Laboratory Study on Improvement of Expansive Soil by Chemically Induced Calcium Carbonate Precipitation

Han, Shaoyang; Wang, Bao-Tian; Gutierrez, Marte; Shan, Yibo; Zhang, Yijiang

doi:10.3390/ma14123372

Cited by 8 publications

(3 citation statements)

References 52 publications

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“…However, with an increase in the Mg 2+ /Ca 2+ molar ratio, the precipitation of carbonate is inhibited and the strength is reduced. Multiple existing studies [22][23][24][25][26] indicate significant variations in reinforcement effects of sands with different properties. Besides the traditional focus on calcium carbonate precipitation, an important indicator for the low-pH approach is calcium carbonate flocculation lag period, which aims to address clogging issues.…”

Section: Introductionmentioning

confidence: 99%

Reinforcement of Different Sands by Low-pH Bio-Mineralization

Lai,

Liu,

Cai

et al. 2023

Materials

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Different sands have significant influences on MICP reinforcement effects. Using calcium carbonate production and bioflocculation lag period as evaluation criteria, this study investigates the optimal theoretical pH values of bacterial solutions with different concentrations. We reinforced four different sands using MICP at the optimal theoretical pH, and based on permeability, moisture retention, raindrop erosion, wind erosion, penetration, and SEM tests, the influence of sand properties on low-pH MICP reinforcement was analyzed and the low-pH MICP mechanism was revealed. The results indicate the following: (1) The optimal theoretical pH values for bacterial solutions with concentrations of 0.67 × 108 cells/mL, 3 × 108 cells/mL, and 10 × 108 cells/mL are 4.5, 3, and 4, respectively. (2) With 0.67 × 108, 3 × 108, and 10 × 108 cells/mL bacterial solutions, the strength of tailings sand containing calcium salt was 21.15%, 44.42%, and 13.61% higher than that of quartz sand, respectively. The effective reinforcement depth of alkaline reclaimed sand was 10, 8, and 6 mm lower than that of neutral calcareous sand, respectively. The strength of fine tailings sand was 70.41%, 58.04%, and 22.6% higher than that of coarse reclaimed sand. The effective reinforcement depth of fine quartz sand was 6, 4, and 4 mm lower than that of coarse calcareous sand. (3) Low pH temporarily suppresses urease activity, delaying calcium carbonate flocculation and enhancing reinforcement uniformity. To achieve optimal reinforcement effects, adjusting the actual optimal pH values of bacterial solution based on sand properties is essential in engineering applications.

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Section: Introductionmentioning

confidence: 99%

Reinforcement of Different Sands by Low-pH Bio-Mineralization

Lai,

Liu,

Cai

et al. 2023

Materials

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“…Based on the experimental investigation, the addition of soda ash led to the increase of pH of the soil and improvement of the compaction properties. Han et al [28] used calcium chloride and SA solutions to decrease the soil expansion potential. The reduction in the expansion parameters was primarily attributed to the strong short-term reactions between clay and stabilisers.…”

Section: Introductionmentioning

confidence: 99%

Strength and Compressibility of Ammonia-Soda Residue from the Solvay Sodium Plant

2021

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This work presents the discussion of the results for an experimental study conducted to characterise the mechanical behaviour of ammonia-soda residue (ASR). The calcareous sludge is an alkaline waste formed during the production of soda ash and deposited at the area of the former Solvay Sodium Plant factory in Krakow, Poland. Isotropically consolidation drained (CID) triaxial tests and constant rate of strain (CRS) consolidation tests include the full saturation with water, completion of the consolidation, and the loading/strain rate choice. For this purpose, ASR undisturbed samples were collected from the ground and submitted to laboratory experiments. These samples show a distinct difference in the initial bulk density, the initial level of compaction, initial void ratio, and the natural water content. The CD triaxial tests were conducted under three different levels of confining pressure; in turn, CRS tests were run with two appropriate input strain rates. According to the physical state of ASR and the depth of sampling, two different evolutions of the critical state in the stress–strain space were observed. In the light of the assessed stress–strain–strength behaviour, key design engineering parameters of ASR were calculated.

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“…Serves as a foundation layer under the surface layer, a binder that has been compacted and placed on top of the sub-base layer and serves to support, spread the load and harden the surface layer. [14] conducted a study on the stabilization of expansive clay with table salt (NaCl). A mixture of table salt (NaCl) as a soil stabilizer can reduce moisture, PI (plasticity index), and increase soil density.…”

Section: Introductionmentioning

confidence: 99%

Analysis of soil characteristics on expansive clay stabilization using shell ash

Sudjianto

Suraji

Susilo

2021

EEJET

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Expansive clay is one of the problems in construction work. The soil has the characteristics of being easy to expand when exposed to water, causing a decrease in the strength value of the soil. The can be overcome by stabilizing the soil. The soil is formed from weathering and contains the mineral montmorillonite. The soil is very sensitive to moisture content, has a high shrinkage rate, thus interfering in construction work. Therefore, additional materials are needed to overcome the problem, one of which is soil stabilization. The study aimed to stabilize the expansive clay soil. This is done by analyzing the physical and mechanical properties of expansive clay with a shell ash mixture. Expansive clay is taken directly (undisturbed) or disturbed. Undisturbed soil is taken using a tube, so that the soil is not disturbed by outside air, while disturbed soil is taken using a shovel and then put into a sack container. Expansive clay stabilization method lies in adding the percentage of shell ash mixture (5 %, 10 %, 15 %, and 20 %). The soil, the initial moisture content (γd) of which has been determined, is mixed, then molded into a cylindrical shape. The mold was stored in a desiccator, then watered with 5 % water every day until the soil became saturated. Then, using a Proctor test, chemical tests (soil chemical test, soil mineral test), physical tests (soil moisture, Atterberg limit), and mechanical tests (unconfined compression test, compaction test, swelling test) were carried out. The results showed that the addition of an oyster shell ash stabilizing agent to expansive clay affected the physical and mechanical properties of the soil. The addition of shell ash can reduce soil moisture with various plasticity indexes. While the soil stress value decreased, the swelling of the soil increased significantly above the original soil.

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Laboratory Study on Improvement of Expansive Soil by Chemically Induced Calcium Carbonate Precipitation

Cited by 8 publications

References 52 publications

Reinforcement of Different Sands by Low-pH Bio-Mineralization

Reinforcement of Different Sands by Low-pH Bio-Mineralization

Strength and Compressibility of Ammonia-Soda Residue from the Solvay Sodium Plant

Analysis of soil characteristics on expansive clay stabilization using shell ash

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