Evaluation of Activated Carbon from Bean Waste in Improving Concrete Performance and Acceptable Properties of Soil and Subgrades

Population growth and urban expansion have intensified the demand for housing and infrastructure, forcing construction on soils with unfavorable geotechnical conditions and accelerating the exploitation of conventional materials such as cement, which accounts for approximately 8% of global CO₂ emissions. At the same time, the accumulation of organic waste in cities such as Huancayo (60 tonnes/day of broad bean husks) generates environmental impacts through methane emissions and pressure on waste management systems. In this context, activated carbon emerges as a sustainable material, characterized by high porosity and adsorption capacity, with promising applications in construction. In this study, broad bean (Vicia faba) residues were valorized through calcination and chemical activation with KOH to obtain activated carbon, which was incorporated into concrete and clay soils at dosages ranging from 0% to 3%. In concrete, workability (slump, temperature) and compressive strength (7, 14, 28 days) were measured. In soils, CBR and bearing capacity were determined under controlled compaction. Results showed that an optimal dosage of 2.5% increased compressive strength from 224.56 kg/cm² to 353.41 kg/cm² (57% improvement at 28 days). CBR values rose from 6.3% to 19.1% in soils, while allowable capacity increased from 0.50 to 2.50 kg/cm², a fivefold improvement. These findings demonstrate that activated carbon from broad bean husks not only mitigates waste disposal but also acts as an innovative, sustainable additive that enhances the performance of concrete and soils, offering replicable solutions for civil engineering.