The Experts below are selected from a list of 16014 Experts worldwide ranked by ideXlab platform
Tao Zhang - One of the best experts on this subject based on the ideXlab platform.
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durability of Silty Soil stabilized with recycled lignin for sustainable engineering materials
Journal of Cleaner Production, 2020Co-Authors: Tao Zhang, Songyu Liu, Hongbin Zhan, Guojun CaiAbstract:Abstract Lignin is an industrial waste derived from the paper plant, which poses a potential threat to the surrounding environment without proper disposal. The present study aims to evaluate the durability performance of recycled lignin stabilized Silty Soil subjected to different adverse environments. A series of laboratory experiments were conducted to determine unconfined compressive strength (qu), moisture stability coefficient (Kr), mass loss (Sm) and pH value of the stabilized silt exposed to water soaking and wetting-drying cycles. The results showed that the strength and durability of natural silt were obviously improved with the inclusion of lignin. Lignin cementation and matrix suction played important roles in the strength behavior of the unsaturated stabilized silt. The compressive strength suffered a dramatic drop after 1 day of soaking due to the dissolution of cementing materials and the loss of suction. Lignin stabilized silt possessed a higher Kr than that of quicklime stabilized one, indicating its superiority in durability. After 28 days of standard curing, 12% lignin stabilized silt had an ability to resist 4 cycles of wetting-drying, resulting in the cumulative mass loss (Cm) of approximately 20%. Soil pH value presented a decreasing trend with wetting-drying cycles, and an exponential correlation of pH with Cm was found by data fitting. Scanning electron microscope analysis revealed that the lignin-based cementing materials are gradually lost during the process of wetting-drying cycles. Additional research is encouraged to explore an effective method to prevent the deterioration of mechanical properties of lignin stabilized Soils in practical projects.
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reclaimed lignin stabilized Silty Soil undrained shear strength atterberg limits and microstructure characteristics
Journal of Materials in Civil Engineering, 2018Co-Authors: Tao ZhangAbstract:AbstractLignin is an organic industrial by-product, stockpiles of which are rapidly accumulating worldwide. A feasibility investigation was carried out with respect to the stabilization of Silty so...
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Application of lignin-based by-product stabilized Silty Soil in highway subgrade: A field investigation
Journal of Cleaner Production, 2017Co-Authors: Tao Zhang, Guojun Cai, Songyu LiuAbstract:Abstract Lignin is a by-product of paper and timber industry, and it has not been fully utilized in both developed and developing countries. Improper disposal or storage of lignin is not only a waste of natural resources, but also posing significant risk to public health and the environment. Sustainable reuse options for lignin in civil engineering infrastructures, such as road embankments and dam foundations, have been recently evaluated by laboratory testing. However, up to now studies on the actual filed performance of lignin in stabilizing Silty Soils in highway subgrade have been noticed to be quite limited. With this in view, a field trial was carried out to verify the viability of using lignin stabilized Silty Soil as a highway subgrade course material. Traditional Soil stabilizer, quicklime, was selected as a control chemical mixture in the field trial for comparison purposes. The construction procedures of the subgrade Silty Soil stabilized by lignin and quicklime in field Sections were presented. A series of field tests, including California Bearing Ratio (CBR) test, resilient modulus (Ep) test, Benkelman beam deflection test, and dynamic cone penetrometer (DCP) test were carried out after the subgrade construction to investigate the effects of the curing time and additive content on the mechanical properties and bearing capacity of the stabilized silt. In addition, moisture content and compaction degree tests were conducted to evaluate the quality of the compacted subgrade Soils. The test results indicate that at the bottom zone of the filled Soil layers with 96% degree of compaction, the 12% lignin stabilized silt exhibits superior mechanical performances (i.e., higher value of CBR and Ep, and lower values of resilient deflection (Hr) and DCP Index) than the 8% quicklime stabilized silt after 15 days of curing. Under the same additive content (i.e., 8%), the bearing capacity of lignin stabilized silt is slightly lower relative to the quicklime stabilized one. The field trial results reveal that as a stabilizer of the subgrade Soil, lignin has negligible environmental influences and induces low construction costs. The use of lignin as a stabilization chemical mixture for Silty Soil may be one of the viable answers to the reuse of biobased organic by-product in civil engineering. The outcome of this study is of great significance for the development of nontraditional, cost-effective, and environmentally friendly Soil stabilizer in solidification/stabilization technology.
Yu-jun Cui - One of the best experts on this subject based on the ideXlab platform.
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Salinity effect on the liquid limit of Soils
Acta Geotechnica, 2020Co-Authors: Zi Ying, Yu-jun Cui, Myriam Duc, Nadia Benahmed, Hela Bessaies-bey, Bo ChenAbstract:Previous studies stated that, with increasing salinity, the decreased liquid limit for expansive Soils was attributed to the shrinkage of diffuse double layer, while the increased liquid limit for non-expansive Soils was explained by the growing particle flocculation. These two mechanisms seem to be controversial and it is difficult to understand how an increasing salinity can promote Soil flocculation. This study aims at clarifying the mechanism controlling liquid limit by conducting cone penetration test, sedimentation and rheological tests on MX80 Na-bentonite and Silty Soil. Results showed that the liquid limit and yield stress of MX80 increased then decreased with increasing salinity, while they increased slightly for the Silty Soil. In sedimentation test, faster settling rate and smaller sediment volume were identified for MX80 and silt suspensions in NaCl solution, evidencing the shrinkage of diffuse double layer and the formation of denser aggregated structure. This suggested that the change of liquid limit is the result of two mechanisms in competition, which depend on the compression rate of diffuse double layer: (1) the water storage in nano-fissures which correspond to the nanoscale spaces among interlayers of clay particles resulting from the slight shrinkage of diffuse double layer, and (2) the water expulsion into larger pores with significant shrinkage of diffuse double layer. For the MX80 at low salinity and for the silt Soil, the first mechanism prevailed and the increasing liquid limit was attributed to the requirement of more water to fill the nano-fissures. In contrast, for MX80 at high salinity, the second mechanism prevailed—the diffuse double layer was compressed significantly, changing the double-layer water to free water and giving rise to the decrease in liquid limit.
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determining the Soil water retention curve using mercury intrusion porosimetry test in consideration of Soil volume change
Journal of rock mechanics and geotechnical engineering, 2020Co-Authors: Wenjing Sun, Yu-jun CuiAbstract:Abstract It is well-known that a close link exists between Soil-water retention curve (SWRC) and pore size distribution (PSD). Theoretically, mercury intrusion porosimetry (MIP) test simulates a Soil drying path and the test results can be used to deduce the SWRC (termed SWRCMIP). However, SWRCMIP does not include the effect of volume change, compared with the conventional SWRC that is directly determined by suction measurement or suction control techniques. For deformable Soils, there is a significant difference between conventional SWRC and SWRCMIP. In this study, drying test was carried out on a reconstituted Silty Soil, and the volume change, suction, and PSD were measured on samples with different water contents. The change in the deduced SWRCMIP and its relationship with the conventional SWRC were analyzed. The results showed that the volume change of Soil is the main reason accounting for the difference between conventional SWRC and SWRCMIP. Based on the test results, a transformation model was then proposed for conventional SWRC and SWRCMIP, for which the Soil state with no volume change is taken as a reference. Comparison between the experimental and predicted SWRCs showed that the proposed model can well consider the influence of Soil volume change on its water retention property.
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changes in mineralogy and microstructure of a lime treated Silty Soil during curing time
E3S Web of Conferences, 2020Co-Authors: Zi Ying, Yu-jun Cui, Nadia Benahmed, Myriam DucAbstract:Lime treatment is widely applied to improve the workability and long-term durability of Soils. In this study, the curing time effect on the mineralogy and microstructure of lime-treated Soil was investigated. The Soil samples were prepared with 2 % lime and statically compacted at dry (w = 17 %) and wet (w = 20%) sides of optimum. X-ray diffraction (XRD) and mercury intrusion porosimetry (MIP) were performed on lime-treated Soil at various curing times. The presence of XRD peaks attributed to portlandite even after 150 days curing time indicated that it was not totally converted in cementitious compounds after reaction with silica and alumina from clay minerals. By contrast, no obvious XRD reflections of well-crystallized cementitious compounds were identified. Furthermore, all samples compacted at dry and wet side of optimum exhibited bi-modal pore size distribution, with a decrease of macro-pore frequency with increasing water content. The microstructure changes with increasing curing time did not follow monotonic tendency. On the whole, the quantities of pores less than 0.006 μm and micro-pores increased and the quantity of macro-pores decreased with increasing curing time due to the possible creation of poorly crystallized or amorphous cementitious compounds.
Ronaldo Luis Dos Santos Izzo - One of the best experts on this subject based on the ideXlab platform.
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effects of porosity dry unit weight cement content and void cement ratio on unconfined compressive strength of roof tile waste Silty Soil mixtures
Journal of rock mechanics and geotechnical engineering, 2019Co-Authors: Eclesielter Batista Moreira, Jair De Jesus Arrieta Baldovino, Juliana Lundgren Rose, Ronaldo Luis Dos Santos IzzoAbstract:Abstract One of the conventional ways to improve the mechanical behavior of Soils is to mix them with cementing agents such as cement, lime and fly ash. Recently, introduction to alternative materials or sub-products that can be adopted to improve the Soil strength is of paramount importance. Therefore, the present study aims to investigate the effects of porosity (η), dry unit weight (γd) of molding, cement content (C) and porosity/volumetric cement content ratio (η/Civ) or void/cement ratio on the unconfined compressive strength (qu or UCS) of Silty Soil–roof tile waste (RT) mixtures. Soil samples are molded into four different dry unit weights (i.e. 13 kN/m3, 13.67 kN/m3, 14.33 kN/m3 and 15 kN/m3) using 3%, 6% and 9% cement and 5%, 15% and 30% RT. The results show that with the addition of cement, the strength of the RT–Soil mixtures increases in a linear manner. On the other hand, the addition of RT decreases qu of the samples at a constant percentage of cement, and the decrease in porosity can increase qu. A dosage equation is derived from the experimental data using the porosity/volumetric cement content ratio (η/Civ) where the control variables are the moisture content, crushed tile content, cement content and porosity.
J Guerif - One of the best experts on this subject based on the ideXlab platform.
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effect of compaction on the porosity of a Silty Soil influence on unsaturated hydraulic properties
European Journal of Soil Science, 2001Co-Authors: Guy Richard, J F Sillon, Ary Bruand, Isabelle Cousin, J GuerifAbstract:Summary Tillage and traffic modify Soil porosity and pore size distribution, leading to changes in the unsaturated hydraulic properties of the tilled layer. These changes are still difficult to characterize. We have investigated the effect of compaction on the change in the Soil porosity and its consequences for water retention and hydraulic conductivity. A freshly tilled layer and a Soil layer compacted by wheel tracks were created in a Silty Soil to obtain contrasting bulk densities (1.17 and 1.63 g cm−3, respectively). Soil porosity was analysed by mercury porosimetry, and scanning electron microscopy was used to distinguish between the textural pore space and the structural pore space. The laboratory method of Wind (direct evaporation) was used to measure the hydraulic properties in the tensiometric range. For water potentials < −20 kPa, the compacted layer retained more water than did the uncompacted layer, but the relation between the hydraulic conductivity and the water ratio (the volume of water per unit volume of solid phase) was not affected by the change in bulk density. Compaction did not affect the textural porosity (i.e. matrix porosity), but it created relict structural pores accessible only through the micropores of the matrix. These relict structural pores could be the reason for the change in the hydraulic properties due to compaction. They can be used as an indicator of the consequences of compaction on unsaturated hydraulic properties. The modification of the pore geometry during compaction results not only from a decrease in the volume of structural pores but also from a change in the relation between the textural pores and the remaining structural pores.
Erol Guler - One of the best experts on this subject based on the ideXlab platform.
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laboratory and field testing for utilization of an excavated Soil as landfill liner material
Waste Management, 2006Co-Authors: Ilknur Bozbey, Erol GulerAbstract:Abstract This study investigates the feasibility of using a Silty Soil excavated in highway construction as landfill liner material. The tests were conducted both at laboratory and in situ scales, and the Soil was tested in pure and lime treated forms. Different levels of compaction energy were used. For the field study, a test pad was constructed and in situ hydraulic conductivity experiments were conducted by sealed double ring infiltrometers (SDRI). Laboratory testing revealed that while lime treatment improved the shear strength, it resulted in higher hydraulic conductivity values compared to pure Soil. It was observed that leachate permeation did not change the hydraulic conductivity of the pure and lime treated samples. Laboratory hydraulic conductivities were on the order of 10 −9 m/s and met the 1.0E − 08 m/s criterion in the Turkish regulations, which is one order of magnitude higher than the value allowed in most developed countries. SDRI testing, which lasted for 6 mo, indicated that lime treatment increased the hydraulic conductivity of pure Soil significantly in the field scale tests. In situ hydraulic conductivities were on the order of 1E − 08 and 1E − 07 m/s, and exceeded the allowable value in the Turkish regulations. Undisturbed samples collected from the test pad were not representative of field hydraulic conductivities. Contrary to laboratory findings, higher compaction efforts did not result in lower hydraulic conductivities in field scales. The study verified the importance of in situ hydraulic conductivity testing in compacted liners.
