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Article

Experimental Study on Solidified Lake Sediment Based on Industrial Solid Waste and Construction Waste: Stabilization and Mechanism

by
Mengyi Liu
1,2,
Yiqie Dong
1,
Meng Zang
1,*,
Guanghua Cai
3 and
Haijun Lu
1,2,*
1
School of Civil Engineering and Architecture, Wuhan Polytechnic University, Wuhan 430023, China
2
State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, China
3
College Civil Engineering, Nanjing Forestry University, Nanjing 210037, China
*
Authors to whom correspondence should be addressed.
Buildings 2023, 13(8), 2053; https://doi.org/10.3390/buildings13082053
Submission received: 20 July 2023 / Revised: 8 August 2023 / Accepted: 10 August 2023 / Published: 11 August 2023
Browse Figures
Versions Notes

Abstract

:
Occupation of land and damage to the surrounding ecosystem may occur due to the accumulation of dredged lake sediments. In order to solve the large amount of dredged lake sediments, industrial wastes (slag, desulfurization gypsum) and urban construction waste were used to solidify the lake substrate, obtained a new construction material. Water content, volumetric shrinkage, unconfined compressive strength and flexural strength parameters and hydraulic conductivity coefficients of the solidified sediment were obtained from water content determination tests, volumetric shrinkage tests, unconfined compressive strength tests, flexural tests and permeation tests. Mineralogical composition and microstructural characterization of the solidified sediment using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were obtained. The solidification mechanism of lake sediment under the coupling of industrial waste and urban construction waste was revealed. The water content of the specimens decreased rapidly, and shrinkage deformation occurred in curing for 7 d. The volumetric shrinkage of 28 d was eventually maintained at 1.27–5.19%. The trend of specimen strength changed with the extension of time in the overall increase state, the compressive strength and flexural strength within 28 d were 3.15–10.96 MPa and 0.64–2.69 MPa, respectively. The solidified sediment material showed excellent anti-seepage performance, the hydraulic conductivity reached stability at 1.22 × 10−8–55.4 × 10−8 cm/s. Gismondine, gypsum, calcite, scawtite and fibrous C-S-H phases were generated in the solidified material.

1. Introduction

China’s river and lake dredging sediment production is huge; over 20 billion m3 of silt is deposited in rivers and lakes [1]. Between 2008 and 2012, a total of 39.1 million m3 of contaminated sediment was removed from the lakes and bays of Zhushan Lake, Meiliang Lake, Gong Lake and Dongtai Lake [2]. In addition to this, for example, the long-term accumulation of silt in the Great Lakes of North America (the world’s largest group of freshwaters) poses a threat to the ecosystem [3,4,5]. Among the sediment ex situ remediation treatment methods, the solidification method is mainly through the addition of solidification materials to the sediment. This leads to a series of physicochemical reactions of the clay minerals in the sediment, the nature of the sediment is changed and utilized again. Materials such as cement, fly ash and lime are commonly used for solidifying sediment. This method has been researched and used by most scholars and enterprises and achieved certain results due to its simple operation, large treatment capacity of sediment and short treatment time and high economic benefits [6].
The experimental results showed that the strength of the specimens was significantly improved after materials such as fly ash, cement, slag and lime were used as curing agents added to the sediment; at the same time, the cement plays a leading role in the increase in strength [7,8,9,10]. Cement and bentonite were used to solidify heavy metals, organic matter and other harmful substances in river and lake sediments. The results of the experiment found that the concentration of heavy metals appeared to stabilize, the concentration of organic matter decreased over time, and bentonite mainly acted as an adsorbent [11,12,13]. Similarly, cement, lime and sludge ash were used to stabilize marine dredged sediments, and the results showed that these materials could be used as substitutes for Polish cement. Hydration products were generated in the reaction process, the strength of the specimen increased, and the heavy metals were stabilized [14,15,16]. Phospho gypsum blended into cement was used for curing of dredged sediment, and the strength of the specimens was significantly improved. The permeability coefficients of the specimens were stable in the order of 10−5–10−6 cm/s, and the specimens showed good freeze–thaw resistance and volume stability [17]. After river and lake dredging, sediments were solidified by blast furnace slag, lime and cement; the main hydration products were found to be ettringite, gismondite and C-S-H by microscopic characterization such as X-ray diffraction and electron microscope scanning [18,19,20]. When cement solidifies river and lake substrates, it was found that too much water content resulted in shrinkage in the volume of the specimens and a decrease in the strength of the specimens. The pore water changed to hydrated water after sediment solidification and the pore structure was induced to be generated [21,22,23].
Rapid industrialization goes hand-in-hand with the generation of municipal waste. Per capita solid waste generation in Malaysia is about 1.1 kg per day [24]. In Bangladesh, urban centers generate about 23,688 tons of municipal solid waste (MSW) per day [25]. Globally, some 1.9 billion tons of municipal solid waste are now generated annually [26]. For industrial solid waste, such as such as tailings [27], sludge and sediment [28,29], fly ash [30,31] and electrolytic manganese residue [32], among others, poses a threat to the environment and human health. Take China, for example; construction waste stockpiles exceed 20 billion tons and industrial solid waste stockpiles exceed 30 billion tons. Of this, the annual production of construction waste is 3 billion tons per year, slag production in 2016 was 101.13 million tons [33]. These solid waste dumps generated large amounts of leachate, leading to contamination of groundwater and soil, and damage to the surrounding environment. In 2014, the release of the Report on the national general survey of soil contamination of the 188 solid waste treatment and disposal sites surveyed, 21.3% of the pollutant exceedance points were found. Therefore, for the realization of the dual-carbon strategy of “carbon peak and carbon neutral”, the resource utilization of solid waste and river and lake sediments is of great significance.
In this study, municipal construction waste and industrial solid waste were solidified on river and lake sediment to obtain a new type of construction material with both environmentally safe, high-strength, and low-permeability properties. Strength characteristics and water infiltration properties of the solidified sediment were investigated by unconfined compressive strength, flexural tests and permeation tests. XRD, FTIR and SEM tests were used to analyze the mineral grouping, functional group characteristics and micro-morphological features of the solidified soils, and the curing mechanism was revealed, and the environmental benefits of solidified substrate were verified by toxic leaching tests.

2. Materials and Methods

2.1. Material

The lake sediment used in the experiment was obtained from the soft sedimentary soil of East Lake in Wuhan City, Hubei Province. Multipoint random sampling of the substrate was performed using manual dredging; the dredged sediment was sealed in plastic buckets and transported back to the laboratory. The physical properties of the lake bottom sediment are shown in Table 1. The slag powder and desulfurization gypsum were purchased from SinoCen Smartec Co., Ltd., Wuhan, China. Desulfurization gypsum is in the form of yellowish-white powder, with no obvious particles seen. The slag powder was gray-white, with a specific surface area of 428 m2/kg, and a particle size of 1–38 µm, density 2.9 g/cm3. The construction waste was obtained from a construction waste recycling plant, dried in a 50 °C drying oven (DHG-9071A, Shanghai Yiheng Science and Technology Instrument Co., Ltd., Shanghai, China) and passed through a 0.15 mm sieve, then stored in a sealed bag. Quicklime is used as an alkali activator; the chemical compositions and contents of the materials are shown in Table 2. As shown in Figure 1, from the X-ray diffraction pattern of the dried sediment, it could be found that the mineral composition was mainly dominated by quartz, albite and anorthite, in that order. The construction waste powder was mainly composed of quartz, calcium carbonate, albite and C-S-H. Desulfurization gypsum was mainly composed of hydrated calcium sulfate. Slag mineral phase composition was more complex, mainly composed of calcium silicon, chromium oxide chloride, potassium iron phosphide, etc.
The lake substrate was removed from the sealed bucket, drained and put into a cement sand mixer (JJ-5, Wuxi Jian Ding Construction Instrument Factory, Wuxi, China). Then construction waste powder, desulfurization gypsum and slag were added sequentially according to different ratios, and mixed at low speed for 2 min. Then quicklime was added to distilled water to make a solution and mixed well, poured into the mixer and mixed at low speed for 5 min, so that the modified material and the sediment were fully mixed and homogeneous. The mixture was eventually pressed into a mold to prepare a solidified sediment specimen.

2.2. Test Methods

2.2.1. Mechanical Properties

In accordance with the GH1–GH9 test ratios in Table 3, the well-mixed solidified sediment material was filled into the mold and compacted. Specimen size was 50 mm in diameter and 100 mm in height. The water content and volume shrinkage changes in the solidified sediment were measured according to “Standard for Soil Test Methods” (GB/T 50123-2019). Specimens after 3, 7, 14, 21 and 28 d of indoor natural air-drying conditions were measured using a microcomputer-controlled electronic rock shearing instrument (YZW-30A, Jinan Puye Electromechanical Technology Co., Ltd., Jinan, China). In accordance with the specification of “Test code on polymer—modified cement mortar” (GB/T17671-1999). The homogenized material was compacted in a 40 mm × 40 mm × 160 mm rectangular mold. The compressive and flexural testing machine (ETM305F-2, Shenzhen Wanji Testing Equipment Co., Ltd., Shenzhen, China) was employed to perform flexural tests on the specimens.

2.2.2. Hydraulic Conductivity

According to the American experimental standard ASTM (D5084-03), the permeation test of the solidified sediment samples was conducted using an environmental geotechnical flexible wall permeameter (PN3230M, GEOEQUIP, Chesapeake, VA, USA) after 28 d of indoor natural conditioning. Before the permeation test, the specimen was first put into the vacuum saturated cylinder for 24 h, and then saturated with water for 48 h before the penetration test. Tests were conducted with upper and lower counter pressures of 30 and 60 KPa, respectively, and an enclosing pressure of 300 KPa. Each sample was a cylinder with 50 mm diameter and 100 mm height.

2.2.3. Toxicity Leaching Test

The leaching toxicity test of GH3 sample was tested using an inductively coupled plasma spectrometer (Aglient 5110, Agilent Corporation, PaloAlto, CA, USA), after 28 d of indoor natural maintenance conditions of GH3 sample, and was immersed in the distilled water 180 d. and environmental effects of curing of substrates was evaluated.

2.2.4. Micromechanics

Specimens GH1, GH3, GH4, GH7 and GH9 with 28 d of natural indoor maintenance as the test object, Combination of XRD (Smart Lab SE, Rigaku, Japan), SEM (Gemini SEM 300, Carl Zeiss AG, Oberkochen, Germany) and FTIR (Nicolet 6700, and Thermo Fisher Scientific, Waltham, MA, USA) were used to analyze the mineral composition, chemical characteristics and surface micromorphology of solidified sediment. The mechanism of action of industrial calcium-containing wastes in synergizing with construction waste powder to solidify sediment was revealed.

3. Results and Discussion

3.1. Moisture Content and Volumetric Shrinkage

Figure 2 shows the water content of solidified sediment samples from GH1 to GH9 as a function of time. The initial water content of GH1–GH9 specimens was 26.30−30.53%, and the water content of specimens decreased rapidly in 1–7 d, and gradually stabilized after 7 d. The water content of the specimens finally stabilized between 0.63% and 2.90% after 28 d. At the initial stage, the increase in temperature in the curing conditions resulted in the evaporation of water inside the specimen before it had time to react. And the addition of the activator introduced a portion of Ca2+; first, the charge on the surface of the substrate particles was neutralized by the exchange of cations such as Ca2+. The thickness of the bilayer of the sediment particles became thinner, the water passages were stretched out and water molecules were lost more quickly. At a later stage, reactive cations such as Ca2+ gradually started the hydration reaction, so the water content of the sample gradually stabilized. In addition, the added hardener was alkaline, deprivation of protein activity occurred in the sediment and hydrophilic groups -NH+, COO− on the surface of sediment colloidal particles were reduced. At this time, the adherent water content in the sediment was reduced [34]. Combined with the results of the XRD tests, it can be seen that the production of substances such as ettringite can convert free water inside the specimen to bound water. This also led to an increase in specimen strength and a decrease in moisture content.
Figure 3 shows the volumetric shrinkage changes in GH1–GH9 specimens at different curing ages. Volume shrinkage occurred mainly within 7 d and did not change after 7 d, gradually stabilizing from an initial 0–4.44% to 1.27–5.19%. Volume shrinkage of specimens GH2, GH5 and GH8 was more than 4% after 28 d. Drying shrinkage of the specimen volume was due to the emission of moisture. The first thing to dissipate inside the specimen was most of the free water, followed by the reduction in adsorbed and capillary water, and finally the interlayer water dissipates. The increase in capillary water led to the formation of negative pressure in the capillaries; as the humidity in the air decreased, the negative pressure gradually increased, creating a contraction force. In addition, due to the attractive force of the evaporation of adsorbed water, the particle spacing became smaller due to shrinkage of the gel inside the curing substrate. It is also partly due to the fact that the total volume of hydration products produced within the curing body was less than the total volume of the substance before the hydration reaction. Hence, it leads to some chemical shrinkage in the volume of the cured sediment.

3.2. Mechanical Properties

Figure 4 shows the graph of unconfined compressive strength of GH1–GH9 specimens versus time. The values of unconfined compressive strength of the specimens were 1.06–5.85 MPa when the specimens were cured for an age of 3 d, and the strength after 28 d was 3.15–10.96 MPa. The overall trend of specimen strength change is in the state of increasing, the strength of the specimens at a conservation age of 28 d was 1.63–9.45 times higher than that at 3 d. Most of the specimens showed an increase and then a decrease in compressive strength as the age was extended. These specimens showed a “strength inflection point” at about 21 d. The strength of the specimens at 28 d decreased by 2.49–25.44% compared to the 21-d strength. Only specimens GH5, GH7 and GH8 showed an increase in strength change with increasing curing time. The strengths of 28 d specimens GH5, GH7 and GH8 specimens were 8.97, 10.22 and 6.85 MPa, respectively. The increase in strength of cured sediment was mainly due to the generation of various hydration products filling the internal pores of the cured sediment, resulting in increased compactness and strength of the specimen.
Figure 5 shows the flexural strength values of GH1–GH9 specimens at a curing age of 28 d. The flexural strength of the specimen increases gradually with time. The strength of the specimens increased from 0.31–1.99 MPa to 0.64–2.69 MPa from 3 d to 28 d of age of maintenance. As with the compressive strength, the specimens showed inverted shrinkage at 21 d, except for specimens GH5, GH7 and GH8. The strengths of GH5, GH7 and GH8 specimens after 28 d were 2.45 MPa, 2.54 MPa and 0.64 MPa, respectively. Both unconfined compressive and flexural strength values in Figs. 3 and 4 increased rapidly in the 3–14 d pre-stage. After 14 d, there was a delay in strength. In the early stages of maintenance, the hydration reaction starts as soon as the curing agent comes into contact with the water in the sediment; large amounts of water were consumed and the hydration reaction was faster. At later stages, due to the dissipation of water molecules and the consumption of most of the reaction material, the reaction rate slows down and the rate of intensity growth was retarded. On the other hand, products such as C-S-H gel, hydrated calcium silica-aluminate gel (C-A-S-H) and ettringite, which were generated by the hydration reaction in the preliminary stage, will adhere to the surface of the slag particles or encapsulate the soil particles. These substances prevented other active materials from coming into contact with water, decreased the curing rate [35] and slowed the increase in specimen strength.
The slag contributed to the turning point of strength in Figure 5 because the used slag was alkaline slag. The slag has silica-rich and calcium-rich phases, and the Ca-O bonding energy was smaller than that of Si-O and Al-O and was easy to break. Slag with a calcium-rich phase was easier to dissolve and hydrate; thus, slag materials show high strength in the early hydration stage [36,37]. The presence of minerals such as tricalcium aluminate (C3A) result in high strength in the early stage of the specimen and, in the later stages, an increase in the strength of the delay or even a shrinkage phenomenon. In addition to this, the soil samples were small when the curing agent was first added. A tightly stabilized skeleton of soil particles was formed after the action of load compaction. With the enhancement of the maintenance time, the nature of the soil itself has changed to some extent; some of the water molecules were stripped away and the soil itself changed from small clayey soil particles to large particles. At this point, the cementing ability of the curing agent to the soil particles is reduced. And due to the early stages when the hydration reaction was intense, there was an increase in the number of soil particle agglomerates and an increase in internal pores and loosening of the structure. After being pressurized with the same load, the strength of the specimen decreased.

3.3. Hydraulic Conductivity

Figure 6 shows the permeability coefficients of GH1–GH9 specimens as a function of time at 28 d of age. The permeability coefficients of the GH1–GH9 specimens were finally stabilized at 1.22 × 10−8–55.4 × 10−8 cm/s. The permeability coefficients of each specimen initially showed a decreasing trend during the infiltration process. This is due to the large amount of free water inside the specimen after vacuum saturation. In the initial stage of pressurization, the pressure inside the specimen was not uneven, resulting in a pressure difference; at this point the permeability characteristics were in a fluctuating state. With upward counterpressure, downward counterpressure and circumferential pressure applied to the specimen all the time, the voids inside the sample were subjected to some external force, and the voids inside the sample became smaller, resulting in a lower permeability coefficient. On the other hand, internal microorganisms in the substrate metabolized during permeation tests; some organic and inorganic substances reacted and produced precipitation, which blocked the holes inside the curing body. After the final pressure was stabilized, the material inside the specimen no longer migrated and the coefficient was in a steady state. The hydration products generated in the cured body were mainly from hydration reactions between the test substrates and within the construction waste powder. In addition to this, the sediment itself contained chemically active components of SiO2 and Al2O3, which could react with Ca(OH)2 in a volcanic ash reaction. Hydration gelation products such as C-S-H, C-A-S-H and ettringite were generated, and the permeability of the specimen was improved.

3.4. Leaching Toxicity

Table 4 shows the identification standard value of leaching toxicity of toxic elements and the actual detection value of GH3 samples. According to the standard value of leaching toxicity identification of inorganic elements required in the specification of “Hazardous Waste Identification Standard Leaching Toxicity Identification” (GB 5085.3-2007), solutions of GH3 samples after 180 d of immersion were examined. The conventional elements Cu, Zn, Cr, Hg, Be and Ag were hardly detected. Leaching concentrations of other elements were 1–3 orders of magnitude lower than normative values; the concentration of harmful toxic elements in the specimens fully meets the requirements of the specification. Cured sediment materials do not pose a threat to the soil and water of the environment and are environmentally friendly.

3.5. Micro-Characterization

Figure 7 shows the XRD physical appearance examination of GH1, GH3, GH4, GH7 and GH9 specimens after 28 d of natural curing conditions. The main phases in the specimens were quartz, gypsum, gismondine, calcite and scawtite. A few peaks related to tobermorite, C-S-H and ettringite also occurred. The quartz in the material came from dried sediment and construction waste powder; gelling material was bonded around the crystal to form a crystalline mass, and the compactness of the specimen was, thus, increased. Gismondine was a rack-shaped silicate structure, large amounts of reactive SiO2 and Al2O3 in the substrate and the activator Ca(OH)2 could react to form gismondine [38]; the presence of this crystal increased the strength of the specimen.
C a ( O H ) 2 + A l 2 O 3 + S i O 2 + H 2 O → C a A l 2 S i 2 O 8 · 4 H 2 O   ( gismondine )
C a ( O H ) 2 + 4 C a S i O 3 + 2 C a ( O H ) 2 + 2 S i O 2 → C a 7 ( S i 6 O 18 ) ( CO 3 ) · 2 H 2 O   ( s c a w t i t e )
As the hydration reaction proceeded, silicon and aluminum continued to dissolve and some of the gismondine began to decompose. Ca2+ reacted with newly dissolved Si4+ and Al3+ to form C-S-H. The interior of the material was in an alkaline environment, and the pore solution inside the solidified body underwent a carbonation reaction when it came into contact with CO2 in the air. Ca(OH)2 crystals continuously dissolved in the hole solution and precipitated CaCO3 crystals, the enhancement of the characteristic peaks of Calcite in the GH4 style, combined with the SEM mapping and FTIR results of GH4 in Figure 8 and Figure 9, clearly demonstrates that CaCO3 was generated. Scawtite was produced by the reaction of calcium carbonate, calcium silicate and silica with Ca(OH)2 [39]; it was one of the silicate minerals. The presence of tobermorite calcium silicate hydrate compounds was due to volcanic ash reaction and alkali–silicate reaction (ASR). This partially hydrated silicate material has been present in construction waste for a long time. The hydration, volcanic ash and ASR reactions intensified with increasing maintenance time [40], leading to continued production of hydrated calcium silicate minerals. On the other hand, ettringite was mainly produced by the hydration reaction of gypsum dihydrate and tricalcium aluminate [41]. SO42- provided by desulfurization gypsum promoted the production of ettringite. In addition to C-S-H providing specimen cohesion and persistence, the ettringite was intercalated in the interstices of the individual gels to further consolidate the strength of the specimens.
The FTIR of GH1, GH3, GH4, GH7 and GH9 specimens after 28 d of natural curing conditions is shown in Figure 8. The absorption band in the vicinity of 3405 cm−1 belonged to the stretching band of water molecules, and 1622–1623 cm−1 absorption peaks were -OH and H-O-H vibration peaks in water molecules. The characteristic absorption peak vibrations of O-C-O were 1454–1474 cm−1 and 875–876 cm−1; this was due to the carbonization of CO2 in the air to produce CaCO3. Ca(OH)2 in the activator has a huge specific surface area to make the substrate particles agglomerated. It promoted the exchange of free Ca2+ with cations adsorbed on the sediment surface while coagulated the sediment, and it could cause the electrical properties to be neutralized and the volcanic ash reaction to be facilitated. The 1030–1031 cm−1 absorption bands were the T-O (T is Si or Al) asymmetric telescopic vibrational bands and symmetric telescopic vibrational bands in tetrahedral zeolite group minerals. This absorption band was caused by valence vibrations of Si-O or Al-O bonds [42].
The peaks of T-O (T for Si, Al) were most prominent throughout the IR spectrum, the entire reaction material was still dominated by hydrated silicate-like materials, and the presence of silicon oxide and alumina bonds may provide sufficient indication for silicate gel formation. When aluminum atoms were attached to the Si site, the cross-linking rate was very rapid, so the specimen has a high concentration of Si-O-Al bonds. The Si-O-Al bond peaks of the GH3 specimen bulge out, the Si-O band appears to peak at 1144 cm−1, which indicated a strong silicate polymerization reaction [43,44]. The vibrational peak of M-O (M for Mg and Al) was 670 cm−1, which was due to the Si-O-Si symmetric telescopic vibrations of the SiO2 crystallites. The symmetric stretching vibrational peaks of the Al-O-Al atom group were 524–529 cm−1. Combined with the infrared spectrum of LiAl2(OH)7·2H2O, it could be deduced that the vibration of this peak was caused by the formation of an Al2O7 skeleton by AlO4 tetrahedra within the substance. And 467–470 cm−1 was the result of anti-symmetric stretching vibrations of Si-O-Si in the silica –oxygen tetrahedron. Due to the presence of silica–oxygen tetrahedra in quartz crystals, the SiO2 in the solidified body mainly existed in the form of quartz crystals. In the GH7 specimen, the intensity of the -OH wave peaks weakened, the Si-O wave peaks disappeared and the CO32- functional groups increased. This may also re-verify the appearance of C-S-H and Fe6(OH)·12(CO3) products in the XRD results.
Figure 9 shows the SEM patterns of specimens GH1, GH4 and GH9. Aggregated, free-standing flakes with a diameter of 1–2 μm were generated in the GH1 specimen. Based on the XRD test results, the flake was tobermorite [45], which was produced by the reaction of different sources of silica and calcium cations; the longer the reaction time, the more tobermorite was produced. The surface morphology of the GH4 specimen was dense with many small smooth and uniform bumps on the surface. These small projections have a diameter of about 0.2–0.5 μm and were closely and uniformly arranged with each other. The material was analyzed as crystals of calcite based on XRD test results [46]. When the reaction time is too long, the calcium carbonate crystals began to glue together, sticking to each other, with a smooth rounded surface. GH9 specimens appeared in the lumpy gel and exhibited a large number of different lengths, thicknesses of fibrous and rod-like fracture material; the arrangement was disorganized. Based on the XRD test results, it could be inferred that these were mainly calcite and fibrous C-S-H phases. The solidified body composed of these substances has many holes and crevices in comparison with other specimens. This may be due to the expansion of the specimen volume as a result of the growth of materials such as ettringite. This could explain the low strength and high permeability coefficient test results of the solidified body of specimen GH9. And the calcium sulfate and Al2O3 in the substrate produce ettringite which was usually needle-like in shape.

4. Conclusions

  • In the study, with the resource utilization treatment of large quantities of river and lake sediments and solid wastes, new materials with certain strength and seepage control properties were obtained at the same time. The service performance of solidified sediment materials was systematically analyzed through volumetric shrinkage tests, unconfined compressive strength tests, flexural tests and permeation tests. By analyzing the mineral composition and microstructure of solidified materials, the coupled solidification mechanism of industrial solid waste and construction waste on river and lake sediment was revealed;
  • No cracks in the solidified materials appeared during maintenance in natural conditions, and volume shrinkage ranged from 1.27% to 5.19%. After 28 d of maintenance, the compressive strength reached 3.15–10.96 MPa and the flexural strength was 0.64–2.69 MPa. The specimen permeability coefficients eventually stabilized at 1.22 × 10−8–55.4 × 10−8 cm/s. The concentration of hazardous and toxic elements in the solution of GH3 samples after 180 d of immersion fully meets the requirements of the specification, with environmentally friendly properties. Under the action of Ca2+ and OH−, SiO2 and Al2O3 in the reactive substrate reacted with Ca(OH)2 to form gismondine. The reaction of Ca2+ and CO32− with SiO32− groups produced zeolites such as scawtite and afwillite. At the same time, C-S-H and ettringite were intercalated with soil particles inside the sediment; this bonding formed a solidified body with strength;
  • In this paper, the solidified materials were investigated only under natural working conditions. However, when this material is subjected to a number of complex environments, such as dry and wet freeze–thaw cycling conditions, acid, alkali, salt solutions and so forth, there is a need for further research to focus on the serviceability, durability and environmental aspects of the material.

Author Contributions

M.L.: conceptualization, methodology, data curation and writing—original draft. Y.D.: conceptualization, methodology and data curation. M.Z.: methodology, writing—review and editing and investigation. G.C.: methodology and investigation. H.L.: funding acquisition. All authors have read and agreed to the published version of the manuscript.

Funding

This work was funded by the National Natural Science Foundation of China (Grant No. U20A20320) and the Natural Science Foundation of Hubei Province of China (Grant No. 2022CFA011), and the authors are grateful for this financial support.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

If readers require the data from this article, please contact the corresponding author.

Conflicts of Interest

The authors declare no conflict of interest.

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Buildings 13 02053 g001aBuildings 13 02053 g001b
Figure 1. XRD patterns of raw materials. (a) Lake bottom sediment, (b) Construction waste powder, (c) Desulfurized gypsum, (d) Slag.
Figure 1. XRD patterns of raw materials. (a) Lake bottom sediment, (b) Construction waste powder, (c) Desulfurized gypsum, (d) Slag.
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Figure 2. Water content of solidified sediment samples.
Figure 2. Water content of solidified sediment samples.
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Figure 3. Volume shrinkage of solidified sediment samples.
Figure 3. Volume shrinkage of solidified sediment samples.
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Figure 4. Unconfined compressive strength of solidified sediment samples.
Figure 4. Unconfined compressive strength of solidified sediment samples.
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Figure 5. Flexural strength of GH1–GH9 specimens at 28 d of curing age.
Figure 5. Flexural strength of GH1–GH9 specimens at 28 d of curing age.
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Figure 6. Hydraulic conductivity of solidified sediment samples.
Figure 6. Hydraulic conductivity of solidified sediment samples.
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Figure 7. XRD patterns.
Figure 7. XRD patterns.
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Figure 8. FTIR patterns.
Figure 8. FTIR patterns.
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Figure 9. SEM charts.
Figure 9. SEM charts.
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Table 1. Indicators of physical properties of lake bottom sediment.
Table 1. Indicators of physical properties of lake bottom sediment.
IndexLiquid Limit (%)Plastic Limit (%)Plasticity (%)ProportionComposition of Particles (%)
Sample Sand (0.02–2 mm)Silt
(0.002–0.02 mm)		Clay
(<0.002 mm)
sediment60.535.325.22.6523.3%56.4%20.3%
Table 2. The material ratio of modified sludge sample.
Table 2. The material ratio of modified sludge sample.
Raw MaterialsMain Chemical Composition/%LOI
SiO2Al2O3Fe2O3CaOMgOSO3Na2OP2O5TiO2K2OMnOOthers
Lake bottom sediment57.3117.449.656.952.24/0.6010.171.183.460.130.877.9
Slag27.3612.471.4137.217.332.320.480.01/1.350.529.540.68
Desulfurized gypsum2.380.900.4845.360.6249.160.170.020.050.180.010.6718.4
Construction waste powder39.878.936.0335.072.013.091.030.170.762.310.180.552.56
Table 3. Material proportioning of GH1–GH9 samples.
Table 3. Material proportioning of GH1–GH9 samples.
Sample
Number		Lake Bottom Sediment (%)Construction Waste Powder:Desulfurized Gypsum:SlagConstruction Waste Powder
(%)		Desulfurized Gypsum
(%)		Slag
(%)		Lime
(%)
GH165%1:1:111.00%11.00%11.00%2.00%
GH265%1:2:26.60%13.20%13.20%2.00%
GH365%1:3:34.71%14.14%14.14%2.00%
GH465%2:1:213.20%6.60%13.20%2.00%
GH565%2:2:39.43%9.43%14.14%2.00%
GH665%2:3:111.00%16.50%5.50%2.00%
GH765%3:1:314.14%4.71%14.14%2.00%
GH865%3:2:116.50%11.00%5.50%2.00%
GH965%3:3:212.38%12.38%8.25%2.00%
Table 4. Identification standard value of leaching toxicity of toxic elements and test value of GH3 samples.
Table 4. Identification standard value of leaching toxicity of toxic elements and test value of GH3 samples.
NumberHazardous IngredientsSymbolConcentration of Hazardous Components in Leachate (mg/L)
Requirements LimitsRequirements Limits
1Copper (as total copper)Cu1000.016
2Zinc (as total zinc)Zn1000.000
3Cadmium (as total cadmium)Cd10.002
4Lead (as total lead)Pb50.025
5Total chromiumCr150.005
6Mercury (as total mercury)Hg0.10.000
7Beryllium (total beryllium)Be0.020.000
8Barium (as total barium)Ba1000.035
9Nickel (as total nickel)Ni50.013
10Total silverAg50.000
11Copper (as total copper)As50.140
12Zinc (as total zinc)Se10.042
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Liu, M.; Dong, Y.; Zang, M.; Cai, G.; Lu, H. Experimental Study on Solidified Lake Sediment Based on Industrial Solid Waste and Construction Waste: Stabilization and Mechanism. Buildings 2023, 13, 2053. https://doi.org/10.3390/buildings13082053

AMA Style

Liu M, Dong Y, Zang M, Cai G, Lu H. Experimental Study on Solidified Lake Sediment Based on Industrial Solid Waste and Construction Waste: Stabilization and Mechanism. Buildings. 2023; 13(8):2053. https://doi.org/10.3390/buildings13082053

Chicago/Turabian Style

Liu, Mengyi, Yiqie Dong, Meng Zang, Guanghua Cai, and Haijun Lu. 2023. "Experimental Study on Solidified Lake Sediment Based on Industrial Solid Waste and Construction Waste: Stabilization and Mechanism" Buildings 13, no. 8: 2053. https://doi.org/10.3390/buildings13082053

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