Unconfined Compressive Strength Tests Research Articles

Mixture composition design of magnesium oxychloride cement-stabilized crushed stone materials applied as a pavement base

Conventional binding materials, such as silicate cement and lime, present high energy consumption, pollution, and carbon emissions. Therefore, we utilize crushed stone as a stabilization material. Magnesium oxychloride cement (MOC) is modified and used as an inorganic admixture owing to its eco-friendly nature and low carbon content. We analysed the control indicators of an integrated design of MOC-stabilized crushed stone by conducting unconfined compressive strength and water-resistance tests. The optimum mixing composition of the MOC-stabilized crushed stone was determined through the response surface methodology. We determined the best approach and dosage for improving the water resistance of MOC-stabilized crushed stone by comparing the effects of four modification methods: fly ash, citric acid + silica fume, phosphoric acid + waterborne polyurethane, and dihydrogen phosphate potassium salt. We also perform a comparison with 5% ordinary silicate cement-stabilized crushed stone. The results indicate that the MOC-stabilized crushed stone exhibits a rapid increase in strength in the early stage, but this rate reduces after 28 days. The mixing design employs the 4-day unconfined compressive strength and 1-day water resistance coefficient as the technical indicators. The best mixing composition includes a 4.27% MOC dosage and a molar ratio of MgO/MgCl2 of 5.85. We use 1% citric acid + 10% silica fume in equal amounts to replace the MOC dopant method for composite modification of the MOC stabilized crushed stone. Consequently, the 1-day water resistance coefficient before water immersion is significantly increased from 0.78 to 0.91 and its 4-day unconfined compressive strength is only reduced by 0.10 MPa. This significantly improves the water resistance of the MOC-stabilized crushed stone and ensures that its strength remains unaffected, which is the optimal modification method. However, this method must ensure that a small amount of citric acid and silica fume are uniformly distributed in the MOC-stabilized crushed stone, which increases the construction difficulty of the road base.

Physico-mechanical properties of halite and of gypsum-mudstone crushed rock backfills of the Mercia Mudstone Group

Permanent disposal of radioactive waste in deep geological repositories (DGRs) relies on engineered barriers, such as crushed rock backfills, to ensure wastes are isolated and contained. The performance of crushed rock backfill, during construction, operation and closure, relies on optimizing its mechanical properties. This paper explores how density and composition influence the strength of (i) crushed halite and (ii) crushed gypsum-mudstone mixtures of the Triassic Mercia Mudstone Group which is a potential DGR host rock in the UK. Unconfined compressive strength (UCS) testing of compacted halite demonstrated that strength correlated with compaction density, with UCS increasing from 220 kPa at a density of 1.72 g/cm 3 up to 6600 kPa at the maximum achieved density of 1.83 g/cm 3 . Direct shear testing revealed an angle of internal friction for crushed halite samples of 39-40° at a density of 1.5 g/cm 3 . Direct shear testing of gypsum-mudstone composites from 100% gypsum to 100% mudstone revealed that higher gypsum percentages provide greater frictional shearing resistance, whilst higher mudstone percentages promote more cohesive strength. Data are also presented on bulk materials characterization by XRF, SEM-EDS and optical microscopy. This research provides insights into how the strength properties of compacted crushed halite and gypsiferous mudstone backfills can be engineered through control of density and composition. Thematic collection: This article is part of the Sustainable geological disposal and containment of radioactive waste collection available at: https://www.lyellcollection.org/topic/collections/radioactive Supplementary material: https://doi.org/10.6084/m9.figshare.c.7237251

Microscopic Mechanism and Reagent Activation of Waste Glass Powder for Solidifying Soil

Glass waste products represent a significant environmental concern, with an estimated 1.4 billion tons being landfilled globally and 200 million tons annually. This results in a significant use of land resources. Therefore, it would be highly advantageous to develop a new method for disposing of waste glass. Waste glass can be recycled and ground into waste glass powder (WGP) for use in solidified soil applications as a sustainable resource. This study is based on solidified soil research, wherein NaOH, Ca(OH)2, and Na2SO4 were incorporated as activators to enhance the reactivity of WGP. The optimal solidified soil group was determined based on unconfined compressive strength tests, which involved varying the activator concentrations and WGP content in combination with cement. X-ray diffraction (XRD) was used to study the composition of solidified soil samples. Microscopic pore characteristics were investigated using scanning electron microscopy (SEM), and the Image J software was employed to quantify the number and size of pores. Fourier-transform infrared spectroscopy (FTIR) was employed to examine the activation effect of waste glass powder. This study investigated the solidification mechanism and porosity changes. The results demonstrate that the addition of activated WGP to solidified soil enhances its strength, with a notable 12% increase in strength achieved using a 6% Ca(OH)2 solution. The use of 2% concentration of Na2SO4 and NaOH also shows an increase in strength of 7.6% and 8.6%, respectively, compared to the sample without WGP. The XRD and SEM analyses indicate that activated WGP enhances the content of hydrates, reduces porosity, and fosters the formation of a more densely packed solidified soil structure.

Exploring for the Future: new geomechanical data in frontier Australian basins

Led by Geoscience Australia, Exploring for the Future (EFTF) is a A$225 million Australian Government program dedicated to exploring Australia’s resource potential and boosting investment. The EFTF program energy component aimed to attract industry investment by delivering a suite of new precompetitive geoscience data in prospective Australian sedimentary basins. Through EFTF, Geoscience Australia has acquired significant amounts of new geomechanical data from underexplored onshore sedimentary basins with identified hydrocarbon prospectivity, from both legacy and newly acquired samples. These data were acquired to build a better understanding of basin sediment rock properties, particularly looking at the reservoir and seal potential of postulated unconventional and conventional targets. Four major datasets are presented herein, representing prospective intervals from the Paleozoic Canning Basin of Western Australia, the Neoproterozoic-Paleozoic Officer Basin of South Australia and Western Australia, the Paleo-Mesoproterozoic South Nicholson region of the Northern Territory and northwest Queensland, and the Paleo-Mesoproterozoic Birrindudu Basin of the Northern Territory and Western Australia. Additionally, the Paleo-Mesoproterozoic McArthur Basin of the Northern Territory is represented by a small number of analyses. Tests include unconfined compressive strength tests, laboratory ultrasonic measurements, single and multi-stage triaxial tests and Brazilian tensile strength tests. These datasets are a precompetitive resource that can facilitate investment decisions in frontier regions, helping to identify elements of conventional and unconventional hydrocarbon systems as well as providing essential data to assess geological storage opportunities.

Mix Design and Field Detection of Large-Particle-Size Graded Crushed Stone Mixtures for Pavement Reconstruction

Large-particle-size graded crushed stone mixtures (LPS-GCSMs) can improve the shortcomings of conventional graded crushed stone, such as low strength, high deformation, and a low modulus of resilience. At present, there is no systematic research on the gradation design and field evaluation of the LPS-GCSMs. In this study, compaction and California bearing ratio (CBR) tests and field construction conditions were combined to design six kinds of gradation of LPS-GCSM, and the optimum gradation was revealed. In order to improve the mechanical properties of LPS-GCSM, 2.5% cement was added to the mixture to prepare a low-content cement-modified LPS-GCSM (LCC-LPS-GCSM) based on the suggested gradation. The mechanical properties of the LCC-LPS-GCSM were investigated through unconfined compression strength (UCS) and compression rebound modulus (CRM) tests. Moreover, the compaction and deflection properties of LPS-GCSM and LCC-LPS-GCSM were examined through the test battery. The results showed that the optimum gradation of LPS-GCSM can be achieved with a combination of aggregate sizes of 20–40 mm, 10–20 mm, 5–10 mm, and 0–5 mm at a ratio of 44:20:10:26. The passing rates of 19 mm and 4.75 mm should be approximately at the median value of the gradation in view of field construction uniformity and a coarse aggregate interlocking effect. The UCS and CRM values of LCC-LPS-GCSM increased rapidly from 0 day to 28 days while they slowed after 28 days, which was similar to those of cement-stabilized materials. The field detection suggested that LPS-GCSM exhibited favorable compaction and that the addition of cement improved the stability of the field compaction of the mixture. Adding a subbase course of LPS-GCSM between the old pavement and the LCC-LPS-GCSM base can lead to more uniform stress on the base. The results of this study provide a reference for the gradation design of LPS-GCSM and optimization of the design indicators.

Macroscopic properties and microscopic characterisation of an optimally designed anti-cracking stone base course filled with cement stabilised macadam

Stone base course filled with cement stabilised macadam (SFC) is a promising solution for addressing reflection cracks in semi-rigid base asphalt pavement due to its satisfactory crack resistance. However, its limited strength and construction challenges have impeded its widespread application. To overcome these challenges, an optimised mix proportion design method of SFC was proposed. Natural crushed limestones with specific particle sizes were selected to serve as skeletal coarse aggregates; fine aggregates and their proportions were step-by-step determined using aggregate and unconfined compressive strength tests. The multi-scale analysis integrating the performance tests and the microscopic detections was performed to evaluate the effectiveness of the proposed SFC, and compared with common cement stabilised macadam (CSM). The results indicate that the material exhibits satisfactory mechanical strength through a tightly interlocked skeleton structure and excellent crack resistance by dissipating strain energy and retarding cracking of SFC through the weak interface transition zone (ITZ).

Study about the rehydration of phosphogypsum hemihydrate in tropical soil mixtures

ABSTRACT The objective of this paper is to verify the occurrence of phosphogypsum hemihydrate (PG-HH) rehydration and its influence on the mechanical behaviour in tropical soil mixtures. The studies were carried out in mixtures with lateritic clay, PG and Portland cement. Were carried out microstructural and mineralogical analyses with scanning electron microscopy and X-ray diffraction experiments, compaction tests at different setting times and unconfined compressive strength tests on saturated samples subjected to weathering. This study showed that PG-HH can rehydrate when it is in contact with water. This fact changes its crystals’ shape and impacts the mechanical behaviour of tropical soil mixtures. Saturated samples exposed to weathering presented strength reduction. However, the strength of mixtures with PG-HH, even when rehydrated, is superior to the strength of mixtures with PG-DH. The incorporation of PG-HH in mixtures with tropical soil and cement in geotechnical works is possible despite its rehydration.

Analysis of Mechanical Properties of Fiber-Reinforced Soil Cement Based on Kaolin.

Adding fibers into cement to form fiber-reinforced soil cement material can effectively enhance its physical and mechanical properties. In order to investigate the effect of fiber type and dosage on the strength of fiber-reinforced soil cement, polypropylene fibers (PPFs), polyvinyl alcohol fibers (PVAFs), and glass fibers (GFs) were blended according to the mass fraction of the mixture of cement and dry soil (0.5%, 1%, 1.5%, and 2%). Unconfined compressive strength tests, split tensile strength tests, scanning electron microscopy (SEM) tests, and mercury intrusion porosimetry (MIP) pore structure analysis tests were conducted. The results indicated that the unconfined compressive strength of the three types of fiber-reinforced soil cement peaked at a fiber dosage of 0.5%, registering 26.72 MPa, 27.49 MPa, and 27.67 MPa, respectively. The split tensile strength of all three fiber-reinforced soil cement variants reached their maximum at a 1.5% fiber dosage, recording 2.29 MPa, 2.34 MPa, and 2.27 MPa, respectively. The predominant pore sizes in all three fiber-reinforced soil cement specimens ranged from 10 nm to 100 nm. Furthermore, analysis from the perspective of energy evolution revealed that a moderate fiber dosage can minimize energy loss. This paper demonstrates that the unconfined compressive strength test, split tensile strength test, scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP) pore structure analysis offer theoretical underpinnings for the utilization of fiber-reinforced soil cement in helical pile core stiffening and broader engineering applications.

Investigating combined effects of saturation–desaturation cycles and cyclic stress resistance of reinforced biopolymer-treated soil

Throughout their service life, subgrades endure significant stress from cyclic traffic and seasonal moisture fluctuations. This study aims to evaluate the moisture variation and cyclic stress resistance of reinforced and biopolymer-treated soils, which were treated with varying percentages (0.25%, 0.5%, 0.75%, and 1.0%) of xanthan gum (XG) and sisal fiber, to determine the level of tolerance a subgrade can sustain. Wetting–drying (W-D) cycle tests, unconfined compressive strength (UCS) tests, and dynamic resilient modulus (DRM) tests were conducted to assess the resistance of the treated soils to moisture variation and cyclic stress. The findings indicate that biopolymer-treated specimens retained over 95% of their original mass after 15 cycles, whereas fiber-reinforced soil exhibited a 9.1% loss in mass. Furthermore, the DRM of the reinforced soil improved, demonstrating greater resistance to cyclic stress compared to biopolymer-treated soils. Fiber-reinforced soils exhibited strain-hardening responses at low cyclic stress levels and maintained stress tolerance even at high cyclic stress levels without signs of strain deformation. Conversely, the UCS of the biopolymer-treated soil surpassed that of the fiber-reinforced soil due to the brittleness of the specimens.

Synergistic effect of Polyvinyl Acetate (PVA) and Enzyme-Induced Carbonate Precipitation (EICP) on the mechanical properties of natural sands

Effective enhancement of the mechanical properties of cohesionless soils is crucial for diverse geotechnical applications, given their inherent vulnerability to load-induced failure due to the absence of inter-particle bonding. Soil failures pose significant risks to both human lives and infrastructure, necessitating the development of environmentally friendly soil improvement methods. Conventional techniques often entail invasive processes and substantial carbon emissions. In response, contemporary approaches seek to minimize environmental impact while preserving organic material characteristics. This study investigates the synergistic effect of polyvinyl acetate (PVA) and enzyme-induced carbonate precipitation (EICP) treatment for enhancing the mechanical properties of cohesionless natural sands. Beach and river sands were treated with varying proportions of PVA in conjunction with an optimized EICP solution for yielding the best results. Unconfined compressive strength (UCS) tests were conducted at 7, 14, and 28-day curing intervals to assess the performance of the soil-polymer-EICP composites (SPEC). The results demonstrated substantial improvements in compressive strength and elastic modulus with increasing PVA content. For beach sand, after 7 days of heat curing, the peak strength increased from 0.89 MPa to 11.07 MPa for composites with 1% and 11% PVA, respectively. Similarly, for river sand, the peak strength increased from 0.87 MPa to 8.96 MPa under the same conditions. The findings also highlighted the softening behavior induced by PVA with heat curing over the period. This softening phenomenon was attributed to the thermo-plastic characteristics of the polymer film induced by temperature conditions.

Experimental study on dynamic and static mechanical properties of polyvinyl alcohol fiber cement soil under salt freezing cycle

A universal testing machine and a 50 mm split Hopkinson pressure bar (SHPB) were used to conduct salt erosion and freeze-thaw (F-T) cycle coupling tests on cement soil specimens with 0.5% polyvinyl alcohol (PVA) fiber and without fiber in order to study the effects of salt solution and F-T cycles on the dynamic and static mechanical properties of cement soil. In four distinct solution settings (clear water, 9 g/L sodium sulphate solution, 9 g/L sodium chloride solution, and 9 g/L sodium sulphate and sodium chloride mixed solution). After F-T cycles, the cement soil specimens underwent the unconfined compressive strength (UCS) test, SHPB test, and SEM test. The findings indicate that as the number of F-T cycles increases, the dynamic and static mechanical properties of cement soil specimens decrease, and the rate of decline is rapid followed by slow. After five F-T cycles, the combined solution's unconfined compressive strength dropped to 15.91% (without fiber) and 29.41% (with fiber), respectively. After five F-T cycles, the dynamic compressive strength in sodium sulphate solution fell by 95.17% (without fiber) and 93.86% (with fiber). Fibers help to some degree by preventing salt erosion and F-T cycles. With more F-T cycles, the absorbed energy declines exponentially, and the order of the solutions' effects on the absorbed energy is: mixed sodium chloride and sodium sulphate solution > sodium chloride solution > sodium sulphate solution > clear water.

Experimental investigation of sandy soil stabilization using chitosan biopolymer

The performance of an environmentally friendly biopolymer synthesised from secondary resources to overcome the wind erosion of sandy soil was investigated in this study. The study employed a multi-scale approach to investigate the mechanical, erosional, and hydraulic properties of sandy soil. At the macroscale, experimental techniques such as unconfined and triaxial compression tests, permeability measurements, contact angle assessments, and wind tunnel experiments were utilized to characterize the bulk behavior of the soil. Concurrently, molecular dynamics (MD) simulations were conducted at the nanoscale to predict surface mechanical characteristics and elucidate chemical interactions at the molecular level. Results show that when the outer surface of the sandy particles is coated with a sparse concentration of biopolymer, the sandy aerosol inhibitory performance is significant even under extreme storm conditions reaching speeds of 140 km/h of storms. The study on the impact of biopolymer content, curing time, and curing conditions revealed that the addition of chitosan biopolymer has the ability to enhance the bonding between particles and significantly enhance the mechanical properties of sandy soil. The atomic insight from molecular dynamics reveals huge entanglement between sandy particles and biopolymer by Van der Waals interaction. The results of the Unconfined Compressive Strength test indicate that chitosan enhances the compressive strength of sand by up to 320 kPa. Additionally, the triaxial test demonstrated that the application of chitosan led to a 34.2 kPa improvement in the cohesion of sand. Furthermore, analysis of the permeability test results revealed a decrease in the hydraulic conductivity coefficient from 1.6 × 10^-6 m/s to 5.7 × 10^-7 m/s, representing a reduction of approximately 35 %.

Utilization of alkali-treated areca fibers for stabilizing silty sand soil for use in pavement subgrades: Analysis using IITPAVE software

AbstractThe increasing growth of urban areas and the rise in infrastructure development activities have put a strain on the availability of land with desirable soil conditions. This has led to the development of several stabilization techniques that can be used to improve the properties of weaker soils for construction. The research presented here explores the impact of inducing randomly oriented alkali-treated areca fibers for stabilization of silty sand soil. A sequence of experiments was carried out on the soil-fiber mixtures to investigate the strength of the soil after stabilization. At increments of 0.2%, the fiber dose varied between 0 – 0.8% of the dry weight of the soil. The tests conducted includes compaction tests, California bearing ratio (CBR), unconfined compression strength (UCS) tests, and unconsolidated undrained (UU) triaxial tests. The results obtained showed a notable increase in the strength of the soil-fiber mixtures. An increase in fiber content was found to increase the OMC (optimum moisture content) values and decrease the MDD (maximum dry unit weight) values. The maximum strength of the soil-fiber mixture was obtained at 0.6% fiber content. This makes it possible to use silty sand soil subgrades for low-volume roads with a traffic of less than 2 million standard axles based on the IITPAVE analysis. In essence, the test findings indicated that the ideal fiber content to be 0.6%. Stabilization of local on-site soils is one of the sustainable practices that can help extend the life of a pavement and lessen the need for more frequent repairs/maintenance.

IMPROVING THE ENGINEERING PROPERTIES OF CLAYEY SOIL USING SILICA FUME AND SISAL FIBER

Building on soft soils continues to be a challenge for civil engineers in the modern world, despite the rapid development of infrastructure projects and advancements in construction technology. They exhibit a large volumetric change upon contact with water, which is the cause of their limited bearing capacity. Various stabilization strategies can be used to handle the soft clay's shear strength issue. In this experiment, sisal fibers and silica fumes were added in different amounts to the clay soil in order to determine the ideal moisture content and strength parameters for reaching the maximum dry density of the soil. By adjusting the amount of sisal fiber for each amount of silica fume, the Unconfined Compressive Strength (UCS) test has been used to examine the strength of both natural clay and clay modified with silica fume (6%, 12%, 18%) and sisal fibers (0.5%, 1.0%, 1.5%) separately, as well as the combination of all the materials. Using a small compaction device, standard proctor test was used to determine the ideal moisture content and maximum dry density. According to the test results, the maximum dry density falls with increasing silica fume content likewise, the maximum dry density increases with increasing sisal fiber content. The addition of 12% silica fume and 2.0% sisal fiber to the clay sample results in a maximum strength when taking the strength parameter into account. Key Words: Compaction test, CBR, UCS, Silica fume, Sisal Fiber

Analysis of Kinang Jingkion Material as Road Subbase Layer Using Soil Cement Method

This research aims to analyze the California Bearing Ratio (CBR) and Unconfined Compressive Strength Test (UCS) values as road foundation layers using local materials, namely Kinang Jingkion. The soil and Kinang Jingkion materials for the study were taken from the Apalapsili quarry in Yalimo Regency. Additionally, the additive or soil stabilizer used was matos obtained from the testing of soil characteristics, including sieve analysis or gradation, Standard Proctor Test for light density, and liquid limit test. After testing, it was found that the soil from the Apalapsili quarry is granular soil and can be categorized as A-1-a according to SNI 03-6797-2002. Subsequent testing involved CBR and UCS testing on Mix Designs made of soil and cement with concentrations of 4%, 6%, and 8%. Next, additional Mix Designs were created with compositions of Kinang Jingkion, soil, cement at 4%, 6%, and 8%. Further Mix Designs included compositions of Kinang Jingkion, soil, matos at 2%, and cement at 4%, 6%, and 8%. From the UCS testing results, Mix Designs with soil and cement concentrations of 4% and 6% did not meet the compressive strength criteria, with compressive strength values of 9.26 Kg/Cm² and 17.4 Kg/Cm² respectively. According to SNI 6887-2012, the compressive strength value after 7 days of immersion should be within 25-35 Kg/Cm², while other Mix Designs met the criteria of SNI 6887-2012. CBR testing also utilized the same Mix Designs, and the highest CBR result was obtained from the Mix Design with compositions of Kinang Jingkion, soil, cement at 8%, and matos at 2%, with a CBR value of 112%. According to the 2018 Revised General Specifications, a CBR value of 112% indicates a Class A Foundation Layer.

Mix optimization and mechanical properties evaluation of lime-fly ash-stabilized loess in various engineering applications

Determining a rational mix ratio for lime-fly ash-stabilized loess (LFSL) can achieve multiple benefits of economy, environmental protection, and engineering quality improvement. This research was designed to optimize the mix ratios of LFSL applied in the pavement structure, subgrade, slopes, and foundations by conducting the unconfined compressive strength (UCS) test, California bearing ratio (CBR) test, resilient moduli (MR) test, triaxial test and uniaxial consolidation test on LFSL and lime-stabilized loess (LSL). Combined with the initial consumption of lime (ICL) test result and relevant specifications, the optimized mix ratios are as follows: 2% lime + 11.82% fly ash and 2% lime + 3.95% fly ash can reach the strength requirement of road base and subbase, respectively; 2% lime + 3.84% fly ash in building foundations and subgrade and 2% lime + 3.55% fly ash in slopes can reach the equal improvement effect of the LSL with 8% lime content. Three-factor comprehensive models were established and fitted in well with the experimental results of the LFSL with 2% lime content. Moreover, the development of correlations between UCS and other mechanical indices offers a shortcut for engineering property estimation. Finally, based on the abundant literature on LSL, another approach to estimating engineering quality was proposed for the LFSL with 2% lime content, which enhances the universality and practicability of the estimation models further.

Influence of the wide range cement content on the properties of cement–treated marine soft soil and bound method of semi–solidified soil

In order to identify the upper and lower boundary cement content for modified marine soft soil (i.e., semi–solidified soils), physical, compaction, and unconfined compressive strength tests of cement–treated soils with a wide range of cement content were carried out to study their variation law of physical–compaction–mechanical properties. The test results show that cement–treated soil can be divided into uselessly treated soil, semi–solidified soil, and solidified soil with the increase of cement content. For uselessly treated soil, the treated soil cannot be compacted even after compaction delay. Cement hydration in semi–solidified soil significantly improved its physical and compaction properties. However, compaction destroyed the skeleton structure of solidified soil, resulting in lower strength than compacted semi–solidified soil. Based on the cement–soil particles–water relationship, soil particles–water transfer mechanism, cement hydration mechanism and the state of soil particles–water before and after treated, the bound method of semi–solidified soils based on cement content and moisture content ratio of untreated soil was established. The test parameters of bound method are simple, easily obtained and have small dispersion, which provides design basis and theoretical support for resource utilization of marine soft soil.

Characterization and mechanism study of sulfate saline soil solidification in seasonal frozen regions using ternary solid waste-cement synergy

Infrastructures built on sulfate saline soil foundations in seasonal frozen regions are highly susceptible to salt-frost heave damage and salt corrosion. To address this issue, a method has been proposed utilizing a ternary blend of industrial solid waste materials - fly ash (FA), silica fume (SF), and brick powder (BP) - in conjunction with Portland cement (PC) for the solidification of sulfate saline soil. The feasibility of this solidification technique has been validated through a series of tests, including unconfined compressive strength tests, freeze-thaw cycle tests, salt leaching tests, and microstructural analysis. The results showed that: The unconfined compressive strength of the solidified saline soil at 56 days increased by up to 61.27 times compared to untreated saline soil. During the freeze-thaw cycles, the volume of salt-frost heave in the solidified saline soil was only 10.75% of that in untreated soil, with a reduction in salt-frost heave force by up to 90.94%. Furthermore, during the salt leaching process, the rate of salt migration in the solidified saline soil could be slowed by up to 4.15 times, while the total amount of salt leached was only 31.34% of that in untreated saline soil. Additionally, through the combined use of X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray Spectroscopy (EDS), it was discovered that the interactive synergistic effect of the solidifying agents in a SO42- rich environment facilitated the dissolution of Si-O and Al-O micro-lattices on the surface of the solidifying agent particles. This led to the extensive formation of C-(A)-S-H gels and AFt products, resulting in the transformation of the soil structure from dispersed to flocculated. The comprehensive test results indicate that the mechanical properties, frost resistance, and salt corrosion resistance of the solidified saline soil have significantly improved, with an optimal solidifying agent mixture ratio of 3% PC, 5% FA, 5% SF, and 6% BP. These findings can provide a reference for the solidification treatment of sulfate saline soil foundations in seasonal frozen regions.

Exploring the Influence of Plastic Powder Incorporation on Geotechnical Properties of Expansive Soil Stabilized with Granite Powder for Building Applications

An experimental study was undertaken to investigate the effect of plastic and granite waste powder on the geotechnical performance of expansive soil, using different mix ratios. The soil studied is Hachem, in the northwestof Algeria. In this context, first reinforcing the plastic powder with granite powder, then add the mixture to the expansive soil. The percentage of plastic powder is (0%, 1%, 2%, 3%, 4%) and reinforced at 2%, 4%, 6% and 8% with granite powder. The experimental results showed a gradual decrease in liquid limits, swell potentials, and swelling pressure as the proportions of plastic and granite powder increase. In terms of the results obtained by reducing swelling and swelling pressure values and increasing unconfined compressive strength (UCS) tests and ductility values, this mixture of waste plastics and granite can be of great importance in improving the mechanical properties of samples.

Cement Kiln Dust as Partial Replacement of Cement for Improvement of Sabkha Soils for road application

Salt-encrusted desert flats or sabkha soil, which particularly formed in arid and semi-arid zones, have raised a noticeable concern because of low bearing capacity and high compressibility. this study is aimed to explore the feasibility of stabilizing Omani sabkha using environmentally friendly stabilizer through Cement Kiln Dust (CKD). Untreated and treated sabkha were characterized using standard proctor compaction test, unconfined compressive strength (UCS) and California Bearing ratio test (CBR). Results show that utilizing 7.5% binder that contained 50% Cement Kiln Dust improved the overall properties of sabkha soil and it can be used as sub-base layers.