The geotechnical and microstructural properties of desilicated fly ash lime stabilised expansive soil

Falayi, Thabo; Okonta, Felix; Ntuli, Freeman

doi:10.1617/s11527-016-0831-7

Cited by 14 publications

(4 citation statements)

References 26 publications

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“…It can be seen that after the seventh cycle, there was a significant reduction in the UCS due to the specimens' porosity, which resulted in water ingress during soaking. The obtained results show that the developed WFGD gypsum specimens can withstand seven wet and dry cycles and make them potential materials for construction [67]. This result matches quite well with the observations of others, confirming their use in hot and dry climates [68,69].…”

Section: The Durability Of Wfgd Gypsum Brickssupporting

confidence: 87%

Physical, Chemical and Geotechnical Characterization of Wet Flue Gas Desulfurization Gypsum and Its Potential Application as Building Materials

et al. 2021

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In South Africa, coal represents the primary source of energy used for electricity generation. Coal power plants use the wet flue gas desulfurization (WFGD) process to remove sulfur dioxide (SO2) from their flue gas. However, this technology produces a large amount of synthetic gypsum, resulting in waste disposal and environmental pollution. This study investigated the physical, chemical and geotechnical properties of WFGD gypsum and its potential application to develop cement-free bricks. WFGD gypsum was collected from a coal power plant in South Africa. It was found that the principal oxides of WFGD gypsum were sulfur trioxide (SO3) and calcium oxide (CaO), which represented more than 90% of the total weight. Calcium sulfate (CaSO4) and calcium di aluminate (CA2) were the predominant minerals in the raw material. The density of the WFGD gypsum was 2.43 g/cm3. The maximum dry density and optimum moisture content values were 1425 kg/m3 and 18.5%, respectively. WFGD gypsum had a liquid limit of 51% but did not display any plasticity characteristics. The optimum curing temperature of gypsum bricks was 40 °C. WFGD gypsum-based bricks exhibited compressive strength of up to 2.3 MPa and a density of about 28% less than that of typical clay bricks. Additionally, there was no significant decrease in compressive strength after seven wet/dry cycles. These results show that WFGD gypsum could be used to produce lightweight building materials with low strength requirements.

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Section: The Durability Of Wfgd Gypsum Brickssupporting

confidence: 87%

Physical, Chemical and Geotechnical Characterization of Wet Flue Gas Desulfurization Gypsum and Its Potential Application as Building Materials

et al. 2021

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“…Affected by the difference in gravity, some portion of the PCM migrated from the upper part of the sample to the lower part, precipitating out from the neighboring area, causing leakage. For the CFA-PCM sample, the hydration of fly ash produced a hardened hydrated calcium silicate gel, which inhibited the deformation of the soil [40]. In addition, due to the porous adsorption performance of CFA, the overall leakage of PCM after phase change and melting was reduced by more than 84%, which improved the stability of PCM.…”

Section: Volume Changesmentioning

confidence: 99%

Fly Ash/Paraffin Composite Phase Change Material Used to Treat Thermal and Mechanical Properties of Expansive Soil in Cold Regions

Chen¹,

Huang²,

Wang³

2022

Journal of Renewable Materials

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Phase change materials (PCMs) can store large amounts of energy in latent heat and release it during phase changes, which could be used to improve the freeze-thaw performance of soil. The composite phase change material was prepared with paraffin as the PCM and 8% Class C fly ash (CFA) as the supporting material. Laboratory tests were conducted to reveal the influence of phase change paraffin composite Class C fly ash (CFA-PCM) on the thermal properties, volume changes and mechanical properties of expansive soil. The results show that PCM failed to establish a good improvement effect due to leakage. CFA can effectively adsorb phase change materials, and the two have good compatibility. CFA-PCM reduces the volume change and strength attenuation of the soil, and 8 wt.% PCM is the optimal content. CFA-PCM turns the phase change latent heat down of the soil and improves its thermal stability. CFA-PCM makes the impact small of freeze-thaw on soil pore structure damage and improves soil volume change and mechanical properties on a macroscopic scale. In addition, CFA-8 wt.% PCM treated expansive soil has apparent advantages in resisting repeated freeze-thaw cycles, providing a reference for actual engineering design.

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“…DFA is capable of removal of sulphates though it contains Phillipsite whose surface is negatively charged. This is probably due to a mix of adsorption and precipitation of sulphates since DFA has a pH of 12.28 [11]. Figure 4 shows the variation in sulphate removal with time.…”

Section: Effect Of Dfa Solid Loadingmentioning

confidence: 99%

Removal of sulphates from acid mine drainage using desilicated fly ash slag

Ntuli¹,

Falayi²,

Thwanane³

2016

WIT Transactions on Ecology and the Environment

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The removal of sulphates from acid mine drainage (AMD) using desilicated fly ash (DFA) was investigated. The effects of DFA solid loading, residence time and removal temperature were investigated. A 2% DFA solid loading gave the highest sulphate removal of 75% at a temperature and residence time of 35ºC and 90 min respectively. The maximum adsorption capacity for DFA was found to be 147.06 mg/g DFA. The sorption mechanism followed the Langmuir isotherm and pseudo second order kinetics. The Gibbs free energy and enthalpy for the sorption was found to be 17.26 and 125.096 J/mol respectively. This research showed that DFA was an attractive alternative adsorbent for sulphates in AMD.

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The geotechnical and microstructural properties of desilicated fly ash lime stabilised expansive soil

Cited by 14 publications

References 26 publications

Physical, Chemical and Geotechnical Characterization of Wet Flue Gas Desulfurization Gypsum and Its Potential Application as Building Materials

Physical, Chemical and Geotechnical Characterization of Wet Flue Gas Desulfurization Gypsum and Its Potential Application as Building Materials

Fly Ash/Paraffin Composite Phase Change Material Used to Treat Thermal and Mechanical Properties of Expansive Soil in Cold Regions

Removal of sulphates from acid mine drainage using desilicated fly ash slag

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