This paper proposes cold-bonded lightweight aggregates (R-CBLA) as substitutes for conventional aggregates and prepares lightweight aggregate-modified soil (LA-Soil) and lightweight aggregate-hydraulic bound mixtures (LA-HBM) for subgrade and base applications. By adjusting the rotation speed of the extrusion granulator, feeding rate, and raw material moisture, R-CBLA can be produced with a granulation rate higher than 90%. Its water absorption shows a significant negative correlation with strength, while bulk density exhibits a significant positive correlation, thus providing a theoretical basis for optimizing performance. In LA-Soil, incorporating 40%–50% R-CBLA with natural coarse grains develops a skeleton-dense structure, which enhances dry density, CBR, and resilient modulus, while still maintaining durability under freeze-thaw cycles. In LA-HBM, two critical replacement thresholds are identified, performance changes are limited below 25%, performance decreases moderately but remains technically feasible between 25% and 75%, the skeleton structure becomes unstable and performance declines sharply beyond 75%. Cost analysis further shows that R-CBLA offers advantages in materials, transportation, and construction, with maximum cost reductions reaching 87%. This economic benefit is especially pronounced in resource-scarce regions. In conclusion, the study verifies the feasibility of R-CBLA in road engineering, proposes a long-life pavement design concept, and emphasizes large-scale production, systematic performance optimization, and long-term durability as priorities for future research.