Resilient Modulus Tests Research Articles

Effect of Fractured Aggregate Particles on Linear Stress Ratio of Aggregate and Resilience Properties of Asphalt Mixes—A Way Forward for Sustainable Pavements

The interlocking and packing of aggregate particles play a key role in achieving high level of linear viscoelastic properties and rutting resistance in asphalt mix for sustainable pavements. In this study, the quantitative effect of fractured aggregate particles (FAPs) on loading (i.e., 500 kPa normal stress), along with the resilience properties of asphalt mixes, was evaluated. Linear and nonlinear stress behaviors of aggregates (from direct shear test) and asphalt mixes (from resilient modulus test) were analyzed. A new quantitative parameter (linear stress ratio), i.e., linear stress (Pi)/maximum stress (Pmax), is proposed to be used in selection of aggregates for asphalt mixes. It was observed that 15.5% increase in FAPs caused 19.5% increase in ϕ and 70.7% increase in linear stress ratio (LSR). The same content of FAPs resulted in 29.4% and 36% increases in total resilient modulus (MRT) and 34.2% and 24.5% increases in instantaneous resilient modulus (MRI) for 0.1 and 0.3 s load durations, respectively. The proposed LSR is observed to be superior to conventionally used ϕ for aggregate resistance in design of flexible pavements.

Effects of maltene on the attributes of reclaimed asphalt pavement: Performance optimisation

The asphalt mixtures using elevated percentages of the reclaimed asphalt pavement (RAP) are of significant interest due to its ability to address environmental issues and reduce cost of asphalt. However, utilising elevated RAP content is associated with several disadvantages. Hence, this study explores the potential application of maltene as a rejuvenator to improve the output of asphalt mixtures incorporating RAP binder. The contents of maltene were optimised according to several parameters, namely penetration, softening point, ductility, and viscosity tests. Thereafter, the specimens containing an optimum maltene percentage were assessed using maltene-to-asphaltene ratio, storage stability, Dynamic Shear Rheometer (DSR), Bending Beam Rheometer (BBR), Fourier Transform Infrared (FTIR) spectroscopy and Thermogravimetric Analysis (TGA) measurements. Subsequently, the mechanical characteristics of asphalt mixtures were analysed using Marshall Stability, moisture damage, resilient modulus (MR), and Cantabro loss tests. The results demonstrated that 8% and 16% of maltene restored the physical properties of 30% and 50% of RAP binder, respectively. In addition, the workability was improved due to the reduction of viscosity, while maltene-rejuvenator managed to compensate the light components of RAP binder that were lost during the lifespan. As a result, the high- and low-temperature performance of RAP binder were restored approximately to that of virgin asphalt (VA). The oxygenated indices of RAP binder were effectively abated by blending with maltene. The TGA exhibited that the thermal stability of rejuvenated asphalts was close to VA. Accordingly, the mechanical characteristics of rejuvenated mixtures were improved compared to the VA mixture. Therefore, the maltene with a suitable dose is recommended to rejuvenate the RAP binder, and reuse it in the pavement construction.

The aging behavior of reclaimed asphalt mixture with vegetable oil rejuvenators

In recent years, the evaluation of aging behavior of different types of asphalt mixture has become an important research field in pavement engineering. The short-term and long-term aging properties of reclaimed asphalt concrete (RAC) under the effects of vegetable/mineral oil rejuvenators are introduced in this research. Eighteen specimens of reclaimed asphalt binders classified by rejuvenator contents and types were evaluated. The viscosity of aged/unaged reclaimed asphalt binder was measured at different temperature. The results proved that the type and content of rejuvenators have significant impacts on the viscosity values of the reclaimed asphalt binder. The reclaimed asphalt binders with vegetable oil rejuvenators have lower viscosity, which also demonstrated a less increase than that with a conventional mineral rejuvenator. Less weight loss, lower complex modulus G* and lower increase rates were also found in the reclaimed binders with vegetable oil rejuvenators than that with mineral oil rejuvenators. Less weight loss, lower complex modulus G*, and lower increase rates were also found in the reclaimed binders with vegetable oil rejuvenators than that with mineral oil rejuvenators. With various RAC were determined by the Marshall design method, the results of indirect tensile strength test (ITST) displayed that the aging procedure increased the ITS of RAC. Furthermore, the results of resilient modulus test, indicated that aging did not significantly increase the resilient modulus for RAC with vegetable oil rejuvenators.

Mechanical Performance of Gilsonite Modified Asphalt Mixture Containing Recycled Concrete Aggregate

Hot-mix asphalts exposed to hot weather and high traffic volumes can display rutting distress. A material that can be used to increase the stiffness of asphalt binders is gilsonite. On the other hand, from an environmental point of view, the virgin natural aggregates of asphalt mixtures can be replaced with recycled concrete aggregates. For these reasons, this study modified the asphalt binder with gilsonite by wet-process to improve rutting resistance, and replaced (by mass and volume) part of the coarse fraction of the aggregate with recycled concrete aggregate in two hot-mix asphalts with different gradations. Unlike other studies, a larger experimental phase was used here. Marshall, indirect tensile strength, resilient modulus, permanent deformation, fatigue resistance, and Cantabro tests were performed. An ANOVA test was carried out. If the replacement of the virgin aggregate by recycled concrete aggregates was made by volume, both materials (gilsonite and recycled concrete aggregate) could be used in hot-mix asphalts for thick-asphalt layers in high temperature climates and any level of traffic. The use of both materials in hot-mix asphalts is not recommended for thin-asphalt layers in low temperatures climates. It is not advisable to replace the aggregates by mass.

Microstructural analysis on the variation of resilient modulus of lime modified soil under freezing–thawing action

Subgrade soil is sometimes modified with lime to improve strength. In this study, lime modified soil (LMS) specimens are subjected to freezing–thawing cycles, the mechanical properties and microstructure of the specimens are investigated by resilient modulus test and scanning electron microscope test. The variation in pore microstructure is investigated by image analysis. The results indicate that the number and area of micropores are reduced due to phase change and expansion of water in the soil under freezing–thawing cycles, and the micropores are subsequently coalesced into macropores. The variations in porosity and resilient modulus are correlated. The largest effect to the microstructure and resilient modulus of LMS is observed after the first freezing–thawing cycle. The main reason for the attenuation in resilient modulus of LMS is attributed to the increase in porosity, decrease in bond strength among soil particles and increase in the number of narrow and long cracks in soil.

Numerical study using stiffness parameters on the nonlinear behavior of RCA pavements under heavy traffic loads

The use of the recycled concrete aggregates (RCA) obtained from construction and demolition wastes not only reduces the demand for natural aggregate, which ultimately leads to economical and eco-friendly designs, but also improves the long-term performance of a conventional flexible pavement. This study aims to investigate the effects of using 100% RCA in the pavement subbase and base courses on the mechanical behavior of the flexible pavement. This study is divided into two stages, i.e., a laboratory study characterizing the properties of RCA and a numerical analysis evaluating the long-term performance of RCA under heavy traffic load conditions. In the laboratory study, along with the determination of the classical geotechnical properties of base and subbase samples, the stiffness properties of the samples were obtained by applying the resilient modulus test (RMT) and permanent deformation test (PDT). Then, by comparing the results of the three different constitutive models, the result of the more appropriate model was selected. In the second stage, the plastic deformation (rutting) of the pavement courses and the maximum value of deflection when subjected to multiple wheel loads were determined using a 3D nonlinear numerical method. Based on the experimental results, RCA demonstrated higher resilient modulus and lower plastic deformation compared to that of conventional base and subbase materials. Regarding the long-term behavior, the permanent strain rate of the samples was reduced at an approximately constant level during the first load cycles. Additionally, the numerical analysis results indicated that the mechanical performance and rutting values of the base and subbase courses constructed using 100% RCA met the specified requirements.

Effects of Combined Environmental Factors on Stiffness and Rutting Properties of Warm Mix Asphalt

Abstract Warm mix asphalt (WMA) is a sustainable clean product that can be fabricated at lower temperatures. This is an environmentally friendly mixture due to its lower emission and energy consumption in asphalt production plants. Moisture conditioning and aging process are two environmental factors that can adversely affect the stiffness properties of this product. In the field, WMAs are subjected to both moisture damage and aging. In this paper, a new laboratory method was used for evaluating the combined effects of aging and moisture conditioning of WMA samples. WMA specimens were fabricated at various compaction temperatures with different amounts of a surfactant-wax warm additive. Stiffness properties of asphalt mixtures were quantified from the resilient modulus and dynamic creep test. The results showed that moisture conditioning and aging are competing to affect the stiffness properties of mixtures. Polymer modified asphalt mixtures were found to be less susceptible to moisture damage when compared to mixtures fabricated with unmodified binder. Compaction temperature was the most significant factor that affected the resilient modulus of WMA. In the dynamic creep test, the combined effects of aging and moisture conditioning reduced the cumulative micro strain of samples regardless of binder type, additive content and compaction temperature.

Performance properties of WMA modified binders and asphalt mixtures containing PPA/SBR polymer blends

The performance properties of asphalt binders and mixtures can be enhanced utilizing several modifiers, including; Poly Phosphoric Acid (PPA), Warm Mix Asphalt (WMA) modifiers, and Styrene–Butadiene Rubber (SBR). The current study evaluated the effect of PPA and WMA contents on rheological behavior of SBR modified binders and SMA mixtures. The modified binders were subjected to rotational viscosity, Dynamic Shear Rheometer, and Bending Beam Rheometer, Multiple Stress Creep Recovery (MSCR), and Linear Amplitude Sweep (LAS) tests. The SBR/PPA and SBR/PPA/WMA modified mixtures were subjected to Indirect tensile strength (ITS), dynamic creep, resilient modulus ( Mr), wheel track, and four-point beam fatigue (FPB) tests. To analyze the data, two-factor analysis of variance (ANOVA) was investigated. Based on the results of the MSCR test at both stress levels, modification of base bitumen by SBR, PPA and WMA additives causes an enhance in permanent deformation performance of original bitumen. LAS test results indicated that, utilization of SBR and WMA additives improves the fatigue life of bitumen. Also, by addition of PPA, the fatigue life of SBR modified binders increases. whereas, the fatigue lives are higher than original binders ones. Based on results, utilization of SBR and PPA enhances the Mr, rutting properties, ITS, FE, and fatigue behavior of specimens. By increasing the PPA percentage, the rutting and fatigue behavior enhances. Whereas, it causes a decreases in Mr and ITS of modified mixtures. Among warm additives, sasobit has better effect on enhancing the performance of binders and mixtures.

Determining optimum fly ash content for Stabilized subbase materials in road pavements

ABSTRACT The investigation of fly ash content for stabilized subbase materials in road pavements was presented in this study. The effects of partial replacement of cement by 17%, 33%, 50% of fly ash contents by total weight of mixture were investigated to evaluate mechanical properties of stabilized subbase materials using the unconfined compressive strength (UCS) test, indirect tensile (IDT) test, and resilient modulus test. It was found that the replacement of cement by 33% of fly ash can use for stabilized subbase material. In addition, a strong relationship between IDT and UCS strength, and resilient modulus and UCS is given which is the coefficient of determination of developed correlation to be 0.9 and 0.82, respectively. It was suggested that the IDT strength or the resilient modulus can be estimated from a UCS test. Finally, the performance of cement replacement with fly ash was evaluated using mechanistic empirical pavement design guide (MEPDG) program. Based on the results of the study, it can be concluded that the cement replacement with 33% fly ash can enhance the performance life significantly and the construction cost reduction can be around 23%, compared to using conventional subbase material.

Investigation on three-dimensional failure criterion of asphalt mixture considering the effect of stiffness

In order to reveal the effect of complex stress state on the characteristics of strength and stiffness of asphalt mixture, the self-developed double confining pressure triaxial test method was used in this study. The one-time failure and resilient modulus tests in complex stress state were carried out on the SMA-13 and AC-13 asphalt mixtures widely used in China's asphalt pavement, especially in the combined tensile-compressive stress state. The failure principal stress of material and its stress-strain data under the step loading condition were obtained. The calculation model of resilient modulus in complex stress state and the failure criterion I1-J2 in the principal stress space were established. On this basis, based on the generalized Hooke's law, a three-dimensional strain failure criterion model for asphalt mixture considering the effect of stiffness was also established by the conversion method. The research results can provide experimental and theoretical support for the reasonable selection and resistance calculation of material parameters of asphalt mixture in complex stress state.

A permanent deformation predictive model for fine tropical soils considering the effects of the compaction moisture content on material selection

The evaluation of the mechanical behavior of soils should be considered as an important step for material selection and pavement design. The analyses of the elastic and plastic behaviors of the pavement unbound materials have generally been based on resilient modulus (RM) and permanent deformation (PD) tests, respectively. Such mechanical characteristics are significantly affected by factors including gradation, traffic speed, loading history, and moisture content. However, special attention should be given to the moisture content, given that the use of inadequate water content during compaction can lead to premature failure of the pavement system. This paper investigates the effects of the compaction moisture content on the plastic behavior of fine soils by means of PD. Based on the analysis of two existing models that take this key factor into account, a predictive model tailored for fine tropical soils is proposed. Four soils of different classifications were tested with three distinct compaction moisture contents (below the optimum, at the optimum moisture, and above the optimum moisture contents) to analyze interaction effects for a PD predictive model. Two additional fine soils are used to validate the model. A statistical analysis considering the six fine soils indicates that the proposed PD model can efficiently predict the effects of the compaction moisture content on the long-term resistance to PD of the fine soils and that the suggested procedure can be potentially used as a tool for material selection.

Performance-Guided Design of Permeable Asphalt Concrete with Modified Asphalt Binder Using Crumb Rubber and SBS Modifier for Sponge Cities.

The construction of sponge city is a major green innovation to implement the concept of sustainable development. In this study, the road performance of permeable asphalt concrete (PAC), which displays pronounced water permeability and noise reduction that are favorable for sponge cities, has been improved with a two-fold modification using styrene–butadiene–styrene (SBS) and crumb rubber (CR). Four percent SBS and three different ratios (10%, 15%, and 20%) of CR have been used to modify the virgin asphalt binder. The Marshall design has been followed to produce PAC samples. To evaluate the asphalt binder performance, multiple-stress creep-recovery (MSCR) test, linear amplitude sweep (LAS) test, and engineering property test programs including softening point test, penetration test, and rotational viscosity test have been conducted. Freeze–thaw splitting test, Hamburg wheel-tracking test, resilient modulus test, and permeability coefficient test have been performed to evaluate the asphalt mixture performance. The test results show that the addition of SBS and CR reduces the permeability coefficient, but significantly improves the high temperature performance, fatigue performance, and rutting resistance as well as the resilient modulus. However, the optimum rubber content should not exceed 15%. Meanwhile, after adding CR and SBS modifier, the indirect tensile strength (ITS) and tensile strength ratio (TSR) increase. It indicates that the moisture stability and crack resistance have been improved by the composite modification effect.

Estimation of resilient modulus of cement-treated construction and demolition waste with performance-related properties

Construction and demolition (C&D) waste is generated for 100 billion tonnes per annum globally, which has caused underground water contamination and farmland occupation when disposing the C&D waste by landfilling. The C&D waste materials have been recycled and used as an alternative to virgin mineral aggregates in pavement construction. This study aims at proposing a convenient method to estimate resilient modulus of cement-treated C&D waste materials when used in pavement base layer based on material performance-related properties and using discrete element simulation tests. Two kinds of materials are investigated, they're blends of two C&D waste materials, crushed bricks (CB) and recycled concrete aggregate (RCA). Fundamental property experiments were carried out on the aggregates to evaluate the engineering performance. Unconfined compress strength (UCS) tests were conducted on cement-treated materials to analyze the effect of curing duration and cement content on UCS. The numerical resilient modulus (Mr) tests by the discrete element method (DEM) were conducted to evaluate the resilient performance of C&D waste. The simulation results were verified with the lab measurements. Test results showed that the test materials have a high water absorption and a low durability. The minimum cement content was determined as 5% to satisfy the strength requirement of 4 MPa according to the national standards. Mr increases with confining pressure. Performance-related properties (UCS, γd, E50) were proposed to build their correlations with k values of the resilient modulus model, which are formulated to predict the k values. The values of Mr predicted by the performance-relatedproperties were consistent to the DEM modeled ones.

Stiffness Properties of Recycled Concrete Aggregates as Unbound Base and Subbase Materials Under Freeze and Thaw Cycles

Freeze and thaw processes are mostly observed in cold regions and impact the short- and long-term performances of road pavements. Thus, freeze and thaw processes should be considered when designing and constructing roads due to the potential change it will cause to the structure, arrangement and properties of the materials used in road construction. This study attempted to understand the effect of freeze and thaw (F–T) cycles on the stiffness properties of recycled concrete aggregates (RCAs). For this purpose, base and subbase samples prepared with RCAs are subjected to varying numbers of F–T cycles, and a series of resilient modulus and permanent deformation tests are conducted. Moreover, the different models were applied to estimate the resilient modulus and permanent deformation, and the suitability of each model was discussed. The experimental study results indicate that the geotechnical engineering properties of RCAs originating from Istanbul-Turkey are suitable for utilization as unbound base or subbase course materials. In the stiffness assessment, the highest resilient modulus was obtained after 5 F–T cycles and then decreased but was still higher than that of the nonfrozen samples except the subbase sample exposed to 20 F–T cycles. Lower plastic strain values were obtained for the base samples, and after F–T exposure, no drastic changes were observed in the permanent strain increments for the base materials, as seen in the subbase samples. Most of the RCA samples exposed to F–T cycles accumulated permanent strains with plastic creep behavior based on the shakedown theory.

Study on Cracking Resistance of Basalt Fiber-Reinforced Microbond Asphalt Macadam

The aim of the present study was to explore the effect of basalt fibers on the cracking resistance of microbond asphalt macadam and reduce the occurrence of cracks in asphalt pavements with semirigid base. To this end, compressive resilient modulus tests, rutting tests, and semicircular bending tests were conducted on microbond asphalt macadam with different fiber contents, and the change trends of the compressive resilient modulus, dynamic stability, and flexibility index (FI) with fiber content were revealed. According to the results of this study, the addition of basalt fibers affected the compressive resilient modulus, dynamic stability, and FI of microbond asphalt macadam significantly. With the increase of fiber content, the compressive resilient modulus, dynamic stability, and FI presented a uniform trend of increasing first and decreasing afterwards. When the fiber content was 0.4%, various indices reached their maximum values, suggesting that the cracking resistance of the basalt fiber-reinforced microbond asphalt macadam was optimal under this content. This study is of great significance for the application and promotion of basalt fiber-reinforced microbond asphalt macadam.

Environmental and mechanical impacts of waste incinerated acidic sludge ash as filler in hot mix asphalt

In this paper, the feasibility of employing waste incinerated acidic sludge ash (IASA) as a viable alternative to the mineral fillers in hot mix asphalt (HMA) with a siliceous aggregate source from environmental and mechanical aspects was investigated. Environmental impacts were analyzed considering four factors: ignitability, reactivity, corrosivity using pH test, and toxicity using toxicity characteristic leaching procedure test. Mechanical properties of mixtures were obtained using indirect tensile strength (ITS), resilient modulus, moisture sensitivity, and permanent deformation tests. Results revealed that all metal concentrations leached from IASA modified HMA and pH of IASA modified samples comply with the United States Environmental Protection Agency (EPA). It was also demonstrated that incorporation of IASA in HMA leads to enhancement of HMA mechanical properties. ITS and resilient modulus of mixtures containing IASA were higher than those of the control mixtures. Replacing 50 wt.% of siliceous stone dust filler with IASA causes an increment about twofold in the flow number and reduction of the rut depth by about 26 % compared to those of the control sample. Moreover, the hydrophobicity and impermeability properties of IASA modified HMA and the stronger interfacial reaction between asphalt and IASA, resulted in improving the moisture susceptibility of the mixture containing IASA. This paper provides more insights on IASA waste management through its application in an environmentally friendly HMA.

Stress and Strain Characteristic of Stone Mastic Asphalt Incorporating Eggshell Powder

Stone mastic asphalt (SMA) is a type of gap graded asphalt mixture. Due to large difference between the gap of large and small size aggregate, this type of mixture suffers a few drawbacks such as low resistance towards permanent deformation. Thus, the usage of ecofriendly and sustainable additive is crucial in enhancing the performance of SMA. Thus, this study is utilizing various amount of eggshell powder as asphalt modifier. Among the tests involve to evaluate the stress-strain characteristic of modified SMA are Resilient Modulus Test and Dynamic Creep Test. From the test, it shows that the addition of 4% eggshell powder produces the highest value of resilient modulus and lowest value of dynamic creep for SMA. In conclusion, this study proves that the eggshell powder is capable in enhancing the performance of SMA especially in terms of permanent deformation resistance.

Repurposing of COVID-19 single-use face masks for pavements base/subbase

The coronavirus (COVID-19) pandemic has not only created a global health crisis, but it is also now threatening the environment. A multidisciplinary collaborative approach is required to fight against the pandemic and reduce the environmental risks associated with the disposal of used personal protective equipment (PPE). This paper explores an innovative way to reduce pandemic-generated waste by recycling the used face masks with other waste materials in civil constructions. In this research, for the first time, a series of experiments, including modified compaction, unconfined compression strength and resilient modulus tests, were conducted on the blends of different percentages of the shredded face mask (SFM) added to the recycled concrete aggregate (RCA) for road base and subbase applications. The experimental results show that RCA mixed with three different percentages (i.e., 1%, 2% and 3%) of SFM satisfied the stiffness and strength requirements for pavements base/subbase. The introduction of the shredded face mask not only increased the strength and stiffness but also improved the ductility and flexibility of RCA/SFM blends. The inclusion of 1% SFM to RCA resulted in the highest values of unconfined compressive strength (216 kPa) and the highest resilient modulus (314.35 MP). However, beyond 2%, increasing the amount of SFM led to a decrease in strength and stiffness.

Evaluating the Performance of Reclaimed Asphalt Pavement Incorporating PelletRAP as a Rejuvenator

In the recent years, the use of reclaimed asphalt pavement (RAP) in the pavement has become inevitable for economic and environmental reasons. However, the brittleness property of aged asphalt in the RAP restrict its usage in a high percentage. Nevertheless, the rejuvenators are introduced into the mixtures to reverse the effect of ageing processes, decrease the stiffness and increase the workability of RAP mixture. In the present research, various percentages of PelletRAP rejuvenator were added to 100% of RAP mixtures. The performance characteristics of rejuvenated mixtures were investigated via resilient modulus (MR), dynamic creep, and wheel tracking tests. The results showed that when the PelletRAP was included into the mixture, the MR values and the creep stiffness modulus (CSM) decreased, while the permanent creep, the creep strain slope (CSS) and the rutting depth increased. However, all the rejuvenated mixtures exhibited better results than that of virgin mixture. Such a trend of findings suggested that PelletRAP can be used as a rejuvenator without a negative effect on the high-temperature performance of asphalt mixtures.

Use of Steel Slag as an Alternative to Aggregate and Filler in Road Pavements.

Today the use of Construction and Demolition Materials (CDM) can be considered as a suitable solution for the construction or the rehabilitation of road pavements. In this context, it is central to minimizing waste production, favoring the reuse through new production cycles to replace virgin natural raw materials. As illustrated in this study, steel slag has mechanical properties that justify its use as aggregate in the manufacture of bituminous mixes. In road construction, their use is focused on the substitution of fine aggregate and filler in bituminous mixtures. Mechanical characterizations, Marshall stability and indirect tensile resilient modulus (ITSM) tests were used to evaluate the laboratory performance of the mixtures. The research aims are to provide the use of these materials for the construction of the entire road pavement structure; in this study authors used these materials both in the characterization of cementitious layers and in those with bituminous conglomerate. In both cases, the use of steel slag has favored an increase of stiffness in the mixtures.