Unconfined Compression Tests Research Articles

Research on the Modulus Decay Model under a Three-Dimensional Stress State of Asphalt Mixture during Fatigue Damage

Fatigue damage can develop within asphalt pavement due to the continuous impact of driving loads and natural elements. Understanding the process of asphalt mixtures’ fatigue damage is crucial for guiding the design, maintenance, and repair of asphalt pavement. This research aims to establish a model that characterizes the mixtures’ modulus decay under a three-dimensional (3-D) stress state. Firstly, asphalt mixes were subjected to direct tensile (DT), indirect tensile (IDT), unconfined compressive (UC) strength and fatigue tests, and the resulting data were analyzed. Then, modulus decay models under DT, IDT, and UC conditions were established, and the modulus decay patterns under the three loading modes were compared and analyzed. Finally, using the fatigue stress strength ratio Δ (a fatigue resistance index for asphalt mixtures that takes into account the impacts of stress state and loading rate), a unified characterization model for asphalt mixes’ modulus decay under a 3-D stress state was created. According to the study’s findings, asphalt mixes’ modulus decay during fatigue damage exhibits obvious nonlinear characteristics. While the asphalt mixes’ modulus decay law with various loading modalities is similar under the same conditions, the decay rate may differ. Essentially, the speed of the modulus decay of a certain asphalt mixture primarily depends on the value of Δ during service. A larger Δ indicates a faster modulus decay. This study offers a theoretical foundation for the conversion from material fatigue damage to structural fatigue damage, which is vital for enhancing the asphalt pavements’ construction quality and longevity.

Engineering properties and mechanical behaviour of problematic soil stabilized by bituminous oil shale ash

This paper investigates the viability of stabilizing expansive brown clays in the Northern region of Jordan using a local bituminous oil shale ash from El-Lajjun, Jordan. A comprehensive experimental programme was designed to i. examine the impact of oil shale ash dose by weight on the strength gain. ii. Evaluate oil shale ash stabilized clays' consolidation and volume change behaviour during loading and unloading. Results revealed that adding 20 % bituminous OSA remarkably improved expansive brown clays' engineering properties and mechanical behaviour. An increase of 140 % in the unconfined compressive strength and a reduction of 19.3 % in the permeability coefficient was obtained at 20 % OSA. Also, the Unconfined Compressive Strength tests revealed that the strength of OSA-treated expansive clays is significantly affected by the curing time. Increases of 35.1 % and 65.7 % in the unconfined compressive strength were achieved after 7 days and 21 days of curing, respectively. Furthermore, the addition of OSA showed an effect on compressibility behaviour, reducing settlement. Regarding the consolidation parameters, the inclusion of 20 % OSA reduced the compression index (Cc) and swelling index (Cs) by 42.67 % and 72.6 %, respectively.

Investigation on coal dust prevention by biomimetic mineralized dust suppressant with polyacrylic acid modifier

Coal dust prevention is crucial for the environment and the safety of coal miners. This study proposed a biomimetic mineralized dust suppressant (BMDS) with polyacrylic acid (PAA) modifier, based on calcium carbonate precipitation technology. The consolidation effect of BMDS on coal dust was evaluated through wind erosion resistance tests, unconfined compressive strength tests, and microscopic characterizations. The results show that the consolidation effect of the BMDS on coal dust heavily depends on the PAA concentration. When the PAA concentration is 4 g/L and the concentration of calcium chloride and sodium carbonate is 0.5 mol/L, the BMDS presents the best dust suppression effect and could realize the practical application requirements. The generated calcium carbonate is mainly calcite type, and the efficiency of cementing coal dust particles is the highest. Moreover, similar to bacteria in biological dust suppressants, it confirms that PAA could effectively modify the nucleation and growth of calcium carbonate, promote the adhesion of calcium carbonate to the surface of coal dust particles, and enable the generated calcium carbonate to effectively bond coal dust particles. Accordingly, the BMDS with PAA modifier can be effectively used in the prevention of secondary coal dust pollution.

The Influence of Bottom Ash Column in the Geotechnical Properties Enhancement of Soft Clay Soil

The utilization of bottom ash in ground improvement studies can cut down the quantity of generated waste which is in response to environmental conservation and enhancing the soil properties. The bottom ash which plays the role of replacing the coarse aggregate like sand and gravel in upgrading the behaviour of soft clay soil can fulfill the sustainability concept in construction. For construction purposes, the soil and ground improvement activities are necessary to carry out by using the relevant techniques, including the vibro-replacement method. This method was applied which suits the limitation of this study as it was executed in the laboratory for the preparation of the bottom ash column. The properties examination of kaolin clay and bottom ash were first studied through its particle size, specific gravity, liquid and plastic limit, and compaction. The following procedure was about the column preparation process, where the column diameter was set to be constant at 20 mm throughout the study. The execution of the Unconfined Compression Test (UCT) on the Bottom Ash Column has shown its impact on the undrained shear strength upgrade and it was focused on the height of the bottom ash column built beneath the kaolin clay at 60mm, 80mm, and 100 mm. As observed from the trend, the height of the bottom ash column shows a direct proportional relationship by the undrained shear strength, ranging from 11.64% - 14.26% by using the control sample (with no bottom ash reinforcement) as reference. Conclusively, the use of bottom ash subsides the disposal waste and in no time provides support to the shear strength of soft clay soil which is sustainable and applicable.

Effect of Curing Time on Compressive Strength Performance of Coconut Shell Charcoal Ash (CSCA) and Fly Ash Stabilized Peat Soil

Peat soils are considered problematic soils and unstable for engineering projects due to geotechnical problems such as high compressibility and poor shear strength. Peatland could be an alternative to future development due to a lack of suitable and pricey land. Stabilization of the peat soil should be done before construction to improve its engineering features. The influence of curing time on the compressive strength performance of Coconut Shell Charcoal Ash (CSCA) with fly ash to stabilized peat is presented in this research. Some engineering variables including physical and mechanical properties were examined. The modified stabilized peat soils were made by adding various amounts of CSCA to the dry weight of the peat soil, ranging from 3%, 6%, 9%, and 12%, while fly ash constant 10%. The treated samples were cured for 0, 7, 14, and 28 days to see how curing affected the results. The results show that when the amount of CSCA with fly ash applied to the peat soil samples increased, the compressive strength also increased. On the other hand, showed that as the amount of CSCA with a constant fly ash content and the curing duration increased, so did the unconfined compressive strength test. The result shows that the addition of CSCA with fly ash into the mixture helps to stabilize and improve the strength of the soil.

Strength Degradation of Foamed Lightweight Soil Due to Chemical Erosion and Wet-Dry Cycle and Its Empirical Model.

Foamed lightweight soils (FLS) have been extensively used as backfill material in the construction of transportation infrastructures. However, in the regions consisting of salt-rich soft soil, the earth structure made by FLS experiences both fluctuation of groundwater and chemical environment erosion, which would accelerate the deterioration of its long-term performance. This study conducted laboratory tests to explore the deterioration of FLS in strength after being eroded by sulfate attack and/or wet-dry cycling, where the influencing factors of FLS density, concentration of sulfate solution, and cation type (i.e., Na+ and Mg2+) were considered. An unconfined compressive test (UCT) was conducted, and the corrosion-resistant coefficient (CRC) was adopted to evaluate the erosion degree after the specimens experienced sulfate attack and/or dry-wet cycling for a certain period. The research results show that the erosion of the FLS specimen under the coupling effect of sulfate attack and dry-wet cycling was more remarkable than that only under chemical soaking, and Na2SO4 solution had a severe erosion effect as compared with MgSO4 solution when other conditions were kept constant. An empirical model is proposed based on the test results, and its reliability has been verified with other test results from the literature. The proposed model provides an alternative for engineers to estimate the strength deterioration of FLS on real structures in a preliminary design.

Stabilization of Soil Using Guar Gum Biopolymer

Abstract: Soil stabilization in a broader sense refers to various methods and techniques employed to improve the geotechnical properties of a problematic soil to enhance its load bearing capacity. Many materials like cement, lime, bitumen etc. are employed to improve the properties but they are not ecofriendly as such. In this study, an effort has been made to study the effect of natural occurring polymer, Guar Gum to improve the mechanical properties of soil rich in clayey minerals. This biopolymer is biodegradable in nature and have less carbon footprint than other conventional materials. Five different varying proportion (0.5%, 1.0%, 1.75%, 2.50% and 3.25%) of Guar Gum with soil has been used to find the optimum dosage required for stabilization. Three major properties like Optimum Moisture Content -Maximum Dry Density relation, California Bearing Ratio Test (both unsoaked and soaked) and Unconfined Compressive Strength Test were studied on the soil and mixes. From the results it was concluded that soil with 1% Guar Gum has shown maximum improvement in the geotechnical properties of soil.

Investigation on the impact of curing conditions on the behavior of controlled low-strength material as basement of rural roads in the Mekong Delta

This study investigates the performance of controlled low-strength material (CLSM) in the challenging Mekong Delta climate, which experiences rapid weather fluctuations, acid rain erosion, uneven mixture gradation, and subpar aggregate quality. Additionally, difficulties in sieving and quality control have led to the disposal of dredged soil in construction sites. The research aims to enhance the practical use of CLSM as a foundation for rural roads in the Mekong Delta by incorporating dredged soil and mineral additives (6% silica fume, 25% bottom ash) under various curing conditions, including normal, acidic, and salted environments. The study assesses CLSM strength through flowability, setting time, and unconfined compressive strength tests. Findings highlight the significant influence of curing conditions on both early and 28-day CLSM strength, with harsh environments compromising cement hydration. Optimizing dredged soil content and mineral components can bolster CLSM strength and promote sustainable use of dredged soil in construction.

EVALUATION OF THE STRENGTH CHARACTERISTIC OF SOIL STABILIZED WITH FLY ASH

High domestic consumption of coal, especially in energy sector, has raised concerns on several environmental issues in Indonesia. Large amount of coal combustion product in the form of solid waste, such as fly ash resulting from coal power plant production causes problems in its disposal since its necessity of land occupancy. Over the last decade, many researchers have put effort to solve this disposal concerns by utilizing these materials for various purposes, such as construction materials as part of circular economy. This paper presents the utilization of fly ash for soil stabilization in Surabaya. Firstly, the index properties of soil samples were determined through a series of laboratory soil test including specific gravity, unit weight, moisture content, sieve analysis and Atterberg’s limit tests. Subsequently, standard proctor test was conducted to obtain the maximum dry density and optimum moisture content of the soil samples. Using those parameters, four types of soil stabilized with fly ash samples were prepared with fly ash content based on weight of soil as follows: 0%, 5%, 10%, and 15%. Finally, unconfined compression tests were performed with cylindrical soil samples to assess the unconfined compressive strength of those samples. The results indicate that soil with fly ash content of 10% showing the highest unconfined compressive strength compared to the other variations of 0.90 kg/cm2.

Multiscale numerical investigation of ratchet growth damage effects in PBX 9502

AbstractThis paper presents results of numerical experiments conducted on the high explosive PBX 9502 to investigate how recently observed grain‐scale damage mechanisms of ratchet growth [1] affect uniaxial compression measurements. Simulations are multiscale in the sense of directly resolving grains, pores, cracks, and grain‐interfaces based upon scanning electron microscope (SEM) images of damaged and undamaged samples. The combined finite‐discrete element method (FDEM) is utilized to resolve both grain‐scale microfracture and elastoplastic deformation of solid grains. Pristine (undamaged) and damaged microstructures are compared in simulation of unconfined compression tests of the same material from the literature. The simulation results show the observed microscale mechanisms of damage, specifically microfracture predominantly around and sometimes through grains and crack‐associated pore growth, can well‐explain the effective degradation of strength and stiffness observed in the laboratory measurements.

Effect of using Oil Shale Ash on geotechnical properties of cement-stabilized expansive soil for pavement applications

Expansive soil is considered an engineering problem that may cause cracks and distresses in structures and roads. Due to its swelling potential and low unconfined strength, expansive soil causes failures in structures and leads to financial losses. Oil Shale Ash “OSA” is the byproduct of the combustion of the oil shale rock to produce electricity. Instead of dumping OSA materials into landfills, which has several negative environmental implications and cost burdens, utilizing these materials as building materials might alleviate the environmental concerns caused by their disposal. This research investigates the possibility of experimentally using the by-products Oil Shale Ash (OSA) and Portland Cement (PC) to enhance the geotechnical properties of problematic expansive soil. OSA and cement have been added to the soil, where OSA is used in four percentages by dry weight of soil (10%, 20%, 25%, 30%), and cement is used in three percentages (2%, 4%, 6%). A laboratory test program was implemented, including Atterberg limits, compaction test, unconfined compressive strength test (UCS), swell test, linear shrinkage test, and California Bearing Ratio (CBR) test. The results showed that OSA and cement have reduced the expansive natural soil's swelling potential, plasticity index, and linear shrinkage. Also, the UCS and CBR values of treated soil have improved significantly. Pavement analyses demonstrated that OSA-cement-stabilized soil could be a suitable stabilization agent for the subgrade and base layers in constructing pavements.

Uniformity evaluation and improvement technology of sandy clayey purple soil enhanced through microbially-induced calcite precipitation

In order to improve the uniformity of calcite precipitation and engineering practicability, a series of tests using bacillus megaterium (BNCC 336739) were conducted to enhance sandy clayey purple soil, with different concentration bacterial solution and cementation reagent flowing to the samples perforated in the center with different grouting speed. Based on the mineral component (XRD) and soil microstructure (SEM), cementation mechanism was analyzed. Based on measurement of CaCO3 production and unconfined compressive strength tests, the influence law of grouting factors on CaCO3 production amount (C), CaCO3 uniformity (s), CaCO3 deposition rate (P), unconfined compressive strength (UCS) and stiffness (elastic secant modulus E50) were analyzed and the correlation between C, s and UCS, E50 were analyzed. The results show that the uniformity can be improved by perforation grouting, and the UCS and E50 of samples treated by MICP increased by 105.58% and 464.14%. The CaCO3 induced by bacillus megaterium are 1–5 µm calcite crystal, which cemented and wrapped soil particles. The higher the concentration of bacteria solution and cementation reagent and the slower the grouting speed are, the bigger the C and the s. The C has a lower threshold of 2.5% and an upper threshold of 5%, the UCS of samples treated by MICP significantly increases with the increase of C in the interval, and the UCS growth becomes slow or even negative outside the interval. The smaller the s is, the bigger the UCS and E50 are, and this effect is small when C< 4% and is significant when C> 4%. With the effect of s, the UCS and E50 of sample treated by MICP increase with different speed and then reduced as the increase of C. It provides scientific reference for the application of MICP technology in purple soil area.

Dissipation mechanisms of crack-parallel stress effects on fracture process zone in concrete

The effect of crack-parallel stresses on the fracture properties of quasi-brittle materials has recently received significant attention in the fracture mechanics community. A new experiment, the so-called gap test, was developed to reveal this effect. While the finite element crack band model (CBM) with the physically realistic Microplane damage model M7 was quite successful in capturing the damage and fracture during the gap test, some questions remain, particularly the near doubling of the fracture energy at moderate crack parallel compression, which was underestimated by about 30%. Presented here is an in-depth meso-mechanical investigation of energy dissipation mechanisms in the Fracture Process Zone (FPZ) during the gap test of concrete, an archetypal quasi-brittle material. The Lattice Discrete Particle Model (LDPM) is here used to simulate the quasi-brittle material at the mesoscale, which is the length scale of major heterogeneities. The LDPM can capture accurately the frictional sliding, mixed-mode fracture, and FPZ development. The model parameters characterizing the given mix design are first calibrated by standard laboratory tests, namely the hydrostatic, unconfined compression, and four-point bending (4PB) tests. The experimental data used characteristic of the given mix design are calibrated by the Brazilian split-cylinder tests and by gap tests of different sizes with and without crack-parallel stresses. The results show that crack-parallel stresses affect not only the length but also the width of the FPZ. It is found that the energy dissipation portion under crack-parallel compression is significantly larger than it is under tension, which is caused by micro-scale frictional shear slips, as intuitively suggested in previous work. For large compressive stresses, the failure mode changes to inclined compression-shear bands consisting of axial splitting microcracks. Several complications experienced in the numerical modeling of gap tests are also discussed, and the solutions provided.

Experimental study on the strength and water stability of concentrated solution sludge solidified with sulfoaluminate cement combined with MSWI bottom ash

Concentrated solution sludge (CSS) produced by the submersion combustion technology conducted on the municipal solid waste (MSW) sanitary landfill leachate has special characteristics, such as high water content, low organic matter and heavy metal content and extremely high salt content. In the present work, sulphoaluminate cement (SAC) was used as main curing agent and municipal solid waste incineration (MSWI) bottom ash was collaborated as auxiliary curing agent to solidify the CSS. A series of unconfined compression tests, water stability test and microscopic observation tests were conducted on the solidified CSS samples with various curing agent combinations to quantitatively investigate the influence of different curing agents on the solidification effect of the CSS, and to interpret the physical mechanism of strength improvement and deterioration of the solidified CSS in curing and soaking stage. Research results indicate that: the 7 d unconfined compression strength (UCS) of the CSS solidified with 10% SAC is 168.6 kPa, 162.8 kPa and 158.8 kPa when the water cement ratio is 0.25, 0.30 and 0.35, respectively, which are larger than 50 kPa and can satisfy the strength requirement of landfill. The UCS of the CSS solidified with 50% SAC after soaking in water for 28 days is 329.4 kPa, 276.5 kPa and 202.0 kPa when the water cement ratio is 0.25, 0.30 and 0.35, respectively, and can satisfy the strength requirement of landfill concerning water stability of the solidified CSS; the 28d UCS of the CSS solidified with 40% SAC and an addition of 0%, 5%, 10% and 15% bottom ash is 1483.8 kPa, 2144.4 kPa, 2431.2 kPa and 1537.0 kPa, respectively, and decreased to 0 kPa, 52.9 kPa, 103.9 kPa and 51.0 kPa after soaking in water for 28 days; a reasonable bottom ash content is capable of improving the USC of the cement solidified CSS and there is an optimal dosage of bottom ash for enhancing the 28 d UCS of the cement solidified CSS, which is 5% for SAC content lower than 40% and 10% for SAC content higher than 40%. The improvement effect of the solidified CSS can be achieved by using 10% bottom ash as replacement for 10% SAC. The SEM and XRD test results indicate that: the formation of the spatial interlocking structure composed of the C-S-H gels and ettringite crystals generated by the interaction between SAC and bottom ash in soaking stage is the key factor for improving the water stability of the cement solidified CSS by adding a certain dosage of bottom ash.

Laboratory investigation of scale effects in bursting failure of quasi-brittle materials

Understanding the scale effect in the behavior of solid materials is important when small-scale models are used to predict the behavior of real structures. Tremendous efforts have been devoted to investigating the scale effect in the strength of quasi-brittle materials. However, limited studies have focused on the whether there is a scale effect in bursting failure, which is a typical failure pattern of quasi-brittle structures. Here, we conduct a series of unconfined compression tests on coal samples using a specialized designed loading machine to produce bursting failure in the laboratory. We use cubic coal samples with a large range of sizes from 50 to 300 mm to investigate the scale effect in bursting failure of quasi-brittle materials. We use acoustic emission technology to monitor microcreaking within the samples and a high-speed camera to capture the bursting failure process. We demonstrate that there is a strong scale effect in bursting failure of quasi-brittle materials in terms of mechanical properties including compressive strength and deformability, strain energy density, bursting severity, and precursor time. We found that ejection of localized pieces from the skin of the structure is a precursor of catastrophic bursting failure of quasi-brittle materials. We conclude that the relationship between the precursor time (T) and structure size (M) of bursting failure is logarithmic and can be described as logT = a + bM where a and b are constants. This relationship provides a guideline when models obtained from laboratory tests are used to predict strength and behavior at the intermediate (mines and rock slopes) and large scales (earthquakes).

A hydromechanical material model for compacted bentonite

This paper presents a new hydromechanical model, developed with the intention to be used for predicting the mechanical evolution of compacted bentonite components in repositories for spent nuclear fuel. The model is based on a thermodynamic relation for the chemical potential of the clay water, and uses empirical functions which are parametrized and calibrated with data on water retention properties at free swelling conditions, swelling pressure, and shear strength; the latter two are central for defining technical requirements for the bentonite buffer components. This results in a model which at its core incorporates all these properties, as well as the hysteresis behaviour. The validity of the model was investigated by analysing nine experimental test conditions, using COMSOL Multiphysics®, with a single set of parameter values. Model results were compared with experimental data for both saturated conditions (free swelling retention test; oedometer tests and triaxial compression tests) and for unsaturated conditions (swelling pressure build-up; swelling or shrinkage at constant load; compression at constant water or constant suction and unconfined compression tests). These comparisons gave a broad demonstration of the predictive capabilities of the model. Some limitation of the model regarding the representation of shrinkage, the shear strength at lower water contents, and the path dependence can nevertheless be noted.

Mechanism of sampling disturbance for peat ground and its influence on mechanical properties

A soil investigation was conducted in peatlands in Japan, using two types of tube sampling methods, and the quality of the samples was evaluated. Unlike clays, peats easily lose water by compressive actions involved in sampler intrusion and core extrusion, leading to a significant loss of pore water. It was shown that this effect could be minimized by careful thin-wall sampling with a stationary piston, whereas open-drive sampling without a piston led to the significant compression of the sample core. The consequence of this disturbance on the in-situ behavior was interpreted through an examination of the mechanical properties of peat samples subjected to the “strain paths” expected during sampling in laboratory tests. By observing the deformation characteristics through a series of constant-rate-of-strain consolidation, unconfined compression, triaxial compression, and bender element tests, it was demonstrated that, contrary to soft clays, fibrous peats with high initial permeability potentially lead to the underestimation of the settlement during construction and the overestimation of strength due to inappropriate sampling. These results can be explained by the dominance of densification by disturbance over soil structure degradation. It was also noted that the sample quality varied considerably within the sampling tube.

Unlocking the potential of iron ore tailings in controlled low-strength material: Feasibility, performance, and evaluation

Iron ore tailings (IOT), the predominant solid by-products of iron ore mining and refining, present significant environmental challenges due to their sheer volume. This paper endeavors to scrutinize the prospective deployment of IOT as an alternative to soft soil in the fabrication of controlled low strength materials (CLSM) for backfill applications. The flowability of the CLSM is evaluated by adjusting the IOT, soft soil, and water contents and subsequent appraisal of mechanical properties of the cured CLSM samples is performed via unconfined compressive tests, dry-wet cycles, and direct shear tests at the flowability of 20 cm. Furthermore, scanning electron microscopy and mercury intrusion porosimetry tests are deployed to investigate the impact of IOT on the microstructure of the cured CLSM. Experimental results demonstrate that an increase in IOT content considerably reduces the requisite water content to achieve a flowability of 20 cm for CLSM. Both unconfined compressive strength (UCS) and direct shear tests signal that the infusion of IOT into CLSM substantially enhances the UCS (e.g., from 200 to 440 kPa) along with improving the cohesion (e.g., from 65.9 to 103 kPa) and friction angle (e.g., from 11.5° to 16.3°) of the cured CLSM samples. The mass loss of CLSM, post dry-wet cycles, is notably mitigated, and the corresponding UCS is also bolstered by increasing the IOT content. Microstructural observations in conjunction with pore size characterizations corroborate that the strength augmentation of the CLSM mixture can be attributed to the densification of the microstructure and the proliferation of cement hydration products with increased IOT content. Consequently, this investigation sheds light on the promising potential of employing IOT as a central ingredient in CLSM production.

DEM analyses of mesoscopic failure mechanism and stress bearing mechanism of compacted snow subjected to unconfined compressive loading

In order to explore the mesoscopic failure mechanism and bearing mechanism of compacted snow under loading. First, the skeleton of dendritic snow crystal was constructed by 13 ice rigid sphere particles which are bonded together using a completed bond contact model. Second, a "falling snow method" was proposed and used to simulate the whole process of natural snowfall, i.e. snow generation, snow falling, snow deposition, and snow compaction. Third, the compacted snow sample was sintered at different temperatures with different times; in sintering process, the snow particles were bonded together by the completed bond contact model. Finally, after contact model parameter calibration by reported snow test results, the unconfined compression tests on the finished sintering snow were carried out and the mesoscopic failure mechanism and stress bearing mechanism were analyzed. Take the sintering temperature of −10 °C and finished sintering samples for example, the results show that the number of compacted snow bond breaks was mainly contributed by tension bond breaks. Meanwhile, with the increase of density, the ratio of bond breaks in tension and compression was higher. When the density was below 475 kg·m−3, the bond breakage was dominated by bending. While the density was above 475 kg·m−3, the bond breakage was mainly shearing. The contribution of the normal contact force to the total axial stress accounted for about 65% which was greater than that of the tangential contact force (ρ = 400 kg m−3). This study can provide support for the mesomechanical failure theory of compacted snow engineering, such as snow roads, compacted snow runways, and snow foundations.

Investigating the strength and durability properties of alkali activated red mud for tailings pond embankment material

This article investigates the applicability of alkali-activated red mud (RM) as a geo-material for the construction of tailings pond (TP) embankments. A series of unconfined compressive strength (UCS) and direct shear tests (DST) are carried out to examine the mechanical performance of RM activated with sodium hydroxide (NaOH). While doing so, the influence of NaOH concentrations, curing conditions and curing period are also investigated. Furthermore, durability tests are performed to examine the weathering resistance of stabilized RM specimens against extreme environmental conditions. Finally, the effectiveness of alkali activated RM (as an embankment material) is demonstrated with the help of numerical analysis performed on a model TP. Based on the experimental results, the compressive strength of bare RM is improved from 0.34 MPa to 5.6 MPa, 0.57 MPa to 10.55 MPa and 0.97 MPa to 29.34 MPa under controlled ambient curing (CAC, 25±2 °C), open air curing (OAC, 25±7 °C) and dry curing (DC, 60 °C) conditions respectively. On the other hand, effective friction angle and cohesion of bare RM is found to increase from 16.76° to 52.85° and 6.58 kPa to 391.11 kPa respectively, after alkali activation. Furthermore, alkali activated RM specimens exhibit a significantly high weathering resistance than bare RM against 12 cycles of alternate wetting and drying. The numerical analysis reveals a notable increase in the factor of safety values when alkali activated RM is utilized for the construction of TP, indicating its potential as an embankment material.