Resilient Modulus Values Research Articles

Comparative mechanistic-empirical analysis for design of alternative cold recycled asphalt technologies with conventional pavement

It is essential to carry out a detailed study on the mechanical behaviour of materials so as to evaluate the distress parameters of flexible pavements. This study can be performed through finite element simulations like ANSYS, KENPAVE, IITPAVE, etc. However, this study was mainly carried out using the pavement designing tool ANSYS to study and compare the mechanical behaviour of a typical conventional pavement with hot bituminous surfacing, with cold recycled emulsified and foamed base pavements with fresh overlay. Further, the results obtained from this ANSYS were compared with other simulations like KENPAVE and IITPAVE. Optimum design thickness of the pavement was determined based upon the predicted tensile and compressive strain from laboratory resilient modulus values. The analytical results showed that, linear elastic analysis in both KENPAVE and IITPAVE match well, but a slight lesser tensile strain and vertical displacement values are observed in ANSYS. Also, the study was extended towards the comparative cost benefit analysis of both recycled and conventional mixes. Through this study, it was observed that recycled mix is economical when compared to conventional mixes.

Studies on resilient modulus value from cyclic loading tests for cohesive soil

Abstract In this article the cyclic CBR test as a reference method in determination of resilient modulus (Mr) is confronted with results of cyclic triaxial and unconfined uniaxial cyclic test. The main idea of conducted experiments is establish relationship between cyclic loading tests in testing of natural subsoil and road materials. The article shows results of investigation on cohesive soil, namely sandy silty clay, commonly problematic soil in Poland. The results of repeated loading triaxial test resilient modulus were displayed in order to compare them with cyclic CBR test results by using the Mr–Ө model. Some empirical correlation between factors obtained from triaxial test or uniaxial unconfined cyclic test and cyclic CBR test was introduced here. The behavior of resilient modulus was also examined in this paper.

Resilient Modulus Characterization of Compacted Cohesive Subgrade Soil

Soil investigations concerning cyclic loading focus on the evaluation, in particular, of design parameters, such as elastic modulus, Poisson’s ratio, or resilient modulus. Structures subjected to repeated loading are vulnerable to high deformations, especially when subgrade soils are composed of cohesive, fully-saturated soils. Such subgrade soils in the eastern part of Europe have a glacial genesis and are a mix of sand, silt, and clay fractions. The characteristic of, e.g., Young modulus variation and resilient modulus from repeated loading tests, is presented. Based on performed resonant column and cyclic triaxial tests, an analytical model is proposed. The model takes into consideration actual values of effective stress p′, as well as loading characteristics and the position of the effective stress path. This approach results in better characterization of pavement or industrial foundation systems based on the subgrade soil in undrained conditions. The recoverable strains characterized by the resilient modulus Mr value in the first cycle of loading was between 44 MPa and 59 MPa for confining pressure σ’3 equal to 45 kPa, and between 48 MPa and 78 MPa for σ’3 equal to 90 kPa. During cyclic loading, cohesive soil, at first, degrades. When pore pressure reaches equilibrium, the resilient modulus value starts to increase. The above-described phenomena indicate that, after the plastic deformation caused by excessive load and excess pore water pressure dissipation, the soil becomes resilient.

Resilient modulus of black cotton soil

Resilient modulus (MR) values of pavement layers are the basic input parameters for the design of pavements with multiple layers in the current mechanistic empirical pavement design guidelines. As the laboratory determination of resilient modulus is costly, time consuming and cumbersome, several empirical models are developed for the prediction of resilient modulus for different regions of the world based on the database of resilient modulus values of local soils. For use of these relationships there is a need to verify the suitability of these models for local conditions. Expansive clay called black cotton soil (BC soil) is found in several parts of India and is characterized by low strength and high compressibility. This soil shows swell – shrink behaviour upon wetting and drying and are problematic. The BC soil shows collapse behaviour on soaking and therefore the strength of the soil needs to be improved. Additive stabilization is found to be very effective in stabilizing black cotton soils and generally lime is used to improve the strength and durability of the black cotton soil. In this paper, the results of repeated load tests on black cotton soil samples for the determination of MR under soaked and unsoaked conditions at a relative compaction levels of 100% and 95% of both standard and modified proctor conditions are reported. The results indicate that the black cotton soil fails to meet the density requirement of the subgrade soil and shows collapse behaviour under soaked condition. To overcome this, lime is added as an additive to improve the strength of black cotton soil and repeated load tests were performed as per AASHTO T 307 - 99 for MR determination. The results have shown that the samples are stable under modified proctor condition with MR values ranging from 36MPa to 388MPa for a lime content of 2.5% and curing period ranging from 7 to 28 days. Also, it is observed that, the CBR based resilient modulus is not in agreement with the laboratory based MR value and therefore it is necessary to use the laboratory determined MR or MR predicted from an appropriate prediction equation for pavement design. An attempt is also made to develop an empirical model for the prediction of MR of lime stabilized black cotton soil. There is a good agreement between the predicted and laboratory MR values with an error of 12%.

THE GEOTECHNICAL PROPERTIES OF RECYCLED CONCRETE AGGREGATE WITH ADDITION OF RUBBER CHIPS DURING CYCLIC LOADING

The following paper presents the results of tests performed on the reclaimed waste, namely the Recycled Concrete Aggregate (RCA). Geotechnical study was undertaken, in order to obtain physical and mechanical properties of RCA improved with rubber grains. Such a mix could exhibit increased elastic strain development during load cycles, which are typical for traffic. For better understanding of its exceptional behaviour under repeated loading, cyclic CBR tests were conducted in various stages of loading. For the purpose of bearing capacity analysis, uniaxial test was also conducted. While the cyclic loading and mechanical stabilization are a cause of aggregates crushing, another particle size distribution could occur and may not fulfil quality requirements. Determination of resilient modulus Mr on the basis of a repeated loading test and development of displacements during the tests have also been presented. The Mr value for pure RCA was equal to 495.6MPa. The addition of rubber chips in amount 0.5% and 1% results in rise of resilient modulus value, equal to 632.4MPa and 698.0MPa respectively. During the tests the plastic strain abate was recognised. The plastic displacement analysis shows increase of the permanent settlement due to cyclic loading in case of 0% and 1% rubber chips content. The 0.5% rubber chips addition results in smaller plastic displacement. The plastic and elastic displacement was later analysed in order to characterize the deformation behaviour of RCA. The paper proposes also a possible guideline for using the RCA mix as a material in pavement subbase construction.

Investigating Stress Dependency of Unbound Layers Using Falling-Weight Deflectometer and Resilient Modulus Tests

Unbound layer materials, such as base and subgrade, exhibit stress-hardening and/or -softening, which can be determined from their resilient modulus values. However, unavailability of required amount of material and compaction variability between field and laboratory necessitate a need to predict stress dependency of the unbound layers by field tests. This study evaluates stress dependency of unbound layers using a falling-weight deflectometer (FWD) test. The FWD tests were conducted at multi-load levels on several pavement sections. The FWD back-calculated layer moduli are then used to determine bulk and octahedral shear stresses using the layered elastic analysis technique. Next, the regression analysis is performed to interpret the stress-dependent parameters, i.e., regression coefficients of pavement ME's resilient modulus model of nonlinear unbound material. It is observed that stress-hardening is dominant in the case of the base layer, whereas subgrade exhibits both stress-hardening and -softening. This was also confirmed by laboratory resilient modulus tests on both base and subgrade materials in this study. Therefore, it is recommended not to ignore either stress-hardening or -softening during nonlinear modeling of the unbound layers. In addition, in this study, empirical relationships are developed to perform inter-conversion of laboratory resilient and FWD back-calculated modulus incorporating the field state of stresses in base and subgrade.

Laboratory Evaluation of Ladle Furnace Slag in Unbound Pavement-Base/Subbase Applications

AbstractSteel is an inherently never-ending product, in terms of recycling and reuse. The steelmaking process creates an industrial by-product termed as slag. Ladle furnace slag (LFS) is produced at the final stages of the steelmaking process in ladle refining furnaces. The potential use of LFS as a base/subbase material requires a thorough knowledge of its engineering properties. In this research, an extensive suite of engineering characterization tests were carried out to evaluate the engineering properties of LFS. The effect of curing on the strength of unbound LFS was investigated using unconfined compression strength (UCS) and resilient modulus tests. The results showed that the UCS of unbound LFS increased by almost four times with 7 days of curing in a temperature-controlled and moisture-controlled chamber. The resilient modulus value of unbound LFS increased when increasing either confining pressure or deviator stress. The specimens with 7 and 28 days of curing had higher resilient modulus values ...

MECHANICAL PROPERTIES OF POROUS ASPHALT WITH NANOSILICA MODIFIED BINDER

This paper evaluates the mechanical properties of porous asphalt (PA) with nanosilica (NS) modified binder in terms of its Abrasion Loss, Binder Draindown, Resilient Modulus and Moisture Susceptibility. These tests are essential to evaluate the performance of NS-PA towards the resistance of moisture induced damage, external loads, abrasion and interlocking structure of PA. Due to porous nature of PA, it is expose to moisture damage and binder draindown. Besides that, raveling is another major problem that closely related to PA. Thus, nanotechnology was promoted in this study in order to enhance the performance of PA. Six different percentages of nanosilica were mixed with PEN 60-70 type of binder in this study. Then, all these blended modified binder were used to prepare PA samples using Marshall Mix Design Method. Nanoparticle used in this study was Nanosilica with the average size of 10 to 15 nanometer. Binder Draindown Test was done using a metal basket with 3mm perforation. Then, abrasion loss value was evaluated using Los Angeles Abrasion Machine without steel ball. In accordance to Public Work Department of Malaysia Specification (JKR/SPJ/2008), it is stated that binder draindown for PA should not be more than 0.3% of total weight of sample, while abrasion loss should not be more than 15% also by weight of total sample. The results for Cantabro Loss Test and Binder Draindown Test indicated that 4% NS was the effective amount of NS to reduce the abrasion loss and binder drained of NS-PA. The maximum resilient modulus value for NS-PA was 4362 MPa while TSR value 91% (2% NS). Meanwhile, for conventional PA (0% NS), resilient modulus value was only 3036 MPa and TSR value 74%. From both tests were also concluded that the optimum amount of NS required for PA to archieved both value was 2%. It can be concluded that with proper concentration, the existence of NS is capable to enhance the physical and rheological properties of asphalt binder and at the same time it dispersed well in asphalt binder. Thus, the performance of PA with NS modified binder is also enhanced.

Performance of geosynthetic reinforced/stabilized paved roads built over soft soil under cyclic plate loads

The benefits of using geosynthetics to enhance the performance of pavement constructed over soft subgrade was evaluated using cyclic plate load testing. A total of six test sections, with varying types and layers of geosynthetics and base thicknesses, were constructed inside a 2 m × 2 m × 1.7 m test box. A cyclic load at a frequency of 0.77 Hz was applied through a 305 mm-diameter steel plate. The test sections were instrumented by a variety of sensors to measure the load-associated pavement response and performance. The test results clearly showed the benefits of geosynthetics in significantly reducing the pavement rutting. The test section with double geosynthetics layers performs much better than all other sections studied in this paper. Geosynthetics placed at the base–subgrade interface function more as weak subgrade stabilization than as base layer reinforcement in this study. Finally, the benefits of geosynthetic reinforcement was quantified, within the context of the AASHTOWare Pavement ME Design guide, in terms of increasing the resilient modulus of base course layer and/or reducing the thickness of base aggregate layer in pavement structure. The results of analysis show that for geosynthetics functioning as base reinforcement alone, the value of resilient modulus of the base course layer can be increased by about one quarter and that the thickness of base layer can be reduced by about one third for the pavement sections, with 457 mm thick base and single layer of geosynthetic placed at the base–subgrade interface, tested in this study. For geosynthetics functioning as subgrade stabilization alone, the test results showed that the resilient modulus of subgrade can be almost doubled.

Multivariate correlation among resilient modulus and cone penetration test parameters of cohesive subgrade soils

Extensive research has been conducted to establish empirical equations between the resilient modulus (Mr) and other testing parameters. Despite an increase in the correlation studies, less effort has been made in developing reliable correlations to predict the resilient modulus using cone penetration testing indices. In this research, an attempt has been made to propose new correlations between Mr and the piezocone penetration test (CPTU) indices of clayey soils by using a multivariate normal distribution approach. A database collected from 16 different sites in Jiangsu province, China, was presented to achieve this study. The database contains 124 sets of resilient modulus (Mr) values at the in-situ stress condition, cone tip resistance (qc), sleeve frictional resistance (fs), moisture (w) and dry density (γd). Four major procedures including the data transformation, correlation analysis, Bayesian updating, and back transformation were applied to derive the correlations among Mr and other indices in the framework of the multivariate normal distribution model. First, each individual parameter was converted to a standard normal variable using the Box-Cox transformation. Later, the correlation matrix of the multivariate normal distribution model was estimated using the product-moment (Pearson) correlation coefficients between all pairwise data. The uncertainties associated with the Box-Cox transformation parameters and the correlation coefficients were evaluated using a bootstrapping technique. Furthermore, the formulas for predicting the posterior mean, coefficient of variation (COV), median, and 95% confidence interval (CI) of Mr conditional on different indices were derived using Bayesian updating combined with back transformation. A new approach based on the Taylor-series expansion was proposed to approximate these statistics in this study. Comparisons between the correlations derived from the multivariate model, the database of Jiangsu clay, and the data collected from the literature demonstrated that the model should be capable of the correlations among the five indices, but it might be slightly biased when applied in the global dataset. This research highlighted a new method to establish the reliable correlations to update Mr using different testing indices.

Resilient modulus of fine-grained soil and a simple testing and calculation method for determining an average resilient modulus value for pavement design

The resilient modulus has been recognised as an important property that governs the performance of pavement materials under the dynamic wheel loads. The resilient modulus can be obtained from a repeated load triaxial test with a series of a combination of deviator and confining stresses. It is traditionally reported as a function of the deviator and confining stresses, which can be a practical challenge in selecting the appropriate resilient modulus value for a pavement design. In this study, eight different Victorian fine-grained soils with different moisture contents were used for the determination of the resilient modulus and the evaluation of a proposed simplified method. The resilient modulus from the simplified method is reported as a single value, which is taken as the average value from the simplified testing method. It has been found that the resilient modulus obtained from the proposed simplified and the standard testing method are almost identical.

Field evaluation of soft highway subgrade soil stabilized with calcium carbide residue

Calcium carbide residue (CCR) is a by-product of acetylene gas production. Stockpiles of CCR continue to accumulate worldwide, in both developed and developing countries. Sustainable reuse options for CCR in civil infrastructures, such as road embankments, have been recently evaluated in the laboratory. However, to date there are limited studies on the actual field performance of CCR in stabilizing clayey soils in highway subgrades. In this study, a field trial was conducted to ascertain the viability of using CCR stabilized clayey soil as a highway subgrade course material. Quicklime was selected as a control binder in the field trial for comparison purposes. The construction procedures of the CCR and quicklime stabilizations in two field sections are presented. A series of field tests, including California Bearing Ratio (CBR) test, plate loading test, Benkelman beam deflection test, and dynamic cone penetrometer (DCP) test were undertaken after the embankment construction. The results indicated that in the top zone of the filled soil layers with 94% degree of compaction, the CCR stabilized subgrade soil exhibited higher values of CBR and resilient modulus, and lower values of resilient deflection and DCP Index relative to the quicklime stabilized soil. The field trial results indicated that CCR had negligible environmental effects and furthermore resulted in low construction costs. Based on the field test results, CCR was found to be a viable alternative binder for stabilizing soft subgrade soils. The outcomes of this research are significant from engineering, economic and environmental perspectives.

Analysis of the multistage cyclic loading test on resilient modulus value64

Abstract Analysis of the multistage cyclic loading test on resilient modulus value. Upon cyclic excitation of soil mass, two types of strain can be recognized, namely elastic and plastic one. Proper analysis of these two types of deformations can help engineers in designing more reliable structures. In this study, a multistage uniaxial cyclic loading in unconfined conditions was performed. Tests were performed in order to characterize strain response to repeated excitation. Soil sample under cyclic loading was recognized as exhibiting the symptoms of a plastic strain growth during the cyclic loading process with exponential manner, when compared to number of cycles. Soil in this study was reconstituted and compacted by using the Proctor method to simulate conditions similar to those affecting the road subbase. The soil was recognized as sandy clay. Results were analysed and a proposition of empirical formula for plastic strain calculation with the use of characteristic stress values was presented. The resilient modulus values were also calculated. The Mr value was within range from 45 to 105 MPa. The conclusions concerning the cyclically loaded soil in uniaxial conditions were presented.

High temperature characteristics of warm mix asphalt mixtures with nanoclay and chemical warm mix asphalt modified binders

With the rising price of energy and the effects of global warming, the demands for the use of warm mix asphalt (WMA) in the construction of pavements have been steadily increasing throughout the world. Due to this, many agencies have been looking forward to implementing WMA technology as a way to promote green culture in every aspect of the industry. In view of this, this study has made an extensive assessment of the performance characteristics of WMA with nanoclay and a chemical WMA additive at high temperatures. The base 80/100 penetration grade binder was modified with 1, 2, and 3% chemical WMA additive and 4% nanoclay respectively. The performance of WMA mixtures blended with base and modified asphalt binders at various mixing and compaction temperatures was evaluated and compared with hot-mix asphalt (HMA). Results showed that apart from the insignificant low resilient modulus value recorded by the WMA mixtures, the modified WMA mixtures performed incredibly well in terms of moisture susceptibility, rutting, and permanent deformation when compared with conventional HMA. This study showed that nanoclay and chemical WMA additive could be effectively used as WMA modifiers.

Possible simplified method for the determination of the resilient modulus of unbound granular materials

The behaviour of flexible pavements is commonly characterised by the resilient modulus, which can be determined from the repeated load triaxial test in the laboratory. The repeated load triaxial testing standard varies from one organisation to another and can take up to 15 hours to complete. This paper presents the results of a possible simplified testing method, which may significantly reduce the testing time to 4.5 hours. The differences between the resilient modulus values from the standard testing method and those from the proposed simplified testing method are found to be insignificant for the 14 different experimental unbound granular materials.

Using Blends of Construction & Demolition Waste Materials and Recycled Clay Masonry Brick in Pavement

In Egypt and many developing countries, the use of Construction & Demolition (C&D) waste and Recycled Clay Masonry (RCM) brick materials as Unbound Granular Materials (UGMs) in pavement construction is generally very limited. There has been reluctance to adopt recycled materials in pavement construction. Despite the fact that there are allocated land fill areas for dumping this kind of waste, in Egypt C&D waste is usually dumped on the sides of canals, minor roads and at the entrance of the cities and towns. This causes environmental problems and affects the daily lives of people. Therefore, blends of C&D waste materials with RCM were evaluated for use as UGMs. The C&D waste and RCM materials were obtained from some dumps on the sides of roads and canals around Mansoura City, Egypt. The collected materials were crushed and mixed in the laboratory. The proportions of the C&D/RCM blends were 100/0, 90/10, 80/20, 70/30, 55/45, 40/60, 20/80, and 0/100% of the total aggregate mass. The characterization of C&D/RCM blends as well as the response to cyclic loading by Repeated Load Triaxial Testing (RLTT) was covered in this research paper. Static triaxial shear tests and RLTT were conducted using a Universal Testing Machine. RLTT and static triaxial shear test specimens were prepared at the optimum moisture content and compacted according to modified Proctor. RLTT were performed in accordance with the AASHTO T307 on triplicate specimens. RCM materials (100%) as UGMs failed to meet the requirements of Los Angeles Abrasion (LAA) test of 50% maximum as specified by the Egyptian Code of Practice (ECP). RLTT data showed that all C&D/RCM blends yielded high resilient moduli however, no significant variation in resilient moduli values were observed between the different C&D/RCM blends.

Properties of Crushed Red-Bed Soft Rock Mixtures Used in Subgrade

Slaking red-bed soft rocks are widely distributed in the south of Anhui Province, China, and several highways will go through this area. It is important to evaluate their physical and mechanical characteristics for the purpose of using this kind of soft rocks as materials for road construction. In this paper, the compacting tests, the resilient modulus tests, the California bearing ratio (CBR) tests, and permeability tests have been carried out on crushed red-bed soft rock mixtures. The test results showed that, for a given degree of compaction, the resilient modulus decreases linearly with the increase of moisture content. For a given moisture content, the resilient modulus and CBR values increase linearly with the increase of compaction degree, while the soaking swelling, water absorption capacity, and permeability coefficient decrease linearly. In other words, the strength and water stability are enhanced with the increase of the degree of compaction. The results demonstrate that the crushed red-bed soft rock mixtures can be directly used as materials for the highway construction by taking corresponding measures.

Optimizing Stability and Stiffness Through Aggregate Base Gradation

Pavement base layer quality is vital for long-term performance. Low stiffness and shear strength can result in a loss of support and increased tensile stresses under loads. To maintain uniform support under concrete pavements and ensure satisfactory performance, a stable, nonerodible, drainable base layer is necessary. The primary objective of this paper is to present the analysis and evaluations conducted as part of the associated research and to recommend improvements to base layer aggregate gradations for the Class 5 and permeable aggregate base specifications used by the Minnesota Department of Transportation. Improved aggregate classes are presented, considering gradation and aggregate shape properties. An analytical gradation analysis was introduced to establish an effective level of gravel-to-sand ratio of 1.4. Other analyses presented in this paper include the use of a revised resilient modulus model that was used in a Monte Carlo simulation to develop probabilities for resilient modulus values depending on gradation and season in Minnesota and the use of the Mechanistic–Empirical Pavement Design Guide for comparing gradation and gravel-to-sand ratio with expected pavement performance. The gravel-to-sand ratio of 1.4 was identified with the following analysis methods: a coordination number and packing analysis, a discrete element model for load-carrying capacity, and a pavement performance analysis using the Mechanistic–Empirical Pavement Design Guide software.

Influence of Unbound Material Type and Input Level on Pavement Performance Using Mechanistic–Empirical Pavement Design Guide

For material characterization, the Mechanistic–Empirical Pavement Design Guide (MEPDG) has three input levels. Level 1 input values must be obtained through direct laboratory testing. Level 2 inputs are determined through correlations with other material properties. Level 3 inputs are simply typical default values. The level chosen for each design input parameter, however, may have a significant effect on project design, cost, performance, and reliability. The influence of the unbound granular base material type and material characterization input level on pavement performance, as predicted by MEPDG, was investigated for a typical flexible pavement section in climatic conditions in Egypt. Researchers analyzed seven types of virgin and recycled base materials at three weather stations representing climatic regions in Egypt: Alexandria, Cairo, and Aswan. For the typical pavement system, Level 1 data for the resilient modulus from measured laboratory values ( k1, k2, and k3 elastic response coefficients) were used for the first set of MEPDG simulation runs. The second set of computer simulation runs was conducted with Level 2 data—values of the California bearing ratio—for the investigated materials. The final set of runs used default resilient modulus values for the investigated materials on the basis of the AASHTO class (Level 3). MEPDG-predicted pavement distresses and roughness for the three input levels and seven base materials were compared, and the results showed significant variation in predicted performance as a result of the change in the input level and material type.

THE EFFECTS OF (RAP) ON THE LABORATORY PERFORMANCES OF HOT MIX ASPHALTS

The use of reclaimed asphalt pavement (RAP) in flexible pavement surface layer has been a major sensitive issue in the construction industry. Due to limited space available in landfills, the amount of high quality virgin aggregate declines, and the high price of oil, the use of RAP in new asphalt concrete mixtures has become very attractive. This research has been conducted to study the laboratory performances of HMA mixture containing RAP, in which Marshall properties and resilient modulus characteristic were evaluated [4,6,7]. A Marshall mix design mixture containing 0% RAP with binder (60/70) was used as the control mixture for evaluating properties of mixtures containing 25% and 40% RAP. Marshall tests and Indirect Tensile Modulus (Resilient Modulus) were performed on samples of the three mixes. Comparing the results of the conducted tests indicated that the use of RAP in Hot Mix Asphalt (HMA) was advantageous in all properties measured. The mix containing RAP showed reduction in Marshall Stability, indirect tensile value, and Resilient Modulus, and the higher the temperature the lower of resilient modulus values, but the results are acceptable by Egyptian code specifications. Therefore, it is preferred to use mixes containing RAP in highways with studied proportions.