Resistance of MgO–GGBS and CS–GGBS stabilised marine soft clays to sodium sulfate attack

Yi, Yaolin; Li, C.; Liu, S.; Al‐Tabbaa, Abir

doi:10.1680/geot.14.t.012

Cited by 75 publications

(21 citation statements)

References 30 publications

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“…3) Less calcium ions in the MSB system also means the formation of expansive gypsum and ettringite can be effectively limited, which has been proved in (Yi et al 2014) where only C-S-H, Ht and a small amount of ettringite were observed in MgO-GGBS paste exposed to Na2SO4 solution. Excessive formation of ettringite can produce high expansive force to crack the matrix leading to spalling and higher hydraulic conductivity (Cai et al 2014;Neville 2004).…”

Section: Discussionmentioning

confidence: 96%

Engineering Properties of Vertical Cutoff Walls Consisting of Reactive Magnesia-Activated Slag and Bentonite: Workability, Strength, and Hydraulic Conductivity

Hao

Jin

et al. 2019

J. Mater. Civ. Eng.

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The soil-cement-bentonite (SCB) vertical cutoff walls are commonly used to control flow of contaminated groundwater in polluted sites. However, conventional backfill consisting of Ordinary Portland cement (OPC) is associated with relatively high CO2 footprint. Potential chemical interactions between OPC and bentonite could also undermine the long-term durability of SCB materials. In this paper, we propose an innovative backfill material for cutoff walls, which is composed of MgO-activated ground granulated blast furnace slag (GGBS), bentonite and soil. The OPC-soil, OPC-bentonite-soil, and OPC-GGBS-bentonite-soil backfill materials are also tested for comparison purpose. Workability of the fresh backfills and unconfined compressive strength of aged backfills are investigated. The hydraulic conductivities of aged backfills permeated with tap water, Na2SO4 and Pb-Zn solutions are assessed. The unconfined compressive strength and hydraulic conductivity of the proposed backfill permeated with tap water for the backfills are in the range of 230-520 kPa and 1.1×10-10-6.3×10-10 m/s at 90-day-curing, respectively, depending on the mix composition. The hydraulic conductivity of the proposed MgO-GGBS-bentonite-soil backfill permeated with sodium sulfate (Na2SO4) or lead-zinc (Pb-Zn) solution is well below the commonly used limit, while the OPC-bentonite-soil backfill shows a significant loss in its impermeability. Environmental and economic analyses indicate that, compared with the conventional backfill made from the OPC-bentonite-soil mixture, the proposed backfill reduces approximately 84.7%-85.1% in CO2 emissions and 15.3%-16.9% cost. The environmental and economic advantages will 3 promote the utilization of MgO-activated GGBS-bentonite mixtures in the cutoff walls and further advocate its application in land remediation projects.

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Section: Discussionmentioning

confidence: 96%

Engineering Properties of Vertical Cutoff Walls Consisting of Reactive Magnesia-Activated Slag and Bentonite: Workability, Strength, and Hydraulic Conductivity

Hao

Jin

et al. 2019

J. Mater. Civ. Eng.

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“…Through a mercury intrusion porosimetry (MIP) test, Yi et al (2014a) quantified that the total pore volume of a 90-day MgO-GGBS-stabilised clay was 10% lower than that of the corresponding Ca(OH) 2 -GGBS-stabilised clay.…”

Section: X-ray Diffractionmentioning

confidence: 99%

Mechanism of reactive magnesia – ground granulated blastfurnace slag (GGBS) soil stabilization

et al. 2016

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Reactive magnesia (MgO)-activated ground granulated blastfurnace slag (GGBS), with fixed GGBS dosages but varying MgO/GGBS ratios, was used for stabilisation of two soils, and compared with brucite (Mg(OH) 2 )-activated GGBS and hydrated lime (Ca(OH) 2 )-activated GGBS. A range of tests, including unconfined compressive strength test, X-ray diffraction and scanning electron microscopy, were conducted to study the mechanical, chemical and microstructural properties of the stabilised soils, and then to investigate the mechanism of MgO-GGBS soil stabilisation.The results indicated that the Mg(OH) 2 had a minimal activating efficacy for GGBS-stabilised soil, while the reactive MgO yielded a higher activating efficacy than the Ca(OH) 2 . The activator-soil reactions in the stabilised soil slowed down the activating reaction rate for GGBS; this effect was less significant in MgO-GGBS-stabilised soil than in Ca(OH) 2 -GGBS-stabilised soil, and hence the GGBS hydration rate in the former was less reduced by the soil than in the latter. The Mg 2+ and OH -ions produced from MgO dissolution participated in the GGBS hydration reactions without precipitating Mg(OH) 2 . The common hydration products in all GGBS-stabilised soils were calcium silicate hydrate-like compounds. Additionally, hydrotalcite and calcite could be produced in MgO-GGBS-and Ca(OH) 2 -GGBS-stabilised soils respectively, especially with high activator/GGBS ratio.

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“…Under those low temperatures, the MgO has high surface area, high reactivity, and low crystallinity (Shand, 2006). The use of reactive MgO with GGBS for soil stabilisation is a recent development offering a range of mechanical and durable advantages over PC or lime-slag blends (Jegandan et al, 2010;Yi et al, 2014bYi et al, , 2014cYi et al, , 2012. Yi et al (2014c) found that MgO-GGBS blend in the ratio of 1:9 by weight induced a higher unconfined compressive strength of stabilised sand and clayey silt than lime-GGBS blend at the same ratio at 7 days, although they obtained a similar strength range at 90 days.…”

Section: Introductionmentioning

confidence: 99%

“…Additionally, the soil treated by GGBS-MgO mixture with proper ratio may achieve a strength ~1.3-4 times higher than the corresponding PC treated soil. Jegandan et al (2010) and Yi. et al (2014b) found that the combination of MgO and GGBS in stabilisation produced higher resistance to sulfate and acid attack than PC stabilised soil, since no expansive phase ettringite formed in MgO-GGBS stabilised soil.…”

Section: Introductionmentioning

confidence: 99%

Incorporation of reactive magnesia and quicklime in sustainable binders for soil stabilisation

Jin

Al‐Tabbaa

et al. 2015

Engineering Geology

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The utilisation of reactive magnesia or quicklime as novel activators for slag offers a range of technical and environmental benefits over conventional caustic alkali activators and showed great potential in soil stabilisation. This paper investigates the mechanical and microstructural properties of two model soils, i.e. a clayey soil and a slightly silty clayey sand, stabilised by ground granulated blastfurnace slag (GGBS) using various techniques including unconfined compressive strength (UCS) test, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). A number of MgO and CaO mixtures with different MgO/CaO ratios were adopted for slag activation. The activator to GGBS ratio was 1:3 and the dosage of the binder (including MgO, CaO and GGBS) was 12% by weight of the dry soil. The result demonstrated that the increasing MgO/CaO ratio in the binder led to an increase in the UCS of the stabilised clayey soil up to 90 days, due to the increased homogeneity of C-S-H gel structure, the decreased Ca/Si ratio of C-S-H gel and the increased amount of voluminous hydrotalcite-like phases. On the other hand, slag activated with MgO-CaO mixtures showed poorer mechanical performance than slag activated with either MgO or CaO alone for sand stabilisation. In addition, strength enhancement was observed for the stabilised clayey soil upon different soaking conditions up to 7 days. After 28 days, although binders with higher MgO/CaO ratios showed slight strength degradation upon soaking, they still exhibited higher strength than those with lower MgO/CaO *Manuscript Click here to download Manuscript: Manuscript_revised.docx Click here to view linked References 2 ratios.

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Resistance of MgO–GGBS and CS–GGBS stabilised marine soft clays to sodium sulfate attack

Cited by 75 publications

References 30 publications

Engineering Properties of Vertical Cutoff Walls Consisting of Reactive Magnesia-Activated Slag and Bentonite: Workability, Strength, and Hydraulic Conductivity

Engineering Properties of Vertical Cutoff Walls Consisting of Reactive Magnesia-Activated Slag and Bentonite: Workability, Strength, and Hydraulic Conductivity

Mechanism of reactive magnesia – ground granulated blastfurnace slag (GGBS) soil stabilization

Incorporation of reactive magnesia and quicklime in sustainable binders for soil stabilisation

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