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Article

Stabilization of Fluidic Silty Sands with Cement and Steel Slag

by
Leilei Gu
1,
Xianjun Deng
1,
Mei Zhang
1,
Shengnian Wang
2,*,
Bin Li
1 and
Jiufa Ji
1
1
CCCC First Highway Engineering Bureau Co., Ltd., Beijing 100024, China
2
College of Transportation Science & Engineering, Nanjing Tech University, Nanjing 211816, China
*
Author to whom correspondence should be addressed.
Buildings 2023, 13(11), 2705; https://doi.org/10.3390/buildings13112705
Submission received: 19 August 2023 / Revised: 20 October 2023 / Accepted: 24 October 2023 / Published: 26 October 2023
(This article belongs to the Special Issue Advances in Low-Carbon Buildings)
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Abstract

:
Fluidic silty sand is often difficult to use directly in engineering construction because of its low strength and plasticity index. This study employed steel slag to replace part of the cement in silty sand stabilization to broaden the feasibility of resource recycling and to reduce the construction cost and carbon emissions in engineering practices. A series of indoor tests investigated the influences of the cement/steel slag ratio, initial water content, curing age, and temperature on the compressive strength of cement- and steel slag-stabilized fluidic silty sands (CSFSSs). Their stabilization mechanism was discussed via microstructural observation and spectral analysis. The results showed that the most economical cement/steel slag ratio could be 9:6, saving 40% of cement and not changing with the initial water content. The compressive strength of the CSFSSs decreased with the initial water content and increased rapidly and then slowly over the curing age. The curing temperature had a positive impact on their strength growth. The microstructure characteristics and spectral analysis showed that adding steel slag indeed affected the formation of gels in the cement-stabilized fluidic silty sands. This study could reference the application of CSFSSs in engineering practices.

1. Introduction

Fluidic silty sands have a high moisture content, low plasticity index, low cohesion, poor bearing capacity, low strength growth rate, and significant post-construction settlement [1,2]. They are thus not easy to use in engineering construction directly. However, traditional disposal measures, including open-air storage and landfill treatment, would bring about significant secondary environmental issues such as land occupation, ground dust, and water pollution [3]. Hence, improving the engineering performances of fluidic silty sands and utilizing them as resources have become hot issues in the current engineering research. Using cement for soil stabilization was a common strategy due to its reliability and rapidity [4]. Still, cement is an industrial product with a high energy consumption and cost, accompanied by dramatic carbon emissions. It always results in cost issues in soil stabilization and is environmentally unfriendly [5]. Particularly, more cement would be used for fluidic soil stabilization. Ensuring the mechanical performance requirements and reducing the cost of soil stabilization with cement have been very attractive topics in engineering practices worldwide.
Mineral admixtures can replace part of the cement and improve the engineering performance of weak soils stabilized with cement [6,7,8]. Many mineral admixtures originate from industrial solid wastes, such as fly ash, steel slag, and blast furnace slag, since they contain high amounts of silicon aluminum mineral components [8,9,10]. Ma et al. [11] studied the influence of fly ash on cement-stabilized rammed earth and found that adding fly ash could improve its compressive strength and secant modulus. Xie et al. [12] pointed out that the strength development of cement-stabilized soils could be increased significantly with the silica fume content. Lang et al. [10] and Jiang et al. [5] clarified the influences of factors such as the particle size and content of steel slag on the compressive performance of soil and pointed out that the optimum content of steel slag for soil stabilization was 5–10%. The tinier the size of the steel slag particles, the better their activities and the more excellent their compressive performances. Toda et al. [3] used two types of steel slags to stabilize dredged soils and confirmed that the SiO2 content in the steel slag was a decisive factor in improving the soil strength. All of these documented studies prove the effectiveness of using mineral waste in soil stabilization.
In terms of soil stabilization, Aziz et al. [13] reported that adding graphene oxide could improve the compressive strength of cement-stabilized silty soils. Horpibulsuk et al. [4] found that the pores in silty clay could be gradually filled with cement-hydrated gels, causing a continuous strength improvement until the hydration reaction ended. Gupta et al. [14] found that the dredging soil with 10% cement and 10% bottom slag had the best bearing capacity and structural compactness. Dungca et al. [15] indicated that the river-dredged soil had the best mechanical performance and good impermeability when stabilized by 30% fly ash. Ingunza et al. [16] pointed out that the largest strength improvement of cement-stabilized soil was with 20% sludge ash. Yun et al. [17], Marzano et al. [18], and Zhang et al. [19] indicated that a high curing temperature would lead to a rapid increase in the early strength and achieve a higher later strength. Lu et al. [20] studied the influences of polypropylene fiber and fly ash on cement-stabilized silty soil. They found that their mechanical performances were increased first and then decreased with polypropylene fiber and fly ash dosages. Sayed et al. [21] and Chaeet al. [22] discussed the reduction in calcium hydroxide (CH) and the generation of calcium silicate hydrate (CSH) gels in cement-based materials through a spectral analysis.
Many scholars have also devoted themselves to understanding the microstructural evolution and stabilization mechanism of cement- and steel slag-stabilized soft soils. Liu et al. [23] pointed out that the massive hydration products generated in the initial curing age contributed to the significant increase in the early strength. Lang et al. [8] and Dong et al. [24] confirmed that adding the proper amount of steel slag powder could efficaciously ameliorate the pore size and distribution of cement- and steel slag-stabilized soil. Mozejko et al. [25] observed that adding 12% steel slag by the weight of dry clayey silty soils increased their unconfined compressive strength by 200%. Lei et al. [8] reported that the maximum long-term strength development of dredged sludges was achieved by using 15% cement and 20% steel slag powder. Deng et al. [26] found a preferable mass ratio of cement, metakaolin, and steel slag to be 50:15:85. Wu et al. [27] indicated that the steel slag’s resistance to seawater erosion was better than that of cement. These studies can provide beneficial references for meeting the engineering performance requirements of cement- and steel slag-stabilized fluidic silty sands (CSFSSs).
This study employed steel slag powder to replace part of the cement to broaden the resource recycling of fluidic silty sands and reduce their construction costs and carbon emissions in engineering practices. A series of unconfined compression tests investigated the influences of the cement/steel slag ratio, initial water content, curing age, and curing temperature on the compressive strengths of CSFSSs. The internal stabilization mechanism of these fluidic soils was disclosed and discussed via Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), and Fourier-Transform Infrared Spectroscopy (FTIR).

2. Materials

2.1. Fluidic Soil

The fluidic silty sand used in this study was collected from an underground site in the Class III channels of the Zhejiang Section of the Beijing–Hangzhou Grand Canal. A screening experiment obtained their grading curve, as shown in Figure 1. Since the density, specific gravity, water content, and liquid plastic limit are the most important physical property indicators of soil, only these indicators of this fluidic soil following the Standard for Geotechnical Testing Method [28] issued by the Ministry of Housing and Urban-Rural Construction of the People’s Republic of China are listed in Table 1. All ratios specified by % in this study are in weight.

2.2. Cement

Ordinary Portland cement (P.O 42.5) was used for fluidic silty sand stabilization. The main chemical components of this cement are listed in Table 2.

2.3. Steel Slag

The steel slag used in the indoor tests was collected from a steel slag yard in Ma’anshan, China. It was crushed into a fine powder of less than 0.075 mm. The SEM and Energy Dispersive Spectrometer (EDS) tests were carried out to determine the steel slag’s particle characteristics and chemical composition. As shown in Figure 2, the most abundant elements in the steel slag were Ca and Si, accounting for about 90% of the total in weight; it had fewer amounts of Fe and Mg; and it had the least amount of Al. Figure 3 shows the morphologic characteristics of steel slag particles at different magnifications via SEM. It can be observed that the steel slag was amorphous, and the particle size was extremely uneven. Table 3 lists the chemical components and their contents in weight. Among them, the highest composition in this steel slag was Cao, accounting for 59.2%; SiO2 followed, accounting for 29.1%; and Fe2O3, MgO, and Al2O3 were the least, accounting for 6.5%, 3.9%, and 1.4%, respectively.

3. Test Design

3.1. Test Scheme

The main aim of this research is to explore the optimum cement/steel slag ratio for fluidic silty sand stabilization and then reveal the influences of the initial water content, curing age, and curing temperature on the mechanical performance of cement- and steel slag-stabilized fluidic silty sands and their stabilization mechanisms. Therefore, the whole test referred to the mechanical strength and microscopic tests.

3.1.1. Mechanical Strength Tests

The control variable method was applied to determine the optimal cement/steel slag ratio and the influences of the previously addressed factors on the strength performance of cement- and steel slag-stabilized fluidic silty sand. A WDW-20E microcomputer-controlled electronic universal testing machine manufactured by Jinan Wuxing Testing Instrument Co., Ltd. (Jinan, China) in 2021 implemented the unconfined compressive strength test. This machine can apply a maximum loading force of 20 kN and a loading rate of 0.001–10 mm/min with an accuracy of ±1% FS (full scale). The displacement resolution was 0.001 mm with a measuring error of ±1%. When testing, the loading rate was controlled at 1.0 mm/min until apparent failure characteristics appeared, and then loading was stopped manually. Engineering practice proves that the cement mixing ratio for soil stabilization is generally 7~15%. Thus, to ensure the reliability of soil stabilization, the total amount of cement and steel slag used for the indoor tests was all 15% of the weight of the dry silty sand. The specific testing scheme includes the following:
(1) The cement/steel slag ratio
Different cement/steel slag ratios, including 12:3, 11:4, 10:5, and 9:6 in weight, were designed to explore the influence of the cement/steel slag ratio on the compressive strength of fluidic silty sand and to find the optimum ratio. The initial water content of fluidic silty sand was designed as 1.0, 1.1, 1.15, 1.25, and 1.5 times the liquid limit of the silty sand. All prepared specimens were cured for seven days.
(2) The initial water content
Considering the large difference in the water content, the initial water content of fluidic silty sand was designed as 1.0, 1.1, 1.15, 1.25, and 1.5 times the liquid limit of the soil. The cement/steel slag ratio was 9:6 in weight. All prepared specimens were cured for seven days.
(3) The curing age
The compressive strengths of cement- and steel slag-stabilized fluidic silty sands curing for 3, 7, 14, and 28 days were investigated to understand their influences. The cement/steel slag ratio was 9:6 in weight, and the initial water content was 1.25 times the liquid limit of the soil.
(4) The curing temperature
Some studies have shown that the curing temperature significantly impacts the strength improvement of cement-stabilized soils [18,19]. To verify the influence of the curing temperature on the strength improvement of cement- and steel slag-stabilized fluidic silty sand, all prepared specimens sealed with cling film were cured for seven days at temperatures of 10, 20, 30, and 40 °C, and then compression tests were conducted. The cement/steel slag ratio was 9:6 in weight, and the initial water content was 1.25 times the liquid limit of the silty sand.

3.1.2. Microscopic Tests

The internal stabilization mechanisms of the CSFSSs were investigated and discussed via SEM images obtained from a JSM-5900LV electron microscope scanner manufactured by Joel Ltd., Tokyo, Japan in 2018. The cement/steel slag ratio was 9:6 in weight, the initial water content was 1.25 times the liquid limit of the silty sand, and the curing ages were 3, 7, 14, and 28 days. When testing, the microstructure characteristics of the soil sample surfaces were captured via zooming by 500 and 5000 times. The microstructure image at the magnitude of 500 times was employed to observe the pore distribution of loose and dense areas on the surfaces of the samples. The microstructure image at the magnitude of 5000 times was used to track the contacts of the soil particles and the evolution characteristics of the gels. Of course, it should be known that these microstructure characteristics were all captured on the local surface of the soil sample, which cannot represent the features of the whole sample due to the inhomogeneity in the soil structure at the microscale and the discreteness of the observation points.
The stabilization mechanisms of the CSFSSs were discussed based on spectral analyses via XRD and FTIR. Similarly, the cement/steel slag ratio was 9:6 in weight, the initial water content was 1.25 times the liquid limit of the silty sand, and the curing ages were 3, 7, 14, and 28 days. When testing, a SmartLabTM-3kW X-ray diffractometer manufactured by Rigaku Corporation, Tokyo, Japan in 2017 was used to measure the changes in the diffraction intensity and crystallization peak of the CSFSSs at different curing ages, thereby disclosing the evolution of products in the soils. A Nicolet6700 Fourier-Transform Infrared Spectrometer manufactured by Thermo Fisher Scientific Inc, USA in 2017 was employed to investigate the changes in the various chemical bonds over the curing ages to obtain the reaction in cement and steel slag co-stabilization.

3.2. Specimen Preparation

(1) Compression test
The dry silty sand, cement, steel slag powder, and water were weighted following the above testing scheme. The silty sand, cement, and steel slag powder were mixed first and then mixed with water thoroughly. The mixture was blended thoroughly until the slurry was homogeneous. Then, these slurries were poured into the mold with a diameter of 39.1 mm and a height of 80.0 mm and compacted via mechanical vibration. When finished, all prepared specimens were first stood for 24 h at the designed curing condition and then de-molded and continued to cure in the same conditions until the specified curing age was reached. Additionally, considering that significant differences in the weights of the specimens might occur due to the vibrating sample preparation method, six specimens were prepared for each experiment case at the initial sample preparation. All of these prepared specimens were cured at a temperature of 20 ± 3 °C and a humidity of 95 ± 5%. When the designed curing age was reached, only three samples with the minimum weight error were selected for final parallel comparison tests to ensure the experimental data’s high reliability.
(2) Microstructure test
The dried specimens of the CSFSSs were cut into small pieces of about 10 mm × 10 mm × 5 mm first and then they were flattened and polished carefully for the SEM tests. Meanwhile, these small pieces were further ground into a powder of less than 2 mm in size for the XRD and FTIR tests.

4. Results and Analysis

4.1. Optimum Mixing Ratio Analysis

Figure 4 presents the unconfined compressive strengths of the CSFSSs with different cement/steel slag ratios in terms of weights and initial water contents. It could be found that the compressive strengths and reduction amplitudes of these cement-stabilized fluidic silty sands generally decreased with the steel slag replacement ratio of the cement regardless of the initial water contents. The compressive strength of these CSFSSs could meet the minimum performance requirement of greater than 100 kPa as the cement/steel slag ratio was 10:5 or 9:6. When the initial water content further increased, the cement/steel slag ratio seemed to no longer be the main factor controlling the strength development due to too much water being left in the soil. Considering that cement was a great resource and energy wastage, high-cost, and complex industrial material accompanied by a large amount of carbon dioxide emissions and the compressive strength of the CSFSS was approximately the same when the cement/steel slag ratio was 10:5 and 9:6, the optimum cement/steel slag ratio was selected as 9:6 since it was more reasonable and economic and more steel slag consumption was beneficial to the cost reduction of fluidic silty sand stabilization. This conclusion also meant that the most effective ratio of steel slag to replace part of the cement was 40%, which is consistent with the conclusions given by other researchers [5,8].

4.2. Influence of Initial Water Content on the Mechanical Performance of CSFSS

Figure 5a shows the strength change in the CSFSS with different initial water contents. It can be found that the compressive strength of the CSFSS decreased with the initial water content. When the initial water content was greater than 1.15 times the liquid limit, the compressive strength of the CSFSS decreased quickly. This change may be because the abundant free water will leave more pores in the soil after evaporating, resulting in slow strength development. Kim et al. [2] and Deng et al. [26] confirmed a similar conclusion that the higher the water content in the soil, the lower the compressive strength. Hence, it should be significant to control the initial water contents of fluidic silty sands before they are stabilized with cement and steel slag. Additionally, when the initial water content was 1.25 times the liquid limit, the workability state of the prepared soil sample was similar to that of the field (Figure 5b), and its compressive strength after stabilization was more than 300 kPa. These characteristics suggested that such an initial water content could better reflect the project’s situation. Therefore, to ensure guiding significance for the project, the subsequent sample preparation shall be completed using 1.25 times the liquid limit.

4.3. Influence of Curing Age on the Mechanical Performance of CSFSS

Figure 6 presents the strength change in the CSFSS at different curing ages. It can be known that the compressive strength of the CSFSS increased over the curing age. Hossain et al. [29] and Lang et al. [8] reported the same conclusion for cement-stabilized soils. When the curing age was increased to 3 days, the compressive strength of the CSFSS rapidly increased to 198.63 kPa, and when it was increased to 7 days, their compressive strength exceeded 300 kPa. When the curing age was increased to 28 days, their compressive strength achieved approximately 484.9 kPa. Still, their growth rates were slowing down. The fact that the compressive strength of the CSFSS at the early stage was slightly higher than that without steel slag implied that adding steel slag could be more conducive to fluidic silty sands’ early compressive strengths [23].

4.4. Influence of Curing Temperature on the Mechanical Performance of CSFSS

Figure 7 shows the strength changes in cement- and steel slag-stabilized fluidic silty sands cured at different temperatures. It was known that the compressive strength of the cement- and steel slag-stabilized fluidic silty sands increased with the curing temperature. When the curing temperature was lower than 30 °C, the compressive strength of the cement- and steel slag-stabilized fluidic silty sands increased linearly but slowly. When the curing temperature was higher than 30 °C, the increasing rates of the sands’ compressive strengths were improved dramatically. These results suggest that a high temperature should be able to accelerate the production of more hydrated aluminosilicate gels, thereby speeding up the stabilization of the soil within a limited curing age [30,31].

5. Discussion

5.1. Stabilization Mechanism

Figure 8 presents the microstructural characteristic evolution of CSFSS over the curing age. By distinguishing its microstructure characteristics by zooming by 500 times, it could be observed that many large-sized pores existed in the CSFSS at the curing age of earlier than three days, and the internal structure of the soils was still loose. However, with the curing age continuing to move forward, the size of these pores continued to decrease, and the aggregation and cementation effects among the soil particles increased dramatically. When the curing age reached 28 days, most of the previous large pores in the silty sands disappeared, and only some tiny pores remained. The structural compactness was thus significantly improved. The microstructure characteristics seen by zooming by 5000 times illustrated many fine-needle-like CSH/CAH gels and hexagonal tabular CH forming on the surfaces of the soil particles at the early curing age, which indicated that cement hydration was proceeding rapidly [4]. When the curing age was increased to seven days, there were more hydrated gels than before, and the CH seemed to decrease. When the curing age was increased to 14 days, the hydrated gels continued to grow into the surrounding pores, resulting in the macropores shrinking into tiny pores. At the same time, the CH almost disappeared. The reason for this may be that the steel slag had a pozzolanic reaction in an alkaline environment [3]. These silicon–aluminum active substances reacted with the cement hydration’s by-products (CH), forming more hydrated gels. The microstructure characteristics at the curing age of 28 days showed that the rod-shaped and flocculent gels were widely distributed, and wrapped soil particles and the typical network cementation structure were prominent. All of them indicated that the integrity of the silty sands and the cementitious contact among the soil particles were significantly enhanced, thereby improving the mechanical performances of the fluidic silty sands.

5.2. Reaction Mechanisms

5.2.1. XRD Pattern

Figure 9 shows the XRD diffraction pattern of the CSFSS with 2θ in the 5–60° range. It can be observed that the diffraction intensity of the CSFSS at the curing ages of 3, 7, 14, and 28 days obviously changed between 15° and 40°. The highest peak of the hump-like structure always appeared with a center of 2θ ≈ 27°. With the development of the curing age, the intensity of SiO2 in the CSFSS gradually decreased. However, it was still the main component in the soil because the fluidic silty sands, cement, and steel slag all contained the component of SiO2. CSH, CAH (calcium aluminate hydrate), Aft (ettringite), and CH products were detected when the curing age was increased to three days [3]. The yield of the CSH gel being higher than that of the CAH gel could be because the active SiO2 content in the CSFSS was more than that of Al2O3. When the curing age was increased to seven days, the intensity of CAH was unchanged, and the intensity of CSH continued to increase. This change meant that the yield of CAH gels had been almost completed because the content of Al2O3 in the cement was limited, and the hydration reaction the cement was still in progress. When the curing age reached 14 days, the intensities of CH and Aft decreased significantly. Theoretically, if the steel slag was not used in the cement-stabilized fluidic silty sands, the intensity of CH as the by-product of cement should be more and more dramatic. However, the intensity of CH in CSFSS was the opposite. It was evident that some substances in the steel slag should react with CH. Namely, the steel slag took part in the hydration reaction of the cement. When the curing age was increased to 28 days, the intensity of SiO2 in the soil was almost unchanged, and the intensity of CSH had not significantly increased, which indicated that the cement hydration and pozzolanic reactions were disappearing [8,26].

5.2.2. FTIR Spectra

The chemical reaction of the cement-based samples could rapidly develop in the early curing age but slowly developed after curing for 28d. Therefore, this study conducted a more detailed spectra analysis on cement- and steel slag-stabilized silty sand after curing for 3, 7, 14, and 28 days to investigate the influence of adding steel slag to the chemical reaction of cement-stabilized silty sand. Figure 10 presents the infrared spectrum evolution of the CSFSS over the curing age. It could be found that there was a strong absorption peak near 700 cm−1 during the early curing age, which was related to the bending vibration of Al-O [32]. An absorption peak near 630 cm−1 was also observed, which is commonly caused by the symmetrical vibration of zeolite-like atomic groups. With the increase in the curing time, the absorption peak near 620 cm−1 was still obvious, indicating the formation of zeolite-like materials [33]. The strong asymmetric stretching vibration peaks near 831 cm−1 and 1340 cm−1 moved to the lower peaks near 821 cm−1 and 1309 cm−1, which implied that the hydration of the cement was in progress. 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 the tetrahedral zeolite group minerals. This absorption band was caused by the valence vibrations of the Si-O or Al-O bonds [34]. The vibration peaks near 1600 cm−1 and about 3500 cm−1 related to the hydroxyl’s stretching and bending vibrations became obvious over the early curing age, indicating the bound water yield in cement hydration over the curing age [7,35]. The vibration peaks near 3740 cm−1 and 3752 cm−1 at the curing age before seven days suggested the formation of CH. However, these vibration peaks continued to weaken over the curing age. That meant that the CH was gradually decreasing. No new vibration peak appeared again, which implied that the CH was sufficient for the later pozzolanic reactions of silicon–aluminum oxide in the steel slag. This finding was consistent with the relevant research results [36,37].

6. Conclusions

This study employed steel slag powder to replace part of the cement and improve fluidic silty sands’ engineering performances and reutilization economies. The contribution of the influencing factors to their mechanical performances was investigated. The microstructural characteristic evolution and reaction mechanism were discussed. Some of the main conclusions that were obtained are as follows:
(1)
Considering the minimum engineering requirement of greater than 100 kPa and the economic and environmental benefits, the optimum cement/steel slag ratio could be 9:6, regardless of the initial water content. Meanwhile, controlling the initial water content of fluidic silty sands before they are stabilized is significant for engineering practices.
(2)
Adding steel slag was more conducive to fluidic silty sands’ early strength improvement. A high temperature accelerated the production of more CSH/CAH gels. Therefore, appropriate curing conditions would favor the mechanical performance development of CSFSS.
(3)
With the development of the curing age, the large pores in the fluidic silty sands shrunk into tiny pores, and their previous loose structures were significantly integrated and compacted. That proved the contributions of cement and steel slag to the mechanical performance improvement of fluidic silty sands. The CH appeared first and then disappeared, indicating that the steel slag should have a pozzolanic reaction with the by-products of cement hydration.
(4)
The addition of steel slag could positively affect the formation of gel materials in cement-stabilized fluidic silty sands. The detected OH and CH vibration peaks indicated that cement hydration and pozzolanic reactions occurred during the soil stabilization. The outcomes of this study could provide a reference for the engineering application of CSFSS.

Author Contributions

Methodology, review and editing, and funding acquisition, L.G., X.D. and S.W.; investigation, formal writing, and data curation, X.D., M.Z. and S.W.; investigation and original draft, L.G., M.Z., B.L. and J.J. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Science and Technology Planning Project of Jiangsu Province, China (Grant No. BE2022605), the Science and Technology Development Planning Project of Nanjing, China (Grant No. 202211011), the National Natural Science Foundation of China (Grant Nos. 41902282 and U1939209), and the Science and Technology Planning Project of Zhejiang Provincial Traffic Department, China (Grant No. 2021038).

Data Availability Statement

The data used to support the findings of this study are available from the corresponding author upon request.

Acknowledgments

The authors gratefully acknowledge the assistance of the editors in preparing the manuscript and the constructive comments of the reviewers.

Conflicts of Interest

The authors declare no conflict of interest.

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Buildings 13 02705 g001
Figure 1. Grading of the fluidic silty sand used in this study.
Figure 1. Grading of the fluidic silty sand used in this study.
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Figure 2. The energy spectrum of the steel slag.
Figure 2. The energy spectrum of the steel slag.
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Figure 3. Morphological characteristics of steel slag at different magnifications.
Figure 3. Morphological characteristics of steel slag at different magnifications.
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Figure 4. Compressive strength of CSFSS with different cement/steel slag ratios and initial water contents.
Figure 4. Compressive strength of CSFSS with different cement/steel slag ratios and initial water contents.
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Figure 5. Compressive strength and workability of CSFSS with different initial water contents.
Figure 5. Compressive strength and workability of CSFSS with different initial water contents.
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Figure 6. Compressive strength of CSFSS with different curing ages.
Figure 6. Compressive strength of CSFSS with different curing ages.
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Figure 7. Compressive strength of CSFSS cured at different temperatures.
Figure 7. Compressive strength of CSFSS cured at different temperatures.
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Figure 8. Microstructural characteristics of CSFSSs at different curing ages.
Figure 8. Microstructural characteristics of CSFSSs at different curing ages.
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Figure 9. XRD patterns of CSFSSs at different curing ages.
Figure 9. XRD patterns of CSFSSs at different curing ages.
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Figure 10. FTIR Spectra of CSFSS at different curing ages.
Figure 10. FTIR Spectra of CSFSS at different curing ages.
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Table 1. Physical parameters of the fluidic silty sand.
Table 1. Physical parameters of the fluidic silty sand.
SoilNatural Water
Content (%)		Specific
Gravity		Liquid
Limit (%)		Plastic
Limit (%)		Plasticity
Index
Silty sand43.62.740.224.315.9
Table 2. The main components of the cement used in this study.
Table 2. The main components of the cement used in this study.
Chemical ComponentsCaOSiO2Al2O3Fe2O3MgO
Mass ratio (%)57.421.77.52.91.7
Table 3. Chemical compositions and contents of the steel slag used in this study.
Table 3. Chemical compositions and contents of the steel slag used in this study.
Chemical ComponentsCaOSiO2MgOAl2O3Fe2O3
Mass ratio (%)59.229.13.91.46.5
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MDPI and ACS Style

Gu, L.; Deng, X.; Zhang, M.; Wang, S.; Li, B.; Ji, J. Stabilization of Fluidic Silty Sands with Cement and Steel Slag. Buildings 2023, 13, 2705. https://doi.org/10.3390/buildings13112705

AMA Style

Gu L, Deng X, Zhang M, Wang S, Li B, Ji J. Stabilization of Fluidic Silty Sands with Cement and Steel Slag. Buildings. 2023; 13(11):2705. https://doi.org/10.3390/buildings13112705

Chicago/Turabian Style

Gu, Leilei, Xianjun Deng, Mei Zhang, Shengnian Wang, Bin Li, and Jiufa Ji. 2023. "Stabilization of Fluidic Silty Sands with Cement and Steel Slag" Buildings 13, no. 11: 2705. https://doi.org/10.3390/buildings13112705

APA Style

Gu, L., Deng, X., Zhang, M., Wang, S., Li, B., & Ji, J. (2023). Stabilization of Fluidic Silty Sands with Cement and Steel Slag. Buildings, 13(11), 2705. https://doi.org/10.3390/buildings13112705

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