Strength performance of low-bearing-capacity clayey soils stabilized with ladle furnace slag

Abstract

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.