Strength Characteristics and Heavy Metal Leaching Behavior of Contaminated Mining Sludge at Extra High Water Content Solidified/Stabilized with Lime Activated GGBS or OPC

Abstract Sludge management is one of the major challenges in mining activities. The direct disposal of contaminated mining sludge can bring severe damages to the environment and community. Solidification/Stabilization (S/S) is a very efficient technology for the treatment of contaminated mining sludge because it not only improves the stability of sludge dumping sites but also reduces the leachability of contaminants. Very few studies investigate the S/S of mining sludge, especially with extra high water content. This paper investigated the effectiveness of S/S for the treatment of mining sludge at extra high water content by using quick lime (CaO) activated ground granulated blast furnace slag (GGBS) in comparison to ordinary Portland cement (OPC). To evaluate the mechanical, leaching, and microstructural behavior of mining sludge at extra high water content stabilized by lime activated GGBS and OPC, a series of laboratory experiments were performed, including unconfined compressive strength (UCS), toxicity characteristics leaching procedure (TCLP), X-Ray diffraction, and scanning electron microscopy (SEM) tests, etc. Experimental results indicated that increasing the binder content led to increased strength and decreased leachability of the heavy metal. In contrast, an increase in the water content of the mixture resulted in a decrease in compressive strength and an increase in leachability of heavy metals. On the other hand, lime activated GGBS had substantially better performance than OPC in the aspect of strength development of treated mining sludge and moreover showed comparable capability of heavy metal stabilization in contrast to OPC.

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Strength and Leaching Behavior of Contaminated Mining Sludge at High Water Content Stabilized with Lime Activated GGBS

Materials ◽

10.3390/ma14216524 ◽

2021 ◽

Vol 14 (21) ◽

pp. 6524

Author(s):

Traore Abdoul Fatah ◽

Rongjun Zhang ◽

Xiaosong Huang ◽

Junjie Zheng ◽

Yu Miao ◽

...

Keyword(s):

Heavy Metal ◽

Water Content ◽

Experimental Tests ◽

High Water ◽

Aluminum Silicate ◽

High Water Content ◽

Strength Development ◽

Efficient Technology ◽

The Stability ◽

Mining Sludge

Sludge management is one of the major challenges in mining activities. The direct disposal of contaminated mining sludge can bring severe damages to the environment and community. Solidification/stabilization (S/S) is a very efficient technology for the treatment of contaminated mining sludge because it improves the stability of sludge dumping sites and reduces the leachability of contaminants. Very few studies investigate the S/S of mining sludge, especially with high water content. This paper investigated the effectiveness of S/S for the treatment of mining sludge at high water content by using quick lime (CaO) activated ground granulated blast furnace slag (GGBS) in comparison to ordinary Portland cement (OPC). To evaluate the mechanical, leaching, and microstructural behavior of CMS at high water content stabilized by lime-activated GGBS and OPC, a series of laboratory experimental tests were performed. Experimental results indicated that increasing the dosage of binder led to increased strength and decreased leachability of the heavy metal. In contrast, an increase in the water content of the mixture resulted in a decrease in compressive strength and an increase in the leachability of heavy metals. On the other hand, lime-activated GGBS mixes had substantially better performance than OPC mixes in the aspect of strength development of treated mining sludge and showed comparable capability of heavy metal stabilization compared to OPC. The microstructural tests revealed the formation of different hydration products such as calcium silicate hydrate, calcium aluminum silicate hydrate, ettringite, hydrotalcite, and heavy metal complexes in CG and OPC mixes.

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Microbial-Induced Carbonate Precipitation for Strengthening Soft Clay

Advances in Materials Science and Engineering ◽

10.1155/2020/8140724 ◽

2020 ◽

Vol 2020 ◽

pp. 1-11

Author(s):

J. Z. Xiao ◽

Y. Q. Wei ◽

H. Cai ◽

Z. W. Wang ◽

T. Yang ◽

...

Keyword(s):

Compressive Strength ◽

Water Content ◽

Unconfined Compressive Strength ◽

Soft Clay ◽

High Water ◽

High Water Content ◽

Carbonate Precipitation ◽

Experimental Conditions ◽

Strength Enhancement ◽

Complex Chemical Composition

Currently, calcite produced in sediments by microbial-induced carbonate precipitation (MICP) is mainly used as a strengthening binder in sand because sands are porous and have good permeability. Conventional wisdom does not consider MICP to be suitable for use in soft clay because of the clay particles’ small size and its minimal porosity. Because of the clay’s high water content and complex chemical composition, very little research has been done and not much is known about the use of MICP in soft clay for strength enhancement. For this paper, soft clay specimens were prepared by mixing a solution containing Sporosarcina pasteurii bacteria, solutions with different concentrations of nutrient salts, and soft clay. Unconfined compressive strength tests were carried out on these specimens after they had cured for 28 days in a moisture-controlled environment. These laboratory tests were used to study the chemical reactions, the clay’s strength, and other influencing factors. The results are as follows: (1) directly mixing a S. pasteurii solution, nutrient salts, and soft clay considerably improves the uniformity of the spatial distribution of the bacteria and the nutrients in the soft clay. Directly mixing these constituents promotes the formation of calcium carbonate and greatly simplifies soft clay sample preparation. (2) It is feasible to use MICP to increase the strength of soft clay. Compared to control specimens cured under the same conditions but without introduced nutrients and bacteria solution, the unconfined compressive strength of MICP-treated specimens can be increased by as much as 2.42 times to an unconfined compressive strength of 43.31 kPa. The water content in MICP-treated specimens was significantly reduced by the MICP reactions and in one case decreased from 40% to 30.73%. (3) The strength enhancement of microbially solidified soft clay is the result of two processes: urea hydration catalyzed by enzymes consumes water in the clay and the bacterially precipitated calcite forms in the sediment’s pores. (4) The micro-organism-produced calcite in the soft clay increases the calcite abundance from 0% to as much as 3.5%. (5) The MICP-treated strength of soft clay varies with the concentration of the nutrients provided. For the experimental conditions used for this paper, the optimum concentration of the CaCl2·2H2O and CH4N2O nutrients is 0.5 mol/L.

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Utilizing preferential vaporization to enhance the stability of spray combustion for high water content fuels

Combustion and Flame ◽

10.1016/j.combustflame.2014.01.012 ◽

2014 ◽

Vol 161 (8) ◽

pp. 2008-2014 ◽

Cited By ~ 7

Author(s):

Fei Yi ◽

Richard L. Axelbaum

Keyword(s):

Water Content ◽

High Water ◽

Spray Combustion ◽

High Water Content ◽

The Stability

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Stability of cactus-pear powder during storage

Revista Brasileira de Engenharia Agrícola e Ambiental ◽

10.1590/1807-1929/agriambi.v20n2p169-173 ◽

2016 ◽

Vol 20 (2) ◽

pp. 169-173

Author(s):

Plúvia O. Galdino ◽

Rossana M. F. de Figueirêdo ◽

Alexandre J. de M. Queiroz ◽

Pablícia O. Galdino ◽

Tâmila K. da S. Fernandes

Keyword(s):

Water Content ◽

Water Activity ◽

Reducing Sugars ◽

Titratable Acidity ◽

High Water ◽

Soluble Solids ◽

High Water Content ◽

Cactus Pear ◽

Total Titratable Acidity ◽

The Stability

ABSTRACT The stability of cactus-pear powder, obtained by the process of spray drying for 40 days, was evaluated under controlled conditions of relative air humidity (83%) and temperature (25 and 40 °C). The whole pulp was characterized with regard to its physico-chemical parameters: pH, total titratable acidity, soluble solids, water content, total solids, ashes, reducing sugars, total sugars, non-reducing sugars, luminosity, redness, yellowness and water activity. The stored samples in powder were evaluated every 10 days for water content, water activity, total titratable acidity and color (luminosity, redness and yellowness). The whole pulp was slightly acidic and perishable, due to the high water content. During storage, the packages did not prevent water absorption, thus increasing water content and, consequently, water activity. Yellowness oscillated along the storage time, but the predominance of the yellow color was not affected.

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Assessment of strength development in cement-admixed high water content clays with Abrams' law as a basis

Géotechnique ◽

10.1680/geot.2003.53.4.439 ◽

2003 ◽

Vol 53 (4) ◽

pp. 439-444 ◽

Cited By ~ 197

Author(s):

S. Horpibulsuk ◽

N. Miura ◽

T. S. Nagaraj

Keyword(s):

Water Content ◽

High Water ◽

High Water Content ◽

Strength Development

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The Role of Superabsorbent Polymer on Strength and Microstructure Development in Cemented Dredged Clay with High Water Content

Polymers ◽

10.3390/polym10101069 ◽

2018 ◽

Vol 10 (10) ◽

pp. 1069 ◽

Cited By ~ 5

Author(s):

Xia Bian ◽

Lingling Zeng ◽

Yongfeng Deng ◽

Xiaozhao Li

Keyword(s):

Compressive Strength ◽

Water Content ◽

Unconfined Compressive Strength ◽

High Water ◽

High Water Content ◽

Strength Increase ◽

Primary Role ◽

Superabsorbent Polymer ◽

Microstructure Development

This paper presents the role of superabsorbent polymer (SAP) on strength and microstructure development in cemented clays with notably high water content. A series of unconfined compressive strength (UCS), scanning electron microscope (SEM) and X-ray diffraction (XRD) tests were performed to identify strength behavior and microstructure. Results showed that SAP significantly influenced the mechanical behavior of cemented clays with notably high water content, characterized by an increase in the unconfined compressive strength and a decrease in the after-curing water content with SAP content. This revealed that the strength increase due to SAP was directly related to the water absorption by SAP. Meanwhile, XRD results showed that the hydration products were controlled by cement and lime content, regardless of SAP content. That meant there was no chemical reaction between SAP particles used in this study and cement or lime. The microstructure analysis by SEM revealed that SAP played an important role in the microstructure of cemented clays. With an increase in SAP content, the water absorbed by SAP increased significantly, leading to a decrease in the pore volume and a denser soil fabric. This behavior indicated that the primary role of SAP on strength increase was to absorb and fix water in cemented clays. Consequently, the clay–cement cluster distance decreased with an increase in solid mass (soil particles and swollen SAP particles) and a decrease in pore water. The corresponding tighter flocculated fabric due to SAP eventually led to the strength increase.

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Field Treatment of Storage Sludge and Stability Analysis of Overlying Municipal Waste Landfilling

Applied Sciences ◽

10.3390/app112412102 ◽

2021 ◽

Vol 11 (24) ◽

pp. 12102

Author(s):

Kaixi An ◽

Duanyang Zhuang ◽

Weian Lin ◽

Albert Argilaga ◽

Yunmin Chen ◽

...

Keyword(s):

Stability Analysis ◽

Water Content ◽

Limit Equilibrium ◽

High Sensitivity ◽

High Water ◽

Treatment Method ◽

Strength Properties ◽

High Water Content ◽

Critical Surface ◽

The Stability

Storage sludge has high water content and low shear strength, which limits the capacity expansion of overlying municipal landfilling. Few studies have addressed the field treatment of large amounts of storage sludge due to the variability of the depth of geotechnical property. This paper proposes a stratified treatment method for storage sludge, based on the in situ characterization of layered sedimentary patterns of the storage sludge acquired from the Qizishan landfill in China. Additionally, the stability of the landfilling above the sludge pond is analyzed using the Morgenstern–Price and limit equilibrium slice method, which considers the layered strength properties of solidified sludge. The treated sludge has a significant decrease in average water content from 1398% to 88% and an increase in average cohesion to 23.52 kPa. The high content of clay particles, low amount of solidification products, and high water content together result in the high sensitivity to the water content of the strength of deep solidified sludge. For a 40-m high waste body, stability analysis suggests a sliding surface across the raw sludge pond, while the critical surface remains outside the treated sludge pond and the safety factor is increased from 0.934 to 1.464. The validated stratified treatment provides valuable references for the treatment of deep sludge.

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Study on the Bearing Characteristics and Application of the Filling Body in Original Roadway Filling and Nonpillar Driving

Lithosphere ◽

10.2113/2021/4238008 ◽

2021 ◽

Vol 2021 (Special 4) ◽

Author(s):

Wenbao Shi ◽

Yan Li ◽

Jucai Chang

Keyword(s):

Water Content ◽

Coal Mining ◽

High Water ◽

High Water Content ◽

Working Face ◽

Geological Conditions ◽

Analysis Laboratory ◽

The Stability ◽

And Control

Abstract Original roadway filling and nonpillar driving can effectively solve the difficulty facing mining replacement in the stope of deep mines. As the bearing characteristics of the filling body in the original roadway play a crucial role in the structural stability of the overlying strata, with the recovery and geological conditions of 62210 working face in Xinzhuangzi Coal Mine, Huainan Mining Group, China, as the background, this study analyzed the stability characteristics of the filling body in the original roadway through comprehensive research methods of theoretical analysis, laboratory tests, and onsite monitoring. The results disclose that the filling body in the original roadway should boost early strength, strong bearing capacity, and long-term weakening. When the water-cement ratios are 1 : 1, 1.5 : 1, 2 : 1, 2.5 : 1, and 3 : 1, the strengths of the filling body are 1.12 MPa, 0.93 MPa, 0.57 MPa, 0.33 MPa, and 0.21 MPa at 2 h and 5.63 MPa, 4.66 MPa, 2.87 MPa, 1.65 MPa, and 1.02 MPa at 48 h, respectively. The strengths surge by 5 times within 2 d on the whole and reach the maximum at about 7 d, i.e., 8.12 MPa, 6.91 MPa, 6.60 MPa, 3.95 MPa, and 2.20 MPa, respectively. As time goes, the water content of the filling body gradually decreases and the compressive strength plunges. This demonstrates that the rapid solidification material with a high water content can satisfy the requirements of the bearing characteristics of the original roadway filling body. With reference to numerical simulation and the data monitored onsite, it can be known that the filling body in the original roadway can support the roof effectively and control the surrounding rock deformation of newly excavated roadways in the lower section. The research results provide theoretical guidance for coal mining under similar geological conditions and serve as reference for safe and efficient coal mining.

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