Unbound Materials Research Articles

Analysis of flexible pavement with cross-anisotropic material properties

Presently, there is a sway from empirical approaches to mechanistic-empirical based methods for pavement design, in which mechanistic pavement responses are related to the pavement performance. It provides a more rational approach for reliable prediction of the pavement distresses and pavement life. In mechanistic analysis, the materials are usually considered as linear elastic and isotropic, which is not realistic and rather exhibit a more complex behaviour. Finite element modelling (FEM) has the ability to handle this complex material properties, however it is time consuming and also needs expertise in this area. Therefore, multilayered linear elastic theory based programs are still favoured over FEM for analysis of flexible pavements. Most of the pavement materials (specifically the unbound materials) are anisotropic, however can be approximated as cross-anisotropic (different properties in vertical and horizontal directions) material. In this study, a multilayered linear elastic theory based program ‘CrossPave’ has been developed, which is capable of considering the cross-anisotropic behavior of the pavement materials. Through a comparison between isotropic and cross-anisotropic analysis of pavements, this study shows that isotropic analysis underestimates and some case overestimates the mechanistic parameters that may lead to incorrect pavement lives.

Prediction of airfield pavement responses from surface deflections: comparison between the traditional backcalculation approach and the ANN model

This study investigated traditional and new approaches for predicting airfield pavement responses from surface deflections measured under Heavy Weight Deflectometer (HWD) testing conducted at National Airport Pavement Testing Facility (NAPTF). In the traditional approach, pavement layer moduli were backcalculated and then pavement responses were predicted based on the multilayer elastic (MLE) theory and the finite element (FE) method. In the new approach, an Artificial Neural Network (ANN) model was developed to predict the pavement response directly from surface deflections without backcalculation. The ANN model was trained using the synthetic database that was built based on the FE simulation results using different combinations of material property, layer thickness, HWD loading magnitude, and pavement temperature. It was found that the backcalculated moduli of the asphalt surface layer were similar between MLE and FEM methods; however, discrepancies were observed for the backcalculated moduli of unbound materials. In general, the traditional approach of backcalculation and forward calculation overestimated tensile strain in asphalt layers, especially for the pavement section with a thin asphalt layer. On the other hand, the prediction accuracy of the ANN model was found better than the traditional method regarding field measurements. Further analysis of the ANN model showed that the Area Under Pavement Profile (AUPP) and Surface Curvature Index (SCI) had good correlations with critical tensile strain and shear strain in the asphalt layer, respectively.

Environmental Impacts of Mixed Aggregates for use in Unbound Layers in Road Construction

Abstract During carbon steel manufacturing, large amounts of electric arc furnace (EAF) slag are generated. EAF slag, if properly treated and processed into aggregate, is an alternative source of high-quality material, which can substitute the use of natural aggregates in most demanding applications in the construction sector, mostly for wearing asphalt courses. In this screening process of high-quality aggregates, a side material with grain size 0/32 mm is also produced, which can be used as an aggregate for unbound layers in road construction. In this study, the environmental impacts of slag aggregate (fraction 0/32 mm) were evaluated in mixed natural/slag aggregates. Different mixtures of natural/slag aggregates were prepared from aged (28 days) and fresh slag, and their environmental impacts were evaluated using leaching tests. It was shown that among the elements, chromium (Cr) was leached from some mixed aggregates in quantities that exceeded the criterion for inert waste. The data from the present investigation revealed that mixed aggregates, prepared from aged slag (fraction 0/32 mm) and natural stone in the ratio 10/90, are environmentally acceptable and can be safely used in unbound materials for road construction.

Geogrid Stabilization of Unbound Aggregates Evaluated Through Bender Element Shear Wave Measurement in Repeated Load Triaxial Testing

This paper describes the use of the bender element (BE) shear wave measurement technology for quantifying the effectiveness of geogrid stabilization of unbound aggregate materials with improved mechanical properties from repeated load triaxial testing. Crushed stone aggregate specimens were prepared with three different gradations, that is, upper bound (UB), mid-range engineered (ENG), and lower bound, according to the dense graded base course gradation specification in Illinois. The specimens were compacted at modified Proctor maximum dry densities and optimum moisture contents. Two geogrids with different triaxial aperture sizes were placed at specimen mid-height, and unstabilized specimens with no geogrid were also prepared for comparison. To measure shear wave velocity, three BE pairs were placed at different heights above geogrid. Repeated load triaxial tests were conducted following the AASHTO T307 standard resilient modulus test procedure, while shear wave velocity was measured from the installed BE pairs. After initial specimen conditioning, and at low, intermediate, and high applied stress states, both the resilient moduli and accumulated permanent strains were determined to relate to the geogrid local stiffening effects in the specimens quantified by the measured shear wave velocities. The resilient modulus and shear wave velocity trends exhibited a directly proportional relationship, whereas permanent strain and shear wave velocity values were inversely related. The enhancement ratios calculated for the geogrid stabilized over the unstabilized specimens showed significant improvements in mechanical behavior for the UB and ENG gradations, and a maximum enhancement was achieved for the engineered gradation specimens stabilized with the smaller aperture geogrid.

Development of elasto-plastic constitutive model for unbound granular materials under repeated loads

This study aims to establish an elasto-plastic constitutive model under repeated loads for unbound granular materials (UGM) used in the pavement. Shakedown theory was employed to analyze the deformation behavior of UGM at different stages. The prediction models of plastic strain rate and resilient strain were fitted with the loading repetitions, axial stress, and other factors. Based on the typical stress-strain curves and the models of plastic strain rate and resilient strain, the yield point model was established using the criterion of spatially mobilized plane (SMP). Using this model, the yield stress was obtained conveniently at certain loading conditions, which provided the movement path of yield surface under repeated loads based on kinematic hardening law. Under single loading, the plastic strain hardening was treated as the isotropic hardening. This simplified method made it feasible to establish the elasto-plastic constitutive model under repeated loads. The proposed model was verified with the measured deformation of mixed-size aggregates using precision unbound material analyzer (PUMA) tests. The comparsions of permanent strain and plastic strain rate obtained from laboratory tests and numerical simulation indicated that the proposed elasto-plastic constitutive model can characterize the deformation behavior of UGM.

A prediction model of permanent strain of unbound gravel materials based on performance of single-size gravels under repeated loads

Permanent strain is an important consideration for the application of unbound gravel materials used in pavement under the repeated vehicle loads. The existing prediction models of permanent strain involved various influence factors, such as load condition, moisture content, compactness, etc. A new model to predict the permanent strain of unbound gravel mixture was proposed based on the performance of single-size gravels. In this study, the significant plastic stage was designated by the nonlinear and linear analyses during the long-term repeated loads tests. The results showed that the plastic strain had an obvious growth rate in the first 20,000 repetitions which was chosen as the significant plastic stage. Then, the plastic strain of unbound gravel materials was investigated and the calculation models of single-size gravels were established considering the load repetition, load intensity, load frequency, moisture and compactness. The contribution of coarse and fine aggregate in the gravel mixture was obtained based on the theory of maximum density and packing theory. After that, the prediction model of gravel mixture was established using the plastic strain of single-size gravels and the contribution of different aggregates. Compared with the measurements of six gravel mixtures, the proposed model was verified with high precision due to the small differences between the predictions and measurements. With the comparison of the previous models, the proposed model has greater accuracy than that of Wolff-Visser and Paute, and similar as the models of Barksdale and Sweere for the investigated materials. Using this model, the permanent strain can be obtained without additional laboratory tests once the gradation composition and working conditions were determined. This model can predict the permanent strain of the gravel mixture from the gradation composition, which will bring new meaningful findings and strong adaptability.

Construction and demolition waste applications and maximum daily output in Spanish recycling plants.

The pursuit of construction sustainability has driven the use of partially or wholly waste-based eco-materials. New applications are being sought for recycled aggregate (RA) to further the use of this material and ensure the survival of the construction and demolition waste (C&DW) industry. RA, currently used in the construction of pavements, fills and embankments and only incipiently to manufacture structural or non-structural concrete, is a mere 8.99% of the total aggregate extracted in EU countries where RA is produced. Against this backdrop, the utility of this study lies in the overview afforded of RA typology, the application of the product in bound or unbound materials, the pursuit of new applications, structural or otherwise, and the assessment of daily maximum output by C&DW recycling facilities in Spain. The findings show that irrespective of its origin, RA most commonly adopts the form of wet mix macadam, gravel or sand used primarily in unbound applications with only dubious quality standards. Plant managers contend that RA from clean waste can feasibly be used in bound applications that require higher-performance materials. Maximum daily output varies widely, with capacity under 200 t d-1 in 30% of the plants. One of the conclusions drawn is that the current business model is in need of revision, with an emphasis on aggregate quality control (certification) and the adoption of technology for separating out impurities, pollutants and undesirable materials to improve the quality of RA.

Feasible Use of Cathode Ray Tube Glass (CRT) and Recycled Aggregates as Unbound and Cement-Treated Granular Materials for Road Sub-Bases.

In the last 15 years, new types of display technologies have increasingly replaced cathode ray tube (CRT) screens, which has led to an increase in landfill of old discarded CRT televisions, which present a great environmental challenge throughout the world due to their high lead content. In addition, environmental awareness has led to greater use of recycled aggregates to reduce the exploitation of existing reserves. This document aims to study the feasibility of incorporating CRT glass waste with recycled aggregate (RA) in combinations for use in civil engineering, more specifically in road bases and sub-bases. For the mechanical and environmental assessment of all of the samples and materials, the following procedures have been performed: the compliance batch test of UNE-EN 12457-4:2004 for RA, CRT, and mixtures; the Percolation Test according CEN/TS 14405 for the mixtures, CRT, and RA; Modified Proctor and load capacity (the California Bearing Ratio, or CBR) in all mixtures without cement addition, and finally, compressive strength of the material treated with cement at different ages of curing. The analysis of the mechanical and environmental properties through different techniques of lixiviation was positive, showing the ability to use CRT for certain dosage percentages mixed with recycled aggregates.

Shakedown analysis of cavities in cohesive-frictional materials and its application to underground energy storage caverns

In this paper, a shakedown analysis is conducted for both cylindrical and spherical cavities in cohesive-frictional materials subjected to cyclic internal pressures. Based on Melan’s lower-bound shakedown theorem, theoretical shakedown conditions for a two-layered cavity system are developed using the stress and strain solutions obtained from cavity expansion and contraction analyses. The shakedown limits are investigated in relation to the dimensions of the two-layered cavity system and the elastic/plastic material parameters. Numerical validation is conducted through a comparison of the stress path of the critical element and the failure lines of the materials. In addition, closed-form solutions for special cases, namely, the analytical shakedown conditions of cavities in an unbound cohesive-frictional material and in a bound material with different boundary conditions, are explicitly expressed. Finally, the shakedown solutions are applied to solve the thickness design problem of underground compressed air energy storage in lined and unlined caverns.

Mechanical Characterization of Fine-Grained Lateritic Soils for Mechanistic-Empirical Flexible Pavement Design

Abstract Fine-grained lateritic soils, which are typically found in tropical regions and have been used successfully in low-cost pavements, are often considered inadequate for the base and subbase pavement layers when the material selection is based on the California bearing ratio (CBR). When analyzed in repeated load triaxial (RLT) test equipment, which is the most frequently used device to analyze the mechanical behavior of unbound pavement materials, fine-grained lateritic soils exhibit low levels of plastic deformation. Thus, to allow more appropriate analyses of the mechanical behavior of such soils compared to traditional CBR-based analyses, resilient modulus and permanent deformation tests using RLT test equipment were performed. Then, multifactorial regression analysis of the experimental results was performed to identify the parameters of the material models that are implemented in the Brazilian mechanistic-empirical pavement design software program, MEDINA. The experimental program included material characterization in accordance with the so-called miniature, compacted, tropical (MCT) methodology that is tailored specifically to classify tropical soils. For one of the lateritic soils, two key parameters, i.e., the stress level and compaction moisture content, were varied in the RLT permanent deformation tests. An additional numerical analysis using MEDINA was conducted to evaluate the structural characteristics of flexible pavements composed of the four lateritic soils analyzed in this study. In general, the results obtained from this study indicate that lateritic soils can potentially be used as base and subbase layers in flexible pavement structures.

Evaluation of horizontal permeability characteristics of granular subbase material

Moisture enters into the pavement structure from the surface by infiltrating through cracks and joints, laterally from shoulders, and as capillary suction from bottom. One of the predominant causes for the accumulation of moisture in the pavement structure is inadequate subbase permeability. The existence of moisture within the pavement structure reduces the structural stability of the system. Therefore, it is essential to provide the subbase layer with sufficient drainage characteristics. In the present study, drainage and strength characteristics of the unbound material of different gradations that are being used as pavement subbase layers in India are evaluated. Horizontal permeability was determined using laboratory-developed horizontal permeameter under constant head mode with different hydraulic gradients. Strength characterization was also done in terms of California Bearing Ratio (CBR) value. It is found that horizontal permeability depends on the hydraulic gradient and density of unbound material. Comparison of the laboratory obtained horizontal coefficient of permeability of different gradations was made with the values recommended in IRC: 37-2012 and found that all gradations have permeability nearer to 300 m/day with hydraulic gradient range from 0.2 to 0.3. A predictive model was developed to predict horizontal permeability from the fundamental material properties and good correlation was established within the considered range of variables and thereby this model is useful to predict horizontal permeability of granular subbase material.

Effect of Silica Fume on Mechanical and Durability Properties of Recycled Coarse Aggregate Concrete

Reusing concrete is the best choice to diminish the eagerness on mind blowing standard assets and to oblige the total of waste which is engineered in landfills. Reused concrete has been regularly used as an unbound material as a touch of dams, bases, and sub-bases. RAC has in like way been utilized as a piece of the improvement of asphalts and wastes yet in less case as the examination in this field is not the most outrageous utmost of RAC has not yet been investigated. In this investigation the reused total was utilized as supplanting with 20%, 40%, 60% and 80% by substitution of typical aggregate. Standard Ordinary Portland cement was supplanted with 10% of mineral admixture silica fume. Tests were coordinated to choose the mechanical properties and durability properties such us rapid chloride penetrability test and water sorptivity test. The results show that increasing the recycle aggregate percentage above 40% with natural aggregate, small modifications to the mix design may be adopted to secure that comparable property to natural aggregate concrete is attained

Feasible use of colliery spoils as subbase layer for low-traffic roads

The aim of this paper is to characterise, both physically and chemically, the colliery spoils of Pozo San José, located in the Guadiato Valley (Córdoba, Spain), and evaluate their possible use as unbound materials or as materials bound with lime or cement in the construction of roads with low traffic intensity. The leaching of the material and its effect on the environment was also studied. The results obtained show that the main limiting property of the material is its high organic matter content. However, colliery spoils can be used unbound or bound with 2% of cement as a subbase, thus giving a second life to the colliery spoils of this mining region that currently have no purpose. The use of colliery spoils bound with lime is not recommended, since their mechanical properties are not improved. Finally, two sections are designed for roads with a traffic intensity of up to 24 heavy vehicles/day. This research contributes to the promotion of the new paradigm of the circular economy in the construction sector.

Experimental analysis of puncture resistance of aramid laminates on styrene-butadiene-styrene and epoxy resin matrix for ballistic applications

The work aimed to evaluate the influence of the type of matrix and the number of reinforcement layers on the puncture of aramid laminates. The samples were examined under laboratory conditions and in ballistic tests. Two series of aramid laminates were produced with different types of the polymer matrix. The epoxy resin (EP) and the styrene-butadiene-styrene (SBS) copolymer were used as the matrix. For comparison, a puncture test was performed for the fabric with the same number of layers in contrast to the laminates. Laboratory tests were carried out using the InstronDynatup 9250 HV drop hammer. The results obtained during the laboratory and ballistic examinations were compared. The samples were fired with a 9×19mm Parabellum projectile. Research into the low-velocity range have shown that SBS laminates absorb impact energy more effectively than epoxy resin ones, but they are similar to fabrics without a polymer matrix. The results of ballistic tests are divergent and indicate that unbound materials are more efficient at absorbing energy than laminates. The reason for this is the different damage mechanisms.

Modeling resilient modulus of fine-grained materials using different statistical techniques

For the realistic prediction of pavement performance, it is very important to accurately characterize the mechanical behavior of unbound material layers and subgrade soils. In pavement analysis using the elastic layered theory, material properties in terms of dynamic elastic modulus and Poisson’s ratio are the major input parameters. The dynamic elastic modulus of pavement materials or resilient modulus (MR) is measured by conducting repeated load triaxial compression tests typically not available to highway authorities due to the high costs involved in acquiring such high-performance equipment and/or lack of knowledge on how to operate this specialized equipment. Therefore, pavement engineers are obligated to use pavement design methodologies based on empirical tests. The main objective of this study is to use multiple linear regression (MLR), nonlinear regression and backpropagation artificial neural network algorithms to develop models to predict the resilient modulus of fine-grained materials based on 3709 soil samples collected from the Long-Term Pavement Performance (LTPP) website. The key input parameters selected for this study are: the confining pressure (σ3), nominal maximum axial stress (σ1), percent of silt (S), Liquid Limit (LL), Plasticity Index (PI), percent passing number 200 sieve (P#200), maximum dry density (ρmax-dry), percent of clay (C), optimum moisture content (wopt), and laboratory-determined resilient modulus. Results revealed that the change of wopt has a higher effect on MR compared with the change in density, the percent fines, percent of silt, percent of clay, confining pressure, PI and LL but less than the effect of changing axial stress. In addition, the best modeling technique to predict the resilient modulus of fine-grained soil was found to be the Artificial Neural Network (ANN) followed by the nonlinear regression and finally the MLR.

Development of Resilient Modulus Prediction Model for Granular and Noncohesive Soils of New Mexico

Abstract The resilient modulus (MR) of unbound materials, i.e., base and subgrade, is an essential property for the Mechanistic-Empirical Pavement Design Guide (MEPDG). The MR of the unbound materials is highly dependent upon several factors such as physical properties of the materials, soil type, stress state, and moisture content. The MR values are usually determined by conducting repeated load triaxial compression tests in the laboratory. However, because of the complexity, difficulty, huge time, and effort associated with it, development of an MR prediction model based on soil physical properties has increasingly become an imperative. In this study, a model is developed to estimate the MR of base and noncohesive (A-2-4) subgrade soils that are commonly available in the state of New Mexico from a set of materials’ physical properties. First, subgrade and granular materials have been collected from different construction sites, and a laboratory MR test is conducted in accordance with the test standard AASHTO T-307, Standard Method of Test for Determining the Resilient Modulus of Soils and Aggregate Materials. The pertinent material constants (k1, k2, and k3) in the constitutive model have been evaluated from the laboratory test data using regression analysis. Materials coefficients are correlated to the selected physical properties. A new set of laboratory test results for another pavement site is used to verify the model. It is observed that the prediction model predicts MR values that agree well with the laboratory results. Therefore, the proposed model can be applied to the base and noncohesive subgrade soils for implementation in MEPDG.

Abstract 3628: Comparison of CD44 expression in pancreatic cancer, pancreatic stem and normal pancreatic cells: Development of CLENs for tumor targeting and therapy using cell models

Abstract Purpose: The incidence of drug resistance in pancreatic cancer correlates with poor prognosis, increased disease progression and unfavorable treatment outcomes. CD44, a surface membrane proteoglycan has been identified to be directly involved in pancreatic cancer drug resistance and metastasis. As such, the aim of this research was to screen various pancreatic cells for their expression of CD44, and to begin the early design and development of cell membrane lipid-extracted nanoliposmes (CLENs) for enhanced targeting and therapy. Methods: Three pancreatic cancer cells- Panc-1, MiaPaCa 2, MS1 VEGF and a normal cell line- hTERT- were employed for this study. Stem cell, Mia PaCa-2, served as a positive control for screening purposes. Four liposome compositions were prepared using various ratios of DOPC, Chol, DPPE-PEG5000, and cellular membrane lipid-extracted (LE) was derived from target cell, Panc 1. To evaluate CD44 glycoprotein expression, cells were seeded in 48-well plates and incubated overnight. Fluorescence measurements were determined at excitation wavelength of 485/25 and emission wavelength at 528/20 nm. G44-26 monoclonal antibody was used for CLENs antibody conjugation studies. A Sephadex G-25 column was used for separation of bound and unbound antibody material, and fluorescence detection was used for cell culture analysis. Fluorescence detection was performed at excitation and emission wavelengths of 530/25 and 590/25, respectively. Results: The relative level of CD44 expression for each of the cell lines was as follows. Panc1>Mia PaCa-2 = hTERT>MS1-VEGF. There was a statistically significant difference between Panc-1 and Mia Paca 2 (P<0.001), between hTERT and MS1 VEGF (P<0.05), and between Panc-1 and hTERT (P<0.0001). The inclusion of Panc1-LE in combination with additional liposome components did not increase cellular uptake significantly. The conjugation of G44-26 monoclonal antibody to the liposomes increased average size of all 4 preparations. Average size for CLENs and G44-26 monoclonal antibody -CLENs increased from 140.75 ± 3.22 nm to 250.23 ± 15.31 nm. Conclusion: Future studies are required to demonstrate the effect of G44-26 monoclonal antibody liposome conjugates to further exploit the optimal expression of CD44 for pancreatic drug targeting. Citation Format: Dotun D. Adegunle, Eugene Boakye Ansah, Danny Nguyen, Kanchi Sanghvi, Drew Goodrich, Robert Campbell. Comparison of CD44 expression in pancreatic cancer, pancreatic stem and normal pancreatic cells: Development of CLENs for tumor targeting and therapy using cell models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3628.

Performance of Unbound Aggregate Materials under Single-Stage and Multistage Loading Modes Based on Precision Unbounded Material Analyzer

This study explored the performance of unbound aggregate materials (UAM). Repeated load tests of single-size, two-size mixed, and three-size mixed gravels were conducted using the precision unbounded material analyzer (PUMA) in single-stage loading mode (SSLM) and multi-stage loading mode (MSLM). The permanent deformation and elastic modulus of the first 400 loading cycles were analyzed under the two loading modes. The modulus of PUMA repeated load tests was compared with modulus models of the repeated CBR test and with constant confining pressure (CCP) and variable confining pressure (VCP) models of the repeated load triaxial test. The results of MSLM showed that the permanent deformation of single-size gravel increased rapidly when the loading strength was lower than 340 kPa and then decreased. The maximum permanent deformation of the mixed gravels appeared as the loading strength was lower than 200 kPa. The increment of permanent deformation tended to single-peak with the large-size aggregate. The loading strength only slightly affected the permanent deformation once it reached a certain extent. The initial-stage permanent deformation of SSLM was the main part of the total, and the proportion increased with the increase in loading strength. A slight difference was observed between the single-size and mixed gravel when the loading strength was under 240 kPa. Then, the permanent deformation of single-size gravel increased rapidly. The permanent deformation of MSLM was smaller than that of SSLM. MSLM can improve the carrying capacity of the unbound materials and reveal the principle of three-stage compaction for UAM. Although the calculated equivalent modulus of the full-friction model was lower than those of the existing studies, it presented the same tendency and was appropriate for the calculation of modulus. The elastic modulus of CCP model was the largest among the four models, and the growth rate of elastic modulus was the highest for VCP model. The effect of confining pressure on the modulus increased with increasing loading strength.

Fundamental characterisation of the anisotropic resilient behaviour of unbound granular materials

ABSTRACT The paper presents an in-depth investigation of the resilient behaviour of an unbound base material. It is based on the assumption that the material is non-linear and cross anisotropic. A testing programme that includes different incremental stress paths, principal stress ratios and confining pressures is proposed. The programme requires the use of a triaxial cell where both the vertical and horizontal stresses and deformations are either controlled or measured. The paper describes the analysis steps whereby only three material parameters, out of the five cross anisotropic parameters, can be obtained in the above conditions. Four specimens of a good quality base material were prepared in the laboratory and tested according to the above testing programme. The analyses of the tests show that: (1) The vertical modulus depends solely on the bulk stress, as expected for a good quality base material; (2) The vertical to horizontal Poisson’s ratio and the horizontal parameter are also nonlinear and function of the first two stress invariants; (3) The material parameter functions from the incremental loading tests are different from those of the resilient modulus test; (4) The characterization is sensitive to the type of loading.

Structural response of an inverted pavement with stabilised base by numerical approach considering isotropic and anisotropic properties of unbound layers

Inverted pavements or inverted base pavements are defined by the presence of stiffer supporting layers below the top bituminous layer, which is contrary to the conventional flexible pavements, where the stiffness of the layers decrease with depth. Response of an inverted pavement depends on the relative stiffness of the successive layers. Therefore mechanistic design of inverted pavements demand analysis of the pavements using realistic elastic parameters of the layers. Studies on unbound granular layers have established the anisotropic properties of the layer that better correlates with the field performance. The present study aims at evaluating structural responses of an inverted pavement using finite element based modelling that considers anisotropic properties of the unbound materials i.e. aggregate interlayer and subgrade. Results show that anisotropy of the aggregate interlayer has a larger role to play in the design on inverted pavements having provision of aggregate interlayers.