Compaction Characteristics Research Articles

Static Compaction for Sustainable Geotechnical Solutions: A Comprehensive Study

The objective of this research is to develop an improved uniaxial static compaction method to address the limitations of the traditional Proctor's dynamic approach for soil compaction. This new approach offers reduced labor, enhanced soil density, and increased compactness. The study compares of static soil compaction characteristics with various soil parameters and explores the concept of Equivalent Static Compaction Energy (ESCE). A diverse range of fine-grained soils with varying range of plasticity was investigated, and a significant correlation of compaction parameters attained by static compaction was observed with the corresponding value of static compaction energy, degree of saturation, void ratio, and plastic limit of soil. The research resulted in the creation of constant-energy curves for static compaction, which were compared to dynamic compaction curves from four compaction attempts. From the study, the ESCE corresponding to standard Proctor, reduced standard Proctor, and reduced modified Proctor tests were found to be within the range of 180-340, 155-308, and 532-664 KJ/ m3, respectively. It was also observed for the static compaction method that after reaching the maximum level of compaction, the dry unit weight of the soil specimen remains constant with further increases in compaction energy.

Enhancing lateritic soil for sustainable pavement subbase with polymer-modified cement: A comparative study of styrene butadiene rubber and styrene acrylic latex applications

This study evaluates styrene butadiene rubber (SBR) and styrene acrylic latex (SA) as modifiers in cement-treated subbase materials (CTSB) to enhance mechanical properties and reduce cement usage sustainably. Optimal ratios for stabilizing sub-standard lateritic soils were identified, reducing water demand and increasing mechanical strength in polymer-modified cement pastes. A 10 % SA and a 15 % SBR as cement replacement by mass significantly improved bearing strength and strain capacities in CTSB, signifying enhanced flexibility and elasticity. Despite slight changes in compaction characteristics, the study identified 1.6 % SA and 2.4 % SBR as optimal binder (i.e., polymer-cement mixture) contents, compared to 3.3 % cement for conventional CTSB with similar unconfined compressive strength standards. SBR-enriched CTSB exhibited superior resilient modulus, indicating stronger inter-particle bonding. The integration of SA and SBR reduced capillary rise and enhanced moisture stability. This sustainable approach enhances pavement durability and reduces CO2 emissions by minimizing cement use. The findings emphasize the potential of polymer-modified CTSB for cost-effective and environmentally friendly road construction, offering significant implications for advancing pavement engineering materials and promoting eco-friendly practices within the industry.

Revealing Microstructure and Enduring Properties of Settled Barite Extracted from an Offshore Well Two Decades Later: Well Abandonment and Slot Recovery

Summary Barite settling in the annulus behind the casing is an undesired yet common occurrence during the life of a well. Over time, the drilling fluid left in the annulus settles, leaving behind solidified barite that can hinder slot recovery and plug and abandonment (P&A) operations by impeding the cut and pull process. During a P&A operation, Equinor acquired settled barite samples from a North Sea well where the casing was held back by these weighting agents, introducing overpull and prolonging the cut and pull operation. A laboratory analysis program that included determination of the particle-size distribution (PSD), electrokinetic potential of particles (zeta potential), crystallography [X-ray diffraction (XRD)], chemical composition [X-ray fluorescence (XRF)], thermogravimetric analysis (TGA), and microstructure [scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and quantitative evaluation of materials by scanning electron microscopy (QEMSCAN)] was carried out on these settled barite samples to understand their properties. The results of this study provided valuable insights into the composition and characteristics of the settled material in the annulus. The solidified barite within the annular space exhibited no signs of chemical reactions. XRD analysis confirmed the barite to be the sole predominant solid in the solidified material, aligning with expectations. However, additional analytical techniques, including XRF, QEMSCAN, and EDS, detected interconnections between barite particles, primarily facilitated by iron or quartz particles. Additionally, trace amounts of calcite, iron oxide, and mixed compositions involving Si, S, Fe, Ba, O, and Cl were identified within the solidified material. SEM results indicated that the particles exhibited strong compaction characteristics but lacked cementation, retaining some porosity. Notably, the absence of bentonite or other clays was consistently observed in all analyses. This study highlights the process of solidification observed in settled barite, suggesting that factors other than chemical reactions may be responsible for this phenomenon. The potential mechanisms contributing to solidification include physical aggregation, compaction, and alterations in surface charge under downhole conditions. This enhanced understanding of the solidification process will contribute to the development of solutions for efficient casing removal and even the usage of settled barite as a barrier material.

Effect of Voltage variation on the Geotechnical Properties and Removal Efficiency of Heavy Metal Contaminants from Contaminated Soil using Electrokinetic Remediation Technique

A lot of research work has shown that despite the effectiveness of the electrokinetic remediation technology in decontaminating heavy metal contaminated soils, more work is still required to fully understand the role of voltage in the remediation process. There is need to establish the optimum voltage that would best remove heavy metals from such contaminated soil and its attendant effect on the geotechnical properties of the remediated soil. Effect of voltage variation on the removal efficiency of lead, copper and the geotechnical properties of remediated heavy metal contaminated soil using electrokinetic remediation technique was investigated in this research. The contaminated soil was remediated by applying direct current (DC) to the remediation setup at 0.5V/cm, 1.0V/cm, 1.5V/cm and 2.0V/cm. The concentration of the heavy metals after remediation were determined using the Oxford Instrument Analyzer to evaluate removal efficiency, geotechnical properties tests were also conducted on the soil specimens at each phase of remediation. The results showed that the lead removal efficiency was highest at 2.0V/cm (86%) with the shortest remediation time of 5days and lowest at 0.5V/cm (39%) at 9days. 52% of copper was removed at 2.0V/cm in 5days and 29% at 0.5V/cm after 9days of remediation. At 1.0V/cm, the lead and copper removal efficiency are 75% and 40% respectively. There was no significant change in the Specific Gravity of all the soil samples with the test results lying between 2.0 and 2.2. The soil is generally silty fine sand with not less than 40% passing the sieve no.200 (75micron). 45% passed through sieve 75micron for unremediated soil and slightly reduced to 40%, 40.4% and 40.2% for 30V, 45V and 60V respectively. The soil is non-plastic with the liquid limit of between 25.8% and 29.5% belonging to the A-4 group of soil. The maximum dry density improved across all the three compactive efforts, from 1.8390g/cm3 to 1.8480g/cm3 with WAS compactive effort and from 1.8000g/cm3 to 1.8320g/cm3 with BSL method with an average optimum moisture content of 10%. The CBR values increases with increase in voltage applied. The unsoaked CBR values averagely increased with 31%, 18% and 7% for BSH, WAS and BSL compactive efforts respectively. The durability index with resistances of 89% and 90% to loss in strength was recorded at 1.0V/cm and 1.5V/cm respectively, this, when compared to the resistance to loss in strength of 71% in unremediated soil has respectively 25.3% and 26.8% durability advantages. There was also a consistent increase in the UCS values, from 381kN/m2 to 474kN/m2 and from 351kN/m2 to 447kN/m2 when WAS and BSL methods of compaction were used. Generally, there was improvement in the geotechnical properties of the remediated soil. These improvements are maximum at 1.0V/cm and 1.5V/cm with little or no further improvement at 2.0V/cm. It is recommended that 1.0V and 1.5V are suitable for remediation purpose since it requires low energy consumption.

Effect of Bio-Oils and Wastewater Sludge on the Performance of Binders and Hot Mix Asphalt with High Reclaimed Asphalt Pavement Content.

Waste Cooking Oil (WCO), Soy Oil (SO), and Wastewater Sludge (WWS) have great potential to increase reclaimed asphalt pavement (RAP) content for economic and environmental benefits. This study explored the effects of SO and WCO on rutting, fatigue cracking, and low-temperature cracking performance of binders and Hot Mix Asphalt (HMA) with high RAP content. The potential effect of WWS on the performance and compaction efforts of high RAP content mixes at a 10 °C (50 °F) lower compaction temperature than the control compaction temperature was also investigated. The results indicated that 85% of the RAP binders can be incorporated while maintaining similar performance compared to the control by using 15% SO or 12.5% WCO as a rejuvenator with 2.5% virgin binder. Adding 1% WWS by weight of the total binder improved the binder's rheological properties, the mix's cracking performance, and the mix's density at lower compaction temperatures.

Impact of initial gradation on compaction characteristics and particle crushing behavior of gravel under dynamic loading

Gravel is a widely used construction material due to its versatility and cost-effectiveness. However, gravel particles are prone to crushing under dynamic loading, causing changes in gradation. The evolution of gradation and its effects on physical properties are not well understood. This study investigates the physical properties of gravel, such as dry density, void ratio, and relative crushing index, under different initial gradations (uniformity coefficient, Cu), using surface vibration compaction tests. A hyperbolic relationship was established between initial Cu and dry density, showing that an increase in Cu can result in a decrease in the void ratio and an increase in the coordination number until stabilization. Particle crushing increases with higher initial Cu, correlating quantitatively with relative crushing indexes. Maximum dry density, minimum void ratio, and fractal dimension also correlate with these relative crushing indexes, suggesting intrinsic relationships among these properties and particle crushing. The size effect can be eliminated by establishing empirical relationships between crushing parameter and particle size.

A Review of Recent Techniques for Granulation

Granulation is the process of designing particles by combining primary power particles into massive multiparticle structures known as granules. Its primary purposes are to boost the flow of power, prevent segregation, improve the compaction characteristics of mix uniformity, and improve the flow and compressibility of powders. It also produces a combination that is uniform. Wet granulation and dry granulation are the two primary categories of granulation methods. The granulation process is contingent upon the description of the ingredient entity and its ability to surge appropriately, compact, and collapse. Choosing the appropriate granulation method necessitates a methodical examination of each ingredient in the combination and how they interact. Granule particle size is determined by the amount and feeding rate of the granulating liquid. New methods have been added to the granulation process to improve it: foam binder granulation, fluidized bed granulation, melt granulation, activated dry granulation, heat adhesion granulation, steam granulation, spray drying granulation, and freeze granulation. The major purpose of this page is to provide an overview of each advancement, including its limitations and relevance.

Influence of grading in compacted tailings behaviour: towards resilient design

The inherent variability of tailings is the main challenge in compacted filtered tailings stacks (CFTS) operation. Despite the advances in dewatering technologies, the filtration efficiency depends on the tailings’ gradation and mineralogy. A usual process is filtering materials separately, which can later be mixed and compacted. This paper studies two iron ore tailings (flotation and slime) from a unique mine and three mixtures (80/20, 70/30 and 60/40) produced from them to investigate the influence of grading on tailings’ compressibility, strength, stiffness, and state measures. The materials were thoroughly characterised and submitted to triaxial tests under low (50 kPa) and high (1,000 kPa) confinement levels and different moulding conditions (loose and dense). The results showed that the behaviour of the range of gradings investigated was similar in terms of compressibility, strength mobilisation (peak and M value), dilatancy and stiffness for similar compaction efforts. The packings produced seem to be affected mainly by the mineral composition and grading, while the mechanical procedures only change the magnitude of the state achieved, maintaining the proportion between them. Understanding how grading and mineralogy affect different geomechanical aspects of tailings is the first step towards resilient projects, which are essential to the mining industry’s future.

Inverse-designed compact silicon waveguide reflector for on-chip resonators

Waveguide reflectors are crucial components in integrated optics and on-chip resonators, with their efficiency and dimensions significantly impacting system performance and integration. This paper presents an compact silicon on-chip waveguide reflector, designed using photonics inverse design, featuring a footprint of only 1.64μm×1.78μm and a simple, smooth structure. The simulation shows a 1 dB bandwidth over 400 nm and a reflectivity above 97.6% in the 1520–1570 nm wavelength range. Experimental measurements, conducted through Fabry-Pérot resonator spectrum analysis, confirm the excellent performance of the waveguide reflector, attaining a reflectivity over 92.8%. Additionally, the study presents two more waveguide reflectors tailored for the 1.31μm and 2μm wavelength, emphasizing the scalability of the design. The compact size and broadband reflectivity characteristics of the waveguide reflector provide increased flexibility in designing cavity lengths and directional couplers, making it a promising choice for applications in resonators and highly integrated photonics systems.

Experimental Studies on Fiber Reinforced Soil Stabilized with Lime and Fly Ash

This study investigates the enhancement in strength of fiber-reinforced soil stabilized with lime and fly ash, focusing on key parameters essential for highway design and construction i.e., California Bearing Ratio (CBR) and compaction characteristics. Laboratory tests were conducted to determine the CBR values, Maximum Dry Density (MDD), and Optimum Moisture Content (OMC) of soil stabilized with varying percentages of fly ash (FA) and lime, and reinforced with different types and percentages offibers, specifically coir fibers (CF) and polypropylene fibers (PF). The addition of stabilizing agents (fly ash and lime) to the fiber-reinforced soil was found to increase the OMC and decrease the MDD. Notably, a significant increase in the CBR value was observed up to an optimum content of these admixtures. However, adding fibers beyond a certain percentage resulted in the sample breaking. This study is novel in its comprehensive evaluation of both natural (coir) and synthetic (polypropylene) fibers in combination with traditional stabilizers (fly ash and lime), offering insights into the optimal mix for enhancing soil strength. The findings contribute to more efficient and durable highway construction practices by identifying the balance between fiber reinforcementand chemical stabilization.

Explosive stress wave propagation and fracture characteristics of rock-like materials with weak filling defects

Filling-type defects have a non-negligible effect on the propagation of explosive stress waves in rock. Combined with the new dynamic caustics experimental system and ANSYS/LS-DYNA numerical simulation platform, the research on the propagation characteristics of explosive stress wave and fracture characteristics of rock-like materials containing weak filling defects with different ductility has been carried out. Firstly, we analyzed the influence of weak filling on the propagation of blast-induced cracks, explored the “guiding” and “stopping” effects of weak filling on cracks, and analyzed the mechanical characteristics of crack propagation. Secondly, the effect of planar weak filling ductility on the damage degree of blasted medium was quantitatively evaluated. Thirdly, the influence of weak filling on the fluctuation characteristics of explosive stress wave was investigated. Then, the mechanical response behavior of the specimens was analyzed, and the results showed that the compaction and slip behaviour characteristics of the weak filling have some variability in degree, some continuity in time, some correlation in space and are affected by the ductility of the planar weak filling. In addition, the stress wave and weak filling interaction mechanism was elucidated. The conclusions of the analysis have positive reference value for understanding the explosion mechanics mechanism of defective rock masses.

Modeling of effect of fly ash amount on microstructure and chloride diffusivity of blended fly ash-cement systems

Reasonable utilization of industrial fly-ash wastage in concrete engineering has been regarded as an effective way to reduce carbon emissions. By adding the reasonable dosage of fly ash to cement paste, the compactness and microstructure characteristics of the blended cement systems can be significantly improved, thereby effectively enhancing the durability of concrete structures. The vector hydration model of blended fly ash-cement systems with the interference effects of different hydration layers of fly ash and cement particles, the solubility equilibrium of solid phases and the electrical neutrality of the pore solution involved is established. By fully comparing with the experimental data of hydration degree, capillary porosity and CH content, the accuracy of the developed hydration model is verified. Based on the hydration model, the effect of fly ash content on the concentration of different ions and pH in the pore solution with curing time is discussed. Additionally, the evolution characteristic of hydration degree, capillary porosity and CH content with curing time at different fly ash content is also analyzed. Based on the reconstructed microstructure of blended systems, the rolling sweep (RS) technique is used to determine the pore size distribution of capillary pores. The effect of fly ash content on cumulative pore size distribution and differential pore size distribution at different curing time is quantitatively evaluated and discussed. By utilizing the first-passage cube, the dual-probability-Brownian motion method is constructed to predict the chloride diffusivity of blended cement systems. After diffusion model is verified by multi-group experimental data, the optimal dosage of fly ash at different water-binder ratio is calculated, which can provide theoretical guidance for practical applications in concrete engineering.

A new miniaturized Split-Ring Resonator-Based inverse double Sigma-Shaped artificial material for Penta-Band wireless communication

This paper discusses a study on creating and confirming the authenticity of an artificial material with a SNG (Singular Negative) attribute. The artificial material was constructed using a metamaterial structured around split-ring resonators forming an inverse double sigma shape. Advanced electromagnetic simulation tools like CST (Computer Simulation Technology) Microwave Studio, Ansys HFSS (High Frequency Structure Simulator) and ADS (Advanced Design System) were employed to extensively analyze the electromagnetic characteristics of the artificial material. Notably, the proposed artificial material exhibits five distinct resonance frequencies spanning L-, S-, C-, X-, and Ku-band operations, specifically at 1.560 GHz, 2.232 GHz, 4.350 GHz, 8.095 GHz, and 17.370 GHz. Achieving an optimal EMR (Effective Medium Ratio) of 23.45, with a compact unit cell size of 8.2 mm × 8.2 mm and a substrate thickness of 1.905 mm, underscores its innovative design attributes. Of significance, the compact size, SNG characteristics, high EMR, and resonant frequencies render this structure particularly noteworthy. The utilization of the L-band for GPS (Global Positioning System), S-band for Wireless LAN (Local Area Network), C-band for Satellite communication, X-band radar system, and the Ku-band for VSAT (Very Small Aperture Terminal) communication applications is well-documented. This article elucidates the intricacies of the design process and conducts various parametric analyses. Remarkably, the simulation results obtained from Ansys HFSS 3D software closely align with those from CST. Furthermore, a comprehensive examination of surface current, E-field, and H-field distributions is provided. Importantly, comparative assessments indicate the superior performance of the proposed structure across multiple metrics, including EMR, SNG frequency range, and compactness, positioning it as an ideal candidate cellular phone, satellite, and radar-based applications.

Improving landfill liner performance with bentonite-slag blend permeated with ammonia for a Municipal solid waste landfill

Leachate emanating from landfills contains ammonia which may cause serious health effects on living things. An effectively designed clay barrier should not allow the contaminant to infiltrate the soil and groundwater systems. The utilization of certain industrial by-products in engineered landfill barriers, not only reduces the need for conventional liner materials but also helps in sustainable waste management. This study investigated the hydraulic conductivity, unconfined compressive strength, compaction, and adsorption characteristics of lithomargic clay blended with an optimum percentage of bentonite (10%) and granulated blast furnace slag (15%) permeated with ammonia. The results revealed that increasing the content of granulated blast furnace slag decreased the maximum dry density while increasing the optimum moisture content. In comparison to lithomargic clay, the hydraulic conductivity of the amended soil liner permeated with ammonia decreased from a value of 3 × 10−8 m/s to 5 × 10−10 m/s. The unconfined compressive strength of the amended soil specimens showed an increasing trend with curing times (i.e., 0, 14, 28, and 56 days). The batch adsorption results revealed that Freundlich and Langmuir's isotherm fits the equilibrium adsorption data and the adsorption of ammonia on clay liner follows non-linear behaviour. Overall, the experimental results implied that lithomargic clay blended with 10% bentonite and 15% granulated blast furnace slag can be used as an impermeable soil reactive barrier in engineered landfills.

Comparative study on in-situ resilient modulus of subgrade estimated using in-situ modulus detector

This study presents a comprehensive evaluation of the resilient modulus of unsaturated subgrade soils using a novel in-situ modulus detector (IMD) along with various laboratory and field-testing methods. The current study employs several testing devices, including bender elements, standard dynamic cone penetrometer, and crosshole-type dynamic cone penetrometer (CDP), to assess the reliability of the IMD in estimating the resilient modulus profiles of small-scale homogeneous subgrade models in unsaturated conditions. The index properties, compaction and strength characteristics of the compacted soils, are evaluated. The resilient modulus values obtained from the IMD are compared with those obtained from repeated load triaxial tests under various stress states. Experimental results show a decrease in the penetration depth per blow with increased dry unit weight. In addition, elastic modulus and shear wave velocity increase with soil density. The resilient modulus estimated from the IMD increase with both depth and soil density. A robust correlation has been established between the resilient modulus values estimated from the IMD and those estimated from the CDP or bender element tests. Furthermore, the resilient moduli estimated from the universal model and the IMD demonstrate linear relationships with a coefficient of determination greater than 0.8. Thus, the IMD may be useful for the in-situ evaluation of resilient modulus in unsaturated subgrade soils, considering influencing factors such as soil density and confining pressure.

Optimizing porous asphalt mix design for permeability and air voids using response surface methodology and artificial neural networks

Easy infiltration of grouting material in Porous Asphalt Mixture (PAM) is one of the crucial phases in the construction of semi-flexible pavement (SFP). The gradation and compaction primarily influence the pores and their arrangement in PAM, which affects the air voids and permeability of porous mixes and effectiveness of slurry infiltration. Complexity of gradation and compaction makes it very difficult to predict air voids and permeability in PAM. Statistical analysis of these parameters based on experimental data requires very high volume of samples which is missing in literature. Compaction effort has been kept constant in most of them which otherwise is important for stability. Also, machine learning models to predict mix design of PAM has not been explored. This study investigates the PAM using systematic experimentation and modelling approaches such as Response Surface Methodology (RSM) and Artificial Neural Networks (ANN) to establish new and low trial-based guidelines for establishing a relationship between air voids and permeability greater than 0.12 cm/sec, while ensuring the stability of the mix. Using a Simplex Lattice design approach, five distinct types of aggregates were utilized as input variables and twenty-six PAM mixes were generated, which were subjected to 5 compaction levels. A total of 260 mixes were tested and then models were prepared based on RSM and ANN, which considered two output variables: air voids and permeability. RSM and ANN models demonstrated strong agreement between predicted values and actual experiment outcomes. It is observed that optimal permeability in PAM is achieved by adjusting aggregate proportions based on compaction levels. Proportion limits for low compaction suggested 60–70 % coarse aggregates and up to 20 % fines. For higher compaction (25–75 blows), it is recommended to increase the coarse aggregates up to70–90 % and limit fines up to 10 %. All proposed limits satisfied minimum permeability criteria (> 0.12 cm/sec) while ensuring the stability of the mixes. The proposed modelling approach offers greater efficiency and accuracy and reduces trial batch time, minimizing the need for destructive experiments and material wastage.

Compaction method and specimen geometry effect on the fracture properties of asphalt concrete in the SCB test at intermediate temperature

ABSTRACT Recent research using the semicircular bending (SCB) test with 100 mm diameter specimen cored from gyratory compacted samples demonstrated the suitability of this sample size for testing dense graded asphalt mixes with a nominal maximum aggregate size (NMAS) of up to 19 mm. Alongside the gyratory compactor, the Marshall compactor remains part of current specifications in many countries, including ASTM international standards. The Marshall compactor uses a 4-inch (101.6 mm) mould, which is slightly larger than the gyratory compactor’s 100 mm mould, and employs a different compaction effort, resulting in different aggregate orientation. This study investigates potential differences in the fracture properties of SCB test specimens compacted using different methods. Sample thicknesses of 30 , 40 , and 50 mm were evaluated in the SCB test at 25°C under a monotonic loading rate of 1 mm/min. A total of 81 specimens were prepared from three asphalt mixes with NMAS of 14 mm and 20 mm, including two dense graded asphalt mixes and one stone mastic asphalt mix. The fracture properties, including fracture energy, fracture toughness, and cracking resistance index (CRI) were evaluated. The study found that the repeatability, evaluated via the coefficient of variation, ranged from 1.1% to 21.7%, with an average value of 8.3%. A directly proportional relation was observed for indexes from the 100 mm and 150 mm samples using the gyratory compactor. The Marshall compactor specimens yielded higher fracture toughness and fracture energy values, while the CRI values were approximately 1.23 times those obtained from the gyratory compactor. This result shows that different compaction methods have direct effect on the fracture properties of SCB test specimens, emphasising the importance of considering compaction methods for the SCB test when determining the threshold value of cracking resistance for asphalt mixes, especially in the balanced mix design for asphalt mixes.

Optimisation of pervious concrete performance by varying aggregate shape, size, aggregate-to-cement ratio, and compaction effort by using the Taguchi method

ABSTRACT The porosity and compressive strength of pervious concrete are critical determinants of its suitability for various applications. Therefore, it is necessary to recognise the factors influencing the performance and its ranks to balance porosity and compressive strength ideally. This study evaluates the impact of aggregate shape, size, aggregate-to-cement ratio and compaction effort on previous concrete performance. The research involved varying aggregate sizes (5–12 mm, 12–18 mm and 18–25 mm), aggregate-to-cement ratios (3.0, 4.0 and 5.0), compaction efforts (0, 30 and 60 blows) and aggregates underwent revolutions in a ball mill (0, 200 and 1000) to change their morphological characteristics. A total of 81 mix designs were tested, resulting in 486 cubes for compressive strength and porosity testing. The acquired data underwent analysis using the statistical analysis and Taguchi method to discern the most influential factors and establish their ranking. The results indicate that revolutions, compaction, aggregate-to-cement ratio and aggregate size contribute 29.42%, 26.19%, 29.13% and 0.96%, respectively, to the compressive strength performance. Regarding porosity performance, revolutions and compaction emerge as significant factors, accounting for 39.95% and 26.91%, respectively. The influence of the aggregate-to-cement ratio and aggregate size on porosity performance appears less pronounced.

Study on compaction characteristics and discrete element simulation for rubber particle-loess mixed soil

The rapid surge in traffic volume in China has resulted in a substantial accumulation of waste tires. By harnessing the lightweight and deformable characteristics of tire rubber particles, they are combined with soil to form rubber particle-loess mixed soil, which is progressively being embraced in civil engineering as a pivotal approach towards attaining green and sustainable development. In this study, waste tire rubber particles were integrated into loess to generate rubber particle-loess mixed soil, and compaction tests were conducted to investigate its compaction characteristics. Furthermore, PFC3D (Particle Flow Code 3D) was utilized for simulating the bearing ratio test of rubber particle-loess mixed soil, thereby validating the feasibility of numerical simulation for calculating CBR (California bearing ratio) values and exploring the relationship between micromechanical characteristics and macroscopic characteristics of such mixtures. The findings indicate that the maximum dry density of rubber particle-loess mixed soil significantly decreases with an increasing content of rubber particles. The utilization of PFC3D discrete element software proves efficacious in examining the bearing capacity of this mixture. Notably, when 20 mesh rubber particles constitute 20% by volume, the CBR value reaches its pinnacle and exhibits optimal bearing capacity. From a micromechanical perspective, the variation in internal porosity of rubber particle-loess mixed soil is positively associated with changes in macroscopic optimal water content, and negatively associated with changes in macroscopic CBR value. incorporating rubber particles enhances resistance against external forces while diminishing deformation within loess. This study provides a guidance for the efficient utilization of waste tires and the improvement of loess’s characteristics.

Silty soil resilient modulus stabilised with cement and recycled aggregate

ABSTRACT The present study analysed the resilient behaviour of silty soils from the southern region of Brazil stabilised with cement and recycled aggregate (RA) from construction and demolition waste, with a maximum diameter of 4.8 mm. Its suitability for use in urban pavement layers has also been assessed. Cyclic triaxial tests were conducted on pure soil, soil-cement, and soil-cement-RA specimens under three compaction efforts: standard, intermediate, and modified. Based on the results of the cyclic triaxial tests, resilience modulus (MR) prediction models were calibrated. Subsequently, using the AEMC software, the useful life of an urban pavement was evaluated, considering the materials tested as base layers and subbase. The results indicate that incorporating cement and RA proved effective in stabilising the soil, significantly improving the resilient modulus compared to pure soil. When compacted at the modified energy and subjected to the highest stress levels, the soil-cement-RA mixture presented MR of 638 MPa, an increase of 50% compared with the soil-cement mixture, with MR of 426 MPa. The mechanistic analysis demonstrated that soil-cement and soil-cement-RA mixtures are suitable for use in base layers and subbase of urban pavements, with the soil-cement-RA mixture presenting better performance as a base material.