Abstract
The treatment of sulfate-bearing soil with calcium-based stabilizers such as cement or lime often results in ettringite formation, consequently leading to swelling and strength deterioration. Ettringite formation has negative environmental and economic effects on various civil engineering structures. This study was conducted to investigate the use of different materials (nano–magnesium oxide (M), ground granulated blast-furnace slag (GGBS), and rice husk ash (RHA)) for gypseous soil stabilization to prevent ettringite formation. Various tests were performed, including flexural strength, unconfined compression strength, linear expansion, and microstructure analysis (SEM/EDX), on lime (L)-, (M)-, (M-RHA)-, (M-GGBS)-, and (M-GGBS-RHA)-stabilized gypseous soil samples to determine their properties. The results indicated that the swelling rates of the soil samples mixed with 20% M-RHA, M-GGBS, and M-GGBS-RHA binders were much lower (less than 0.01% of volume change) than those of the soil samples mixed with 10% and 20% lime-stabilized binders after a curing period of 90 days. Meanwhile, the strengths of the soil samples mixed with 20% of M-RHA, M-GGBS, and M-GGBS-RHA soil specimens after soaking of 90 days were obviously higher (with a range from 2.7–12.8 MPa) than those of the soil samples mixed with 20% of lime-stabilized binder. The SEM and EDX results showed no ettringite formation in the M-RHA-, M-GGBS-, and M-GGBS-RHA-stabilized soils. Overall, the test results proved the potential of M-RHA, M-GGBS, and M-GGBS-RHA as effective soil stabilizers.
Highlights
Gypseous soils are soils containing significant amounts of calcium sulfates (CaSO4 × 2H2O)
The test results proved the potential of M-rice husk ash (RHA), M-ground granulated blast-furnace slag (GGBS), and M-GGBS-RHA as effective soil stabilizers
The most common equipment and tests are unconfined compressive strength tests used to reveal the influence of ettringite on the strength of soil samples containing sulfate, and linear expansion to observe the magnitude of swelling induced by ettringite formation
Summary
Gypseous soils are soils containing significant amounts of calcium sulfates (CaSO4 × 2H2O). Sulfate-induced heave is well known to have serious negative impacts on the general performance of runways, highways, and other structures that are constructed on lime- or cement-stabilized sulfaterich soil layers [1,4,11]. The most common equipment and tests are unconfined compressive strength tests used to reveal the influence of ettringite on the strength of soil samples containing sulfate, and linear expansion to observe the magnitude of swelling induced by ettringite formation. Unconfined compressive strength and linear expansion tests were conducted on gypseous soil containing a high level of calcium sulfate (10%, 15%, and 20%) treated with 7%, 8%, 9%, and 10% calcium-based stabilizer (cement). The outcomes illustrated that the strength reduced by a factor range of 6–47% at 28 days of curing, while the swelling magnitude depended mainly on the sulfate concentration, with the highest rate of swelling observed in the presence of sulfate at 10%
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