Improvement of Cement-Stabilized Compacted Lateritic Soil Reinforced with Steel Fibers Recovered from Waste Tires

This study investigates the engineering properties of lateritic soil stabilized with Type I Portland cement and reinforced with recycled steel fibers recovered from end-of-life tires (0–5% by dry soil weight), aiming to enhance tensile/flexural performance and durability under moisture variations. The lateritic soil was classified as coarse-grained A-1-a with a low plasticity index (PI ≈ 2.32%). Specimens were prepared under controlled compaction conditions using MDD ≈ 1.952 t/m³ and OMC ≈ 11.8%. Unconfined compressive strength (UCS) tests were conducted to determine an appropriate cement content (1–7%) under both dry and 2-hour-soaking conditions, resulting in the selection of 3% cement as the baseline mixture. Subsequently, indirect tensile strength (ASTM C496) and flexural strength of beam specimens (ASTM C1609) were evaluated for fiber contents of 0–5% at curing ages of 7–28 days, together with durability assessment under wet–dry cycling (ASTM D559/D559M). The results indicate that approximately 3% fiber content provides the most favorable overall performance, increasing the 28-day indirect tensile strength from ~ 350 to ~ 481 kPa and the flexural strength from ~ 276 to ~ 851 kPa, while also promoting a more ductile post-cracking response. However, excessive fiber addition adversely affected compaction due to bulking and clustering, resulting in non-proportional strength gains and, in some cases, reduced durability. Overall, cement-treated lateritic soil reinforced with recycled steel fibers shows strong potential for pavement base/subbase applications requiring improved crack resistance and durability under fluctuating moisture conditions.