scholarly journals Investigation On Stabilization/Solidification Characteristics of Lead Contaminated Soil Using Innovative Composite Model of Cement And Soda Residue

2021 ◽  
Author(s):  
Xiaoyu An ◽  
Dianjun Zuo ◽  
Fei Wang ◽  
Chao Liang
Keyword(s):  
Compressive Strength ◽  
Contaminated Soil ◽  
Contaminated Soils ◽  
Unconfined Compressive Strength ◽  
Large Scale ◽  
Scientific Data ◽  
Composite Model ◽  
Engineering Practice ◽  
Curing Agent ◽  
Site Remediation

Abstract The cement solidification/stabilization method of heavy metal contaminated soils has been promoted in engineering practice and applied on a large scale for site remediation, but it still reveals some scientific problems in the current complex and variable global extreme climate. To solve these problems and explore cement-based soil remediation technology, this study used the waste soda residue produced in large quantities in the "ammonia-soda process" as a composite additive, and established an innovative composite model of cement and soda residue by adding different ratios, which was applied to the remediation experiments of lead-contaminated soil. The innovative composite model solidification/stabilization of cement and soda residue for unconfined compressive strength and toxic leaching properties under different soil environmental conditions were investigated. Moreover, curing and leaching mechanisms are discussed, and future industrial practice was evaluated. The results showed that the addition of soda residue improved the early (20 days) unconfined compressive strength (UCS) of the composite curing agent for lead-contaminated soil by an average of 23.1% Mpa. When the percentage of soda residue composite was 40%, the UCS strength was 0.96 Mpa, which reached the maximum. The concentration of Pb2+ in the leachate of the cement-soda residue composite curing agent was greatly reduced (average 3.28 times) compared with that of a single cement in the same situation, with an average leached Pb2+ concentration of 1.87 mg·L-1. This indicates that the addition of alkali residue improved the curing effect. The curing mechanism was divided into four steps, mainly a complex physicochemical reaction between the cement-soda residue composite and soil particles. The leaching mechanism of cement-soda residue to aqueous solution is mainly the consumption of acid ions by alkaline substances. This study will provide scientific data to support potential lead-containing soil in site remediation technologies and future large-scale engineering applications.

scholarly journals Effect of Ca/Al Ratio on Stabilization/Solidification of Lead-Contaminated Soil by Ettringite

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Lian Xiang ◽  
Huamei Zhu ◽  
Ruoyun Zhou
Keyword(s):  
Compressive Strength ◽  
Contaminated Soil ◽  
Contaminated Soils ◽  
Unconfined Compressive Strength ◽  
Lead Concentration ◽  
Ph Value ◽  
Microstructural Characteristics ◽  
Ph Values ◽  
Lead Leaching ◽  
Time Lead

Ettringite is commonly used for the stabilization/solidification for heavy metal-contaminated soils, and its treatment effect will be influenced by Ca/Al mole ratio. Lead-contaminated soil samples were solidified using ettringite with different Ca/Al mole ratios. The pH value, unconfined compressive strength of solidified samples, and leaching concentration were investigated to understand the influence of Ca/Al mole ratio on properties of ettringite-solidified contaminated soils. The microstructural characteristics of solidified contaminated soils were also explored. The results show that lead leaching concentration decreases dramatically with increasing the content of lime and curing time. Lead concentration drops from 49.89 mg/L to 0.19 mg/L when Ca/Al mole ratio increases from 4 : 3 to 10 : 3 at 28 days and from 36.57 mg/L to near 0 mg/L at 90 days. In addition, the unconfined compressive strength of samples drops at first and then increases with the increase of Ca/Al mole ratio. Besides, the pH values of solidified soil and leachate rise with the increase of content of lime. The pH values of solidified soil increase from 9.68 to 11.34, and there is little difference between 28 days and 90 days. However, the pH values of leachate increase from 5.56 to 8.59 at 28 days, and 90-day pH values increase from 5.65 to 9.44. The results of SEM, XRD, and EDS tests also indicate that Ca/Al mole ratio affects the shape of ettringite, the stabilization/solidification effectiveness of contaminated soil, and the pore of solidified soil. When Ca/Al mole ratio equals to 8 : 3, ettringite content has a substantial increase, and lead leaching concentration is lower than 5 mg/L.

scholarly journals Study on Strength Characteristics of Solidified Contaminated Soil under Freeze-Thaw Cycle Conditions

2018 ◽  
Vol 2018 ◽  
pp. 1-5 ◽  
Author(s):  
Qiang Wang ◽  
Jinyang Cui
Keyword(s):  
Electron Microscopy ◽  
Compressive Strength ◽  
Contaminated Soils ◽  
Unconfined Compressive Strength ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Strength Tests ◽  
Freeze Thaw Cycle ◽  
Microcosmic Mechanism ◽  
Scanning Electron

Cement solidification/stabilization is a commonly used method for the remediation of contaminated soils. The stability characteristics of solidified/stabilized contaminated soils under freeze-thaw cycle are very important. A series of tests, which include unconfined compressive strength tests, freeze-thaw cycle tests, and scanning electron microscopy (SEM) tests, are performed to study the variation law of strength characteristics and microstructure. It aims at revealing the microcosmic mechanism of solidified/stabilized Pb2+ contaminated soils with cement under freeze-thaw cycle. The results show that the unconfined compressive strength of the contaminated soils significantly improved with the increase of the cement content. The unconfined compressive strength of stabilized contaminated soils first increases with the increase of times of freeze-thaw cycle, and after reaching the peak, it decreases with the increase of times of freeze-thaw cycle. The results of the scanning electron microscopy tests are consistent with those of the unconfined compressive strength tests. This paper also reveals the microcosmic mechanism of the changes in engineering of the stabilized contaminated soils under freeze-thaw cycle.

Research on the Strength Growth Model of Peat Soil

2014 ◽  
Vol 1030-1032 ◽  
pp. 860-863
Author(s):  
Jing Wei Wang ◽  
Wen Pan ◽  
Zhuo Yin Jiang
Keyword(s):  
Compressive Strength ◽  
Growth Model ◽  
Unconfined Compressive Strength ◽  
Peat Soil ◽  
Curing Agent ◽  
Construction Waste

The Dian Lake Peat soil is studied as the research object in this paper, through the strengthening treatment by adding the cement and some suitable additives as well as a certain amount of waste residue, the compressive strength are taken into consideration in comparison in the different curing composition and other factors in performance of solidified soil. And it importantly discussed the applicability of curing agent and different variables (cement, the formula of curing agent, construction waste, age) in the incremental changes of unconfined compressive strength of curing peat soil.

scholarly journals Effect of lime on the mechanical response of a soil for use in unpaved forest roads

2019 ◽  
Vol 42 ◽  
pp. e44764
Author(s):  
Gissele Souza Rocha ◽  
Claudio Henrique de Carvalho Silva ◽  
Heraldo Nunes Pitanga ◽  
Ecidinéia Pinto Soares de Mendonça ◽  
Dario Cardoso de Lima ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Unconfined Compressive Strength ◽  
Mechanical Response ◽  
Soil Mass ◽  
Base Layer ◽  
Unit Weight ◽  
Engineering Practice ◽  
Technical Literature ◽  
Forest Roads ◽  
Strength Tests

The main objective of this study was to propose the application of soil-lime mixtures asa primary coating layerof unpavedforestroads based on the premise that this layer can be considered mechanically similar to a flexible pavementsub base layer, aiming to fill a gap in the current technical literature and engineering practice in this field of knowledge. In the study, a laboratory test program was carried out in a residual gneiss soil encompassing: (i) geotechnical characterization tests; (ii) compaction tests at the standard Proctor energy on soil specimens and on soil-lime mixturespecimens prepared with lime contents of 2, 4 and 6% related to the dry soil mass; (iii) unconfined compressive strength tests on soil specimens compacted at the standard Proctor optimum parameters; and (iv) unconfined compressive strength tests on specimens of soil-lime mixtures compacted at the standard Proctor optimum compaction parameters with lime contents of 2, 4 and 6%, and cured at 22.8°C in the curing periods of 3, 7, 28 and 90 days. The results showed that the addition of lime resulted in: (i) reduction in soil maximum dry unit weight (gdmax) and increase in soil optimum water content (wopt);and(ii) significant gains in soil unconfined compressive strength that evidenced the expressive occurrence of pozzolanic reactions in the mixtures.Based on the hypothesis of a similar requirement for soil-cement and soil-lime mixtures, the tested soil-lime mixtures met the minimum mechanical strength (1.2MPa) required for application as a primary coating layer of unpaved forest roads.

scholarly journals Experimental Study on Electrical Resistivity of Cement-Stabilized Lead-Contaminated Soils

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Zhiguo Cao ◽  
Lian Xiang ◽  
Erxing Peng ◽  
Kai Li
Keyword(s):  
Compressive Strength ◽  
Electrical Resistivity ◽  
Contaminated Soils ◽  
Unconfined Compressive Strength ◽  
Cement Content ◽  
Resistivity Measurement ◽  
Lead Content ◽  
Electrical Resistivity Measurement ◽  
Fundamental Parameter ◽  
Curing Time

Geotechnical applications based on soil resistivity measurement are becoming more popular in recent years. In order to explore the potential application of the electrical resistivity method in stabilization/solidification of contaminated soils, two kinds of lead-contaminated soils stabilized with cement were prepared, and the electrical resistivity and unconfined compressive strength of specimens after curing for various periods were measured. The test results show that a high lead content leads to a low value of electrical resistivity of cement-stabilized soils, and increasing cement content and curing time result in a significant increase in electrical resistivity. The reduction in porosity and degree of saturation, as a result of the cement hydration process, leads to an increase in electrical resistivity. The ratio of porosity-lead content/cement content-curing time, combining together the effect of lead content, cement content, curing time, and porosity on electrical resistivity of stabilized soils, can be used as a fundamental parameter to assess electrical resistivity of cement-stabilized lead-contaminated soils. Archie’s law can be extended to apply to cement-stabilized lead-contaminated soils by using this ratio, replacing the porosity. The new resistivity formula obtained in this paper is just empirical. There is a power function correlation between unconfined compressive strength and electrical resistivity of lead-contaminated soils stabilized with cement. Electrical resistivity measurement can be used as an economical and time-effective method to assess the quality of cement-stabilized lead-contaminated soils in practice.

scholarly journals Isolation of bacteria from diesel contaminated soil for diesel remediation

2019 ◽  
Vol 28 ◽  
pp. 33-41 ◽  
Author(s):  
OA Oyewole ◽  
SS Leh Togi Zobeashia ◽  
OE Oladoja ◽  
IO Musa ◽  
IT Terhemba
Keyword(s):  
Bacillus Subtilis ◽  
Bacillus Cereus ◽  
Soil Sample ◽  
Contaminated Soil ◽  
Contaminated Soils ◽  
Large Scale ◽  
Bacterial Species ◽  
Plastic Container ◽  
Hydrocarbon Concentration ◽  
Optimum Ph

This study is aimed at isolating bacterial species that inhabit diesel contaminated soil and also screened these isolates for the ability to be used for remediating diesel contaminated environment using their potential to degrade diesel as carbon and energy source. Top soil sample was collected from an ancient diesel-powered generator house in Minna, Nigeria, in a sterilized plastic container while diesel oil was obtained from local petrol bunk. Four bacterial isolates were isolated from the diesel contaminated soil sample and were screened for their ability to degrade diesel using mineral salt medium (MSM). The isolates with highest biodegradation potential were identified as Bacillus subtilis and Bacillus cereus. The optimum pH (5, 6, 7 and 8) and hydrocarbon concentration (1%, 2%, 5% and 10%) of the isolate was determined by spectrophotometry and the result revealed that the optimum pH for biodegradation of diesel by Bacillus subtilis and Bacillus cereus, was 7 (1.170) and 8 (1.745) respectively while the optimum hydrocarbon concentration degradation for both isolates was 5% (2.22) and 1% (2.37) respectively. The results of this study showed that these isolates were able to degrade diesel and can be useful for large scale bioremediation of diesel contaminated soils. J. bio-sci. 28: 33-41, 2020

Study on the Strength Characteristics of Sludge Solidification

2015 ◽  
Vol 744-746 ◽  
pp. 628-631
Author(s):  
Yi Xiang Chen ◽  
Kai Xi An ◽  
Ke Xin Zhou ◽  
Chen Hao Xu
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Unconfined Compressive Strength ◽  
Strength Test ◽  
Experimental Results ◽  
Strength Characteristics ◽  
Curing Agent ◽  
Foundation Treatment ◽  
Compressive Strength Test ◽  
Stabilized Soil

In order to reveal the effect of type of admixture and its content on the strength of stabilized soil, this paper uses the sludge as raw soil and cement, fly ash as curing agent, and analyzes the strength characteristics of samples mixed stabilized according to certain content. Using the unconfined compressive strength test, the compressive strength of the samples is tested. The effect of curing agent type and its content on the compressive strength is investigated. From the experimental results, it can be seen that the content of cement and fly ash has much effect on the strength. The conclusions obtained can have some conference values on the foundation treatment and reuse of waste resources utilization.

scholarly journals Test on the Stabilization of Oil-Contaminated Wenzhou Clay by Cement

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Chuang Yu ◽  
Raoping Liao ◽  
Chaopeng Zhu ◽  
Xiaoqing Cai ◽  
Jianjun Ma
Keyword(s):  
Contaminated Soil ◽  
Contaminated Soils ◽  
Unconfined Compressive Strength ◽  
Liquid Limit ◽  
Soil Samples ◽  
Experimental Results ◽  
Engineering Properties ◽  
Contaminated Sites ◽  
Coastal Cities ◽  
Scanning Electron

Oil-contaminated soils have been paid much attention due to the reclamation of industrial lands in coastal cities of China. As known, oil-contaminated soils are inapplicable for construction due to their weak engineering properties, thus leading to the requirement of remediation and reclamation for oil-contaminated sites. This study presents an experimental investigation on the stabilization of contaminated soils with Portland cement. Investigations including the Atterberg limits, unconfined compressive strength, direct shear strength, and microstructure of cement-stabilized soils have been carried out, verifying the suitability of applying cement to improve engineering properties. Experimental results show that the geotechnical properties of contaminated soil are very poor. With the application of cement, the liquid limit and plasticity index of contaminated soil samples decrease dramatically, and the strength of treated soils has been improved. Experimental results from scanning electron microscope (SEM) indicate that cement-stabilized oil-contaminated soil is featured with a stable supporting microstructure, owing to the cementation between soil particles. This also confirms the applicability of cement to be served as an additive to treat oil-contaminated soils.

Prediction of end-bearing capacity of rock-socketed shafts considering rock quality designation (RQD)

2010 ◽  
Vol 47 (10) ◽  
pp. 1071-1084 ◽  
Author(s):  
Lianyang Zhang
Keyword(s):  
Compressive Strength ◽  
Rock Mass ◽  
Unconfined Compressive Strength ◽  
Empirical Relation ◽  
Intact Rock ◽  
Engineering Practice ◽  
Rock Quality Designation ◽  
End Bearing Capacity ◽  
Rock Quality ◽  
Empirical Relations

Existing empirical methods for determining the end-bearing capacity, qmax, use empirical relations between qmax and the unconfined compressive strength of intact rock, σc. As rock-socketed shafts are supported by the rock mass, not just the intact rock, one should consider not only the intact rock properties, but also the influence of discontinuities on rock mass properties when determining qmax. Although semi-empirical and analytical methods have been developed that can consider the effect of discontinuities, they are more complicated than the empirical relations and require information about discontinuities that is often not available or difficult to obtain in engineering practice. In this paper, an empirical relation between qmax and the unconfined compressive strength of rock mass, σcm, is developed. The new empirical relation explicitly considers the effect of discontinuities represented by rock quality designation (RQD), which is the parameter normally obtained in engineering practice. The accuracy of the expression for estimating σcm based on RQD is verified by comparing its estimation values with those from the existing empirical expressions based on rock mass classification. Two examples are presented to show the application of the newly developed empirical relation between qmax and σcm.

scholarly journals Stabilization/Solidification of Zinc- and Lead-Contaminated Soil Using Limestone Calcined Clay Cement (LC3): An Environmentally Friendly Alternative

2020 ◽  
Vol 12 (9) ◽  
pp. 3725 ◽  
Author(s):  
Vemula Anand Reddy ◽  
Chandresh H. Solanki ◽  
Shailendra Kumar ◽  
Krishna R. Reddy ◽  
Yan-Jun Du
Keyword(s):  
Compressive Strength ◽  
Contaminated Soil ◽  
Contaminated Soils ◽  
Low Cost ◽  
Construction Material ◽  
Environmentally Friendly ◽  
Cementitious Materials ◽  
Low Carbon ◽  
Untreated Soil ◽  
Calcined Clay

Due to increased carbon emissions, the use of low-carbon and low-cost cementitious materials that are sustainable and effective are gaining considerable attention recently for the stabilization/solidification (S/S) of contaminated soils. The current study presents the laboratory investigation of low-carbon/cost cementitious material known as limestone-calcined clay cement (LC3) for the potential S/S of Zn- and Pb-contaminated soils. The S/S performance of the LC3 binder on Zn- and Pb-contaminated soil was determined via pH, compressive strength, toxicity leaching, chemical speciation, and X-ray powder diffraction (XRPD) analyses. The results indicate that immobilization efficiency of Zn and Pb was solely dependent on the pH of the soil. In fact, with the increase in the pH values after 14 days, the compressive strength was increased to 2.5–3 times compared to untreated soil. The S/S efficiency was approximately 88% and 99%, with increase in the residual phases up to 67% and 58% for Zn and Pb, respectively, after 28 days of curing. The increase in the immobilization efficiency and strength was supported by the XRPD analysis in forming insoluble metals hydroxides such as zincwoodwardite, shannonite, portlandite, haturite, anorthite, ettringite (Aft), and calcite. Therefore, LC3 was shown to offer green and sustainable remediation of Zn- and Pb-contaminated soils, while the treated soil can also be used as safe and environmentally friendly construction material.

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