Resilient Modulus Tests Research Articles

Evaluation of rutting potential of asphalts using resilient modulus test parameters

Rutting potential of asphalts can be evaluated in the laboratory by different tests. Any visco-elastic parameter of the mix evaluated at a high pavement temperature can be considered to be a possible parameter to distinguish mixes in terms of their rutting susceptibility. In this study, the potential of the time lag (between load and deformation) observed in a resilient modulus test as an appropriate parameter to explain the rutting resistance of different mixes has been examined. Resilient modulus is a parameter routinely evaluated by many agencies and is used as an input for design and evaluation of pavements. Time lag values were extracted from the resilient modulus test conducted at 35°C and 50°C on asphalt mixes prepared with (a) nine different types of binder and one aggregate gradation and (b) nine different aggregate gradations and with VG30 binder. A wheel tracking test was conducted on the mixes at 60°C. Time lag has been found to be sensitive to bitumen type and aggregate gradation. A strong correlation was observed between the time lag and rut depth measured in the wheel tracking test. It is evident from the present study that time lag measured from the resilient modulus test, which is conducted routinely by many agencies, has the potential to be used as a mix rutting parameter.

Investigating the indirect tensile stiffness, toughness and fatigue life of hot mix asphalt containing copper slag powder

ABSTRACTThis paper presents the results of an experimental investigation accomplished on hot mix asphalt (HMA) containing copper slag powder (CSP) as filler material compared to conventional HMA prepared with limestone powder (LSP). Indirect tensile strength (ITS), resilient modulus (Mr) and fatigue tests were performed on four groups of HMAs containing 6% LSP, 4% LSP + 2% CSP, 2% LSP + 4% CSP and 6% CSP by total weight of aggregates. Furthermore, the environmental impacts of using CSP were investigated using toxicity characteristics leaching procedure test. Based on the obtained results, the mechanical properties of HMA improved by increasing the CSP content. On average, the ITS, TIit, Mr and fatigue life of HMA containing 6% CSP were 10.2, 8.5, 7.5 and 21.6% higher than the control mix. The results of correlation analysis showed a significant relationship between the fatigue life-Mr and fatigue life-TIit parameters. For all strain levels, the correlation coefficients obtained for TIit were higher than those obtained for Mr. Concentration of heavy metals in leachates gathered from the CSP and the HMA containing this filler satisfied the needed criteria.

Performance of warm mix asphalt containing Moringa oleifera Lam seeds oil: Rheological and mechanical properties

The existence of an environmental crisis resulting from the unbalanced exploration of natural resources is a concerning situation and entails the need for sustainable development. In the paving sector, warm asphalt mixtures, which are produced in lower temperatures than conventional mixtures, reduce the impacts to the environment and workers health, and the energy consumption. Among the techniques developed to the production of warm mixtures, it is highlighted the addition of an oil, usually organic, to the conventional binder, decreasing its viscosity. Moringa oleifera Lam seeds have an oil content varying between 38 and 40% and have antioxidant and lubricant properties. The present work aimed to analyze the rheological properties of asphalt binder and the mechanical properties of asphaltic mixtures using modified binders by the addition of Moringa oil in the contents of 0.5 and 1.0%. It was performed the physical characterization of binders and aggregates used. The Marshall Mix design method was performed and specimens for mechanical tests were produced. The results for Marshall Stability, Flow, Cantabro Loss, Indirect Tensile Strength, Resilient Modulus, Fatigue Life and Dynamic Creep tests were satisfactory when compared to results for the reference sample (using pure binder).

Mechanical performance of asphaltic concrete incorporating untreated and treated waste cooking oil

In recent years, various oil-based modifications that involve the use of waste cooking oil (WCO) have been applied to deliver obvious benefits to the pavement industry. This effort is in line with the response to the issue of waste management. The current constraint in dealing with WCO is its declining rutting resistance performance at high temperatures. This issue is observed globally and remains unresolved. Adverse rheological performance induces the rutting issue due to the high susceptibility of WCO toward temperature exposure. The pretreatment of WCO is proposed as an extensive research work that aims to produce treated WCO before its addition to HMA. However, the potential of treated WCO is still at the empirical stage and still questionable. Therefore, a mechanical test was performed on the control, 5% untreated WCO, and 5% treated WCO mixtures to evaluate any improvement in the performance of the HMA incorporated with untreated and treated WCO. The mechanical test included the Marshall Stability, resilient modulus, creep stiffness, and indirect tensile strength (ITS) tests. Microstructure observation was performed using an atomic force microscope (AFM) to identify the surface roughness related to the adhesion properties. Results shows an improvement in Marshall Stability, resilient modulus, and ITS performance was recorded with the replacement of 5% treated WCO in bituminous mixture. In addition, the highest creep stiffness, with an enhancement of about 25% relative to the control mixture, was achieved with the 5% treated WCO mixture to resist permanent deformation. The microstructure observation revealed that the lowest surface roughness produced with the treated WCO in modified binder contributed to the improvement of adhesion bonding that increased the strength of the asphalt mixture.

Performance Evaluation of Elvaloy as a Fuel-Resistant Polymer in Asphaltic Concrete Airfield Pavements

This paper investigates the influence of fuel-resistant polymer on the consistency and performance properties of asphalt binder and hot mix asphalt (HMA) mixtures. The study uses wearing course gradation (nominal maximum size of 19 mm), penetration grade 60/70 bitumen, and Elvaloy reactive elastomeric terpolymers (RET) 4170 as a fuel-resistant polymer. Laboratory tests conducted on unmodified and modified (1-4% Elvaloy) mixtures include an indirect tensile (IDT) strength test and a resilient modulus (M) test for evaluating cracking potential and stiffness parameters, respectively; a Hamburg wheel tracker (HWT) test for quantifying the rut propensity; and a solubility test to determine the fuel-resistance capacity. The two-level factorial design of the experiment is conducted on the rheological properties of the binder including elastic recovery/complex modulus and creep stiffness values, which suggest that 1% polymer-modified binder (PMB) is least susceptible to high-temperature and low-temperature variations. Performance evaluation reveals that 1% PMB is an optimal proportion of Elvaloy in asphalt concrete mixtures, yielding maximum M values (both before and after conditioning in fuel), the lowest rut susceptibility, and high fuel resistance. This research is useful for public aviation/highway agencies and private contractors to minimize the deterioration caused by fuel slippage and to control foreign object debris damage to aircraft.

Effect of copper slag on performance of warm mix asphalt

ABSTRACTCopper Slag (CS) is a by-product obtained during the matte smelting and refining of copper. It is classified as waste materials and, therefore, is considered as an environmental issue to cope with. It can be effectively used for construction of pavement layers. On the other hand, in order to save energy and reduce the amount of pollutants released during asphalt production, Warm Mix Asphalt (WMA) technology can also be employed. This paper presents the influence of replacing limestone aggregates by copper slag on the performance of warm mix asphalt. Optimal Binder Contents (O.B.C) of asphalt mixes containing CS proportions of 0, 10, 20, 30 and 40% by total weight of aggregate were determined using Marshall procedure. Results of Indirect Tensile Strength, resilient modulus, flow number and wheel tracking tests indicated that 20% CS in WMA enhances resilient modulus, Marshall stability, rutting and cracking resistance the most and has substantial positive effect on moisture susceptibility.

Exploration in the test of splitting resilient modulus of asphalt mixture

In terms of the non-correspondence about the bottom layer tensile stress provided by the compressive resilient modulus and the allowable tensile stress obtained by the splitting test, this paper puts forward the methods about splitting stepping testing by contrasting the compressive resilient modulus testing methods. Both the stepping load and resilient deformation are recorded. With the help of the concept of splitting stiffness modulus, the expression of splitting resilient modulus can be obtained to gain the splitting resilient testing flow. The results show that the resilient modulus which is measured by splitting stepping load can meet the design ranges of asphalt mixture and the stepping loading methods about splitting resilient modulus are worth popularizing.

Laboratory characterization of reclaimed asphalt pavement for road construction in Egypt

This paper presents the engineering characteristics of reclaimed asphalt pavement (RAP), blended with virgin aggregate for unbound base and subbase layers. The proportions of RAP were 0%, 20%, 60%, 80%, and 100% by total mass of the blend. The experimental laboratory testing included index properties such as gradation, modified Proctor compaction, California Bearing Ratio, and hydraulic conductivity. Repeated load resilient modulus testing was conducted on the blends. The impact of load duration on resilient modulus was also investigated. A strong inverse trend was found between resilient modulus and California Bearing Ratio. An accurate model was proposed for the prediction of the resilient modulus as a function of stress state and reclaimed asphalt pavement percentage with coefficient of determination of 0.94. Finally, multilayer elastic analysis of typical pavement sections with the base layer constructed of virgin aggregate and reclaimed asphalt pavement blends showed good performance.

Application of the theory of viscoelasticity to evaluate the resilient modulus test in asphalt mixes

This paper deals with the analysis of indirect tensile resilient modulus (IT RM) tests for asphalt mixes. In Brazil, for instance, asphalt mix stiffness is obtained from a classical elastic analysis of the referred test, which may not be suitable for a viscoelastic material. A method is proposed to compare IT RM results from classical experimental analysis and from tests simulated with viscoelastic models. Four different asphalt mixes with four different binders were analyzed using IT RM tests, with varying loading time and temperatures. Complex modulus (E∗) tests were performed to characterize the linear viscoelastic behavior of the investigated materials on a wide range of temperature and frequency. 2S2P1D model and general Kelvin Voigt (GKV) model were then fitted to the E∗ data. IT RM tests results were calculated using an analytical method and the viscoelastic GKV models obtained for the four mixes. Differences found for the stiffness results obtained from the distinct procedures are discussed, and pavement analyses showed that such differences substantially affect the structural response. This is to be expected as a consequence of the missing of fundamental considerations on the material behavior.

Evaluating the performance of very weak subgrade soils treated/stabilized with cementitious materials for sustainable pavements

Abstract This paper presents the results of laboratory tests that were conducted to determine the proper treatment/stabilization recipe of very weak subgrade soils at high moisture contents, and to evaluate the corresponding performance-related properties [e.g., the resilient modulus and permanent deformation] for use in the design of sustainable pavement structures. Four different subgrade soil types of different plasticity indices were considered in this study. Three different moisture contents were selected at the wet-side of optimum that correspond to a raw soil strength value of 172 kPa (25 psi) or less. All the soils were treated with different combinations of class C fly ash (or Portland cement type I) and hydrated lime to achieve a 7-day target strength values of 345 kPa (50 psi) to create a working platform and 690 kPa (100 psi) to stabilize the subgrade for subbase application. Repeated load triaxial (RLT) tests were performed on laboratory molded specimens to evaluate their resilient modulus and permanent deformation behavior under cyclic loading. The AASHTO T-307 procedure was followed in this study to conduct the resilient modulus tests. A good correlation was observed between the water/additive ratio and the resilient modulus/permanent deformation, such that the soil specimens prepared at low water/additive ratio showed better performance than those prepared at high water/additive ratio. The results of laboratory tests showed that the use of direct correlation between unconfined compressive strength (UCS) and resilient modulus for cementitiously treated/stabilized soils can be misleading.

A comprehensive field and laboratory test programme and electronic database of pavement material properties for MEPDG

ABSTRACTTo locally calibrate the Mechanistic-Empirical Pavement Design Guide (MEPDG) for the state of Wyoming, a comprehensive test programme and analyses were conducted. The field test programme included falling weight deflectometer tests, standard penetration tests, dynamic cone penetration tests and soil sampling. These field tests were conducted at 12 locations or 36 sites in the state of Wyoming. Subgrade soils collected from the field were characterised by a series of laboratory soil tests including resilient modulus tests, resistance-value tests and standard Proctor density tests. This test programme accumulated significant valuable soil data for local MEPDG calibrations. To efficiently store the results from the field and laboratory testing, an electronic WYOming MEPDG Database was developed using Microsoft® Access. Specific data or inputs requested by user are efficiently and easily sorted, filtered and queried using the database. Laboratory measured resilient modulus, resistance-values and standard Proctor properties of subgrade materials were used to develop both multivariate and univariate multi-regression models to accurately estimate resilient modulus for MEPDG Level 2 design inputs. Statistical parameters were used to effectively evaluate the performance of developed regression models. The resistance-value and optimum moisture content of subgrade soils were determined as important predictors in both models. The research outcomes facilitate the local calibration and implementation of the MEPDG.

USE OF CBR MOULD FOR EVALUATION OF CONSTRAINED MODULUS-BULK STRESS RELATIONS OF PAVEMENT STRUCTURE MATERIALS

One of important parameters used in the mechanistic pavement engineering design is resilient modulus (MR) of pavement structure materials. In general, MR is evaluated in a complicated and thus expensive triaxial compression test in that a number of repeated loads are applied at various stress states. This researchpresents an alternative method to determine the constrained modulus (M) of a dried sand, a lateritic soil and a crushed rock, under one-dimensional compression. At various vertical stress levels, M values were determinedby applying small strain-amplitude cyclic loadings to the compacted soil specimens prepared in a CBR mould. In the present study, the CBR mould was made special in that it can measure the lateral stress confining to the specimen during a test. Hence the bulk stress () can then be determined, and M- relations for the tested materials were presented. In addition, an analytical method for eliminating the effects of bedding error was attempted so as to obtain the true M value. It is found that M is not constant but increases with , similar to MR- relations found with the resilient modulus test. In addition, the bedding error is important and can result in a significant underestimation of the true M value.

Investigation of fatigue cracks on RAP mixtures containing Sasobit and crumb rubber based on fracture energy

Fatigue cracking, rutting and low temperature cracking are three major distresses of asphalt mixtures. In last years, different methods based on fracture mechanic have been developed to measure performance of asphalt mixtures due to cracking. In this study, fracture mechanic method developed by Roque et al. has been employed to evaluate fatigue cracking performance of modified asphalt mixtures. Samples containing Reclaimed Asphalt Pavement (RAP) with different percentages of Sasobit (as a Warm Mix Asphalt additive) and crumb rubber were built. Resilient Modulus, static creep and Indirect Tensile (IDT) tests also conducted on samples and Resilient Modulus, creep compliance and Indirect Tensile Strength were measured. Based on fracture mechanic, Dissipated Creep Strain Energy (DCSE) was calculated for each sample, and fatigue strength of mixtures were investigated. The results indicated that the use of RAP, crumb rubber and Sasobit simultaneously caused desirable fatigue performance of modified mixtures. These mixtures had better Resilient Modulus and more loading capacity, as well as, lower cumulative damage rates rather than virgin sample. The ITS results also indicated more appreciable improvement in crack initiation threshold, Fracture Energy (FE) and Energy Ratio (ER).

Mechanical performance of asphalt mixtures using polymer-micronized PET-modified binder

The global engineering plastics market has been growing as it replaces materials such as glass and metal. It can be used in a wide variety of products and technologies in other sectors of the economy such as energy generation, automotive, maritime, construction, electronics, packaging, and others. However, this increase in global use presented problems with respect to the increase in plastic waste generation. The existence and destination of plastic waste in the soil and hydric resources has been recognised as an emerging issue in preserving the environment. In this research, Micronized Polyethylene Terephthalate (micronized PET) was used as an additive for asphalt mixtures. The polymer was mixed in amounts of 4%, 5%, and 6% by weight with an asphalt binder base and mechanical tests were performed. Two SUPERPAVE mix design methods were performed. The first one was made with pure binder and the optimum binder content was determined and the specimens were analysed according to the following parameters: Resilient Modulus (RM), Lottman, and Indirect Tensile Strength (ITS). A second mix design procedure was performed with the optimum PET content according to the best results obtained in the first one, and analysed according RM, ITS, Lottman, Fatigue, and Flow Number tests. The results show significant improvements on mechanical properties of the asphalt mixtures with micronized PET compared with asphalt mixtures without additive.

Long-term ageing of asphalt mixtures

Ageing of asphalt mixtures occurs during production and construction and continues throughout the service life of the pavement. Although this topic has been studied extensively, recent changes in asphalt mixture components, production parameters, and plant design have raised a need for a comprehensive evaluation that considers the impacts of climate, aggregate type, recycled materials, WMA technology, plant type, and production temperature. In this study, field cores were acquired from seven field projects at construction and several months afterwards, and raw materials were also collected for fabricating laboratory specimens that were long-term oven aged (LTOA) in accordance with selected protocols. The resilient modulus and Hamburg wheel tracking tests were conducted on both specimen types to evaluate the evolution of mixture stiffness and rutting resistance with ageing. The concepts of cumulative degree days and mixture property ratio were proposed to quantify field ageing and its effect on mixture properties. Test results indicated that the LTOA protocols of two weeks at 140°F (60°C) and five days at 185°F (85°C) produced mixtures with equivalent in-service field ageing of 7–12 months and 12–23 months, respectively, depending on climate. Finally, among the factors investigated in the study, WMA technology, recycled materials, and aggregate absorption exhibited a significant effect on the long-term ageing characteristics of asphalt mixtures, while production temperature and plant type had no effect.

Volumetric Analysis and Performance of Hot Mix Asphalt with Variable Rap Content

Incorporating Reclaimed Asphalt Pavement (RAP) to the asphalt concrete mixture for highway construction offer many benefits including energy consumption, conservation of natural resources and preservation of the environment to associated emissions. This paper presents a study on performance of Hot Mix Asphalt with variable RAP content. The study is carried out to evaluate the Marshall Properties and Performance of RAP-Asphalt mixes using conventional asphaltic concrete mix AC14. Marshall Mix Design Method was used to produce control mix (0% RAP) and RAP-Asphalt mixes samples which consist of 15% RAP, 25% RAP and 35% RAP in accordance with Specifications for Road Works of Public Works Department, Malaysia. The Marshall Properties analysis was performed to ensure compliance with Marshall Requirements, The resilient modulus test was performed to measure the stiffness of the mixes while Modified Lottman test was conducted to evaluate the moisture susceptibility of these mixes. The results obtained showed that there were no substantial difference in Marshall Properties, moisture susceptibility and indirect tensile strength between RAP-Asphalt mixes with the control mix. The test results indicated that recycled mixes performed as good as the performance of conventional HMA in terms of moisture susceptibility and resilient modulus. It is recommended that further research be carried out for asphalt mixes containing more than 35% of RAP material.

Effect of Waste Plastic as Bitumen Modified in Asphalt Mixture

The objectives of this study are to investigate the engineering properties of the asphalt mixtures containing waste plastic at different percentages i.e. 4%, 6%, 8%, and 10% by weight of bitumen. The experimental tests performed in the study were stability, tensile strength, resilient modulus and dynamic creep test. Results showed that the mixture with 4% plastic has the highest stability (184kN). However, the stability slightly decreases with the increase of plastic additive. On the other hand, the highest tensile strength among the modified asphaltic concrete is 1049kPa (8% plastic added). The modified asphalt mixture with 8% plastic has the highest resilient modulus, which is 3422 MPa (25°C) and 494Mpa (40°C). Where the highest creep modulus recorded is 73.30Mpa at 8% plastic added. It can be concluded that the addition of 8% plastic gave the highest value properties of asphalt mixture. Finally, it can be said that 8% plastic is the optimum value adding.

Bender Elements Successfully Quantified Stiffness Enhancement Provided by Geogrid–Aggregate Interlock

Lateral restraint is a primary mechanism of geogrid base reinforcement contributing to the performance improvement of flexible pavements, and the interlocking between the geogrid and aggregate is responsible for stiffness enhancement in a zone formed around the geogrid. A novel application of bender elements is introduced: as shear wave transducers for quantifying local stiffness increase in the vicinity of a geogrid. Several triaxial test specimens of a dense-graded granite-type aggregate were prepared at two moisture contents for resilient modulus testing. Reinforced specimens also included a punched and drawn geogrid piece placed at specimen midheight. Two pairs of bender elements installed on the membrane at two heights enabled measurement of shear waves horizontally across the specimen. Shear wave velocities and axial resilient strains were recorded under the applied stress states. The test results show that the resilient modulus of the reinforced specimen was similar to that of the unreinforced one tested at the same moisture content. In contrast, the shear moduli obtained at midheight of the reinforced specimen were always greater than those obtained from the unreinforced specimen, indicating a local stiffness increase in the vicinity of the geogrid. In the reinforced specimens, the shear moduli obtained near the upper end were always less than those obtained from the specimen midheight. The small-strain shear modulus determination by bender elements was effective for evaluating the stiffness enhancement provided by geogrid–aggregate interlock.

Preliminary <i>k</i>-Values of Unbound Natural Quartzitic Gravels for Mechanistic-Empirical Pavement Design

The generalized constitutive model relating the resilient modulus (MR) of flexible pavement layer materials to stress state, adopted by the Mechanistic-Empirical Pavement Design Guide (MEPDG), contains a set of constants known as k-values (k1, k2, and k3) which are associated with the physical state of the layer materials. In Ghana, natural gravels constitute the predominant and sometimes the sole layer materials for most flexible pavements yet representative k-values of gravel materials, have not been determined to permit full application and implementation of the mechanistic-empirical design concept to pavements involving such materials. In this study, k-values characterising typical natural quartzitic gravels used for road construction in the country were derived by regression techniques from MR values determined using laboratory repeated load triaxial test. Using multiple linear regression technique, correlation relationships were then developed between the k-values and the physical properties of the gravels, namely, percentages of materials passing the 9.5 mm (P9.5) and 2.0 mm (P2.0) sieves, liquid limit (LL), maximum dry density (ρdmax), and optimum moisture content (wopt). The regression analysis returned k1 values which ranged between 441 and 958 with a mean of 516; k2 which varied between 0.0636 and 0.2168 with a mean value of 0.1216; and, k3 values which ranged between 0.1257 and 3.1590 with a mean value of 1.723. Contrary to what is mostly reported in literature, the analysis returned positive k3 values for all but one gravel material, suggesting stress hardening under octahedral shear stress for those materials. While an expanded sample base is required to fully characterize the whole gamut of natural gravels used in pavement construction in the country, this study on limited quartzitic gravel samples has given a good indication of strong linear correlations between the k-values and the index properties of the gravels, to permit estimates of the constants for such gravels be made where capability and opportunity for conducting resilient modulus tests do not exist.However, further work is recommended to fully characterise the exact nature of k3 values for quartzitic gravels in the country.

Reinforcement of Asphalt Concrete Mixture using Recycle Polyethylene Terephthalate Fibre

Objectives: To determine the reinforcing effect of a cheap Recycle Polyethylene Terephthalate (PET) fibre on asphalt concrete strength. The aim of this study was achieved by performing Resilient Modulus (MR) test in the laboratory on both unreinforced (i.e. neat asphalt mixture) and recycle PET fibre reinforced asphalt concrete mixtures. Methods: The percentage additions of recycle PET fibres are 0.3%, 0.5%, 0.7% and 1% of the total weight of the mixture. The result was analyzed by means of Response Surface Methodology (RSM) using Design Expert 7.0 software and validated using analysis of variance (ANOVA). Findings: The results indicated that recycle PET fibres have significantly increased the mixtures’ resilient modulus in lower temperature hence improved fatigue resistance, and moderately increased mixtures, resilient modulus at higher temperature hence improved rutting resistance. Novelty/Improvement: This research has introduced a sustainable means of producing Recycle fibres for the reinforcement of asphalt concrete mixtures. Recycle PET fibre have proved to be effective in strength improvement at 0.7% of total weight of asphalt concrete mixture.