Mechanical Performance of Cement–Additive Stabilized Soils With Different Plasticity Indices for Road Subbase Applications

Abstract

This research presents a laboratory study of the mechanical efficiency of engineering processes for cement-stabilized soils with varying plasticity indices in road subbase applications. Soils with low, medium, and high plasticity were selected from areas of selection in Papua Province, Indonesia. The soils were stabilized by a fixed composition with 10% ordinary Portland cement supplemented with 2% chemical additive, and the engineering performance of these mixes was assessed using Atterberg limits and compaction characteristics, unconfined compressive strength (UCS), and the California Bearing Ratio (CBR) test. All mechanical tests were performed after 7 days of curing to characterise early strength development. The findings suggest that the soil plasticity index, which serves as the engineering classification parameter, relates to differences in UCS and CBR performance after identical stabilization. Lower-plasticity index soils showed high UCS and CBR results across a large group of tests. In contrast, higher-level soils exhibited minimal initial performance but significant performance recovery after stabilization. The stabilized soil mixtures attained UCS and CBR values that complied with the basic performance standards in the Indonesian General Specifications (Bina Marga) for lower subbase layers. This work establishes that the performance of cement–additive stabilized soils depends on plasticity level, underscoring the importance of considering the plasticity index in preliminary soil characterization for pavement design. It is not well established under the conditions of laboratory-scale experiments and early curing, and requires investigation for both long-term performance and field performance.

Keywords: Soil Stabilization; Cement; Chemical Additive; Plasticity Index; UCS; CBR; Road Subbase.