Publication: Effective suppression of ettringite formation in sulphate-bearing soil using blends of nano-magnesium oxide, ground granulated blast-furnace slag, rice husk ash, and metakaolin
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Date
2023-05-01
Authors
Khaled Ibrahim Azarroug Ehwailat
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Abstract
Sulphate-bearing soil is one type of expansive soil that is widely distributed worldwide. Generally, cement and lime are the most common methods of stabilising expansive soil. Still, the main problem is that lime-treated sulphate-bearing soil is weak in terms of its durability due to the formation of ettringite, a highly deleterious compound. Moisture ingress causes significant swelling of ettringite crystals, thereby causing considerable damage to structures and pavements on such soil.
This study aims to evaluate the performance of different soil stabilizers; rice husk ash (RHA), metakaolin (MK), and ground granulated blast-furnace slag (GGBS) as a partial replacement for hydrated lime (L), and nano magnesium oxide (M), based on previous studies, as stabilizing agents (L-RHA, L-MK, L-GGBS, L-GGBS-RHA, L-GGBS-MK, M-RHA, M-MK, M-GGBS, M-GGBS-RHA, M-GGBS-MK), has not been observed any researches used these mixtures for the treatment of high-sulphate soils, with mix ratio; (1:3, 1:1, 3:1) and (1:7, 1:3, 1:1.7) for binary mixture, (1:0.5:0.5) and (1:1:2, 1:2:1, 1:2.5:0.5) for ternary mixture. Various tests were performed, including flexural strength, unconfined compression strength, linear expansion, and microstructure analysis (SEM/EDX and XRD) on treated soil samples to determine the soil specimens’ properties that were cured for 7, 28, 90, and 180 days.
The results showed soil samples treated with of L-System (5%L-15%RHA and 5%L-12.5%GGBS-2.5%MK) and M-System (5%M-15%MK, 5%M-15%GGBS, 5%M-12.5%GGBS-2.5%RHA, and 5%M-12.5%GGBS-2.5%MK) exhibit lower swelling rates (less than 0.005% change in volume) than those treated with 10% and 20% of lime after 90 days of curing. Meanwhile, the strengths of the soil samples mixed with 20% of (M-GGBS, M-GGBS-RHA, and M-GGBS-MK) exhibited higher strengths after 180 days of soaking (ranging from 8–15 MPa) compared to those stabilized with 10% and 20% lime. From the microstructural studies, the SEM/EDX and XRD analysis evidenced no formation of ettringite in the samples stabilized with M-MK-, M-GGBS-, and M-GGBS-MK. These results demonstrate the suitability of M-MK, M-GGBS, M-GGBS-RHA, and M-GGBS-MK as effective agents for stabilizing Sulphate-bearing soil and suppressing the ettringite formation with higher durability.