In this paper, the performance of ladle furnace slag (LFS), a by-product of secondary steel refning, is evaluated as a binder
to stabilize clayey soils of low bearing capacity. The aim is to defne whether additions of this by-product to clayey soil can
stabilize the soil in accordance with the technical specifcations of Spanish standards. To do so, three diferent soils stabilized
with 5% LFS were compared with the same soils stabilized with 2% lime and with no stabilization, in order to investigate
their diferent behaviors. The chemical and mineralogical characterizations of all the soil mixes were conducted using X-ray
fuorescence, X-ray difraction, and scanning electron microscopy. The Atterberg limit test was used to study the plastic
behavior of the soils, and the results of compaction, bearing capacity, unconfned compressive strength, and direct shear
strength (cohesion and friction angle) tests defned their strength characteristics. The analysis was completed with the pH
monitoring of the mixes along the curing time in order to relate the pH changes with the strength evolution. The addition
of LFS to the soils has resulted in an increase in the liquid limit and plastic limit, causing therefore a slight decrease in the
plasticity index. All the soils showed increases between 30% and 70% in their California Bearing Ratios immediately after
mixing with 5% LFS, and after 90 days of curing, improvements of 30–188% in their unconfned compressive strength were
noted in comparison with untreated soil, which were higher than the lime-stabilized soils. The cohesion of soils stabilized
with LFS at 28 days of curing obtained improvements ranging from 40 to 300% depending on the type of soil. However, the
friction angle showed a slight increase of 10% in two of the soils and zero in another. The high initial pH in LFS-stabilized
soils was maintained during the curing time, which favored the development of pozzolanic reactions that improve the soil
strength. These results confrmed that the substitution of lime with LFS is a feasible option for soil stabilization.
