Unbound Materials Research Articles

Comparison of Lab vs. Backcalculated Moduli of Virgin Aggregate and Recycled Aggregate Base Layers

The resilient modulus (MR) and the backcalculated modulus from the FWD testing (EFWD) of the unbound layers are critical inputs in the analysis/design of pavements. Several studies have tried to develop a conversion factor between these two parameters, while the nonlinear stress dependency of unbound materials and the pavement strain response are mostly missing from the literature. This study aims to compare the laboratory-measured MR of recycled aggregate base (RAB) materials and a virgin aggregate base using field-based EFWD and tries to establish pavement’s responses to loading using vertical strains from both the MR and EFWD values of the respective materials as comparability parameters between the two. For this purpose, a control virgin aggregate (VA, limestone) and three types of RAB materials were selected to construct four test sections. The test sections were modeled in layered elastic- and finite-element-based pavement response models to calculate the vertical strains at the mid-depth of the base and top of the subgrade layers. A comparison of the lab-calculated vertical strains using MR with actual vertical strains in the field from EFWD showed that there was no relationship between the two stiffness parameters in all tested RABs. The vertical strains, based on the lab MR, undermined the stiffness of the recycled aggregates in the field. In contrast, the values of EFWD based on the vertical strains remained close to the MR strains of limestone (VA) throughout the testing period, establishing an EFWD vs. MR relationship (MR = 0.87 EFWD). The results also show that fine RCA was a better-performing material over three years. This research not only explores how the hydration process in RABs limits the development of MR-EFWD correlations but also underscores the need to consider real-world conditions when assessing their performance.

Empirical Correlation of Hossaena Town Soil Index Properties with California Bearing Ratio (CBR) Values

California bearing ratio (CBR) is a key input factor in pavement structural design that is used to determine character size, the strength of unbound materials, and subgrade soils. The construction of a straightforward and logical regression model to forecast the CBR of unbound materials as a function of the index properties of the material. This work explains the relationship between compaction parameters and Atterberg limit tests. Laboratory test was conducted to get the independent (percent finer, liquid limit, plastic limit, plastic index, maximum dry density and moisture content), and dependent variables (CBR). A statistical package for social science software (SPSS) used to develop the mathematical model both in single and multiple regression. The viability of using multiple linear regression analysis to relate CBR values to soil index features was investigated. In this study, SPSS is used to examine each independent variable's significance individually. The multiple linear regression analysis was used to create the correlation, which had an eighteen-person sample size and a modest determination coefficient of R2 = 0.821. The CBR has good relation with maximum dry density and optimum moisture content compared to other parameters. This model applicable for small structure in the specified soil type, MH.

Modelling permanent strain behaviour of soil for flexible pavement design utilizing LWD measurements

ABSTRACT This study aims to improve understanding of unbound material behavior by modeling permanent strain using Light Weight Deflectometer (LWD) measurements, as part of VTI’s broader LWD research. By comparing permanent strain modelling from LWD data with Repeated Load Triaxial (RLT) tests on silty sand soils, it validates LWD data accuracy and explores material property influences on permanent strain parameters, revealing a clear correlation with water content and stress levels. Using LWD data validated against RLT tests, the study delves into material behaviour understanding under varied conditions, focusing on comparing model parameters of permanent strain prediction derived from LWD and RLT tests. Despite minor differences, both methods produce acceptable values, affirming the modelling approach’s robustness. The findings demonstrate LWD’s potential to improve pavement design by providing insights into permanent strain behavior that supports mechanistic-empirical approaches, leading to more efficient designs and better resource use for improved performance.

Dust formation in common envelope binary interactions – II: 3D simulations with self-consistent dust formation

ABSTRACT We performed numerical simulations of the common envelope (CE) interaction between thermally pulsing asymptotic giant branch (AGB) stars of 1.7 and 3.7 M$_{\odot }$, respectively, and a 0.6 M$_{\odot }$ compact companion. We use tabulated equations of state to take into account recombination energy. For the first time, formation and growth of dust is calculated explicitly, using a carbon dust nucleation network with a C/O abundance ratio of 2.5 (by number). The first dust grains appear within $\sim$1–3 yr after the onset of the CE, forming an optically thick shell at $\sim$10–20 au, growing in thickness and radius to values of $\sim$400–500 au over $\sim$40 yr, with temperatures around 400 K. Most dust is formed in unbound material, having little effect on mass ejection or orbital evolution. By the end of the simulations, the total dust yield is $\sim 8.4\times 10^{-3}$ and $\sim 2.2\times 10^{-2}$ M$_{\odot }$ for the CE with a 1.7 and a 3.7 M$_{\odot }$ AGB star, respectively, corresponding to a nucleation efficiency close to 100 per cent, if no dust destruction mechanism is considered. Despite comparable dust yields to single AGB stars, in CE ejections the dust forms a thousand times faster, over tens of years as opposed to tens of thousands of years. This rapid dust formation may account for the shift in the infrared of the spectral energy distribution of some optical transients known as luminous red novae. Simulated dusty CEs support the idea that extreme carbon stars and ‘water fountains’ may be objects observed after a CE event.

Comparative study of moisture and stress dependent unbound material modulus for flexile pavement response modeling

Moisture can significantly impact the resilient modulus of pavement base and subgrade. Although various resilient modulus models exist, their accuracy in predicting pavement responses have not been examined and verified. This study aims to compare the accuracy of pavement response modeling using different resilient modulus, considering moisture and stress dependent unbound material modulus. Comprehensive pavement information including pavement structure, viscoelastic property of asphalt concrete, unbound material properties, moisture gradient, water table, temperature gradient and FWD deflections were collected from Long-Term Pavement Performance (LTPP) program. Based on collected data, finite element models were developed to predict pavement deflections under FWD load and pavement responses under traffic loading, respectively. The results show that the moisture-suction-stress dependent (MSS) model has the best prediction accuracy as compared to field measurements, followed by the Witczak model, while the generalized constitutive model displayed the largest deviation. Under traffic loading, the critical pavement responses predicted from Witczak and generalized constitutive model can have a significant deviation from those predicted from MSS model. The generalized constitutive model was found to constantly overestimate the responses, and the deviation of Witczak model depends on other factors such as pavement structure. Using results from MSS as the baseline, these deviations were found to result in up to 50% errors in service life of selected pavements in this study. These findings highlight the importance of taking matric suction into account for accurate modeling of flexible pavement responses.

Experimental and numerical analyses of crushing resistance of unbound road materials

ABSTRACT Aggregate breakage in unbound pavement layers can lead to pavement distresses that affect their functionality and service life. Thus understanding the mechanics and clarifying the factors affecting materials breakage resistance are important for ensuring adequate performance of these layers. In this study, aggregate breakage in unbound granular materials (UGM) is investigated experimentally and numerically. Experimentally, aggregate breakage under uniaxial compression is examined for two UGMs prepared with the same aggregate type but different gradations. To capture the experimentally observed influence of gradation and load magnitude on aggregate breakage, a Discrete Element Method (DEM) model was developed, based on granular mechanics particle contact and failure laws. A simple procedure to identify the contact and failure law parameters from experiments is proposed. With those parameters, the model’s capability of capturing the effect of gradation and loading on the aggregate breakage in UGM is evaluated. Based on comparison with experimental findings, it is shown that the model can capture macro-scale properties of UGM, such as its deformation response under uniaxial compression, as well as the amount of aggregate breakage in the material.

Evaluation of pavement resilience to flooding with inverted pavement structure

Conventional pavement structures are vulnerable due to degradation of unbound materials after water inundation. Inverted pavement structure has been proven to be cost-effective and energy efficient, while its resilience has not been investigated. This study is aimed at assessing the resilience of inverted pavements to flooding events using an integrated hydraulic and mechanical modelling approach. Two-dimensional hydraulic models were established to analyse flooding-induced moisture variations in the pavements. Based on the moisture distribution results, three-dimensional mechanical models were developed to calculate critical pavement responses under moving load. The results show that the subgrade with higher groundwater table or larger hydraulic conductivity was more likely to be invaded by water. Compared with conventional pavement, the increases of critical pavement responses in inverted pavement were significantly smaller after long-period flooding, which indicates the potential benefits of inverted pavement in enhancing the resilience to flooding impact.

Optical Appearance of Eccentric Tidal Disruption Events

Stars approaching supermassive black holes can be tidally disrupted. Despite being expected to emit X-rays, tidal disruption events (TDEs) have been largely observed in optical bands, which is poorly understood. In this Letter, we simulate the tidal disruption of a 1 M ⊙ main-sequence star on an eccentric (e = 0.95) orbit with a periapsis distance 1 or 5 times smaller than the tidal radius (β = 1 or 5) using general relativistic smoothed particle hydrodynamics. We follow the simulation for up to 1 yr postdisruption. We show that accretion disks in eccentric TDEs are masked by unbound material outflowing at ∼10,000 km s −1. Assuming electron scattering opacity, this material would be visible as a ∼100 au photosphere at ∼104 K, in line with observations of candidate TDEs.

Evaluation of Subgrade Resilient Modulus using CBR Test Data to Facilitate Mechanistic-Empirical Pavement Design (MEPD)

Sri Lankan road pavement design has relied on empirical design guidelines, and it is now transforming to a more modern approach known as the Mechanistic-Empirical Pavement Design (MEPD) method, aligning with global best practices. One crucial input parameter in this new methodology is the Resilient Modulus (RM) of unbound materials. Determination of RM and establishment of typical values is essential to implement the MEPD. This study has devoted significant attention to the RM evaluation process and developing predictive models for determiningRM from CBR values. Furthermore, typical RMvalues for locally available soil types have been established. In addition to that, ageospatial database has been established with information on soil properties and RMvalues throughout Sri Lanka. This database is a valuable resource for M-E road pavement design, providing quick reference data to conceptual designs and Level 3-MEPD.

SUBSTANTIATION OF THE ROAD CONSTRUCTION UNBOUND MATERIALS CALCULATION MODEL WITH GEOGRIDS STABILIZATION

Summary. Based on the results of experimental studies conducted on different types of flexible pavement structures, the authors of the article examined the behavior of unbound material reinforced with geogrid. A series of static plate load tests were carried out, and the deformation modulus values of traditional and reinforced pavement structures were determined. The impact of the geogrid, installed at the base of the unbound layer of the pavement structure, on its deformation modulus was investigated. It was found that the use of geogrids significantly increases the equivalent deformation modulus of the pavement, depending on the thickness of the inert material layer and the deformation characteristics of the subgrade soil. The effectiveness of the reinforcement depends on the ratio of the deformation characteristics of the pavement and the subgrade soil, as well as the relative depth of the geogrid installation. The greatest effect is achieved on weak soils under large deformations. The results obtained are significant for further research and practical application of pavement reinforcement technology using geosynthetic materials. Keywords: highway, pavement structure, biaxially oriented geogrid, geosynthetic reinforcement, plate load tests, deformation characteristics, loading, reinforcement coefficient, field experiment

Pavement Analysis with the Consideration of Unbound Granular Material Nonlinearity

Accurate pavement design and evaluation requires the execution of response analysis. Pavement materials’ behavior does not necessarily conform to the assumptions of the multi-linear elastic theory usually adopted during pavement analysis. In particular, the unbound granular materials located in the base and sub-base layers behave in a nonlinear elastic manner, which can be captured through advanced constitutive modeling of their resilient modulus. The finite element method enables us to code constitutive models and quantify potential variations in pavement responses because of different mechanistic assumptions. In this study, variations in response are investigated for a typical structure of a flexible pavement considering the nonlinear anisotropic behavior of the unbound materials together with their initial stress–strain state. To demonstrate the impact of their behavior on the outcome of pavement analysis, variable asphalt concrete layer thicknesses and moduli are assumed, such that they cover a large spectrum of roadways. It was found that pavement responses can be calculated up to 3.5 times higher than those retrieved from the conventional linear analysis. This comparison means that the alterative mechanistic modeling of the unbound granular materials can be proved to be more conservative (i.e., leading to higher strains) in terms of pavement design and analysis. From a practical perspective, this study alerts pavement scientists and engineers engaged in pavement design to a more reliable performance prediction, which is needed to bridge the gap between advanced modeling and routine analysis.

Resilient Modulus of Compacted Granular and Lateritic Materials Used as Base Layers for Flexible Pavements in West Africa

The objective of the study is to synthesize resilient modulus data available in Senegal and to propose linear and nonlinear elasticity parameters, which can be used directly for the design of flexible pavements in west Africa. The materials tested are unbound aggregates of basalt and quartzite and gravel lateritic soil from Senegal and Burkina Faso. The Repeated Load Triaxial device is used according to French and American procedures to measure resilient modulus. Different models of the resilient modulus are used to determine the parameters of the nonlinear models and the summary and/or characteristic resilient modulus used in the elastic linear calculation. For the nonlinear calculation, the parameters of the models of Seed et al. (1967), NCHRP (2004) and Boyce (1980) are determined. For the linear elasticity calculation, at the optimum water content and at the dry density of 95% of its maximum value, a maximum modulus of between 300 and 350 MPa is proposed for laterites in the base layer. Values ​​of 220 MPa and 150 MPa are proposed for basalt and quartzite respectively. The moduli obtained are not correlated to the CBR values of the materials. A strong variability in the modulus of laterites is also noted, contrary to the modulus of unbound aggregates. Laterites sometimes have higher modulus than unbound aggregates due to cohesion, but they are more sensitive to water. We recommend that unbound materials (untreated gravels and laterites) be compacted in situ to 97% of the maximum dry density and, for laterite, to the optimal water content -1.5 but also to ensure a good waterproofing and good drainage of the structure. Keywords: Resilient modulus; unbound aggregates; gravel lateritic soil; West Africa.

A numerical framework for modelling settlements of railway ballast layers

Permanent deformation in ballast layers is a major contributing factor to the railway track geometry deterioration. In spite of a considerable amount of research on understanding and predicting performance of ballast layers, accurately capturing their settlements remains a challenge. In order to contribute to solving this important issue, a new numerical method for predicting ballast settlements is presented in this paper. This method is based on the finite element (FE) method combined with a constitutive model that captures permanent deformation accumulation in unbound materials under cyclic loading. This allows predicting permanent deformations of large structures and at large number of load cycles in a computationally efficient manner.The developed constitutive model is validated based on triaxial test measurements over wide range of loading conditions. Stress state in ballast layers has been examined with a 3D FE model, for several embankment structures and traffic load magnitudes. The determined stress distributions and loading frequencies were used as an input of the constitutive model to evaluate permanent strains and settlements of ballast layer. The influence of embankment structural designs and traffic loading magnitudes on the ballast layers settlements is examined and the results obtained are compared with the existing empirical performance models.

Investigating particle breakage and compressibility characteristics of unbound aggregate materials recycled from building demolition wastes

Investigating particle breakage and compressibility characteristics of unbound aggregate materials recycled from building demolition wastes

B-347 Performance Validation of an In-house Assay for Soluble Mesothelin Related Peptides

Abstract Background Mesothelin is a glycosylated phosphatidylinositol glycoprotein located on the surface of mesothelial cells. Mesothelin is released from the cell in a form denoted as Soluble Mesothelin Related Peptides (SMRP), that can be measured in the blood. Although mesothelin is produced by normal cells, studies have shown an overexpression in individuals suffering malignant mesothelioma, with an increase in serum SMRP concentration associated with the disease. The in-house ARUP MESOMARK® ELISA is a 96-well microtiter plate formatted sandwich immunoassay for the quantitative measurement of SMRP in human serum. The ELISA incorporates two separate monoclonal antibodies specific for SMRP (including megakaryocyte potentiating factor); one (4H3) bound to the microtiter well for capturing SMRP and the second (OV569), enzyme labeled with horseradish peroxidase (HRP), for bound SMRP detection. After several incubation and wash steps to remove unbound materials, color is produced by HRP turnover of a chromogenic substrate during a final incubation step. A direct relationship between the color intensity and the SMRP concentration of the specimen is generated, with results expressed as nmol/L SMRP. Methods Deidentified residual serum specimens sent to ARUP Laboratories for routine testing, as well as serum specimens from healthy volunteers, were collected under University of Utah’s Institutional Review Board approved protocols. Commercial kit (Fujirebio Diagnostics, Inc., Malvern, PA) testing was completed according to manufacturer’s protocol. ARUP ELISA measurements were conducted according to an established in-house protocol. ARUP ELISA performance characteristics evaluated included a method comparison against the commercial assay, linearity, recovery, precision, analytical sensitivity, and dilution studies. A reference limit was also verified. Results A method comparison study against the commercial SMRP ELISA generated a slope of 0.989, intercept of 0.0422, r2 of 0.998 and bias of -1.2% (n = 45, Deming regression, Bland-Altman analysis). Clinical agreement near the 1.5 nmol/L cutoff was 100%. The limit of detection was 0.3 nmol/L (20 determinations each of a blank and low-level serum pool). Linearity was established by combining serum specimens with high and low SMRP concentrations at different ratios, creating 10 specimens of varying SMRP concentrations. Each specimen was tested in triplicate. Regression analysis (measured vs expected concentration) produced a slope of 1.002, intercept of -0.739 and r2 of 0.998, with percent recoveries ranging 86.1 to 100.0%. Precision was determined from two serum pools of differing SMRP concentrations tested over 5 days, four replicates per pool per day. Repeatability and within-laboratory CVs were 3.0 and 5.0% at 1.6 nmol/L, and 1.7 and 1.7% at 17.3 nmol/L, respectively. Back-calculated results from a 10-fold dilution study of four serum specimens were within -9.8 to -8.1% of their corresponding neat values. The previously established reference limit of 1.5 nmol/L was verified for the ARUP ELISA, with 95% of results below the cutoff value (n = 20, sera from healthy volunteers). Conclusions The in-house ARUP MESOMARK ELISA demonstrates acceptable performance for quantifying SMRP in human serum and compares favorably to a well-established commercial ELISA. A reference limit of 1.5 nmol/L was also verified. Overall, the ARUP MESOMARK ELISA is acceptable for serum SMRP testing.

Magnetic field effects on nucleosynthesis and kilonovae from neutron star merger remnants

ABSTRACT We investigate the influence of parametric magnetic field configurations of a hypermassive neutron star (HMNS) on the outflow properties, nucleosynthesis yields, and kilonova light curves. We perform three-dimensional dynamical space–time general-relativistic magnetohydrodynamic simulations, including a neutrino leakage scheme, microphysical finite-temperature equation of state, and an initial poloidal magnetic field. We find that varying the magnetic field strength and falloff impacts the formation of magnetized winds or mildly relativistic jetted outflows, which in turn has profound effects on the outflow properties. All of the evolved configurations collapse to a black hole ∼38–40 ms after coalescence, where the ones forming jetted outflows seem more effective at redistributing angular momentum, which result in earlier collapse times. Larger mass ejecta rates and radial velocities of unbound material characterize the systems that form jetted outflows. The bolometric light curves of the kilonovae and r-process yields that are produced by the post-merger remnant system change considerably with different magnetic field parameters. We conclude that the magnetic field strength and falloff have robust effects on the outflow properties and electromagnetic observables. This can be particularly important as the total ejecta mass from our simulations (≃10−3 M⊙) makes the ejecta from HMNS a compelling source to power kilonova through radioactive decay of r-process elements.

Investigating real-time monitoring indices of compaction quality from particle movement characteristics of distinctly-graded unbound aggregate materials subjected to vibratory compaction

The compaction quality greatly affects the in-service performance of unbound aggregate materials (UAMs); however, there still lack real-time, non-destructive, and effective indices for compaction quality assessment. This paper aimed to reveal meso-scale mechanisms of macroscopic vibratory compaction behavior and evaluate compaction quality from particle movement characteristics. A series of newly-developed laboratory vibratory plate compaction tests were conducted on UAM specimens of different gradations. The innovative self-powered, wireless sensors resembling realistic particles (termed as “SR sensors”) were placed inside UAM specimens to monitor three-dimensional (3D) particle accelerations and Euler angles during vibratory compaction. The effects of gradation and vibratory frequency on both macroscopic compaction behavior and meso-scale particle motion characteristics were analyzed. The results show that the entire vibratory compaction process can be divided into three distinct stages according to discernibly-staged particle movement patterns. The degree of compaction (DOC) of UAMs is significantly correlated with two novel particle-motion-based compaction quality indicators.

Unsaturated hydraulic property of recycled concrete aggregates blended with autoclaved aerated concrete grains for unbound road base and subbase materials in Vietnam

Roadbed materials of base and subbase layers are frequently unsaturated caused by rainfall, drainage, and evaporation. However, the movement of water in these layers is still poorly understood because of lacking data on unsaturated properties such as the water retention curve (WRC) and unsaturated hydraulic conductivity (K). This study, therefore, recycled concrete aggregates (RCA) blended with autoclaved aerated concrete (AAC) grains (% of substitution on the mass basis from 0 to 50%) were used to examine the WRC and K for unbound roadbed materials in Vietnam using the evaporation method. Natural aggregates (NA) and Toyoura sand were used as control and reference material. Results showed that compared to NA100% and RCA100%, the water capacity of RCA mixed samples was much improved by blending AAC grains. Toyoura sand showed higher water capacity at saturation compared to RCA100% and NA100%, but quickly became lowest when matric potential exceeds 10 kPa. Toyoura sand showed the highest saturated hydraulic conductivity, but decreased dramatically around 10 kPa, while other tested samples remained higher K. The original van Genuchten – Mualem model was well fitted for Toyoura sand and underestimated for other tested samples, but showed an agreement with estimated conductivity parameter ranging from – 3.0 to -4.4.

Evaluating potential expansion and strength of compacted steel slag aggregates at different compaction density

Steel slag aggregates can be utilized as unbound materials for road bases or as fine/coarse aggregates in asphalt/cement paving concrete. However, the availability of free lime (f-CaO) in the materials is detrimental to volumetric stability, affecting the strength or durability of resulting paving products incorporating steel slag aggregates. This paper investigates the potential expansion of fine and coarse steel slag aggregates compacted at different compaction densities. The experimental results exhibited a higher stability of the coarse granular mixture exposed to water than the fine one. Also, more compaction increased expansibility in the fine mix, especially at high compaction density. Furthermore, the graded steel slag aggregate exhibited higher strength than the other aggregates. The findings provide reference information on the useability of steel slag in cement-based materials, like the replacement of coarse aggregate is better than the fine ones in volume stability of steel slag concrete.

Study of association of vitamin D levels in children and adolescents on antiepileptics drug therapy

Background: Epilepsy is a common non-communicable disease that affects both young and the elderly, with a cumulative lifetime incidence of 3%. Bone health may be impacted by prolonged AED use, and the study aims to investigate the relationships between long-term antiepileptic usage, vitamin D levels, and other outcomes. Methods: Comparative observational research was conducted on 60 children with 30 healthy controls and 30 cases of antiepileptic drug users. Low vitamin D levels were identified based on monotherapy versus polytherapy, treatment duration, and severity of seizure control. 25-hydroxyvitamin D separated from its binding protein during incubation and competed with labelled vitamin D. A wash cycle was used to remove unbound material and a flash chemiluminescent reaction was started. The statistical analysis was done using R software 3.2.2 with a power of 90% and an alpha error of 5%. Results: An observational comparative study found no significant relationship between vitamin D levels and antiepileptic drug therapy in children aged 4-16 years. Vitamin D levels in AED-treated children with well-controlled seizures and those with poorly controlled seizures were found to be statistically significant, with 77% of patients and none of the controls being vitamin D deficient. Conclusions: Vitamin D deficiency is linked to antiepileptic medication, length of antiepileptic therapy, and increased risk of vitamin D insufficiency. It is important for pediatric neurologists and paediatricians to pay attention to the vitamin D status of children with epilepsy.