scholarly journals Strength Characteristics and Microstructure of Cement Stabilized Soft Soil Admixed with Silica Fume

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 1929
Author(s):  
Nan Jiang ◽  
Changming Wang ◽  
Zeping Wang ◽  
Bailong Li ◽  
Yi-ao Liu
Keyword(s):  
Silica Fume ◽  
Soft Soil ◽  
Hydration Product ◽  
Soil Improvement ◽  
Hydration Reaction ◽  
Pozzolanic Material ◽  
Stabilized Soil ◽  
Construction Efficiency ◽  
Cement Hydration Reaction ◽  
Recycled Material

Soft soil improvement is an important subject in civil engineering, and searching for an effective admixture is an important research. Silica fume (SF) is a kind of recycled material, it can be used in engineering as a pozzolanic material. The main objective of this study is to assess the effectiveness of industrial waste silica fume (SF) as an admixture to improve the cement stabilized soft soil. The unconfined compressive test (UCT) and scanning electron microscopy (SEM) test of cement stabilized soil with different SF contents and different curing times have been carried out. UCT after 28 days revealed that the addition of SF can effectively increase the strength of cement stabilized soil and reduce the amount of cement, and 1.5% SF content is considered optimum, excessive SF will not further increase the strength. SF helped to accelerate the cement hydration reaction and significantly improve the early-age strength of stabilized soil even at 3 days, which can improve construction efficiency in actual projects. SEM analyses shows that the proper SF content could make the hydration product calcium silicate hydrate gel (CSH) fill the pores and increase the strength of the material, but excessive SF will increase the large pores content of the material and reduce the strength. This provided a basis for application of SF in improving soft soil.

Influence of Bagasse Ash as Partial Replacement of Cement on Soft Soil Improvement

2017 ◽  
Vol 728 ◽  
pp. 373-378
Author(s):  
Hatairat Poorahong ◽  
Naphol Yoobanpot
Keyword(s):  
Electron Microscopy ◽  
Soil Structure ◽  
Soft Soil ◽  
Dry Weight ◽  
Soil Improvement ◽  
Soil Strength ◽  
Partial Replacement ◽  
Hydration Reaction ◽  
Stabilized Soil ◽  
Scanning Electron

Compressive strength of soft soil improvement using cement only and cement partial replacement with bagasse ash were studied. The strength characteristic of stabilized soil was investigated with various curing times of 7, 14 and 28 days. Tested result reveal the stabilized soil strength have trend to increase with time. Using 20% of bagasse ash by dry weight was suggested as optimum content for cement replacement to obtain highest strength. Comparing with cement improved soil, the stabilized soil strength of 20% BA replacement had higher over 25% and modulus of elasticity (E50) was increased up to 37% at 28 days of curing. Change on stabilized soil structure was observed by scanning electron microscopy (SEM) reveal that the formation of hydration reaction product, CSH fabric and rod-like ettringite, have transformed stabilized soil structure denser and harder consequence increase in soil strength with time.

scholarly journals Strength Performance and Microstructure of Calcium Sulfoaluminate Cement-Stabilized Soft Soil

2021 ◽  
Vol 13 (4) ◽  
pp. 2295
Author(s):  
Hailong Liu ◽  
Jiuye Zhao ◽  
Yu Wang ◽  
Nangai Yi ◽  
Chunyi Cui
Keyword(s):  
Soft Soil ◽  
Hydration Product ◽  
X Ray Diffraction ◽  
Calcium Sulfoaluminate Cement ◽  
Strength Performance ◽  
X Ray ◽  
Calcium Sulfoaluminate ◽  
Stabilized Soil ◽  
Calcium Silicates ◽  
Hydrated Calcium

Calcium sulfoaluminate cement (CSA) was used to stabilize a type of marine soft soil in Dalian China. Unconfined compressive strength (UCS) of CSA-stabilized soil was tested and compared to ordinary Portland cement (OPC); meanwhile the influence of amounts of gypsum in CSA and cement contents in stabilized soils on the strength of stabilized soils were investigated. X-ray diffraction (XRD) tests were employed to detect generated hydration products, and scanning electron microscopy (SEM) was conducted to analyze microstructures of CSA-stabilized soils. The results showed that UCS of CSA-stabilized soils at 1, 3, and 28 d firstly increased and then decreased with contents of gypsum increasing from 0 to 40 wt.%, and CSA-stabilized soils exhibited the highest UCS when the content of gypsum equaled 25 wt.%. When the mixing amounts of OPC and CSA were the same, CSA-stabilized soils had a significantly higher early strength (1 and 3 d) than OPC. For CSA-stabilized soil with 0 wt.% gypsum, monosulfate (AFm) was detected as a major hydration product. As for CSA-stabilized soil with certain amounts of gypsum, the intensity of ettringite (Aft) was significantly higher than that in the sample hydrating without gypsum, but a tiny peak of AFm also could be detected in the sample with 15 wt.% gypsum at 28 d. Additionally, the intensity of AFt increased with the contents of gypsum increasing from 0 to 25 wt.%. When contents of gypsum increased from 25 to 40 wt.%, the intensity of AFt tended to decrease slightly, and residual gypsum could be detected in the sample with 40 wt.% gypsum at 28 d. In the microstructure of OPC-stabilized soils, hexagonal plate-shaped calcium hydroxide (CH) constituted skeleton structures, and clusters of hydrated calcium silicates (C-S-H) gel adhered to particles of soils. In the microstructure of CSA-stabilized soils, AFt constituted skeleton structures, and the crystalline sizes of ettringite increased with contents of gypsum increasing; meanwhile, clusters of the aluminum hydroxide (AH3) phase could be observed to adhere to particles of soils and strengthen the interaction.

Experimental Research on High-Strength Super Sulphate Cement Paste Mixed with Superfine Mineral Admixtures

2014 ◽  
Vol 629-630 ◽  
pp. 150-155
Author(s):  
Jun Wang ◽  
Bao Ying Yu ◽  
Long Yang ◽  
Yu Xin Gao ◽  
Jia Yu Xiang
Keyword(s):  
Silica Fume ◽  
High Strength ◽  
Hydration Product ◽  
Mineral Admixtures ◽  
Hydration Reaction ◽  
X Ray Diffraction ◽  
Cement Ratio ◽  
X Ray ◽  
Early Strength ◽  
Scanning Electron

Aimed at the performance affect of high-strength super sulphate cement (SSC) paste mixed with superfine mineral admixtures, influence of microbead and silica fume replacing SSC quantity on high-strength SSC paste compression strength were studied under water-cement ratio 0.18; Hydration product morphology and phase were further compared by scanning electron microscopy and X-ray diffraction analyzer in this paper. Results show that, compared with sample HS-1, 3-day strength of HS-2 and HS-3 were increased by 5% and 10%, 28d strength basically unchanged; Furthermore, early strength of HS-7 sample slightly higher and late strength basically unchanged. SSC by adding 5% microbead and 3% silica fume (HS-11) has compressive strength 50.8MPa at 3 days and 86.1MPa at 28 days is significantly higher than other samples. Early strength of HS-11sample mainly depends on hydration reaction of SSC and particle filling effect of admixtures, later strength is due to accelerating consumption of gypsum and promoting formation of ettringite.

Chemical characteristics and leachability of organically contaminated heavy metal sludge solidified by silica fume and cement

2001 ◽  
Vol 44 (2-3) ◽  
pp. 399-407 ◽  
Author(s):  
K.-S. Jun ◽  
B.-W. Hwang ◽  
H.-S. Shin ◽  
Y.-S. Won
Keyword(s):  
Heavy Metal ◽  
Silica Fume ◽  
Industrial Wastewater ◽  
Cement Matrix ◽  
Hydration Reaction ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ettringite Formation ◽  
Microstructural Studies ◽  
Cement Hydration Reaction

This paper discusses the development of mixtures with silica fume as a stabilization/solidification agent and binder for industrial wastewater residue containing organic and heavy metal contaminants. The UCS (Unconfined Compressive Strength) gradually increased to 66.7% as the silica fume content increased to 15%. The leaching of TOC and chromium decreased as more OPC was substituted with silica fume. When the mix had 5% silica fume, it retained about 85% TOC, and chromium leached out 0.76mg-Cr/g-Cr in acidic solution. Also, microstructural studies on the solidified wastes through the scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) and X-ray diffraction analysis showed that the silica fume caused an inhibition to the ettringite formation which did not contribute to setting, but coated the cement particles and retarded the setting reactions. The results indicated that the incorporation of silica fume into the cement matrix minimized the detrimental effects of organic materials on the cement hydration reaction and contaminant leachability.

scholarly journals Effect of Silica Fume as a Waste Material for Sustainable Environment on the Stabilization and Dynamic Behavior of Dispersive Soil

2021 ◽  
Vol 13 (8) ◽  
pp. 4321
Author(s):  
Murat Türköz ◽  
Seyfettin Umut Umu ◽  
Ogan Öztürk
Keyword(s):  
Silica Fume ◽  
Dynamic Properties ◽  
Soil Improvement ◽  
Waste Material ◽  
Resonant Column ◽  
Engineering Applications ◽  
Positive Effects ◽  
Sustainable Environment ◽  
Earthen Dams ◽  
Dispersive Soils

The use of dispersive soils, which are common in many parts of the world, in engineering applications such as water structures, earthen dams and road embankments is possible with their improvement. Recently, the effects of different chemicals on the stabilization of dispersive soils have been investigated. The use of waste materials in stabilization is preferred both because of the more sustainable environment and the economic advantages it provides. The use of silica fume (SF) as a waste material in different engineering applications provides an important advantage in environmentally and economically sustainable ways. Many studies have been carried out regarding silica fume, especially in the construction industry. Although SF is used in many industries, there is no study about its potential impact on the stabilization and dynamic properties of dispersive soils. In this study, first, Atterberg limits and standard Proctor compaction tests were performed on the mixtures prepared by adding different SF percentages (0, 5, 10, 15, 20, 25 and 30%). Afterward, pinhole tests and resonant column tests were performed to determine dispersibility and dynamic properties on the samples prepared by compaction characteristics for each SF percentage reached. In general, it was determined that SF contributed to a change in soil class, and improvement in dispersibility and dynamic properties of the soil sample, depending on SF content; positive effects of SF were observed in terms of shallow soil improvement.

scholarly journals An Improved Mechanistic-Empirical Creep Model for Unsaturated Soft and Stabilized Soils

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4146
Author(s):  
Xunli Jiang ◽  
Zhiyi Huang ◽  
Xue Luo
Keyword(s):  
Water Content ◽  
Unsaturated Soils ◽  
Simulation Analysis ◽  
Soft Soil ◽  
Creep Model ◽  
Subgrade Soils ◽  
Stabilized Soil ◽  
Deformation Behaviors ◽  
Creep Models ◽  
Moisture Conditions

Soft soils are usually treated to mitigate their engineering problems, such as excessive deformation, and stabilization is one of most popular treatments. Although there are many creep models to characterize the deformation behaviors of soil, there still exist demands for a balance between model accuracy and practical application. Therefore, this paper aims at developing a Mechanistic-Empirical creep model (MEC) for unsaturated soft and stabilized soils. The model considers the stress dependence and incorporates moisture sensitivity using matric suction and shear strength parameters. This formulation is intended to predict the soil creep deformation under arbitrary water content and arbitrary stress conditions. The results show that the MEC model is in good agreement with the experimental data with very high R-squared values. In addition, the model is compared with the other classical creep models for unsaturated soils. While the classical creep models require a different set of parameters when the water content is changed, the MEC model only needs one set of parameters for different stress levels and moisture conditions, which provides significant facilitation for implementation. Finally, a finite element simulation analysis of subgrade soil foundation is performed for different loading levels and moisture conditions. The MEC model is utilized to predict the creep behavior of subgrade soils. Under the same load and moisture level, the deformation of soft soil is largest, followed by lime soil and RHA–lime-stabilized soil, respectively.

scholarly journals PLANNING OF SOFT SOIL IMPROVEMENT WITH PRELOADING AND PREFABRICATED VERTICAL DRAIN METHOD

2018 ◽  
Vol 2 (01) ◽  
pp. 19
Author(s):  
Ana Crosita Ningsih ◽  
Luthfi Amri Wicaksono ◽  
Mokhamad Farid Ma'ruf
Keyword(s):  
Urban Areas ◽  
Soil Structure ◽  
Soft Soil ◽  
Soil Improvement ◽  
Building Site ◽  
Planning Time ◽  
Coral Sand ◽  
Rapid Construction ◽  
Prefabricated Vertical Drain ◽  
Surrounding Areas

The northern coastal areas of Java such as Gresik and surrounding areas have a soil structure of alluvium consisting of gravel / coral, sand, clay soil and shells. Soil basic conditions are soft enough to cause land subsidence (settlement). The need for rapid construction causes the urban areas to become less and more for development land. This requires the improvement of soft soil to be used as a building site. As for the method to be done in this planning using a combination of preloading and PVD methods to accelerate the process of land degradation. Based on the planning result, the total height of embankment (preloading) is 3.5 m and the planning time lasted 4 months. Soft soil improvement is done up to 25 m depth with PVD design using triangle pattern and space 1.3 m. The 95% consolidation decrease due to the load of embankment caused the soil to fall as deep as 1,928 m. In this planning use modeling Plaxis 8.6 2D and the resulting yield of soil is 1,990 m. Wilayah pesisir pantai utara Jawa seperti daerah Gresik dan sekitarnya mempunyai struktur tanah berupa alluvium yang terdiri dari batu kerikil/koral, pasir, tanah lempung dan pecahan kulit kerang. Kondisi tanah dasar yang cukup lunak menyebabkan terjadinya penurunan tanah (settlement). Adanya kebutuhan konstruksi yang semakin pesat menyebabkan wilayah perkotaan menjadi semakin sedikit untuk dijadikan lahan pembangunan. Hal ini mengharuskan dilakukannya upaya perbaikan tanah lunak agar bisa dijadikan lahan bangunan nantinya. Adapun pada metode yang akan dilakukan pada perencanaan ini menggunakan kombinasi metode preloading dan PVD untuk mempercepat proses penurunan tanah. Berdasarkan hasil perencanaan didapatkan total tinggi timbunan (preloading) adalah 3,5 m dan waktu perencanaan berlangsung 4 bulan. Perbaikan tanah lunak dilakukan sampai dengan kedalaman 25 m dengan desain PVD menggunakan pola segitiga dan spasi 1,3 m. Penurunan konsolidasi 95% akibat beban timbunan menyebabkan tanah turun sedalam 1,928 m. Pada perencanaan ini menggunakan pemodelan Plaxis 8.6 2D dan hasil penurunan tanah yang dihasilkan adalah sedalam 1,990 m.

scholarly journals ANALISIS PENGGUNAAN PREFABRICATED VERTICAL DRAINS (PVD) PADA TANAH LEMPUNG LUNAK YANG TERDAPAT LAPISAN LENSA

2020 ◽  
Vol 3 (1) ◽  
pp. 119
Author(s):  
Andreyan Prasetio ◽  
Aniek Prihatiningsih
Keyword(s):  
Soft Soil ◽  
Soil Improvement ◽  
Cohesive Soils ◽  
Consolidation Process ◽  
Prefabricated Vertical Drains ◽  
Soil Layers ◽  
Vertical Drains ◽  
Vertical Drain ◽  
Installation Depth ◽  
Consolidation Time

Problem that often occurs in soft cohesive soils is settlement caused by consolidation process. If  construction activities doing when the soils has not been consolidated, settlement can occur. To accelerate  the consolidation process, soil improvement are usually do, one method of soil improvement to accelarate the consolidation process is vertical drain using prefabricated vertical drains (PVD). The soft soil layers in the field are not always continuous, sometimes found soft soil layers that have a lens layer. In this study, will discuss about the settlement and consolidation time of soft  soil layers that have a lens layer which has been improved by PVD with 1 meter distance. Infrastructure that stand on a location that is installed by PVD is taxiway and loading by Airbus A380 aircraft of 18,22ton/m2. Analysis using the 1 dimensional consolidation theory of Terzaghi. For PVD installation to a depth of 50 meters, preloading settlement of 234,80 cm with a consolidation time of  2260 days for the square pattern PVD and 1918 days for triangle pattern PVD. Post loading settlement for PVD installation depth of 50 meters by 2,50 cm. AbstrakMasalah yang sering terjadi pada tanah kohesif dan lunak adalah penurunan yang disebabkan proses konsolidasi. Penurunan dapat menyebabkan keretakan pada struktur konstruksi yang berada di atasnya. Jika suatu kegiatan konstruksi dilakukan saat tanah belum terkonsolidasi, maka konstruksi tersebut dapat mengalami penurunan.. Untuk mempercepat proses konsolidasi biasanya dilakukan perbaikan tanah, salah satu metode perbaikan tanah untuk mempercepat proses konsolidasi yaitu vertical drain dengan menggunakan prefabricated vertical drains (PVD). Lapisan tanah lunak yang terdapat di lapangan tidak selalu kontinu, terkadang ditemukan lapisan tanah lunak yang terdapat lapisan lensa. Pada penelitian ini, penulis akan membahas mengenai waktu konsolidasi yang dibutuhkan oleh lapisan tanah kohesif dan lunak yang terdapat lapisan lensa yang telah diperbaiki dengan menggunakan PVD berjarak 1 meter. Infrastruktur yang berdiri di atas lokasi yang dipasang PVD berupa taxiway dengan beban berupa pesawat Airbus A380 sebesar 18,22 ton/m2. Analisis dilakukan menggunakan teori konsolidasi 1 dimensi Terzaghi. Untuk pemasangan PVD hingga kedalaman 50 meter diperoleh penurunan pra pembebanan sebesar 234,80 cm dengan waktu konsolidasi selama 2260 hari untuk pemasangan PVD pola persegi dan selama 1918 hari untuk pola segitiga . Penurunan pasca pembebanan untuk pemasangan PVD hingga kedalaman 50 meter sebesar 2,5 cm.

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