Resilient Modulus Tests Research Articles

Performance of asphalt mixture incorporating kaolin clay at different aging

In the fast-changing construction industry, the usage of natural material resources is tremendous. In order to comply with the demand of construction, waste materials have been used as a replacement of natural mineral resources. In pavement engineering, waste materials can be added into road composition. Kaolin clay is one of industrial waste materials successfully been used as a replacement of cement in concrete, but in the pavement, it has lack extensive study. In this investigation, kaolin clay partially replaced bitumen and the performance of aged asphaltic concrete AC14 were investigated. Kaolin clay replaced bitumen at 0%, 3%, 6% and 9% by weight of bitumen were used through this study. Tests conducted to measure the mixture performance were Marshall Stability, resilient modulus and dynamic creep test. Generally, it shows that the samples of unaged and long-term aging of asphalt mixture containing kaolin clay at 6% to 9% showed excellent, while 9% kaolin clay were most favorable for short term aging.

Creep and resilient modulus properties of asphaltic concrete containing black rice husk ash

Black rice husk ash (BRHA) is one of the agro-waste that could be used to improve the properties of asphalt mixture. In this investigation, the BRHA was grounded using a laboratory ball mill with porcelain balls to fine particles size less than 76 μm. Four different BRHA contents were considered in this study namely 0%, 2%, 4% and 6% by weight of binder. The performance of asphaltic concrete containing BRHA was evaluated through resilient modulus and dynamic creep test. It was found that the BRHA can be satisfactorily used as a filler material in order to increase the properties of creep and stiffness modulus asphaltic concrete. Test results also indicate that asphaltic concrete containing 2% to 4% BRHA showed excellent performance to resilient modulus and dynamic creep properties.

Evaluation of cement stabilized recycled concrete aggregates treated with waste oil and asphalt emulsion

This research was undertaken to comprehensively evaluate the performance of cement stabilized recycled concrete aggregates treated with waste oil and asphalt emulsion from the aspect of strength, stiffness, and shrinkage properties. A suite of laboratory tests were carried out, including vibratory compaction test, unconfined compressive strength (UCS) test, indirect tensile strength (ITS) test, resilient modulus test, drying shrinkage test, and temperature shrinkage test. The results of UCS and ITS tests showed that both treatments resulted in an acceptable reduction in early-age strength of mixture, but later the treated mixtures had a relatively rapid increase in strength compensating for this deficiency to some extent. The asphalt emulsion treated mixture has a higher strength than the mixture treated with waste oil. The results of resilient modulus test showed that both treatments effectively decreased the stiffness of mixture within the appropriate range and this decrease was much pronounced for the mixture treated with waste oil. The drying shrinkage test indicated that drying shrinkage properties of mixture were improved obviously after treatments and waste oil treatment produced a better effect compared with asphalt emulsion treatment. Furthermore, both treatments also caused a slight improvement to temperature shrinkage properties of mixture revealed by temperature shrinkage test. Overall, both treatments have achieved a satisfactory effect and the use of waste oil and asphalt emulsion is environmentally friendly.

Evaluation of performance and moisture sensitivity of glass-containing warm mix asphalt modified with zycothermTM as an anti-stripping additive

The rising repair and maintenance costs of road and airstrip pavements subjected to frequent and repeated traffic loading is a major impetus for researches to delve into the use of additives and admixtures in the asphalt mixture production. The primary goal of these efforts is to improve the durability and load-bearing performance of asphalt mixtures. Due to favorable properties, such as high stiffness, all-around fracture, and high internal friction angle, crushed glass may be used as a high-potential additive for improving asphalt mixtures’ quality. Despite the many advantages of crushed glass, the inadequate adhesion between bitumen and glass particles can lead to stripping and reduced strength of glass-containing asphalt mixtures (glass-asphalt). In this study, glass particles were used, as aggregates in warm mix asphalt (WMA) mixtures. Four different amounts of zycothermTM were used in WMA mixtures to serve as bitumen modifier and anti-stripping agent. The performance properties of the pure bitumen and the zycothermTM-modified bitumen were evaluated through Scanning Electron Microscopy (SEM), Fourier Transform Infrared spectroscopy and bitumen tests. The WMA specimens and control specimens were also subjected to the modified Lottman test, resilient modulus test, and creep test. The results showed that use of zycothermTM as an anti-stripping agent considerably improves the performance properties and moisture sensitivity of glass-asphalt.

Influence of aging on properties of polymer-modified asphalt

Although the use of polymeric additives has been widely accepted as a promising strategy to improve broad spectrum of pavement deficiencies, aging-induced mechanisms of polymer-modified asphalt binders and mixtures still have critical aspects that should be studied to a comprehensive extent. The primary objective of this paper is to advance the understanding of aging effect on the properties of polymer-modified asphalt binders and mixtures. In this study, six different polymeric products were of specific interest: styrene-butadiene-styrene (SBS), polypropylene (PP), styrene-acrylonitrile (SAN), high-density polyethylene (HDPE), polycarbonate (PC), and acrylonitrile-butadiene-styrene (ABS), each was applied at rates of 2% and 5% (by the wt. of asphalt binder) to prepare polymer-modified binders and mixtures. The prepared binders passed thin film oven test (TFOT), while the mixtures were subjected to normal and 16 h production aging. The compositional analysis of asphalt binders was discussed based on the elemental analysis tests while the penetration, ring and ball, and rotational viscosity tests were further studied to evaluate the physical properties. The asphalt mixtures were evaluated based on a series of engineering performance-based properties using indirect tensile strength (ITS), moisture susceptibility, uniaxial static creep-recovery, resilient modulus, and diametral fatigue tests. The fatigue tests were conducted without and with rest period so as to provide insight into the healing potential of different modified mixtures. The results showed that the aging increased the carbon component in all blends; however mixed results were attained regarding hydrogen, sulphur, and nitrogen. No obvious trends were ascertained for carbon, hydrogen, nitrogen, and sulphur due to polymer modification. Aging induced effects on polymer-modified binders and mixtures are highly dependent on the polymer type and modification level. Polymer modification had positive influence on ITS, creep strain and recovery ratio, resilient modulus, resistance to moisture damage, and fatigue life. Fatigue tests with rest period proved that the polymer-modified mixtures have higher tendency to heal compared to the unmodified mixtures, which resulted in an improvement in the fatigue performance of the mixtures. Except for the fatigue life, the aging of polymer-modified asphalt mixtures had no detrimental effect on the studied mechanistic properties.

Considerations for laboratory resilient modulus testing of unbound pavement base materials

This paper explains equipment related considerations on differences between the lab and field conditions that can lead to variations in resilient modulus (Mr) values of unbound materials as determined in accordance with AASHTO T307 standard. Three different granular materials and an elastic polyurethane (control) sample were tested using commercially available laboratory test equipment. A field test bed was also constructed to measure vehicle (Class 3) induced loading conditions at the bottom of an unbound granular layer underlying new hot-mix asphalt pavement to determine stress pulse duration as a function of vehicle speed. Various interpretation issues were identified within the framework of the testing methods and equipment including: (1) insufficient laboratory sensor sampling rate (per standard); (2) the laboratory specified 0.1 s load-pulse duration and haversine shape are not matching the field stress pulse duration and shape; (3) the need for careful tuning of the load system gain settings; (4) the number of LVDTs used in the vertical strain calculation; (5) limiting quality control and quality assurance to deformation ratio values in the preconditioning sequence; and (6) limiting the load step calculations to the last 5 of 100 load cycles. The goal of this paper is to provide equipment users and specification developers with user knowledge concerning laboratory resilient modulus determination.

Equivalent Modulus of Asphalt Concrete Layers

A flexible pavement structure usually comprises more than one asphalt layer, with varying thicknesses and properties, in order to carry the traffic smoothly and safely. It is easy to characterize each asphalt layer with different tests to give a full description of that layer; however, the performance of the whole; asphalt structure needs to be properly understood. Typically, pavement analysis is carried out using multi-layer linear elastic assumptions, via equations and computer programs such as KENPAVE, BISAR, etc. These types of analysis give the response parameters including stress, strain, and deflection at any point under the wheel load. This paper aims to estimate the equivalent Resilient Modulus (MR) of the asphalt concrete layers within a pavement structure by using their individual MR values. To achieve this aim, eight samples were cored from Iraqi Expressway no. 1; they had three layers of asphalt and were tested to obtain the MR of each core by using the uniaxial repeated loading test at 25 and 40 °C. The samples were then cut to separate each layer individually and tested for MR at the same testing temperatures; thus, a total of 60 resilient modulus tests were conducted. A new approach was introduced to estimate the equivalent MR as a function of the MR value for each layer. The results matched the values obtained by KENPAVE analysis.

Optimum parafibre length according to mechanical properties in hot mix asphalt

Fibre is additive to hot mix asphalt that can improve fatigue life, rutting resistance, durability of asphalt concrete mixtures, creep compliance, tensile strength, dynamic modulus, elasticity, viscoelasticity, and reflective cracking. The fibres can be useful in controlling the cracks. Previous studies on various fibres have mostly focused on changing and optimising fibre percentage. No study has been conducted on appropriate fibre length in the mixture. Therefore, the effect of various fibre lengths on mixture properties needs to be clearly determined. The aim of this study was to evaluate the effect of various parafibre lengths on mechanical properties of hot mix asphalt through Marshall strength, indirect tensile strength, and resilient modulus tests. To achieve this, we added 0.5% fibre by weight of the asphalt mixture with lengths of 3, 6, 9, 12, 15, and 18 mm to hot mix asphalt samples and performed the above tests on the samples. The results showed that fibre improves hot mix asphalt mechanical properties; however, fibre percentage needs to be increased as the length increases, so that there are sufficient fibres present in the mixture to act against cracks. Accordingly, in all three tests, 12 mm fibres at 1% fibre content created the highest values. Therefore, the optimal fibre length was 12 mm, and for this length the most affected properties were resilient modulus, indirect tensile strength, and Marshall strength, respectively.

The use of copper slags as an aggregate replacement in asphalt mixes with RAP: Physical–chemical and mechanical behavioural analysis

Copper slag (CS) is a derivative of copper production that is mainly composed of heavy metals. The large amount of this material accumulated around the world entails a serious environmental danger. Its use as a replacement of mineral aggregate in asphalt mixtures would allow to increase the durability and resistance, taking advantage of its physical-chemical properties. In this research, physicochemical analyses of different combinations of CS, reclaimed asphalt pavements (RAP), asphalt cement and aggregates by X-Ray Diffraction (XRD) and Fourier-Transform InfraRed spectroscopy (FT-IR) were developed. Subsequently, Marshall stiffness ratio, indirect tensile strength (IDT) and resilient modulus tests were performed to determine their implication in mechanical behaviour.Asphalt mixes with ranges from 45 to 55% of recycled material have improved stability, Marshall Flow and Stiffness ratio, obtaining values comparable with those from a conventional mixture. At the same time, its resilient modulus and IDT values increased by 35% compared to conventional mixes. To maintain values similar to conventional mixes, when the amount of RAP decreases the amount of CS should be increased, with a maximum value of 35%. This behaviour is explained by the presence of fayalite and magnetite in CS, which are hard, dense and hydrophobic components that produce increased elastic deformation of the binder before breaking.

The Effect of Bottom Ash on Soil Suction and Resilient Modulus of Medium-Plasticity Clay

The effect of adding bottom ash to medium-plasticity clay as a soil stabilizer was evaluated in this study by performing triaxial resilient modulus tests. Two log–log resilient modulus prediction equations found in the literature (MEPDG and NCHRP 1-28) were selected and calibrated for mixtures of bottom ash and clay at different moisture contents. It was found that, with 25% bottom ash in the mixture, the resilient modulus increased between 5% and 23% under different stress states. The soil total and matric suctions of the mixtures were indirectly measured using the filter paper method, and the total suction parameter was incorporated in the two log–log prediction models. The nonlinear regression analysis revealed that the average goodness-of-fit statistics for one of the modified models showed highly satisfactory performance in predicting the resilient modulus values.

Mechanical Characterization of Pavement Granular Materials Using Hardening Soil Model

Various testing methods, such as the static triaxial test, cyclic resilient modulus test, repeated-load static triaxial test, repeated-load California Bearing Ratio (CBR) test, and repeated-load oedometer test, were explored to characterize pavement granular materials. Using such methods, an experimental data set of the stress–strain response of a typical granular material was collected. The modulus values as obtained from the cyclic triaxial tests and the various repeated-load tests were compared. The feasibility of predicting the behavior of the granular material using the hardening soil model was analyzed. Hardening soil model parameters were calibrated using simple static triaxial test data. The effectiveness of the model in predicting the material behavior was then verified by predicting the other experimental results using the hardening soil model with a finite-element implementation. The stress–strain behavior as predicted by the model matched well with the experimentally measured stress–strain values; hence the validity of the hardening soil model was ascertained.

Low cement/fly ash blends for modification of Crushed Rock Base material

Crushed Rock Base (CRB) material sometimes needs to be modified typically due to the moisture susceptibility. Resilient modulus is the dominant design parameter of unbound materials and should be high enough to avoid distress or failure of a pavement. In Western Australia (WA), some modification methods such as dry-back or Hydrated Cement Treated Crushed Rock Base (HCTCRB) have been implemented in trial sections of pavements. But they could not provide the desired performances by poor drainability or widely-spaced open cracks in surface of thin bituminous pavements. As such, this paper attempts to review the challenges of each method and show how design requirements can be provided by another option so-called low cement/fly ash blends even in saturated conditions. This method covers the deficiencies of two previous methods in terms of cracking or moisture susceptibility as observed in limited field tests. Series of laboratory tests including uniaxial compression strength, resilient modulus, tube suction and shrinkage tests are undertaken to explore the key features of this modification method. Typical results indicated that resilient modulus improved two times while strength, shrinkage and capillary rise of this material are in the acceptable level.

Effect of aging conditions on the fatigue behavior of hot and warm mix asphalt

The aging process has a significant effect on the mechanical properties of asphalt mixtures, especially on fatigue parameter. Many approaches have been suggested to better understanding of the fatigue behavior of asphalt mixes. However, in many of these cases, the effects of aging are not considered. In this study, investigations were conducted to more accurately predict the fatigue life of asphalt mixes, independent of their ages. In this regard, the responses of the existing fatigue models in a wider range of asphalt mixtures were validated. For this purpose, hot and warm asphalt mixtures were used in both aged and unaged conditions. For the production of warm mixtures, Sasobit and RheoFalt were used as modifier additives. Indirect tension (IDT) test, resilient modulus and four-point bending fatigue beam test were performed separately WMA and HMA specimens. The results indicated that in all specimens, the aging of the asphalt mixture was always accompanied by increasing fracture energy and failure resistance. In addition, it was also found that those fatigue models that were based on simple performance tests failed to well predict the fatigue life of mixtures independently of the type of compounds, aging and loading conditions. Eventually, validations indicated that the behavior of dissipated energy during repeated loading to failure, have a significant role to precisely characterize the fatigue behavior independent of their age.

Investigation of the mechanical properties and carbonation of construction and demolition materials together with rubber

One of the ways to improve the strength properties of construction and demolition (C&D) wastes is to adopt the accelerated carbonation technique. The main objective of this study was to evaluate the effects of the eco-friendly carbonation approach on the mechanical properties of C&D aggregates together with crumb rubber. Crumb rubber with particle sizes ranging from 400 to 600 μm was added to the 20 mm recycled concrete aggregate (RCA) and crushed rock (CR) at 0.5, 1, and 2% by weight percentage of the aggregates. Then, the unconfined compression strength (UCS) and resilient modulus (Mr) tests were conducted on the carbonated RCA and CR samples together with crumb rubber, and the results were compared with those of the uncarbonated specimens. The results showed that the carbonation process led to a significant increase in the UCS values. However, carbonation resulted in a decrease in the deformability of the specimens compared with the uncarbonated specimens. Moreover, carbonation resulted in a significant increase in the Mr values compared with those of the uncarbonated values. Also, the carbonation process had a more substantial effect on the Mr values of the CR than of the RCA.

Evaluating the feasibility, usability, and strength of recycled construction and demolition waste in base and subbase courses

Demolition and repairing of buildings produce large amounts of construction and demolition waste. The produced debris not only takes up space, but also leads to environmental degradation, unpleasant scenery, and above all, waste of construction materials and money. In this regard, recycling is a good solution that has received less attention in the construction section than other sections of industry. In road construction, part of the large amount of aggregates used in pavements can be provided from recycled construction and demolition (C&D) Waste. The aim of this laboratory study was to evaluate feasibility and usability of C&D in base and subbase courses of pavement. For this purpose, usable C&D materials were separated and the proportion of each was determined. Each material was passed through a crusher and a 25 mm sieve. The segregated materials were then mixed and technical specifications of the mixture were controlled against AASHTO standards. Finally, mix proportions were determined so that AASHTO technical specifications were satisfied. For this purpose, different percentages of C&D were mixed with control sample materials and technical specifications of the result were evaluated using compaction, California bearing ratio (CBR), and resilient modulus tests. The results showed the necessity of C&D decomposition, using crusher and sieve to control maximum grain size allowed, and exclusion of materials not complying with technical standards, before performing strength evaluations. Proportions of waste components must be selected so that all technical specifications are satisfied. Sometimes it might be necessary to mix waste materials with additional standard ones to achieve a technically standard final result. In this study, compaction and CBR tests showed that the obtained mixture is suitable for use in base and subbase layers but minimum requirements of resilient modulus for the base course are not met. Alterations in mixture components resulted in a significant reduction in C&D content for the base course. Therefore, it is recommended that C&D is used only in subbase layers of pavements.

Resilient modulus testing with application of cyclic CBR test for road subgrade materials

This article is not available for publication.

The Performance of Controlled Low-strength Material Base Supporting a High-volume Asphalt Pavement

A lack of proper base and subbase materials in pavement construction is one of the common problems in the tropical region worldwide. In many countries such as Thailand, cementitious materials are usually used for ground improvement. Controlled Lowstrength Material (CLSM) was considered in this study as a pavement base material. The CLSM mixes were prepared by varying cement, fly ash and fine aggregate content. Each mixed component was studied for their physical and chemical properties. After mixing, properties of the CLSM were investigated based on the standard testing of fresh concrete and cement-treated base material. The flowability, setting time and bleeding were checked to ensure that the CLSM were self-compacting. The mechanical properties of hardened CLSM were determined by means of CBR, unconfined compressive strength and resilient modulus tests. The resilient modulus results were used in the analytical design of flexible pavement with CLSM base. The critical traffic data under high-volume road collected by the Thailand Department of Highway was adopted in this study. Results show that the CLSM base considerably increased the performance as well as design life of asphalt pavement compared with the conventional crush rock base pavement.

Modeling Stress-Dependent Anisotropic Elastoplastic Unbound Granular Base in Flexible Pavements

Unbound granular base (UGB) has a cross-anisotropic and nonlinear (stress-dependent) modulus with a plastic behavior. Existing UGB models address nonlinear cross-anisotropy and plasticity separately. It is unknown how the two characteristics are coupled into a finite element model (FEM) and how this will affect the pavement responses. This study presents a coupled nonlinear cross-anisotropic elastoplastic (NAEP) constitutive model for the UGB and implements it in a weak form equation-based FEM. No material subroutine is needed to address the circular dependence between the stress-dependent anisotropic modulus, structural stress responses, and elastoplastic deformation. The NAEP model was calibrated by triaxial resilient modulus and strength tests and validated using laboratory measurements in a large-scale soil-tank pavement structural test. It is found that the NAEP model is valid and effective in predicting the UGB responses in flexible pavements. The model predicted less horizontal tensile stresses at the base bottom and introduced compressive stresses in the middle and top of the base course. This is caused by an increasing confinement resulting from a horizontal plastic dilation in the base course, which cannot be modeled without considering plasticity. The stress-dependent modulus for the UGB material decreases with depth and the distance from loading centerline. Compared with a nonlinear anisotropic elastic model, the NAEP model predicted the same tensile strain at asphalt layer bottom, a higher base modulus, and a higher subgrade compressive strain. Thus, the nonlinear anisotropic elastic UGB model results in the same fatigue life as the NAEP model but may riskily under-predict rutting damage.

A Practical Approach for the Estimation of Strength and Resilient Properties of Cementitious Materials

Cementitious stabilization of granular soils has been proven to be a cost-saving option for the use of materials with marginal quality in the construction and rehabilitation of pavement structures. The orthogonal load distribution capacity of the Cement-Stabilized Materials (CSM) is typically characterized by Unconfined Compressive Strength (UCS), Indirect Tensile Strength (IDT), and Resilient Modulus (Mr) tests in the laboratory. The aforementioned parameters and properties are integral components of the analysis and design of pavements with stabilized layers. Time and budget constraints make it impractical for many state agencies to complete the full laboratory characterization protocols to determine all the design input parameters. Therefore, in many cases, the design engineers opt out of laboratory testing and primarily rely on past experience and engineering judgments to assign design input parameters. Such an approach compromises the reliability of the pavement life predictions, and can potentially incur unforeseen costs to the traveling public. This study was designed to bridge this gap by developing a series of statistically robust relationships between the laboratory achived data to provide an estimate of the design input parameters. To accomplish this objective, 570 stabilized cylindrical specimens were prepared and subjected to UCS, IDT, and submaximal modulus tests at three strength ratio levels. Subsequently, the relationships between the IDT, UCS, and resilient modulus at small-strain and intermediate strain levels were developed in this study. Such relationships can serve as a valuable means for the estimation of the tensile and compressive strength of the CSM for pavement design.

Mechanical performance of asphalt mixture containing nano-charcoal coconut shell ash

Rutting and fatigue cracking are issues in pavement engineering that led to numerous studies for improving pavement performance. Bitumen modification by nanomaterials is a method that can enhance the performance of asphalt mixtures due to the large surface area and small size (1–100 nm) of nanomaterials. Therefore, this research was focused on the influence of nano-charcoal coconut shell ash (NCA)-modified bitumen towards the engineering properties of asphalt mixtures. Engineering property tests were carried out on 0% (control), 1.5%, 6% and 7.5% NCA asphalt mixtures. These tests include Marshall analysis, indirect tensile strength (ITS), resilient modulus and dynamic creep test. The microstructure properties of the asphalt mixtures were evaluated using Atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). Results showed that the Marshall stability, ITS, resilient modulus and dynamic creep of the asphalt mixture were significantly improved with the addition of 6% NCA. AFM results showed that 6% NCA has the lowest surface roughness which improved the adhesion of asphalt mixture. Flat and dense asphalt mixture was observed from FESEM which contributed to the enhancement of asphalt mixture engineering performance.